Just to make this clear for everyone, this box with battery cells will not be a mobile solution. The box will be set up in my garage and won't be moved at all. It's a stationary installation.
I understand that it's not a mobile pack BUT why not build it on a heavy-duty "Moving Dolly" so that it's semi-movable? You will thank yourself later ;-)
Great to read all the comments, just ordered 48 cells, 100 amp Daly BMS, 100amp dc breakers to build 3 batteries, I will order ss set screws, thanks for the info guys. I plan on building a metal enclosure using 20 or 22 gauge mild steel and semi compress the cells using high density foam strips. My thinking is to use 3, 1 inch strips on each end cell to semi compress and still leave space for cooling . Also ordered a Deye 8kw split phase inverter, the specs look very similar to the sol ark.
It will not be portable at all. with 80kg it's far too heavy, the bottom would fall through when lifted. This is a stationary setup, not mobile. Once in place, it will not be moved again.
Thanks for the video. This is a good topic. I have 8 x 280 AH batteries built up into an 8S -24V 2x4 cell pack for a stationary off grid application for part of my home. As I recall, the data sheet for my cells said that the cycle life was better if the cells were compressed. I think the rating is 3,500 cycles to 80% capacity if compressed and only 2,500 cycles to 80% capacity if not compressed. I have also seen comments from other users saying that it is better to compress the pack, especially if they are used in a mobile application. I took a hybrid approach to building my pack. I put the batteries together using a 1 inch square piece of VHB tape in each corner of the batteries that faced each other, and then compressed the entire pack using a 10"H x 18"L x 3/4"T piece of plywood on each end of the pack, compressed and held together by four threaded 1/4" rods about 14" in length. This gives you the best of both worlds - a very slight gap between batteries with the whole pack secured and compressed to avoid shifting of the individual cells when the pack is moved. Cooling is not an issue in my application because I rarely go above 0.2 C charging or discharging the pack. By the way, I would not recommend compressing the pack with a metal bar as you were considering. That concentrates the expansion stresses on a small surface area of the battery case which could lead to problems down the road. The plywood endcaps distribute any expansion stress across the entire surface area of the battery, with the added benefit that plywood is not conductive. I'm keenly interested in how your project turns out.
Thank you for you reply and feedback. That is a great setup you have there. I wasn't going to use the metal brackets for compressing (although I have seen this online). A piece of plywood as large as the full side of the cell would evenly spread the load as you suggested. But I'm still not convinced I should compress at all. It does not say anything in the specs for my type of batteries.
@@OffGridGarageAustralia check out a top view photo of my battery pack at the link below showing the way I compressed my batteries.. I went back and checked the spec sheet and other comments on Will Prowse's DIY Solar forum, and the general consensus of many is that compressing the battery pack extends the cycle life of the batteries. diysolarforum.com/threads/xuba-electronics-deal-280ah-lifepo4-cells-purchase-review.3850/page-61#post-96433
Nearly 200 lbs in that tub. Don’t know it’s weight rating, but I’d seriously consider putting some plywood in the bottom to keep it from falling through even when stationary. I’m building three 24v batteries with these cells (24 cells) and 100 lbs each is tough to handle (probably put my totes on wheels). Love your enthusiasm, keep the videos coming!
Thanks for the feedback! I thought about some plywood as the bottom but this will be a stationary setup, so once the box is in its place, it will not move again.
I have read some feed backs I think It will be a good idea to keep space + adding a plywood in the bottom + adding 4 wheels also. I know that it is stationary but maybe in future you decide to make some new arrangements or changings in your place, so it will be very helpful.
@Tech Boy, I agree with everything except the wood: something inert like plastic or rubber would be better. I would avoid wood unless it was charred (and I couldn't find some suitable plastics).
Hey Andy, remember me from the PHEV days? I just got my M3LR. I rigged my garage up as a solar garage nearly three years ago and it’s still giving good service including charging my EV in the summer (we also have eGolf). It’s great what you are doing with this channel & it’s giving me some great ideas for upgrading my garage (I only have 2.2kwh of battery capacity). Really enjoying this channel 👍
Of course, I remember you, Harry! Welcome back and great to have you here on the channel again. A lot of PHEV owners have upgraded to a pure EV in the last year. Hope that wasn't all my 'fault' 😁
@@OffGridGarageAustralia yep, it’s all your fault. Keep up the good work, I haven’t stopped grinning since I got it & keep looking for excuses to go for a drive. Such an awesome machine.
this is exactly what I figured, that's why I wouldn't use bus bars, use thick cables instead, they allow for movement. especially important if installed in a car
One thought on your concept of leaving space allows for air flow. If there isn't air flowing in sufficient quantity, air is actually an amazing thermal insulator, so you are actually better off coupling the cells thermally in order to dissipate heat. Others have mentioned but the expansion is a result of high voltage during charging so could be a non issue depending on how you are going to handle charging but in general compression is beneficial but I'm not planning on doing it.
I'll keep them at 80%/85% SOC max so this should not be an issue. Also I have charged some of the cells to 3.65V a few times to do capacity measurements and never noticed any expanding (yes, I looked for it).
I like your thoughts of why you should keep space between them. My only concern is how you hold them in that exact configuration. Any time you move them at all it will put pressure on the terminals since they're not held rigidly against each other. Maybe you could put a square of double sided adhesive foam at each corner to hold them in position but still leave a gap between.
