280Ah and 135Ah batteries with different BMS in parallel. See what happens when discharging...
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- เผยแพร่เมื่อ 29 ธ.ค. 2022
- After the discharge test of the single #Seplos Mason 280 battery in the last video, I have connected both batteries together again as a unit. We now have the 280Ah battery and 150A BMS in parallel with the 135Ah and 100A BMS. As I explained in the video, this is not recommended by Seplos, but I wanted to know if it works or if there are any major issues. So, different capacity and different BMS in each of the boxes.
Of course, I have also connected and configured the communication between both battery banks and enabled RS485 comms back to the computer, so we can monitor everything while discharging.
It is really interesting to watch the batteries while discharging and we can learn a lot from this setup. I really think, this is working great. At least, when discharging....
In terms of the communication, I'm not sure what benefit we got out of that. Both battery banks reacted the exact same way as any other standalone BMS would do
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Hi Andy, i run 3 Batteries (24V) in parallel. 150Ah, 280Ah and 560Ah. The oldest is over 3 years old and they run 24/7 with no communication. Up until now I've never had any problems, they behave exactly like the ones you showed. Greetings from Germany.
Welche BMS nutz Du?
@@marcelprivat 2x Daly und 1x HiBMS, alle ohne Balancer (bzw. nur mit dem 30mA Onboard). Ich lade meine Zellen beim bau der Batterie immer mit einem Labornetzteil auf 3,65V. Selbst bei der ältesten 3 Jahre alten Batterie sind die noch immer 1A, kein drift und das obwohl die schon ~600 volle Zyklen hat.
Ya In the end it is better to have all cells same. The 150 a will lose cell first maybe then the others one at a time. But you have a poorer decision making then if you add new cell will result poorer reliability and useful ness. It is better to use same cells. So if you want bigger should be 150ah, 300 ah then 300ah, 300ah,. 150ah und so on and on.
@@x3n4t0r ich habe auch vor eine 100Ah an die vorhandene Bank aus 560Ah zu hängen. Ich kannte ja das erste Video wo Andy den krassen Versuch gemacht hat. Also ist das Problemlos möglich. Die 100Ah ist mein 1. Versuch gewesen vor 5Jahren. Seitdem steht sie rum. Achso ich habe alle durch JKBMS ersetzt.
Can you tell us the 3 battery brands and ages?
Also did you test or determine what your combined amp hours ?
I have 4 - 24v new batteries one set is 100ah and 200ah and want to connect them in series …..
Andy, I don't comment often but just wanted to say, you're a gem! A lot of what I'm learning from your channel is theoretical as I may never build as system that puts all of this in practice (some but not all), but it's just a pleasure to 'hang out' with you. Thanks for all the time and effort you put into your channel.
Lots of comments, but I didn't see much about the RS485. It is a Master-Slave communications. It does not allow Slave-Slave communications. Only the Master (the PC) can poll via address one slave at a time and retrieve one slaves data, then switch to a poll of the other address to retrieve its data. The only thing that the cable between batteries does is to connect in parallel all data communications lines, 2 for transmit from the computer, and 2 for receive by the computer. The address that the computer sends in the poll determines which slave will answer.
Thank you for the demo of different battery capacities in parallel. This matches my findings. I think that the only reason that manufacturers don't recommend this is they don't want people to by another companies batteries so they threaten to void the warranty if you combine different batteries. I have experimented with 6 totally different brands of battery and many different BMS. As long as the cell chemistry matches they are fine in parallel. Just don't tell the manufacturer or the sales people.
Good morning
I just read your comments on setting // different battery
so what you are saying is that there is no need to put a special module on each battery pack to make // between the 2 packs?
I have a pack of 9S 200 AH brand Winston LFP (almost new)
and another pack that I built from 9S to 1000AH in EVE brand LFP
I can assemble the 2 packs together + with + and - with - the amperage will add up?
I understood that before putting in // the 2 packs they must be charged at the same voltage and 3.65 volts per cell
what do you think?
no risk?
and regarding the wiring on my pure sine converter
if I put the 2 packs together in parallel, do I take the + from which pack?
and the - of the other pack? or 2 cables for each pole?
THANKS
laurent
ps: I was thinking of buying 2 modules and 2 special BMS from Dally to do the setup // I'm thinking!
Just got 8 cells delivered the other day, in the process of charging and capacity testing now, your video helps the time pass :)
Great test, and I reckon they did pretty well discharging proportionally. The comms between the batteries to the PC was present and you were able to see both packs, but do we know for sure that the BMS's were communicating with each other, this would be very difficult to determine. More testing needed....HAPPY NEW YEAR !!!
Thanks Andy! Interesting information, as we all learn along the journey!
