The Role of Top Balancing - How to build a 48v Lifepo4 battery (Ep. 6)
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- เผยแพร่เมื่อ 26 มิ.ย. 2021
- Here we dodge a mistake and talk about the role of top balancing. Why it's important even with a matched set of "Grade A" cells, and talking about how it will be done.
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![Easy way to Top Balance DIY LiFePO4 battery [using EVE 304Ah LiFePO4 cells]](/img/n.gif)
Never had anyone explained it so clearly and simply. Thanks
Love your channel. Your videos are always thorough and very educational. Keep up the great work.
I must say you did a great job sharing this information, thank you!
I was wondering were are all my ladies tech videos boom thank you for stepping up 💪🏻 as a female that love to do everything my self this is a proud moment ❤️
This is just awesome.
I see no "experts" on YT explained this. I see them using the 10A charger and I did the same thing. Then I measured the voltage drop across the parallel connected batteries and I see the problem. Thank you for digging this out.
You're very welcome! Sometimes maybe it takes a new user to explain things in a useful way to other new users. :)
Great video! An option is to hook up your 16s pack and charge the pack until the BMS disconnects. That will get all of your cells mostly charged quickly without damaging any of them.
10amps at 58.4v is 584w/hr with 16s vs the same power supply pushing 36.5w/hr on 10amps for 16p.
That being said, I'm not in a hurry and am charging 16p at 36w at the moment! 😁
Thanks for giving such useful knowledge
nice video! Just installed my batrium bms on two european battery packs of 4kW each.
Will switch over to 16 eve k cells with better mounting screws but with the same capacity.
Don't forget to connect all the batteries parallel for some days in order to equalize.
Thanks for this.... best explained video
Love that kitty on the couch.
Haha, that's Mr. Tatters, he's a chonky floof. ^_^
CPRS power supply is a great use to power that Battery charger. Thanks for sharing (I will post on every video, gotta make the TH-cam algorithms work for you)
Great video ,thanks so much
Nice job on this! Just built a 2P 16S system. Top balanced and working great hooked up to a Sol Ark.
Lucky dog, what kind of cells and bms did you use? I just installed a grid tied 10.5 kw array with a SolArk 15k last winter. Turns out that without a battery bank my inverter generator is useless to provide some backup power if we lose power. So I want to add a couple of 48v lfp batteries which will allow me to use the generator. I am thinking of buying prismatic cells and fabricating some enclosures.
@@c2gutbuster hello from idaho. i used 32 3.65 v with a total of 544 amp hours. battery wired for 48 Volt. cost was about $3k. my BMS was from Overkill in FL. hope that helps!
First time I've seen you. Good explanation. And the sed command literally made me lol😆😆😆
^_^ - Welcome, and thanks for watching!
Thanks, going through this process now, got a 24v 20A power suply, 8s active balancer, 4S BMS, 8-16S BMS and a bunch of copper busbars 😮 lookout!!!
Sounds like my kind of fun!
@@TheDigitalMermaid yup, trial and terror 😜
Thanks DM. Great video. New Sub and bell ringer!
Welcome, and thank you!
had a tear in my eye when i saw the regex ... :)
A fellow human of fine taste and refinement, I see!
I’m working on a 400 amp @ 3.6 VDC power supply. Had to limit output because household current draw of 14 amps and buss bar limitations. I may be able to sell the kits for under $200 or may just lease them.
this was awesome. love how you cat is just chilling in the back lol
Thanks! That's Mr. Tatters
Hi there, yes top balancing is important, however, if you are lazy like many of us you can use an active balancer and have your cells balanced in a few days with a slow charging current. They make these for different configurations and a 16s active balancer would be the ticket for you. Unlike a balancer that is a resister this will take voltage from the highest cell and start moving current to lower cells, up to 5 amps.
Love the sed substitue command for your mistake.