This is a stationary setup, once the box is in its final destination in the garage and filled with these cells, it will not move any more. I should have made this clearer, ey?
Just a thought, maybe if you use a small square piece of double sided tape on each corner then you still have the air flow while making sure you have a consistent gap between each cell. Then get the terminals to be in the middle of the busbar slot, then you can always change the gap to smaller or bigger. At the lowest point of the box maybe make one or 2 drain holes just in case some liquid gets in so it can drain.
Im waiting for my shipment of the same cells i ordered 4 but seems like they provided extra cells at no other cost. Im turning my jeep xj into a a overland camper with a ton of battery capacity with the 280 ah cells :D
Hi You never want to compress the cells! You can brace/ strap the cells and this is to prevent them expanding due to any over/ undercharged situations. Mainly overcharge I believe. I have been running my pack without any bracing for some time.e now without issue but I have never overcharged. Which bms will you use?
Thanks for your feedback on this topic. I have ordered a 200A BMS from AliExpress with BT and 600A peak current. It was cheaper than the Daly ones so I thought I'll give it a go and see how it performs. It's on its way...
Having the gap between the batteries is better not only for expansion and contraction heat dissipation the batteries will cool faster and not get as hot when charging and discharging you are correct by doing so
These batteries don't get hot unless you do very high C rates (not common in solar applications or battery banks like this). If you read the datasheet, the manufacturer recommends clamping these together at a specific pressure.
There are some scientific research papers which speak about longer longevity when you keep them compressed. My 100Ah cells expanded 3-5 mm each during there lifetime till now. Your cells are very big. The "Jelly-roll" inside that can has a lot of windings. So even if it just swells a tiny bit per winding, it will eventually add up a bit :) But its your choice...
A really good source of information is the endless sphere forum. There has been a discussion about compression there. It is good, but has to be the right amount.
Thank you. I have ready this online too. These prismatic cells are not pouch cells though so I don't really see the advantage of doing this. The manufacturer does not advise of any compression either...
@@OffGridGarageAustralia I think that is the definitive answer, ie follow what the manufacturer suggests as you then have a come back at a later stage.
Depends how many watts u want to pull out of the battery how hot they will get while discharge my advice is pressing them together because with time they puff upand don't contact back !
This is a very interesting topic Tronor. I want to use my 48V/272AH pack in a mobile off-road environment - compressing them should help with vibrations and also with the expansion/contraction due to temperature, charge/discharge and aging of cells. Unless one is using them for >1C discharge/charge (I won't - BMS is limited to 200A discharge, 100A charge), then heating from charge/discharge won't be a problem.
@@MiniLuv-1984 ur totally right if u don't stress the cells u will never overheat them and pressing them thogeter prevents ugly puffed cells i mean they puff up after some time and u can put some thin separator 0.5-1 mm plastics sheet's in between every cell! I u have concerns fore a short on cell casing recommended when mounted in an rv or car !
@@tronor5 The idea of using 0.5-1mm plastic sheet is perfect for mobile situations - thanks for pointing that out. Steel or thicker aluminium end plates too. Thanks. My thoughts for mobile use is to pack them as either 2 x 8 cells or 4 x 4 cells packages - compressed with plastic sheets in between and 6mm aluminium end pieces with steel threaded rod holding the two aluminium plates under compression. I might go for 4 cell package since an 8 cell package is a little too heavy to move around without risking an injury.
I followed your reasoning and agreed with not to compress. I then watched a new system video, SEPLOS PUSUNG Energy Storage System, and they said to compress to prevent "irreparable swelling damage". I wonder if the manufacturer would have a recommendation?
There is not a single topic in the specification for these cells about compressing. I will ask the manufacturer though so we are not missing anything here.
@@OffGridGarageAustralia This was the TH-cam video 30KWh On-grid Back up Battery Pack With Growatt Inverter Setup - SEPLOS PUSUNG Energy Storage System
@@jimmysquires5093 in that video they do not compress the cells, they only hold them firmly with custom-made plastic holders. I am more in favor of holding the cells firmly together instead of compressing them, for me they are different things Something like this, but for our 272-280ah cells would be ok: jiasaw.en.alibaba.com/product/1600142841614-819391428/Four_Seasons_100ah_Brakectabs_Pc_Jiasaw_Unisex_Battery_Holder.html?spm=a2700.shop_pl.41413.35.42d15a02gYhrcV P.S. I also bought them from Sheila
For the bin box I'm thinking plastic does not provide much protection. In the least create yourself a metal dolly for underneath to roll it with lockable feet. Long term I'm think you should build yourself a heavy duty metal rack with multiple shelves and bundle the cells in groups of 4 either with metal straps or their own boxes. That way your can work with and transport it. P.S. I'm slowly going through all your videos from oldest to newest... so you have obviously changed things by now.
The primary purpose of compression isn’t to prevent individual battery insulation breakdown due to rubbing (very low probability event if it were to occur at all). Instead it is to minimize delamination of the internal battery structures that will then decrease the efficiency of the battery over time. This is something that is of primary concern in high drain (e.g. high current) applications. If you don’t pull a lot of current from your batteries (use heaters or induction cook tops, etc) or don’t expose them to extreme environmental conditions then it probably isn’t a big deal to compress or not compress.