This just shows how much marketing is pushed at mostly unknowing consumers. Good work Andy!
Another great video. I have enjoyed watching your videos for a couple of years.
Awesome, thank you!
Great experiment an d great video. Exactly what I’ve been looking for! Thank you, Andy!
Really interesting experiment! I love your videos!
Hi Andy! Thank you for another great video. With all your videos you made me a solar nerd too ;). Just wanted to wish you, your loved ones and the shed a Happy New Year! 🎉 Take care🤗
Perfect timing of this video I was doing a very similar test today myself, with a 50Ah and 75Ah battery in parallel. My results were very similar to yours.
Great, thanks for the information.
Wish you happy new year, from Romania, wery happy to find your channel
Another informative video.
Thank you Andy😊
My pleasure!
Really good experiment and informative video, Thank you
Hilarious every time have looked up a question I get this channel as first suggestion.. even when not on my account that has been subscribed. Great job on handling answers to iffy questions out there on Solar equipment. Thanks
Thanks for the well conducted test Andy. It turned out pretty much the same as I've observed paralleling smaller EV and eBike Battery packs. I also tested a 300watt hour, 120amp 13S Li-Ion pack with a 600wh 16S LifePo4 pack in parallel and the result was essentially the same. I did like how the Li-Ion pack improved hi-load response and the LifePo4 pack stabilized voltage drop, together the two different chemistries complemented each other very well. I was also able to charge them in Parallel to 54.6v using a Li-Ion changer with no issues, and still got about 98% capacity out of the LifePo4 pack.
I believe there's a simple mathematical relationship that captures this. If you overlay the charging curves of each of your packs, then each pack will receive current in inverse proportion to the slope of their charging curves at this charging voltage. Steepest curve gets the least current. Complicated because each chemistry also changes its curve based on charging rate.
In other words... Q: how many Ah does each of these packs need to increase their charging voltage by 0.0001V? A: The system voltage can't increase until every battery has received those Ah, and more/less Ah means more/less amps to keep them in balance.
Question for you - you'd expect cell types to sag their cell voltage differently if you suddenly cut charging. Does that give you voltage imbalances between the packs?
Hi Andy, thanks to your educative videos. I recently installed my second offgrid system with JK Bms.
My new 11Kw inverter (Tommatech) is new model and I can see all data and make setup changes remotely with my mobile phone 4G internet connection. Stay connected.
Wish you and your followers a happy new year.
Sounds interesting, do you have a link to ur new Tommatech 11kw? Is it a Hybrid or AIO? Cheers
great test!
Another peek into the window of how these batteries and BMS's work. I , like you, do not see what the communication did, if anything.
Thanks Andy for once again adding to the understanding of LifePo4 world.
Wow, this video is very interesting but a little above my pay grade as I have a humble 200 watt Renogy starter kit with a Redodo 100AH lifepo and want to get another one to have 200AH, but the batteries will be 7 months apart in age and worried about them working OK together. Love this channel and learning alot. Thanks for sharing your knowledge and experience.
Paralleling your batteries should be no problem. Just ensure, each has their own BMS.
Thanks Andy, Happy New Year to you and your family 🎉🎊
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At that point before you charge them I would balance all cells to see if that makes a difference in total capacity next test. I have 4 battery packs. I used to see a big difference between each BMS state of charge when I first setup my system. Now they are within 3% when I used to have 25%. I top balance at 3.3v to .004 as my setting is .005. I would think in another month my packs should be between 1% since all cells came in 1 shipment. Very interesting regardless. Another great video Andy thank you.
This is really interesting. Received wisdom is all batteries should be twins. Same make, capacity, age etc. This test appears to show that with lifepo4 this does not have to be the case. I guess all batteries should be in similar condition. But it does mean that if, when we setup our system, we didn't have enough capacity, we can add to it if required. Great video. Thanks.
Great test Andy, thx a lot.
Value from the communication would for me be that the "system" reports total view of the battery bank.
Happy new year !
Hey Andy, the main purpose of the comms cable to the Victron that I can see is to dynamically control the charge and discharge limits. I have had 4 of these BMS packs @ 100ah each for about 6 months. The other details such as temperature, highest and lowest cells and which sets are currently running. I did have a BMS cell cable that came loose and disconnected the entire supply which is of course not desirable for redundancy. Thanks, Matt.