^_^
Thanks, I wish I had seen your video prior to pulling all my hair out, I'm also waiting for a charger, hope it works.
How about adding active balancer
I like things in more even numbers.
This video is great! Can I go to sleep and let them charge overnight with this method? Is it safe if they hit full capacity (the power supply is at 0.1A) and stay connected to the power supply for 6-8 hrs, or do I need to disconnect the circuit ASAP? Thanks :) .
So long as your charger won't go over 3.65v, it should be safe to leave them overnight.
Totally accurate ^^
Nice vid…. I’m still unclear why you do only 4 at a time. If you do all 16 it is still the same time as 4x 4 cells right? Just more work
That video was a while ago, but if I remember right, I was worried about how long it would take to do all at once, so I did four to be able to get the video done sooner.
Smart lady
may i know what size of cable lugs did you use for the 7AWG wire of jk bms, thanks!
4awg
Hey what about a Switching Supercapacitor BMS.. does it Exist? (Instead of that common 200ma restistor type bms stuff..)
Yes, that's how the JK BMS that Andy has featured recently works. I have one on order to play with.
Hi, just wondering if you are aware of the difference between an active and a passive BMS, as you mentioned resistor bleeding that's passive ... haven't hear you discuss active.
Among the benefits of active is that active can handle a greater delta V between cells. Interestingly I'm yet to see this discussed much in LiFePO4 world but its "the norm" in lithium cobalt where 3 wire (not 2 wire) bms's are more common (presumably because we don't pretend they are drop in replacements for a FLA battery). You may already know this by now, but I thought I'd drop this point for your research.
Best Wishes
Thanks! I do know, and it's what made me switch to JK actually. However enough other things bothered me about JK that I decided to switch to focusing on other topics. Especially given how well Andy covers the topic on his channel.
@@TheDigitalMermaid err ... Andy?
@@chriseastwood6673 Off-Grid Garage
I'm pretty sure that you answered this question already. I just recently followed you example and built my first 48v battery from these cells. Until today I have built a bunch of 18650 batteries to make my own 1.6 kWh solar generators. My question is this once I top balance these cells to 3.2v do I then charge the battery to a 3.6v per cell batter. Ie 14.4 for 12v - 28.8v for a 24v - etc. sorry for the bother.
You top balance by charging all the cells to 3.65v with a constant voltage charger (a proper bench charger, or something like I did with the x8). Then they should all be at the same state of charge, and the BMS's internal balancing should keep them more or less balanced.
@@TheDigitalMermaid Thank you so much. I had thought I heard you say that in this video. Waiting on buss bars to turn these 2 12v into the 24v needed. Thanks again...
Robert
ALL WAYS read the manual several times, then read it again! especially when dealing with expensive stuff!
is it true that kind of vattery will expect 8 years of life span?
That depends on how you use it. At 0.2C (I think) charge/discharge, it should cycle 6000 times before it drops to 80% of rated capacity. If you do a full charge/discharge every day, that's 16 years! I suspect other things will kill them before that much time passes. The harder you charge/discharge them, and the more frequent you cycle them, the shorter they'll live.
Still catching up on channel. While waiting for iChargerX8, consider connecting everything in parallel (no charger). As long as SOC is near the same, all the cells will balance. You may do this in next video. Thanks for sharing.
They won't auto ballancing in parrallel and she explained why not.
You clearly have never worked with LiFePO4 cells in series. If you did you would know if you balance them at 3.2v and connect them in series they will be way out of balance at the top where the BMS is trying to balance.
Si existe un método más rápido de alcanzar el equilibrio superior y consiste en cargar con el balanceo en serie hasta que corte por arriba y entonces, desmontar el balanceo y ponerlo en paralelo con una fuente de alimentacion ya que la mayor parte del trabajo habrá costado menos tiempo
Así lo he estado haciendo últimamente. Me di cuenta de que lo hice lentamente usando el cargador pequeño desde el principio la primera vez.
