Looking for some help please. We manufacture small off road Land Rover Defenders for holiday parks and the likes. Up until recently these cars have run off 3x 8v lead acid batteries with a potentiometer accelerator pedal operating a DC 24v motor through a Curtis control unit. These cars only does 4/5 mph and are braked by the motor via the control unit (this can be adjusted). The problem we have is we’ve upgrade to a single 24v lithium battery. All has been good with this until following scenario happens,
When the battery is fully charged and the car is driven down a hill the regen energy isn’t able to be returned to the batteries and the BMS cuts the power.
We have bought a number of these batteries (not returnable) the control we have used for years with no issues so don’t want to have to look for another type, is there any form of capacitor/diode we can use to accept the regen? We don’t need to use it, as it’s minimal, we just need it to affectingly go away!! Any help is much appreciated!!

 

It sounds like the regen current or voltage is too high for the "BMS" (protection module) in the battery. It (rightly) thinks you're trying to overcharge the battery. Have you asked the speed controller manufacturer for help? I'd guess the answer is to replace the regenerative braking with a power resistor. Otherwise, try some EV/ebike forums like endless-sphere https://endless-sphere.com/sphere/

 

Hi, thanks for the reply. yes we’re working closely with Curtis and the battery manufacturers. At this point we are looking to adjust the Victron smart charger so it will only charge to around 80%, if this fixes the issue it will also have a positive effect on the battery life I believe. If it doesn’t work how would a power resistor work? Cheers