That was very very informative 👏👏👏 please continue on defrent capacity batteries in parallel
Thank you Andy always the best
Best regards from Philippines 🇵🇭☕☕
Another Great vid! I always wondered the same with all the comms. Maybe its just seeing everything on a pc in one place. Shirt looks great on you!!💥🤘
Heya that is a nice test to see the differant batteries are working independently of each other so your using all the capacity from each battery pack
Hey Andy I got 8 200 ah plastic encased prismatic cells for 400.00 they go for 1,000 something for 4 of them ! These where in those KS2 corp road trek battery boxes with a weird bms setup but I'm running a vnszr/Daly 200 amp 4s 12 v BMS this setup is working awesome
More screen time yes but informative 👍, keep going Andy.
Agree have done the same on my Ebike tours. Weak point is always the bms.
Happy new year Andy 👍
Happy new year!
I guess the main advantage of a communication is the ease of checking the status. You don't have to connect to all banks separately but have a single POC.
Guten Rutsch!😁
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The only proposed to the comunicación between packs is to communicate to the inverter all of the packs states . If you conect the master pack to the inverter and both packs between them connected. If one of them have some alarm that means to stop the inverter this is what will happens. Is not really good method always. I have 2 seplos working and I just have both working w/o comunicación between them and just one to the inverter . Nice test I suppose that this is not a problem because the voltage of the battery make both to work together .Thanks Andy !
Thank you again Andy for this great video and the last of this Year!
We could see that the 135Ah battery is efficient!!! when discharging at end of charge with 60A!
The cells follow each other well! impressive!,
About the communication of BMS between them, it's not true! It's certain!! the connection cables between them is only used for monitoring, only.
I have been using this type of battery for several years, and I have noticed that the BMS do not communicate with each other?!
this is just for monitoring.
and to me this BMS communication story is just marketing.😆🤣
I wish you a happy new year Andy🎊🎉🎈, and thank you again for your quality videos.
Happy New Year everyone!✨🎉
Great test Andy, and you nailed it on the need for proper communication and simultaneous low voltage shutdown. There might also be some paralleling safety issues with the smaller battery as well due to the presence of the big battery. I would be a bit concerned over the worst case amperage on that smaller battery if the firmware doesn't do its job right when shutting everything down.
Simultaneous low voltage shutdown would negate any benefit of having larger capacity batteries in the bank. As soon as the any one of the batteries run out, all the other batteries which still have capacity would be shut down too = major loss of capacity. If all the cells in the larger battery were balanced, both batteries should share the load according to their capacity & discharge fairly evenly.
@@arthureschner9319 Remember that when batteries are connected in parallel, the voltage is the same for all of them. So when you hit the low-voltage shutdown it is because ALL of the batteries have reached that voltage.
Even if a battery, due to differing SOCs, runs out of gas earlier, its voltage will still be locked to and propped up by the other batteries. It simply won't contribute much in the way of current.
Where the problem lies is that depending on the BMS low-voltage shutdown... the BMS in each battery will trigger at different times. More or less around the same time, but probably differing from seconds to a minute or two verses the other batteries. This can cause assumed current sharing to devolve down to a single battery taking the full load of the system which we definitely never want to have happen.
In anycase, this points to the fact that nobody should EVER depend on the BMS in the batteries to handle either the low-voltage shutdown condition or the high-voltage shutdown (charge complete) condition. Whether they are synchronized or not.
The inverter should handle the low-voltage shutdown itself, by turning itself off, at least 0.10V higher than the BMS in the battery would otherwise trigger its low-voltage shutdown.
And similarly, the charge controllers in the system should handle the fully-charged condition by limiting the voltage to 3.55V/cell (enough so the BMS can balance the cells), then stay there and not go higher. Because you absolutely do not want to trigger the BMS's high-voltage shutdown condition (usually at 3.65V).
Of course, the charge controller doesn't know what the individual cell voltages are, but you still program it that way x N cells. So on a 24V battery, for example, you would program it to go no higher than 28.4V (3.55V/cell). If the cells are reasonably balanced, the BMS's high-voltage shutdown will not trigger. If they aren't, then it might, but at least it will happen while the current is trailing off and low.
Ultimately the BMS in the batteries will sort things out. The cells will get balanced, the differing SOCs of the multiple batteries placed in parallel will equalize. It might take three or four full charge/discharge cycles to do it, but it will do it. Which means, most of the time, you can safely connect batteries up in parallel as long as their voltages are the same, even if their SOCs are not. Just take some care and exercise them through a few cycles before really putting on the big loads and the system will be fine.
-Matt
Hello from cloudy Missouri USA
Hi Andy, I would replace the 3 batteries in the big pack which are not right, that gives a better equalisation of the pack and a better representation of the actual state. Gives ease of mind also. I wish you "ein guten rutsch ins neue jahr" which is in a half hour. I really enjoyed your footage!
