One last attempt at a BMS

Hi guys,

I am trying to add a BMS to my two 4s lipo setup. I am using a cheap BMS to bypass for charge only, P- on my BMS is not connected. Links are below. I am measuring 4 untill 32 volts from b1 to b8, and 32.8v at the charger when unplugged. The problem I have is that the charger LED remains green, indicating it is not charging. Does anybody have any ideas? I am really close to removing the BMS and attaching my enclosure using clevis pins so I can more easily charge with a regular balance charger :slight_smile: plaatje

Check the balance of the cells and make sure they are all similar. Also check connections and maybe even the charger plug.

Finally have you charged the battery up until this point or is this the first time you have plugged it into charge? You might be able to also try discharging it a bit and try again to rule out the charger output voltage being a bit low

did you check if you can charge your packs without bms? just to be sure everything is good with your charger and your cells.

all between 4.00 and 4.01. Connections seem fine, I will try discharging the batteries a bit. The batteries have been charged and discharged before using a balance charger, first time using a bms and cc cv charger

DO you mean connecting the charger negative directly to battery negative?

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Yep, he means connecting the main power wires of the battery to the charger, this is a good method to rule out the bms

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just hook your charger up to the pack without bms and look if the charger turns red and start charging.

Thanks guys, will try

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What charger are you using? Did you check the output voltage of your charger while charging?

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Link of the charger in the description :wink:

The link is just giving me a blank page

Thanks for the help guys, I found the issue. The female dc charge connector seemed to work when I used the beep function of the multimeter (sorry, not an electrical engineer), but I didnt measure anything when the charger was connected. Is it possible that the connection wasn’t very solid, some resistance occured and the charger wouldn’t start? Anyway, I switched to xt-60 and it’s working fine now.

Thanks again for your effort!


Now link isn’t working for me too. Just to complete, it was a 2a Laptop brick style charger.

@TiMMaTTie good that you found the issue :ok_hand: