Battery charging bms help!!

Hi, I have recently built a 18650 battery pack using inr 25r 2500mah 20a discharge, the battery is a 20s (72v) 5p (100a discharge) my question is; I have just charged my battery from 72v to 75.8v and that's its maximum - my charger cut out, any idea if this is normal? I'm guessing 4v will drain very quickly

To anyone interested this is my bike (sabvoton 100a controller) still waiting for my brake levers, rear motor (3000w) and another rear shock

The bike as cooling (powered by thermostat) multiple lights including rear, secret throttle cutout switch (pedal assist only)

25r is a 4.2v battery multiply by 20s equals 84 volts

you might be able to adjust your charger, do you have a DMM to confirm the voltages?

goatman said:

25r is a 4.2v battery multiply by 20s equals 84 volts

you might be able to adjust your charger, do you have a DMM to confirm the voltages?

Click to expand...

What's a DMM? my charger charges at 86v 8a - I know this because when I plug in it reads 86v on the display
My bms can only handle 90a though while my parallel groups can go upto 100+A but I can change the max discharge in the controller to avoid burning out the bms

I also have a step down to 12v 5a for the accessories - would this be the cause of reduction in voltage (via the display)?

Yes I have a multimeter, I'm going to check the voltage at the battery and get back to you.

dmm/digital multi meter. if the charger puts out 86v, thats too high, open up the charger and there might be a little pot you can adjust.

sounds like bms is the issue

heres a video on how to adjust a charger, only thing different i do is after adjusting i put a dab of silicone on the adjusting screw so it doesnt move from where i set it

https://endless-sphere.com/forums/viewtopic.php?f=14&t=108170&p=1581893&hilit=adjust+charger+pot#p1581893

goatman said:

dmm/digital multi meter. if the charger puts out 86v, thats too high, open up the charger and there might be a little pot you can adjust.

sounds like bms is the issue

Click to expand...

I can't open up the charger as its a seal unit, what would be the problem with the bms? Could it be a balance wire not properly connected?

could be, i dont use a bms so i dont know but maybe the 86v from the charger is tripping something in it. what charger you have?

goatman said:

could be, i dont use a bms so i dont know but maybe the 86v from the charger is tripping something in it. what charger you have?

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I've just checked the voltage output of the charger and it's output is 84v, but the battery terminals read 76v - does the bms require 8v or so to power? My bms has b- and c- which I found the correct wiring diagram for - I checked all the connections before heat shrinking - I did however connect the balance wires with the bms still connected (I got a few of them wrong causing the bms heat sink to heat up a little before I realised) I then disconnected the bms while adding the rest of the balance wires,

I think I've fried half of my balance board only allowing half the pack to be charged and balanced
Would this seem plausible? I should of gone with a Bluetooth bms so I can see what's going on in there,
I will do on a new battery pack when I get round to building it

sounds like it. i run my 25r packs with no bms but i have the bms leads on it so i can check each group every 6months or couple thousand kms, its a good cell. you might want to pull the bms check the voltages on each group and balance them, connect the negative battery to controller (bypass the bms) and ride til your next bms comes

goatman said:

sounds like it. i run my 25r packs with no bms but i have the bms leads on it so i can check each group every 6months or couple thousand kms, its a good cell. you might want to pull the bms check the voltages on each group and balance them, connect the negative battery to controller (bypass the bms) and ride til your next bms comes

Click to expand...

Yes I think I'll end up replacing the bms to a Bluetooth one in the future, I will leave the pack as it is for now as it should balance itself out still with only half the bms operating and there isn't any load on the pack until my motor arrives (leaving at 72v)
I was planning on building split packs upto 72v with separate bms wires but it just seemed to much work and extra monies which I don't have at the minute,
This is the only reason I can think of as to why my battery isn't reaching 84v

battery wont balance itself, yank the bms and make sure it hasnt killed a p group

goatman said:

battery wont balance itself, yank the bms and make sure it hasnt killed a p group

Click to expand...

I don't think it has damaged the battery's because I checked all the p group's before and after I installed the bms and they read the same, currently discharging the battery down to 72v, I think I've damaged the bms by getting the balancing wires the wrong way round, the bms heat sink was pretty hot before I realised