Andy, I have such a setup running for more than 9 month now (280Ah parallel to 90Ah, Seplos BMS). The main benefit of the communication is that if you have a inverter which needs communcation to work properly (like my Sofar inverter), this is the only solution to get them working. On a Victron system the benefit is less. Only benefit is that you have a total pack SOC (which is average of both SOC's) and Seplos can ask using DVCC to lower the charge voltage while charging. During discharge this could be a thing also while using grid mod. Not during off grid indeed.
Sehr interessant. Danke
I think the communication is more usefiull for automation purposes like creating triggers and automates with Home Assistant for example.
It is also possible to send the voltage seen by the BMS to the inverter instead of the inverter probing the voltage on it's input. It is like a 4 wire voltage measurement of the battery pack.
Very good test, that´s what I wanted to know. Result: It´s working fine but we still don´t know what the BMS´s are talking about. I´m sure you are going to find it out.
Thanks. More testing under way...
Greet job
@Andy The purpose of connecting the BMSes is probably only the ability to show all parameters of the connected batteries to one screen in stead of switching between two or more BMSes, i think.
Comms is great for me as I use my battery’s for time of use energy shifting. The seplos comms allows my inverter to lower its charge rate based on cell voltage so it can charge up to a cell voltage and then settle down at a lower current when topping off and balancing.
Could almost think you like the Seplos product Andy!
The Voltage is the Kommunikation Andy , see You next Year
HI Andy. Thanks for great video!
As I have similar situation with Seplos BMS DIY 280Ah battery by EEL (95% similar to Mason) with Amy supplied batteries and 105 Ah battery with JK BMS
I like to share my little findings during few days. I connected them in parralel this week and see similar load sharing as you had.
The difference is that they not communicating together, but both can talk with Cerbo GX and I also have SmartShunt measuring both batteries. I will do more tests after NY.
EEL DIY was put in service this week and we have winter in Lithuania now. No sun. Just snow :)
My feesback to your test
Communication between batteries is to path trough data to inverter via Canbus.
What I been thinking based on your test is that master battery shall be last shuting down. If not all communication to cerbo or inverter will be lost. Maybe you can try this next time including canbus communication to see 3 parts bahavior
My expierience with seplos bms+ smartshunt was that despite I been using SmartShunt as battery meter in VRM settings loosing Seplos battery or disconnecting canbus from it was raising low voltage alarm on Multiplus. Need to test it again to see if Inverter is switching to pathtrough mode to grid or stays on inverter.
Lets share our findings mext year and big thanks for your job! Danke und auf wiedersehen!
Mindaugas
Very interesting comment, thanks, I have also bought a EEL DIY case, I hope it is a good choice (not receive it yet).
Can you tell me on which store does Amy sell batteries?
Thanks for sharing your experience.
If you have the smart shunt AND the smart BMSes, that doubles up and will most likely confuse your system. You should deactivate the Smart Shunt and use the BMS function only. Do some testing on how this goes...
I'm running two 280ah and one 202ah in paralell. No problem's at all. Daly, JK, and jD doing it's job.
The small battery has better balanced cells, so it discharged to a bit lower voltage (since the big battery shut down when cell #6 bottomed out.) So when you turned the charger on, power went from the big battery (cell #6 rebounded a bit) to the small battery until it shut down again. It should be ok once the small battery comes up to the voltage of the big battery.
I have parallel 2x 100Ah powerwall and 2x 280Ah DIY eve lf280k. Very stable no issues.
Great test Andy,
It would be interesting to see them both being charge by the multiplus at the same time and the multiplus under the BMS control. I have seen the bms taken actions during the charge if cell voltage go to high and change the charging current. But I have only one pack right now
It would would really interesting to see what happened with two packs especially with you having some cells that is a little weak. Could be seen as an age thing that could happen in our systems with the cells we have.
This will probably never happen as my MP is off-grid and will most likely never be connected to the grid...
But I have something similar in mind.
@@OffGridGarageAustralia you have multiple victron inverter, you could totaly setup one inverter to act as grid and the other as hybrid inverter to test this and see how it can regulate discharging with multiple BMS.
@@Pey5531 that's what I have setup since we finished the PowerWall and Battery Shelf. That's just not what is connected to the Seplos batteries.
@@OffGridGarageAustralia Sounds interesting, control functions are something we don't have that much of in DIY system. That has been the domain for commercially built systems before.
Been lurking for a while now....
Putting a victron shunt on to compare with what seplos was saying would have been interesting.
I have 4 x 280 Ah seplos units arriving in Feb (I hope) and my dilemma is to go with what seplos is saying to victron (cheaper), or (more cost) use victron shunt like in your battery 2.
More seplos tests please!
Отличный тест, очень интересно рассказываете, смотрю как Санта Барбору. Привет из Москвы!
4:25 3V is indeed a huge voltage delta.