I totally agree with your comment, Tony. In solar applications it's not worth the extra effort in my opinion. They gained the extra cycles under certain test conditions which we never meet with solar, 0.5C charging and 1C discharging. I achieved 0.2C charging once in 7 months for a peak moment and never went over 0.3C while discharging as a peak. If people achieve these numbers regularly it's either by design for their specific application or the system is totally wrong designed.
I don't think heating from charge/discharge will ever be a problem in a static environment like a home or a caravan. A a 5KVA inverter, for example will pull around 100A @ 45V - 56V, so cell heating due to resistive losses won't be much of a concern. Several comments have come up with what I think are damn good reasons for compressing the cells and it seems to me they all make a lot of sense. Remember the metal rod or bar that is used to compress the cells also have a coefficient of thermal expansion, so if that material is matched well to the cells, then expansion compression of the cells due to temperature should be matched with the expansion/contraction of the metal rods. Question in my mind is not whether you compress the cells, but whether the rod/bar used for compression is made of aluminium, steel stainless, steel or perhaps even some woven fibre?
@@OffGridGarageAustralia No, nor mine. Yet I see plenty of reasons that **seem** reasonable and will compress, though my application is mobile, so I have a mechanical reason that demands holding the cells rigidly. I'll keep you in the loop. This is great isn't it? So many people contributing to each other through experience, opinion, facts and some even daydreams...I mean, in my case, watching you go through the process of deciding and ordering, testing and considering has prompted me and several others to take the plunge too. Really thank you, thank you and THANK YOU.
They will expand over 5mm with time as the cells age. Another main reason to compress is to keep the terminals from being damaged due to the expansion as they age. I have cells that have expanded around 8 percent
It's not the heat that creates pressure and deforms the cell, it is high charge state. The reason you compress the cells is to get a longer lifetime and slower aging and capacity loss. You can see both on the battery spec sheet. You want to compress, and you want to do it with threaded rods. There is no situation where you should not compress.
They are in the resources section of the diy power wall forum. The spec is 12 psi or 600 pounds (300kg i think it says). Ideally between 6-17 psi according to their engineers.
Can batteries with different specs (ratings) be used to build a battery bank? For example, if I initially get 4 batteries of 280Ah, can I add (after I can afford another set) 4 more batteries that have a higher Ah rating? Does the Voltage rating have to be the same?
@Raj Mandavilli Andy has a couple of videos about building a new battery pack for his solar gate, and how to match the cells in each pack (series + parallel) The same would apply to your plan. Check them out.
Do not use the 6m bolts they supplied. Go to eBay and they sell 6m stainless steel 6m studs with a beveled end that goes into the threads and a hex allhin key on the other end. the Beveled end sits in the bottom of the hole perfectly and if you cut all thread it will not sit in the battery as nice as these pre made studs. Crank them down gently with an Allhin wrench and leave them. I use 6m thumb bolts. I ordered 16 mm, 20 mm, and 24 mm and I ended up using the 20mm length
Yes, that might be the case. I have to wait until it's here and see how hot it gets. If I put it in the top of the box I will add a fan for air circulation.
Great video! Subscribed! I'm thinking of getting 32 of those 3.2V 280ah which you ordered and recommended. So I want to 16 in series and parrellel 2 of this 16 series, and connect them to my off grid Growatt SPF 5000 es. What BMS should I get? Thanks!
I like the sound of what you are doing….please let me know how you get on as I’m thinking about doing the same. How long would your batteries last running an average home? Thanks.
@@OffGridGarageAustralia I was looking at a tool box like champion tools. Expensive tho. I like your price better. Thrn if a cell goes wild would it be safer in a metal enclosure? All questions I don't have answers to.
@@JerryScroggin lifepo4 chemistry is very save does not burn if anything goes wrang each cell hase a overpressure valve that releases litium pressure but no flames !
@@tronor5 I've got 3 7s 14p battery banks. All on pcb .. the 18650 cells I have always been warned about. That box size you are putting together is very appealing.
@@OffGridGarageAustralia Well... maybe not. They are grey market cells that probably didn't pass every checkbox at the oem, and are sold at lower prices through resellers (for now). There are various opinions on this topic, but it could be that these are the cells 'left over' after not being able to match them in a bank for EV's. In this configuration, you want cells that are capacity/IR matched over the entire charge/discharge curve. EVE supply is running out by the way (they stopped putting these cells through third parties), and is mostly replaced by Lishen cells now (which may or may not be better, the verdict is still out).
Specs go to 131F, so all good. I doubt the battery will ever get that got in a stationary setup. If so you may have done something wrong and the capacity is to low for your load.
@@OffGridGarageAustralia At higher temperatures they wear out quicker. Li-ion batteries are often spect to operate 0 to 60°C Would suggest to keep them in conditioned space if ambient temperature gets under 5°C or over 25°C
The datasheet for the cells shows compressed vs uncompressed performance and has in writing the compression amount to use. Cell compression results in longer life but a faster degradation over the first 1000 cycles according to the datasheet and is not required. Compression will result in better overcharge tolerance if that should occur, and that information is NOT in the datasheet.
Compression is a specific word. Does it show up in the documents or is “fixtures” used? What I have been seeing is a fixture in videos. Fixtures and jigs are a topic/jargon in mechanical design. For example, a fixture that does not yield to a force of 300kg. That is different from a compression perspective.
I thought the case was positive? This is the only the second i have heard anything in reference to the polarity of the case , once it was positive, then now negative, easy to tell with a volt meter, I would atleast put some construction paper between the cells, or toolbox liner, a kinda rubbery plastic, even in a stationary application, something could hit the box, pushing the cells together, causing a possible short, all that current would likely destroy the casing, if shorted, I'd like to eventually get a few of these, for my 12v and 24v banks, awesome!!!