My recommendation is to go and watch the Off-Grid Garage on TH-cam. Andy has tested every scenario you could ever think of for these batteries.
Can anyone explain to me what the reason for the differences in voltage for a pack? Why would you want 12v, 24v, or 48v? Will the 48v run 120v appliances better?
I am electrically challenged, but I am trying to do the full time RV life, while saving my pennies to get some land for off grid living. So I am going to build a 12v solar system for my camper, but want to figure out what I need to do later for when I try to build a big system to run a cabin/small farm off grid.
The simplest way to think of it is like this; Your load needs so many watts to run. Say, 1000w (like a microwave). To get a 1000w, you need some combination of volts and amps. If you run 12v, then you need 83A (1000w / 12v = 83.3A). If you run at 48v, you need 21A (1000w / 48v = 20.8A). So the higher the voltage, the lower the amperage.
Knowing this, next we need to think about wires. The size of wire you need depends on how many amps will go through it. So a wire that can handle 80A will be (very roughly) 4x the size of a wire that needs to handle 20A. Heavy wire is hard to work with and expensive, so higher voltage means lower amps, which means cheaper and easier to work with wire.
So the question of "what works better for AC 120v" isn't really the right question, 12 or 48 are both fine. It's the wire benefit. Also, the lower the voltage, the greater the loss over longer wires. Higher voltages are better over longer distances, also helping you use smaller wires. That is to say, a wire that needs to handle 80A over a short distance can be smaller than a wire that needs to handle 80A over a longer distance.
Lastly, because 12v has been common in RVs, boats and cars for a long time, there are more devices sold that use 12v. I chose to go with 48v or the reasons above, but it does mean it is harder to find DC powered appliance that work with 48v.
@@TheDigitalMermaid can't you install a 12v relay in your 48v system, as a step down, to run your 12v applications, while keeping the benefits to wire size?
@@carllennen3520 Relays are used to switch large loads using a small signal current, they're not used to convert voltage. For that, you can use DC/DC converters, and yes I plan to have some of those to step down to 24 or 12 volts as needed. The trick is that they're added cost, and perhaps more of a concern, they are inefficient, 86~88% efficient for the Victron models I plan to use. So that means over 10% of the power going to the device is lost. So it's always best to have appliances that match the native voltage when you can. Now this said, there's an argument that the losses of 12v systems in the wires is greater than in 48v systems, so in practice the overall efficiency might be not that bad.
The point remains; Use the highest DC voltage you can, but make note that point-of-use DC-DC converters are losy.
@@TheDigitalMermaid I only mentioned the relay thing, because literally watched a Will Prouse video he made showing how to make a basic solar setup, right before I watched your video.
He made a 24v setup, and installed a 12v relay inline to the converter so he could run 12v systems. I cant remember what he actually did, so do not quote me on anything. Im still at the very beginning of learning this stuff.
I have 8 304ah EVE cells in my cart right now, and just scared to pull the trigger on them, until I get a firm grasp on the balancing, and set up first.
I am in a camper right now, and with all the crazy going on, I want to get off the ever more expensive power grid as fast as possible.
Quick question, if you have the time.
With 8 304ah cells, what can I power, and for how long? I have 12v lights, a 12v fridge, all the basic 12v stuff in a camper, but Im really wondering if it will run the A/C in the summer, and how long would it run it? Im worried that isnt enough batteries to keep everything running constantly.
@@carllennen3520 "How long can I run" is a very installation-specific question. The only way to get an accurate answer is to look at the power consumption of all the equipment you have. If you built a 4S2P 12v system, you'll have 608Ah of capacity, or 7782 watt hours. There are calculators that you can use to calculate voltage drop, and DC/DC converters and DC/AC inverters list their efficiencies. So for each load, take the draw, factor in the voltage losses and efficiency losses if converting/inverting, and you'll get the true load. Then you need to think about how often these things will be used. In short; it's very tricky to calculate.