I have 2 batteries with JK BMSes with SCC charging ~35A to each of them. When I disconnect Battery A (via a Circuit Breaker) and let Battery B charge with ~70A for a few minutes. When I reconnected Battery A back, I noticed a huge current flow out of Battery B (Negative 100A+) (as reported on JK App).
The voltage delta between these two should be relatively same before and after the reconnection and I witness.
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Great test & conclusion Andy, I have often wondered if the comms bring anything more to the party than a link to ur computer for individual visuals of each battery BMS situation.
I have 3 x Seplos “Suntorque” 5.2kw Batteries, they are all in parallel & no communications & I have similar results, they all charge & discharge at similar rates with a few exceptions. I use an AIO to charge the batteries by day at 40Amps takes about 5 hrs & then run several fridges & tv’s etc off them from 3pm-9am next day.
They all charge & discharge at similar rates without comms.
First comment?! Andy, wish you a Happy New Year with a lot of Amps outside!
I was watching one of Will Prowse‘s videos on multi battery banks being hooked up to one inverter/charger.
All I know is you need to have the same chemistry of battery, the same charge controller settings for both battery banks.
Otherwise, you could destroy your batteries!
The advantage with comms to the inverter is - if for some reason the software in the BMS that switches off the mosfets when an undervoltage at cell level happens were to fail then the inverter would shut down output power independently and preserve the battery. More importantly in an overvoltage situation if the BMS fails then the inverter can shutdown charging. While I think this is highly unlikely, it can't hurt to have a backup. Also using Venus OS you can consolidate all your information in one place and you're not restricted to BT as you are with many BMS's.
The purpose of link between 2 packs is for monitoring on PC and for victron inverter, in my opinion.
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Watch this space...
But how does this work if linked to victron GX? I’m running 1pack old leaf cells with jk bms which communicate to GX system on a raspi.
If you have DVCC enabled, then the master pack communicates to the system what can be the maximum charge and discharge current from your batterys thats the main benefit i see.
if you check your battery parameters in venus os, you will see CCL and DCL values ( Charge Current Limit ) and ( Discharge Current Limit )
if one pack can do 100A, 2 pack connected together with communication will tell the victron system that it can do 200A in total, if one pack shuts down it will limit the charge and discharge current to 1 pack value.
You should do a test with the load connected to the smaller battery first then paralleled to the large one. If you have time do it with communications and without. See if there's any point to communications between the 2 batteries other than reading the data or changing parameters on bms.
Suck it up princess! Love it Andy...
I wondered about if they did that myself. I found out with my setup that they do a good job of sharing small and large loads. To even out. Makes me think its a Voltage thing.
hi Andy, i run a multiplus II + cerbo with 3 pylontech batteries with communication and it auto sets the charge/discharge current depending on SOC and number / capacity of batteries. it does need DVCC to be enabled and I am grid connected fwiw
I have successfully paralleled a 280ah pack and a 176ah pack for the last several months and not had any issues. Both deliver nearly their full capacity over a full charge/discharge cycle. SOCs of each battery and charge/discharge current ratios vary throughout the cycle, but they move to similar SOCs at the top and bottom ends of a cycle.
Was this with Seplos BMS as well?
@@OffGridGarageAustralia no it was two DIY banks with no communication between them. The smaller of the banks is normally in my camper but since it is winter here in Michigan, I thought I would run a parallel test with the bank I have at home. Both are LiFePo4 packs. I’ve come to the conclusion that you don’t really need communication for a small solar setup. I use Victron equipment and it just works using info from my battery monitor
same here, i have 4x 100amp and 3x200amp in parallel ,same happen to me, some different soc on ordinary use but flatting on top charging, i never go under 30% soc before i charge again.had this going on 3 years now and noting wrong.200amp charge and discharge little bit more/faster but flattening out all by it self 👍
Yeah I have a 100ah connected to a 200ah. Works great. Why wouldn’t it using smaller amp draws and appropriate sized cables. Batteries equalize themselves just fine. I’ll definitely Keep them above 20% or use the generator to bring them back up before then. Extreme amp draws are the only cases I would be wary (like over 50 amps - which is not a typical RV use).
Hi Andy
These seplos batteries are "industrial" batteries, probably intended to be for standby backup power. If these batteries are at near full state of charge for most of their life the balancer would be adequate to balance.
Since your use case is different with potential lots of cycles you're right that these balancers are inadequate.
It would be extremely nice if there was a programmable relay in these bmses so a external active balancer could be connected.
Regarding the communication
Rs485 again heavy use in industry and there would be a custom control system monitoring the state of the packs, for you..... it's useless
I do remember the CAN video where the CAN showed a total battery capacity as one battery for multiple packs, that would be useful for you because its regarded as one battery and shows as one battery in software, the Victron software. I do believe that even in CAN mode the BMS would act independent and shutdown the same as they do now.