I read it now several times and there is nothing mentioned about swelling, compressing or similar action you need to take. Not even if discharged with 1C.
The case is not connected to any terminal. That would be way to dangerous. There is some path through the electrolyte that fooled my multimeter to show 0 ohms but it is not able to provide any real current. Try to connect a load between the case and a terminal and measure the current.
We now have three different views on this, positive, negative, not connected at all. I have not tested it myself and probably don't want to scratch the isolation just to find out... 😉
My Winston cells for the battery I built in my caravan, (400Ah x 12v) have flexible copper bus connections, with a kind of inverted U shape, much better IMHO to allow for any expansion and contraction. Just my opinion: I don’t like the idea of rigid connections. Cheers Andy
If your not draining at high current then you don’t need to compress. There won’t be much expansion if any if you keep the C count down. and it’s SERIES not serious haha
Enjoying your videos and following you along trying to set up my own system in Canada, ordered 16 cells 3.2v 272amp from another dealer as your link was sold out, if you leave a expansion joint between the cells will you still have full contact on the battery terminal or does it matter William
I don't think that thermal expansion is the reason you compress them, the expansion due to charge/discharge is the issue. en.wikipedia.org/wiki/Lithium_iron_phosphate_battery
Reading a lot of comments here about compressing the cells, when I get my cells (just a small astronomical problem with freight to New Zealand to overcome), I will be compressing them to ~12psi, as that will prevent any possibility of delamination of the jelly-roll, or plate-stack over time which does seem to happen on just about every ‘dry’ construction cell. Other people mention using wood, laminated or other to either stand the battery pack on in the bottom of the box, or to even-out the compression loading of the end plates, I strongly warn against that as the treatment and othe resins in the wood will react with the aluminium casings over time, corroding the bottom ofthe can away, especially if the bottom of the cell doesn’t have a tape or other covering (not sure on these particular ones) - I would as a minimum cover any exposed aluminium casing with capton or other nylon based tape if standing on wood, and even thinking that the treatment vapours of any wood in an enclosed box could eventually corrode the aluminium terminals, though they are a lot thicker than the can so probably not as detrimental.
Hi Phil, Im in NZ as well. Very interested to see how you go about freighting to NZ. Shipping method and cost etc. I would like some cell but the shipping blows it out of the water!
Thanks Phil, how will you compress your cells and how do you measure 12psi, what tool do you use for that? I read in other forums, people use springs and experiment a lot with that but there is no clear solution or explanation of that process.
As a Long Islander (NY, USA), I have great memories of frogs ribbitting, but your fellows are baratone. BTW....You are not helping me with my obsession. (You are) I admit the problem. Step 1
Just to make this clear for everyone, this box with battery cells will not be a mobile solution. The box will be set up in my garage and won't be moved at all. It's a stationary installation.
I understand that it's not a mobile pack BUT why not build it on a heavy-duty "Moving Dolly" so that it's semi-movable? You will thank yourself later ;-)
Great to read all the comments, just ordered 48 cells, 100 amp Daly BMS, 100amp dc breakers to build 3 batteries, I will order ss set screws, thanks for the info guys. I plan on building a metal enclosure using 20 or 22 gauge mild steel and semi compress the cells using high density foam strips. My thinking is to use 3, 1 inch strips on each end cell to semi compress and still leave space for cooling .
Also ordered a Deye 8kw split phase inverter, the specs look very similar to the sol ark.
Wow, that's a big project. Thanks for sharing.
I really, REALLY enjoy your videos. I can't wait to watch the next one... Keep up with the great job you are doing!
Thanks heaps for your feedback ;)
I love the box. There is a little wasted space at the top but not bad at all for the price. It’ll make a great, portable unit.
It will not be portable at all. with 80kg it's far too heavy, the bottom would fall through when lifted. This is a stationary setup, not mobile. Once in place, it will not be moved again.
Thanks for the video. This is a good topic. I have 8 x 280 AH batteries built up into an 8S -24V 2x4 cell pack for a stationary off grid application for part of my home. As I recall, the data sheet for my cells said that the cycle life was better if the cells were compressed. I think the rating is 3,500 cycles to 80% capacity if compressed and only 2,500 cycles to 80% capacity if not compressed. I have also seen comments from other users saying that it is better to compress the pack, especially if they are used in a mobile application. I took a hybrid approach to building my pack. I put the batteries together using a 1 inch square piece of VHB tape in each corner of the batteries that faced each other, and then compressed the entire pack using a 10"H x 18"L x 3/4"T piece of plywood on each end of the pack, compressed and held together by four threaded 1/4" rods about 14" in length. This gives you the best of both worlds - a very slight gap between batteries with the whole pack secured and compressed to avoid shifting of the individual cells when the pack is moved. Cooling is not an issue in my application because I rarely go above 0.2 C charging or discharging the pack. By the way, I would not recommend compressing the pack with a metal bar as you were considering. That concentrates the expansion stresses on a small surface area of the battery case which could lead to problems down the road. The plywood endcaps distribute any expansion stress across the entire surface area of the battery, with the added benefit that plywood is not conductive. I'm keenly interested in how your project turns out.
