battery issues bms??

[paddycork]

hello, i just bought a second hand carerra crossfire e bike. it didnt have the charger, the guy couldnt find it so i have just bought a new one from cycle republic https://www.cyclerepublic.com/chg-vp-e-bike-battery-charger.html

Before charging the voltage was reading around 31v. i plugged in charger and it was charging away and i checked the voltage periodically ( i think it was 39.5 last time i checked) and it was rising. just before going to bed i plugged it out and checked the voltage again and it was 20.4v,

I have just taken it apart today and tested the batteries and they are all reading 4v in their series connections.. any ideas cause im stuck and frustrated!

thanks

paddy

 

[vfr400]

The normal meaning of 20v is that the BMS has switched off the discharge.

Are you measuring the voltage directly on the battery terminals?
Is there a switch on the battery?

 

[paddycork]

oh ok, thanks for replying. i dont fully understand what that means.. when i measure a the terminals on the outer casing it measures 20.4v.. when i open the battery up and measure between the cells themselves it measures 40.9v.

when i measure from the positive of the terminal (on outer casing to the negative of the battery it reads 40.9v. when i do the opposite it reads 20.4v.

there is not a switch as such to turn the battery on that i can see. just a battery indicator which is a series of leds