What i believe how the CAN mode works is that you select one battery to act as master and tell that one (by dip switch) how many batteries are connected, the master battery polls the slave batteries and Adds up the total capacity, amps and available remaining capacity
Hopes this helps you understand these batteries a bit more
Thanks for your comment. Not sure if these batteries/BMSes were intended for standby backup power only and we 'misuse' them for our solar purposes now. Even leaving them sitting over night, the balancer did not make any progress.
Yes, the overall capacity is being reported to the Victron system, so that's a plus. You're right. We have seen this in previous videos where I tested this.
I use this exact seplos kit with grade A cells and I have no issues with them getting out of balance. An active balance port would be nice in a future BMS version though.
When I expect a spark, like when connecting a invertor to a battery, I always use a long thin single strand copper wire or short wire with a resistor inline to first charge the capacitors. With connecting batteries to each other I never had a problem if the voltage is not to far apart.
Hi Andy. Ich wünsche dir einen guten Rutsch, bzw kann man jetzt wohl schon ein gesundes Neues wünschen. Ich habe aktuell 6 14s liion Batterien jeweils 30 bzw 40p aus gebrauchten 18650 laufen. Verbaut in 2HE 19" Gehäusen Tendenz steigend. Bisher liefen die alle als eigene Einheit. Manche mit Daly BMS, 1 sogar nur mit nem akt. Balancer. Die aktuellen werden alle mit dem diyBMS von Stuart betrieben. Die älteren werden darauf umgerüstet. Ich fand es immer gut wenn ein akku einzeln agieren kann ohne das gesamte System abzuschalten. Das lässt sich auch mit dem von Stuart machen.
If you get the Chinese cracker graphs for the 135 + 280 cells does the voltage graph shape differ in the 50-20% range? maybe that's why they shifted %age SOC vs voltage - matching voltage not SOC as they discharge. Maybe internal pressures of smaller cells or something weird, subtle but weird enough to show on the test ?
Cool test. You didn't say how long the small battery lasted after the big one shutdown but it didn't appear to be long (seemed like they shared the load pretty well). Could you repeat the test without the communication cable or would you not be able to monitor the batteries in the same way? Doing the same thing without the cable is the first thing to pop in my head.
Hello from sunny hot Martinique 😊
I even have my Lifepo4 battery in parallel with lead (gel) traction battery... works fine. The main work is done by Lithium. If needed, Lead is mostly in action only at low voltage for last supper ;-)
Comms in this case is largely for monitoring and configuring. The comms for the inverter/chargers it can help when charging for example, it can tell the inverter/chargers to reduce the current as needed if the battery is getting close to cell over voltage, or getting too hot or too cold etc. Would be interesting to see if you connected the Seplos CAN to the Victron system, can it control the charges to reduce their charging current etc?
Hi, yes it can. My Seplos BMS is controlling my Victron Multiplus II both voltage and amps, when charging and discharging the charge or discharge protections are not needed to be activated by the BMS because it will tell the multiplus to stop before the protections are needed.
@@tx75e94 Andy is not using the Multiplus to charge he has multiple separate victron solar chargers that would need to be controlled.
Thanks for this vidéo Andy. I don't think that the bmss communicate with each other. The link just allows the controller (pc or venus) to access each bms data with a single rs485 or CAN port.
Based on the cell current loaded voltage slump on cell #6 I don't think there is anything wrong with it from a use/aging perspective. I think it is just at the lower tolerance of electrode thickness which gives it less LFP or graphite material, meaning it will yield less capacity. Just manufacturing build tolerance.
EVA spec for cell weight is 5.22 kg +/-0.2 kg. 100 to 200 grams lite in weight would corresponds to the AH results you are seeing. 200 grams, if all due to LPF electrode shortage would be 5-7% less capacity.
LFP cells usually have extra graphite than initially needed since it undergoes more long term degradation over use lifetime compared to LFP cathode. Graphite electrode thickness shortage will show up later in life of cell. LFP electrode shortage will show up immediately as lower capacity.
17:45 The average cell voltages of two batteries in parallel are always exactly the same = BatteryVolt / 16
They don't have to be. Unless it calculates this as simple as you said and not averaging all cell voltage individually.
Another video 🎉
If they are transistor based BMS’s I would assume the communication would be letting the charge/discharge mosfets increase and decrease the rates to try and help keep the SOC somewhat closer. The way the discharge current was bobbling around on each one possibly that was happening? Hard to tell. I wonder what the manufacturer has to say?