Thank you for you reply and feedback. That is a great setup you have there. I wasn't going to use the metal brackets for compressing (although I have seen this online). A piece of plywood as large as the full side of the cell would evenly spread the load as you suggested. But I'm still not convinced I should compress at all. It does not say anything in the specs for my type of batteries.
@@OffGridGarageAustralia check out a top view photo of my battery pack at the link below showing the way I compressed my batteries.. I went back and checked the spec sheet and other comments on Will Prowse's DIY Solar forum, and the general consensus of many is that compressing the battery pack extends the cycle life of the batteries.
diysolarforum.com/threads/xuba-electronics-deal-280ah-lifepo4-cells-purchase-review.3850/page-61#post-96433
Nearly 200 lbs in that tub. Don’t know it’s weight rating, but I’d seriously consider putting some plywood in the bottom to keep it from falling through even when stationary.
I’m building three 24v batteries with these cells (24 cells) and 100 lbs each is tough to handle (probably put my totes on wheels).
Love your enthusiasm, keep the videos coming!
Thanks for the feedback!
I thought about some plywood as the bottom but this will be a stationary setup, so once the box is in its place, it will not move again.
@@OffGridGarageAustralia I would think about some castors - you say the box won't be moved but, believe me, sooner or later it will
I have read some feed backs
I think It will be a good idea to keep space + adding a plywood in the bottom + adding 4 wheels also.
I know that it is stationary but maybe in future you decide to make some new arrangements or changings in your place, so it will be very helpful.
@Tech Boy, I agree with everything except the wood: something inert like plastic or rubber would be better. I would avoid wood unless it was charred (and I couldn't find some suitable plastics).
Hey Andy, remember me from the PHEV days? I just got my M3LR. I rigged my garage up as a solar garage nearly three years ago and it’s still giving good service including charging my EV in the summer (we also have eGolf).
It’s great what you are doing with this channel & it’s giving me some great ideas for upgrading my garage (I only have 2.2kwh of battery capacity). Really enjoying this channel 👍
Of course, I remember you, Harry! Welcome back and great to have you here on the channel again. A lot of PHEV owners have upgraded to a pure EV in the last year. Hope that wasn't all my 'fault' 😁
@@OffGridGarageAustralia yep, it’s all your fault. Keep up the good work, I haven’t stopped grinning since I got it & keep looking for excuses to go for a drive. Such an awesome machine.
this is exactly what I figured, that's why I wouldn't use bus bars, use thick cables instead, they allow for movement. especially important if installed in a car
Great video, I am enjoying watching your design and implementation process.
Your frogs seem to enjoy being in the video.
They are! 😁 Especially when it finally rains again after months of drought.
One thought on your concept of leaving space allows for air flow. If there isn't air flowing in sufficient quantity, air is actually an amazing thermal insulator, so you are actually better off coupling the cells thermally in order to dissipate heat. Others have mentioned but the expansion is a result of high voltage during charging so could be a non issue depending on how you are going to handle charging but in general compression is beneficial but I'm not planning on doing it.
I'll keep them at 80%/85% SOC max so this should not be an issue. Also I have charged some of the cells to 3.65V a few times to do capacity measurements and never noticed any expanding (yes, I looked for it).
I really enjoy your videos. You have some great ideas and your viewers have some excellent comments.
I appreciate that, thanks for your feedback.
I like your thoughts of why you should keep space between them. My only concern is how you hold them in that exact configuration. Any time you move them at all it will put pressure on the terminals since they're not held rigidly against each other. Maybe you could put a square of double sided adhesive foam at each corner to hold them in position but still leave a gap between.
This is a stationary setup, once the box is in its final destination in the garage and filled with these cells, it will not move any more. I should have made this clearer, ey?
A nice idea for a 8s config case is a car trailer box. This boxes are watertight, come in the perfect shape and they are cheap.
Just a thought, maybe if you use a small square piece of double sided tape on each corner then you still have the air flow while making sure you have a consistent gap between each cell. Then get the terminals to be in the middle of the busbar slot, then you can always change the gap to smaller or bigger. At the lowest point of the box maybe make one or 2 drain holes just in case some liquid gets in so it can drain.
Im waiting for my shipment of the same cells i ordered 4 but seems like they provided extra cells at no other cost. Im turning my jeep xj into a a overland camper with a ton of battery capacity with the 280 ah cells :D
Hi
You never want to compress the cells!
You can brace/ strap the cells and this is to prevent them expanding due to any over/ undercharged situations. Mainly overcharge I believe.
I have been running my pack without any bracing for some time.e now without issue but I have never overcharged.
Which bms will you use?
Thanks for your feedback on this topic.
I have ordered a 200A BMS from AliExpress with BT and 600A peak current. It was cheaper than the Daly ones so I thought I'll give it a go and see how it performs. It's on its way...
The manufacturer's datasheet states otherwise thought.
Having the gap between the batteries is better not only for expansion and contraction heat dissipation the batteries will cool faster and not get as hot when charging and discharging you are correct by doing so
These batteries don't get hot unless you do very high C rates (not common in solar applications or battery banks like this). If you read the datasheet, the manufacturer recommends clamping these together at a specific pressure.
There are some scientific research papers which speak about longer longevity when you keep them compressed. My 100Ah cells expanded 3-5 mm each during there lifetime till now. Your cells are very big. The "Jelly-roll" inside that can has a lot of windings. So even if it just swells a tiny bit per winding, it will eventually add up a bit :) But its your choice...
