That bms u used has had some bad reviews I was going to ask u how it was a while ago but forgot
I got the Battery Supports from Supower, everybody use but I had issues with it.
I didnât know you needed a professional power supply to be able to use the BMS to itâs fullest capabilities, but if you buy a good power supply then why do you need a BMS in the first place?
If your cells are balanced on charging and you keep an eye on individual packs every once in a while then thereâs really no need for a BMS, Iâm starting to understand @whitepony
My mistake thought it was a different one
The BMS if itâs working will balance the pack. It just takes many charge cycles because of how small the resistors on the BMS are.
The way I understand balance charging to work is:
You pump voltage through pack, if one of the series cells is charged higher than the others, you apply drain to that pack, via sensor wire or balance lead until the other packs catch up. BMS can only apply something like 50mA of drain because of how small its resistors are.
You can do the math. If you are charging at 1A current 50mA of drain is not a lot. You could try charging your pack using very very low current over a very long time to allow the rather poor balancing capabilities of the BMS a better chance.
Either way though, it will attempt to rebalance every charge cycle if BMS is working. It just may take 10+ cycles because of how slowly it applies drain.
After some testing and research I found out the BMS does not balance at all, because it never reaches the balancing stage with a regular brick charger. You need a 0-60V power supply to balance your cell or your BMS wonât work at all for charging, itâll only balance through discharging
Why would you need 60V for 36V(42V) bms?
Iâm using a Supower(Battery Supports) BMS for charging and discharging without issue
Itâs also important to make sure the cells are all the same voltage before building a pack. I build mine into a 1S40P with nickel strip and magnets to make sure all the cells are exactly the same voltage then build out to 10S4P
The 0-60V power supply is mandatory to be able to balance any unbalanced individual packs, BMS if you use a brick charger it will not reach the balancing voltage which is higher that 42V. You will know your individual packs are unbalanced when the pack does not reach 100% or it has less than 42V and the led from the charger is green.
Mandatory based on what? You canât do blank statements like that without any proof.
I am also using a batterysupports BMS with a brick charger and it balances just fine
How is that possible when the âOver-charged Protection: 4.2 ± 0.05 V.â
It says that balancing starts at 3.9V per cell or 39V on a 10S pack.
Charging shuts off at 42.5V. If anything, with a 60V charger, you are trying to throw more voltage at an object that canât accept it. Isnât that why Boosted had issues with their BMS/batteries? They were using a higher voltage charger than pack voltage?
The proof (maybe itâs not good enough yet) comes from my own experience and from @Namasaki experience with brick chargers, I also tested several brick chargers and was never able to balance the packs, however when some packs got unbalanced he was able to balance them with a power supply.
Iâm not really sure what is going on exactly. But your experience with a BMS is similar with a lot of peoples. They donât work very well for balancing. I explained above why that is, but Iâll do it in more detail here.
Imagine you charge your 12 Amp hour pack(12000mAh) at 12 amps. It takes 1 hour to charge.(just for example)
Now your BMS is capable of applying 50mAh of drain to each of your 10 packs simultaneously.
Lets say one series pack reaches 4.1v but another pack is at 4.0v if you consider full charge 4.2v and full discharge to be 3.0v then each .1v is 1/12th of the charge state right?
At this point the BMS is pumping 42v into your 10S pack trying to bring each cell up to 4.2v. The cell that is at 4.1 will start to be drained at a rate of 50mA as per capabilities of the BMS. So the 4.1v cell is now getting 11950mA current in, while every other pack is getting 12000mA. Obviously this wonât do much, and the 4.1v cell will still reach 4.2v charge state before the 4.0v cell leaving your pack out of balance. Over many charge cycles this may eventually be rectified.
This is also why charging at a lower current could help. If your BMS is capable of applying 50mA of drain and you charge at 12A that isnât very much. But if you charge at 1A that 50mA drain is going to make a bigger impact.
I hope my rather poor explanation makes sense. This is why BMS are a rather poor solution. Balance chargers need fans to dissipate the heat they generate from draining overcharged cells, thats why BMS is limited to something like 50mA of drain.
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The issue is that his charger was turning off because it was triggering the low current cutoff in his power supply. Nothing to do with the speed of balancing. It was simply not balancing at all. If a single cell reaches 4.2V it will not just turn the BMS off, it will try to balance the cells. BMS usually have their safety cutoff 50mV higher than 4.2 just for that reason. Now if youâre running a 60V charger then yes, the BMS will cut off any and all current
How is your pack getting so out of whack though? The BMS is only an issue as you described if you are using low quality cells.
This has peaked my interest.
Are you using the Meanwell LED drivers (HLG series) or their power supplies with fans?
Whatâs the reason the wall power is killing them?
@Eboostin ask @Eboosted, he had two dead cells in his pack.
@jaykup, I have a brick charger from a group buy that works just fine. @Eboosted is the one having all the issues with the BMS. The wall power is not killing anything, his cells are going out of balance. The BMS is not balancing as it requires lower current than the shutoff value for the brick charger and he wasnât discharging through a BMS so there was no low voltage cutoff for the individual cells. I think he said he had 2 cells completely dead at 0V. Check out this thread for more info: http://www.electric-skateboard.builders/t/at-what-voltage-your-pack-reaches-100/19302/98
you know whatâs funny⊠is people are always telling me to stop using the ones I use because theyâre allegedly terrible and that i should use meanwells, but other than being a little loud and warm, i have zero complaints with the 4amp ebike chargers from Battery Supports. Theyâre super reliable in my experience and the only time iâve seen one blow was when they shipped me one with a bad auto-switching circuit to adjust to 220 or 110. That problem was evident immediatly upon plugging in the unit and never got beyond that.
I also have had zero issues with thier 60 and 80 amp BMSs. None. At all.
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Sorry - was replying to your comment a few months ago in this thread -
Just wondering which meanwell chargers you had issues with and why running them through the UPS seemed to make them last longer. I was under the impression the LED drivers (aluminum fanless potted ones with adjustable voltage and current) were decent chargers for $40, but I havenât used mine long enough to see if itâs going to last. Since youâve run yours for a few years I wanted to know more.
Ohhh! We have some of these at work: http://www.progressiverc.com/mean-well-rsp-2000-24-power-supply.html
Some of our wall outlets are notorious for having sh!tty power. The voltage may vary from 110V to under 100V when loaded moderately. We had not had any issues with it until we started using and killing these power supplies and theyâre not cheapâŠ
Using a UPS helps keep the power clean and if we ever get a drop below 105V then the battery kicks in to help. Thatâs why they last longer now although they are still dying overtime.
We have moved to modifying server power supplies to power our 1500W charger which have no issues with the dirty wall power. We still keep them on UPS though