Hi Andy,
die Kommunikation ist meiner Meinung nach nur interessant beim Laden. Ich hab eine Anlage mit 3 Studer und gesamt 130KW Bleiakku und LEFEPO4 parallel. Beim Laden habe ich das Problem das die Balancer die ungleichen Zellen nicht mehr balancen können da der Balancer den erforderlichen Strom bei der höher liegenden Zelle nicht mehr her bekommt. Durch die Kommunikaton sagen sie nun dem Studer das er die Ladeleistung herunter fährt so das dass balencen wieder geht und die Zellen nahezu an ihr maximum geladen werden können. Nach einer Zeit werden die Zellen durch dieses Verhalten konditioniert. Ist wirklich sehr interessant das Verhalten.
Das ganze ist in den Sommermonaten bei uns in Bayern intensiv im Einsatz.
Gruß aus dem nicht so sonnigen Bayern ;-)
Andy
I was surprised when communication disconnected completely after the shutdown. Also I expected the bms to send some sort of a command to the inverter to turn it down or switch to the backup before battery shuts dead off. Other than that option i don't see a purpose for communication
That was really just for testing purposes to see what happens. You are right, usually the inverter would shut down (or switch to grid) before any of the BMS gets to such a critical stage.
Hi Andy,
Die BMS-Komunikation ist für das Laden der Batterien.
Unter 12 Grad Celsius muss der Ladestrom reduziert werden.
Wenn der Master-BMS den Ladestrom nicht steuern kann, war's das mit den Batterien.
Es ist wichtig sich auch über Telegram zu informieren. Man sollte immer aktiv gegen Zensur handeln!
Thanks for the love. Send me a text on telegram with the username above🔝🔝🔝 You've been shortlisted for my New year giveaway.......
Andy, the communication allows you to collect data on a monitoring device like your laptop using only one RJ45 cable. Your computer doesn't need to know how many 'umbilicals' are attached to it, but it needs to know how many packs your rack is composed of, so it can reports the specific warnings of the bank affected. An ethernet token ring communicates with independent stations for shared data or access privileges. Likewise a Seplos rack is more likely to perform the same scheme. I agree with you that parallelling batteries with individual BMS presents no issue. I have a 280Ah and a 100Ah with separate Ant BMS and they just work until they shut off upon tripping on over or under volage protection. Their individual bluetooth screens report the errors on their own separate apps. I guess that were the "unifying' communication may gain some traction. It may allow to handle the monitoring of many battery banks within one app. That is actually a saving and selling feature for the batttery manufacturer software wise..
Yes, but this is not working correctly with the Seplos batteries. There is a major flaw in their design. Video is coming soon...
Hi Andy, another great video.
Does the RS485 link only allow you to see both packs states on the Computer ?
With the RS485 disconnected you could only see the state of the pack the the computer was connected to.
Seplos bms when reached the maximum overcharge current is instantly reduced to 10amp. and every few minutes I think its 20min it checks to see if the current is still too high and if it is still too high it will stay at 10amp until the charge current is under the maximum overcharge current. I love this feature because it let's you connect batteries with different voltage without having to worry about huge flow of current going to the lower voltage battery. for this alone i like the seplos bms. bms like jk and overkill don't have this feature
The only thing that comes to mind regarding the communication is the inverter. If only battery one communicates with the inverter, it cannot see info from the other ones. It's not for communicating between batteries, but for moving info from each battery to the inverter. Did you check what the inverter sees?
Hi Andy,
As both (or several) batteries are connected in parrallel, isn´t the communication between BMS´s there to avoid charging the discharged battery by the remaining battery (which still holds capacity)? As such avoiding that some capacity is "wasted" instead of all of it being used to power your home appliances.
I'm building one of those 280 pack with one of those case I get from Ally Express, I currently have a EG4 100ah pack and when I finish with the 280 pack I was planning to parallel it with the EG4 and see if it would communicate too
Lower capacity battery will have higher internal resistance than the larger battery so will discharge at a lower rate for the same terminal voltage
Hey Andy, loving your channel, just a thought, could you use the the programmable relay in the Victron smart solar mppt to start an active balancer to top balance the Serplos battery banks?
I guess the benefit of the comms between batteries is a single wire to communicate and monitor all the batteries. It would make wiring simpler if you have 16 of them.
Hi Andy @OffGridGarageAustralia
I have a suggestion about how to properly control your three rogue cells (6, 7 & 8), in spite of the pathetic balancing in the Seplos BMS...
You tried out the PowerPaul 4S balancer, which is great because it only switches on at 3.4V-per-cell, but you need *four* of those to "tame" your bad cells.
Move cell 6 (the worst) to position 1, the next worst (cell 8?) to position 5, and the third-worst (cell 7?) to position 9. Find/pick a fourth-worst /"victim", and move it to position 13.