I was looking for some advice on this but cannot seem to find any. Some people are saying its bad if you don't, some saying it is bad if you do so.
@@OffGridGarageAustralia remember the aluminum case can be destroyed for the stress.
For this reason you need to compress them
A really good source of information is the endless sphere forum. There has been a discussion about compression there. It is good, but has to be the right amount.
compression is mainly used for pouch cells that are usually not Lithium Iron Phosphate chemistry.
Thank you. I have ready this online too. These prismatic cells are not pouch cells though so I don't really see the advantage of doing this. The manufacturer does not advise of any compression either...
@@OffGridGarageAustralia I think that is the definitive answer, ie follow what the manufacturer suggests as you then have a come back at a later stage.
Depends how many watts u want to pull out of the battery how hot they will get while discharge my advice is pressing them together because with time they puff upand don't contact back !
This is a very interesting topic Tronor. I want to use my 48V/272AH pack in a mobile off-road environment - compressing them should help with vibrations and also with the expansion/contraction due to temperature, charge/discharge and aging of cells. Unless one is using them for >1C discharge/charge (I won't - BMS is limited to 200A discharge, 100A charge), then heating from charge/discharge won't be a problem.
@@MiniLuv-1984 ur totally right if u don't stress the cells u will never overheat them and pressing them thogeter prevents ugly puffed cells i mean they puff up after some time and u can put some thin separator 0.5-1 mm plastics sheet's in between every cell! I u have concerns fore a short on cell casing recommended when mounted in an rv or car !
@@tronor5 The idea of using 0.5-1mm plastic sheet is perfect for mobile situations - thanks for pointing that out. Steel or thicker aluminium end plates too. Thanks. My thoughts for mobile use is to pack them as either 2 x 8 cells or 4 x 4 cells packages - compressed with plastic sheets in between and 6mm aluminium end pieces with steel threaded rod holding the two aluminium plates under compression. I might go for 4 cell package since an 8 cell package is a little too heavy to move around without risking an injury.
@@MiniLuv-1984 use non conductive material!!
Yes but put plastic in between steal
I'm new to lithium batteries I'm an fla man spacing between batteries is important because of heating l have my batts at least 1.5 inches apart
I followed your reasoning and agreed with not to compress. I then watched a new system video, SEPLOS PUSUNG Energy Storage System, and they said to compress to prevent "irreparable swelling damage". I wonder if the manufacturer would have a recommendation?
Sure! Aluminum case will be destroyed for the stress
There is not a single topic in the specification for these cells about compressing. I will ask the manufacturer though so we are not missing anything here.
@@OffGridGarageAustralia This was the TH-cam video
30KWh On-grid Back up Battery Pack With Growatt Inverter Setup - SEPLOS PUSUNG Energy Storage System
@@jimmysquires5093 in that video they do not compress the cells, they only hold them firmly with custom-made plastic holders.
I am more in favor of holding the cells firmly together instead of compressing them, for me they are different things
Something like this, but for our 272-280ah cells would be ok:
jiasaw.en.alibaba.com/product/1600142841614-819391428/Four_Seasons_100ah_Brakectabs_Pc_Jiasaw_Unisex_Battery_Holder.html?spm=a2700.shop_pl.41413.35.42d15a02gYhrcV
P.S. I also bought them from Sheila
For the bin box I'm thinking plastic does not provide much protection. In the least create yourself a metal dolly for underneath to roll it with lockable feet. Long term I'm think you should build yourself a heavy duty metal rack with multiple shelves and bundle the cells in groups of 4 either with metal straps or their own boxes. That way your can work with and transport it.
P.S. I'm slowly going through all your videos from oldest to newest... so you have obviously changed things by now.
The primary purpose of compression isn’t to prevent individual battery insulation breakdown due to rubbing (very low probability event if it were to occur at all). Instead it is to minimize delamination of the internal battery structures that will then decrease the efficiency of the battery over time. This is something that is of primary concern in high drain (e.g. high current) applications. If you don’t pull a lot of current from your batteries (use heaters or induction cook tops, etc) or don’t expose them to extreme environmental conditions then it probably isn’t a big deal to compress or not compress.
I totally agree with your comment, Tony. In solar applications it's not worth the extra effort in my opinion. They gained the extra cycles under certain test conditions which we never meet with solar, 0.5C charging and 1C discharging. I achieved 0.2C charging once in 7 months for a peak moment and never went over 0.3C while discharging as a peak. If people achieve these numbers regularly it's either by design for their specific application or the system is totally wrong designed.
I don't think heating from charge/discharge will ever be a problem in a static environment like a home or a caravan. A a 5KVA inverter, for example will pull around 100A @ 45V - 56V, so cell heating due to resistive losses won't be much of a concern. Several comments have come up with what I think are damn good reasons for compressing the cells and it seems to me they all make a lot of sense. Remember the metal rod or bar that is used to compress the cells also have a coefficient of thermal expansion, so if that material is matched well to the cells, then expansion compression of the cells due to temperature should be matched with the expansion/contraction of the metal rods. Question in my mind is not whether you compress the cells, but whether the rod/bar used for compression is made of aluminium, steel stainless, steel or perhaps even some woven fibre?
It does not say anything about compression in the specs of my type of cells. I'm 100% un-convinced.