Rougher, and easier, would be look at the consumption of devices (lights, fridge, etc). For each, think about how long you use it each day. So for a 1000w microwave that you use for 30 minutes a day total, you have 1000w / 0.5h == 500w. If your DC/AC inverter is 85% efficient, then 500wh * 1.15 == 575w/h. Round up to account for losses in the wiring and you can say, roughly, 600w a day for the microwave. Repeat this process for all your devices, and you'll get a rough idea of how long your batteries will last.
Note also that your batteries will lose capacity over time, so factor in how long you want to go between charges. So say you do your math and figure that you can run for 50 hours on a single charge. Knock that back and say, again very roughly, that you might be down to 80% over the life of the cells, dropping your run time to 40 hours over the life of the batteries. Is that enough?
These numbers are not real numbers, to be clear. They're meant to show you how to figure for yourself before you press the buy button. :)
If you parallel 4 cells and assuming they all have different state of charge, when one reaches 3.65v they all get cut off. It doesn't mean those 4 cells will be fully charged. You still have to check the resting voltage to be safe or charge individually.
If you connect cells in parallel, they'll balance themselves out, with power leaving high cells to go into low cells until all are at an equal SoC. If you connect in parallel, wait, then top balance you're fine.
@@TheDigitalMermaid I just got 16 cells of 120ah, they tested between 3.285-3.292v, I guess I'll have to parallel them overnight to equalize everything before charging. I think most people do not emphasize this point enough. Or maybe it's usually implied so they don't dwell on it since it's considered "obvious". But to me it's very important before top balancing.
@@KoiAquaponics If you have a 12v charger, to save time, set it up as a 12v pack, charge it until the BMS shuts it down (first cell hits 3.65v), then configure the cells in parallel to balance out. Then hit all the parallel cells with a constant voltage 3.65v until the parallel bank stops accepting power. Much faster way to top-balance than how I did it here.
@@TheDigitalMermaid that makes sense thanks, I got find a BMS and charger now. My 48v bank will be used for bike. Do you think it's a good idea to rebalance the cells every 6 months or is the BMS accurate enough once you balance the cells the first time?
@@KoiAquaponics I can't speak to your battery or your build. I'd probably just use it, and check if there's a need to balance if/when you notice less than expected capacity.
Great video, you explain everything well. However, with active balancing BMS (now BMS supports 1A 2A or 6A depending on the model) you actually don't need to top balance your grade A brand new LifePo4 cells. I made my battery back using 105 EVE cells and a 2A baance JK BMS everything workes great, cells have 0.020 or low voltage differance and sometimes it goes low as 0.003V. Here's a video of how I made my LifePo4 battery pack -th-cam.com/video/13itWthR9Co/w-d-xo.html
Thanks again for the cool video.
Why not just charge all 16 cells at 3.65 ? Why 4 cells at a time? I charge all 16 cells with solar first and maybe damaged a cell because one went to 4.1v because i got busy and left it unattended for a few minutes. all others to 3.4 ish now I'm balancing all 16cells at 3.65. I know some people use a 12v battery charger to rapidly charge groups of 4 but then charge all 16 to 3.65 just because it's quicker but if you have 1 cell at 5% and another at a 95% then you charge in a group of 4 that cell at 5% will be at 10% that's a large difference and your bms will take many months to balance it so charge in 4 groups then 16 and your all good
Can i order
I'm sorry, I don't understand. Order what?
Just buy ACTIVE balancer (not bleeding BMS balancer).
So many words to say so little. Why didn't you research properly BEFORE you started the project?
Why is TH-cam so full of idiot, self-taught mistake-makers -- ie, the blind leading the blind? The proper way to learn something is to humbly take the role of a student around a master and/or do full study of the theory before embarking on the practice. I would have thought that for $5,000 worth of LFP cells you'd look into it thoroughly. But nooooo.
You missed the entire point of this channel, I think.