You have 12 good cells left. Pair the three strongest of those cells into the first "quarter" (positions 2-4), and connect "quarter one" to whichever balancer has the lowest trigger voltage. Pair the three next-strongest cells with the next-lowest-triggered-balancer as "quarter two" (cells 6-8 + 5), and repeat for quarters three & four.
From the videos, you were frustrated that those weak cells get into high voltages far too quickly, and then the BMS kills charging before the good cells can get a good top balance.
Once charging voltage gets over ~3.4V within any one quarter, that balancer will apply a dedicated 5A of current just to reign in *one* bad-boy cell. I think that 15A+ of total balancing current may well be possible.
As I see it, those weak cells are always going to run away. They are currently not controlled, so they stop the good cells from charging fully.
Clamping each bad cell to three good cells reins it back, so that the good cells can fully absorb / top-balance. Then when they discharge, those good cells can give more Ah before the weak cells kill the BMS.
You are never going to get more performance from the weak cells, but I think this allows the good cells to get very closer to 100% at the top end, so they can deliver more Ah before the bad cells trigger a low-voltage cutoff?
Thoughts, everyone?
PS I think there are also several slightly-out-of-spec cells on the 135A battery, so that would also benefit from the same.
PPS what would be ideal is if you could treat the "quarters" as individual ~14V batteries, then have them four-way balance across those four quarters.
If I dump this stupid idea here I hope to have a clear mind to celebrate New Years in a few minutes...
So, Happy New Year, everyone...
Take the four "quarters" of good and bad cells I mentioned but wire each quarter as 4P (so averaging to 3.2V @ ~1080ah). They're in parallel, so their voltages are locked together, and the strong and weak cells must average to give their combined capacity.
Then wire each of the 4P in series to make 4P4S 12V @ ~1080ah.
Oh, and then you can balance them using the PowerPaul 4S balancer.
Happy New Year to all!!! So would communication make a difference if these were mismatched batteries in series? I just wonder if building a 48v system out of two 24v batteries with differing ah ratings would make a difference.
Im more surprised about what happened at the end, you would think they would communicate to prevent that exact situation.
Yeah, I wasn't sure what to expect, but nothing to see here... exact same behaviour as my 3 standalone BMSes in the shelf.
Awesome as usal :) - would the coms have worked if the computer was wired off the other battery, i think it would have gone down with the big battery shutting down. I too would love to know what is the comms that happen between batteries and also between inverter etc.. thanks for a great video!
I think the total shutdown is based on what the maximum discharge limit is set for each pack's BMS. If when large pack shut down the smaller pack shifted to taking more current than its set maximum discharge limit it too would have shut down regardless of its state of charge.
You really need to make sure the maximum charge and discharge currents for each individual pack's BMS are set appropriate for the battery size in that pack to avoid the inverter pushing too much charge or pulling too much discharge current on each of the single battery packs.
Question is if you approach a charging single cell overvoltage on any pack does inverter/charger back down charging current to avoid a BMS overvoltage shutdown on the single pack with the cell approaching overvoltage.
The BMS just reports the situation to inverter/charger. The inverter/charger needs to make decisions on that info. Since it would be difficult for inverter/charger to manage multiple parallel battery packs I think it just goes after the worse situation, so my money is on it backs down charging rate based on single cell in single pack saying it is approaching overvoltage limit.
Okay, let's say that the total current exceeds the remaining active BMSses.
Are you saying that the inverter should then tell the remaining active BMSses to shut down?
But then: what is the difference between that and an individual BMS to shutdown, if the current is too high?
I reckon that if the current of the 2 remaining BMSses would be too high -when not communicating to each other-, both will shutdown quickly after each other.
But does that matter?
A shutdown is a shutdown.
Without communicating, I would say it's more reliable.
Only thing in my mind is a remark made (on this channel??) Some time ago, that a mosfet burned down.
But i can't remember the reason.
@@gubbernl inverter/charger should not tell bms anything. It does not know what is good for a particular battery.
Good It is really a fireplay experiement. You did it great. But in case of any BMS failure, should there is any fuse protection is required between the paraplling busbar connectors?. Any knife switch isolator with precharge resistor to equalise voltages in a controller manner is not safe engg practice?
Hopefully the Victron doesn't see them as one battery, it should see two batteries individually. The individual batteries don't need to communicate together, they all need to communicate with the inverter/monitoring system.
It's not about control, it's about monitoring. More numbers.
It's also disappointing that the BMSs don't keep communicating when they've shutdown. If I had such a system, I'd like to see the state of the battery even if it's undervolted.
Andy can you make a video about a acktive balance on the big batteri