@@OffGridGarageAustralia No, nor mine. Yet I see plenty of reasons that **seem** reasonable and will compress, though my application is mobile, so I have a mechanical reason that demands holding the cells rigidly. I'll keep you in the loop. This is great isn't it? So many people contributing to each other through experience, opinion, facts and some even daydreams...I mean, in my case, watching you go through the process of deciding and ordering, testing and considering has prompted me and several others to take the plunge too. Really thank you, thank you and THANK YOU.
They will expand over 5mm with time as the cells age. Another main reason to compress is to keep the terminals from being damaged due to the expansion as they age. I have cells that have expanded around 8 percent
It's not the heat that creates pressure and deforms the cell, it is high charge state.
The reason you compress the cells is to get a longer lifetime and slower aging and capacity loss.
You can see both on the battery spec sheet.
You want to compress, and you want to do it with threaded rods.
There is no situation where you should not compress.
I'm not planning to charge the batteries to a high SOC on a regular base. I have read the specs and cannot find anything about compression.
Can you publish the compression specifications for this particular battery type, we all love to see them. Thanks
They are in the resources section of the diy power wall forum. The spec is 12 psi or 600 pounds (300kg i think it says). Ideally between 6-17 psi according to their engineers.
Can batteries with different specs (ratings) be used to build a battery bank? For example, if I initially get 4 batteries of 280Ah, can I add (after I can afford another set) 4 more batteries that have a higher Ah rating? Does the Voltage rating have to be the same?
@Raj Mandavilli Andy has a couple of videos about building a new battery pack for his solar gate, and how to match the cells in each pack (series + parallel) The same would apply to your plan. Check them out.
Waiting on mine to also get here has been about 4 weeks
Do not use the 6m bolts they supplied. Go to eBay and they sell 6m stainless steel 6m studs with a beveled end that goes into the threads and a hex allhin key on the other end. the Beveled end sits in the bottom of the hole perfectly and if you cut all thread it will not sit in the battery as nice as these pre made studs. Crank them down gently with an Allhin wrench and leave them. I use 6m thumb bolts. I ordered 16 mm, 20 mm, and 24 mm and I ended up using the 20mm length
Could I trouble you for a link for these? I seem to keep coming up with everything but m6 stainless studs when I search ebay.
@@MiniLuv-1984 they are really called set screws. Grainger sells them #31KA52.
Well, you usually use the screws only once and once this is all in place it stay that way for a long time. Hopefully!
@DIY Projects when you order new batteries from other suppliers now, they supply the stainless steel gub screws allen socket set screws in 6m
www.ebay.com/itm/M4-M5-M6-M8-Stainless-Steel-Grub-Screws-Allen-Socket-Set-Screws-Cup-Point-DIN916/173493711598?ssPageName=STRK%3AMEBIDX%3AIT&var=472186224653&_trksid=p2057872.m2749.l2649
You should get a couple of 3kw space heater/air conditioners to use as a load when testing capacity.
I've got a Tesla and will use this as a load ;)
@@OffGridGarageAustralia do you have a 7.2kw EV charging station?
Regarding cooling inside the box, I would expect the BMS to generate much more heat than the cells themselves.
Yes, that might be the case. I have to wait until it's here and see how hot it gets. If I put it in the top of the box I will add a fan for air circulation.
Great video! Subscribed! I'm thinking of getting 32 of those 3.2V 280ah which you ordered and recommended. So I want to 16 in series and parrellel 2 of this 16 series, and connect them to my off grid Growatt SPF 5000 es. What BMS should I get? Thanks!
I like the sound of what you are doing….please let me know how you get on as I’m thinking about doing the same.
How long would your batteries last running an average home? Thanks.
Would it be useful to surround the batteries in glycol in this configuration?
You cannot put them in contact with any liquid or even submerge them.
From what I have learned it is best to compress,cells swell while charging and could tear one of the terminals apart.i could be wrong
14k is amazing! That plastic worries me. Will switches and battery monitors and battery posts stay solid in there when you move it?
It's a sturdy box and after installation, I won't move it anymore. It's a stationary setup?
@@OffGridGarageAustralia I was looking at a tool box like champion tools. Expensive tho. I like your price better. Thrn if a cell goes wild would it be safer in a metal enclosure? All questions I don't have answers to.
@@JerryScroggin lifepo4 chemistry is very save does not burn if anything goes wrang each cell hase a overpressure valve that releases litium pressure but no flames !
@@tronor5 I've got 3 7s 14p battery banks. All on pcb .. the 18650 cells I have always been warned about. That box size you are putting together is very appealing.
@@JerryScroggin depends on the safety mechanism u build into yore sistem u can look up videos on youtube lifepo4 safety !
Thanks for sharing my question is the battery grade A or B are they used or new?
They are new A Grade cells.
@@OffGridGarageAustralia thanks, I will wait for the capacity test result before I order any. god luck
@@OffGridGarageAustralia Well... maybe not. They are grey market cells that probably didn't pass every checkbox at the oem, and are sold at lower prices through resellers (for now). There are various opinions on this topic, but it could be that these are the cells 'left over' after not being able to match them in a bank for EV's. In this configuration, you want cells that are capacity/IR matched over the entire charge/discharge curve. EVE supply is running out by the way (they stopped putting these cells through third parties), and is mostly replaced by Lishen cells now (which may or may not be better, the verdict is still out).
Great video Thanks
Where did you buy these cell
What about the 120 temperature in Arizona
Specs go to 131F, so all good. I doubt the battery will ever get that got in a stationary setup. If so you may have done something wrong and the capacity is to low for your load.
