Battery doesn't fully charge anymore

Thanks for your input. I appreciate the help that I always receive from this community.

Just charge your board for a longer time, let the charger plugged into your board also when the charger says that the battery is full. It just means the that your cells are not balanced perfectly, one cell hitted 4,2V and the charger stops, than the bms will slowly discharge that cell and the charger will start again for a couple minutes. It just takes a long time but once you did that it won’t give problems in the future.

One cell is 4,2V and the others will be around 4,05V. That’s really not a problem at all, believe me. I’ve had a 16S pack and 1 cell was at 4,2V while the others were only 4V and plugged my charger in for around 20h and the cells were all perfectly balanced.

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Now I charged all the cells up to 41V. I already see the same led on(few post above to see the picture) which is wierd. I will now charge them to 42V and leave it. I hope I will see more led turn on over time. I will keep you all post it.

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IMG_20180623_203455 This was my pack with lifepo4 cells so 3,6V means fully charged. You can see one cell was 3,7V so the bms stopped and slowly discharged only that cell. Than start charging again when the cell is below 3,55v. At the left you can see the result after 20h charging, perfectly balanced. I got a bluetooth bms so I could check everything on my phone and computer. Just set your charger between 42V - 42,5V and you will be fine.

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My 1st bms arrived damaged, would only charge cells to 80% upon further inspection (separating the metal sandwich heat sinks) I found the last 2, either resistors or diodes, burned up on this bank of 10… logic says 2 out of 10 burnt means only 80% charge… they said it wouldn’t harm the cells to run so I did u til my new bms arrived

I think that part it’s fine form me since I reach 41v and in the past I charged up to 42V. Anyhow this BMS does what they want:smile:

YEh I got know abot the bluethooth one too late. It would have been fantastic! Anyhow now charger at 42V and let’s see


HI! I left the battery charging the whole evening and night and I see that the only led that was on is now off menaing the bms balanced that one, but the overall voltage is exactly 41V when the charger should go up to 42V> I think the bms doens’t resume the charging and stops everything at 42V. Althought I remember the first time I charged them all the led were on becasue the all battery pack reached 42V. Which BMS did you use? would you reccomemended? I think it’s useful being able to read the single pack Volt. Thx

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I have this bms now:

41V isn’t bad at all that 1V more maybe like 3% range of your whole battery. When you drive a full 42V pack, the voltage in the begin drops so fast so that 1V won’t make any difference. 0L This is 10A discharge on 30Q cells.

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Funny it is the same vendor I bought mine :sweat_smile: I do not understand then why mine seems not work as it should do. Did you choose the one with bluetooth only? or also PC?

Both, bluetooth and pc. If you really want them at 4.2V charge them seperate with a lithium charge module, like the one in a powerbank. 1529826940372202724487 You can plug them in the balance connector, very easy

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I agree that 41V it’s ok, It’s just wierd that the charger doesn’t try to reach 42V and moreover that if I spin the moto one sec so that the bms will allow the charger to start the cycle I see onyl the same led show up, suggesting that the packs are still unbalanced. I do not know what to think, I just don’t want to open the battery pack for nothing. That’s it. Do you use it for charging only? I see that it is also programmable

I also use it for discharging. Yeah you can adjust a lot of settings, actually everything. IMG-20180616-WA0013 And you can also change the setting via bluetooth in the app so I’m really happy with it. I just like to be able to see every cell voltage, makes everything so much easier :sweat_smile: These are the settings for my Lifepo4 16S pack IMG-20180616-WA0016 I has also 4 temp sensors so you can put one in your battery pack, bms, esc and maybe one close to your motor. But you don’t need to connect them, it’s just for information or you can set a max temp. value for these.


Then I will go for it. If I can program it is the way to go. Thx!

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Hi! I finally found the bravery of open partially the battery so that I can access to the BMS. I then charged the battery al lteh way up and I am waiting the BMS finish to balance two cells (I can see it becasue it has a led light for each cell lead + that turn one when fully charged). Aftercharging I just checked the cells and these one the results 10s battery: |1|4.1| |2|4.1| |3|4.1| |4|4.17| |5|4.1| |6|4.1| |7|4.1| |8|4.13| |9|4.21| |10|4.1|

The cells group are out of balance and indeed the leds are on so seems the BMS is working, but why it allowed to get so unbalanced? I will report back in a while but I was wondering to manually discharge the single cells can I connect a small led to the single led pin (the pin that usually connect to the BMS). If it is possible the + wire goes to the unbalanced cell, but the + one should be connected to the B- pin or the pin form the previous cell group? The reason why I am asking it, is because if I measure with a multimeter placing the - probe to the B- lead and the + probe to let’s say Cell 9 + lead I get the total Voltage (around 37.8V when fully charged). On the other hand if the - probe to the pin of group 8 I get only the voltage of the single 9 cell group. So I am not sure where to place the - of the light bulb, I do not want to give it to much Voltage. Thx! I made this simple circuit for discharge the cell. IMG_20180715_203336

you should seriously consider getting a higher-end BMS and use it to balance discharge. I commute up and down some big hills in LA daily and have never had issues with balance discharging after a year. Best advice to move in this direction would be to see if @barajabali will sell you one of the BMS’s he uses. they’re fantastic and I can’t be sure he doesnt do something special to make them balance discharge at higher amperages.

Yeh, I am in EU so if I can find something locally would be better. I do not know why my BMS allowed the cell to get so unbalanced. @bartroosen12 talked about a BMS with Bluetooth that you can set it for higher overcharge protection, plus monitoring the single cell voltage. I like the idea to be able to check it without open the battery. I check all the connections, nickel strips ecc… everything looks good. really solid. I really think is the BMS :expressionless:

Even if you buy a BMS, I am a firm believer that everyone should also buy a hobby charger. BMSs work pretty well, but never seem to work quite as well as a hobby charger. 1-2 times a year it’s a good idea to balance charge your pack with a hobby charger to make sure everything is well balanced. That is why I build 2s li ion packs and connect them with bullet connectors to make a 12s pack. Much easier to troubleshoot and charge with a hobby charger.

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@kuphjr @onepunchboard @itsmikeholland New results after 1.30h of balancing

1 4.1 4.12
2 4.1 4.12
3 4.1 4.12
4 4.17 4.18
5 4.1 4.12
6 4.1 4.12
7 4.1 4.12
8 4.13 4.1
9 4.21 4.18
10 4.1 4.12
Ore 17 Ore 18.26

Now group 8 it’s better the other still not

I started to discharge some cells. I am doing like that to be able to monitor it IMG_20180715_211944