@@OffGridGarageAustralia At higher temperatures they wear out quicker. Li-ion batteries are often spect to operate 0 to 60°C
Would suggest to keep them in conditioned space if ambient temperature gets under 5°C or over 25°C
it reaches higher temperatures here in India. lfp performs great
The datasheet for the cells shows compressed vs uncompressed performance and has in writing the compression amount to use. Cell compression results in longer life but a faster degradation over the first 1000 cycles according to the datasheet and is not required. Compression will result in better overcharge tolerance if that should occur, and that information is NOT in the datasheet.
What datasheet are you talking about?
Compression is a specific word. Does it show up in the documents or is “fixtures” used? What I have been seeing is a fixture in videos. Fixtures and jigs are a topic/jargon in mechanical design. For example, a fixture that does not yield to a force of 300kg. That is different from a compression perspective.
I thought the case was positive? This is the only the second i have heard anything in reference to the polarity of the case , once it was positive, then now negative, easy to tell with a volt meter, I would atleast put some construction paper between the cells, or toolbox liner, a kinda rubbery plastic, even in a stationary application, something could hit the box, pushing the cells together, causing a possible short, all that current would likely destroy the casing, if shorted, I'd like to eventually get a few of these, for my 12v and 24v banks,
awesome!!!
We tested this and the case voltage is only a leakage. I shorted it out to test that :) It's mentioned in a thread on diysolarforum.
They sell a good roll around cart on amazon for under $100
Read the spec sheet. It will talk about compression
No, it does not.
@@OffGridGarageAustralia ask to your reseller
Where specifically in the spec sheet does it say this?
I read it now several times and there is nothing mentioned about swelling, compressing or similar action you need to take. Not even if discharged with 1C.
And the box will be very heavy 10Lbs per battery I think x 15 = 150 LBS !
DO NOT COMPRESS THE CELLS!!! if one swells or fails, replace it
The case is not connected to any terminal. That would be way to dangerous. There is some path through the electrolyte that fooled my multimeter to show 0 ohms but it is not able to provide any real current. Try to connect a load between the case and a terminal and measure the current.
We now have three different views on this, positive, negative, not connected at all. I have not tested it myself and probably don't want to scratch the isolation just to find out... 😉
@@OffGridGarageAustralia I used the QR code cutout to test to case. Don't scratch your amazing batteries :o
Did you deal with Emily on batterys
I dealt with Sheila every time.
@@OffGridGarageAustralia thanks im Leary of getting taken dealing on Ali baba not to sure of how to order safely
@@willrobertson826 I've just done that and dealt with Sheila. I'll let you know how it goes when I get them (I expect February).
My Winston cells for the battery I built in my caravan, (400Ah x 12v) have flexible copper bus connections, with a kind of inverted U shape, much better IMHO to allow for any expansion and contraction. Just my opinion: I don’t like the idea of rigid connections.
Cheers Andy
Yes, I've seen these busbars and thought they make a lot of sense. Thanks Dave.
Have seen 2 variants. One with a braided couted copper strip in between. And another one with thin sheets copper in the middle.
If your not draining at high current then you don’t need to compress. There won’t be much expansion if any if you keep the C count down.
and it’s SERIES not serious haha
Seriously, why do you need to compress the cells? I think it's bad.
Enjoying your videos and following you along trying to set up my own system in Canada, ordered 16 cells 3.2v 272amp from another dealer as your link was sold out, if you leave a expansion joint between the cells will you still have full contact on the battery terminal or does it matter
William
I don't think that thermal expansion is the reason you compress them, the expansion due to charge/discharge is the issue.
en.wikipedia.org/wiki/Lithium_iron_phosphate_battery
Use active balancing my friend!
New cells, they don't need balancing at all. And, my friend, active balancing is not worth it...
@@OffGridGarageAustralia But you will top balance them once, wright?
@@kalinkaturbo5253 yes, I will.
Reading a lot of comments here about compressing the cells, when I get my cells (just a small astronomical problem with freight to New Zealand to overcome), I will be compressing them to ~12psi, as that will prevent any possibility of delamination of the jelly-roll, or plate-stack over time which does seem to happen on just about every ‘dry’ construction cell. Other people mention using wood, laminated or other to either stand the battery pack on in the bottom of the box, or to even-out the compression loading of the end plates, I strongly warn against that as the treatment and othe resins in the wood will react with the aluminium casings over time, corroding the bottom ofthe can away, especially if the bottom of the cell doesn’t have a tape or other covering (not sure on these particular ones) - I would as a minimum cover any exposed aluminium casing with capton or other nylon based tape if standing on wood, and even thinking that the treatment vapours of any wood in an enclosed box could eventually corrode the aluminium terminals, though they are a lot thicker than the can so probably not as detrimental.
Hi Phil, Im in NZ as well. Very interested to see how you go about freighting to NZ. Shipping method and cost etc. I would like some cell but the shipping blows it out of the water!
Thanks Phil, how will you compress your cells and how do you measure 12psi, what tool do you use for that? I read in other forums, people use springs and experiment a lot with that but there is no clear solution or explanation of that process.
As a Long Islander (NY, USA), I have great memories of frogs ribbitting, but your fellows are baratone.
BTW....You are not helping me with my obsession. (You are)
I admit the problem. Step 1
no no no no no no no no no no no no - don't use the terminals as a battery bracket
Not compress