openinverter forum

As a test i charged the batteries to 4.0v/cell just before driving.

When i used the brakes the regen kicked in and out repeatedly, i assume because regen was enough to push the pack voltage over the parameter set in the inverter, but as soon as regen was off, the voltage dropped to under and regen kicked back in.

The obvious solution is to push up the max pack voltage param but in the event there is large regen just after starting off (unlikely where i live) it could over charge the pack.

The other solution might be have a new parameter that sets the min voltage to regen at, or i could achieve this via CAN using the BMS values i guess, but as per my other post, this isn't possible i believe until i go to CAN throttle which i am reluctant to do as currently my Arduino is not mission critical to driving the car, only for charging, and i am trying to keep it that way.

A better solution is perhaps to just not complicate things and accept that you will occasionally use your friction brakes for tiny, insignificant amounts of stopping only at the beginning of your journey.

In my OEM car, the maximum regeneration depends on the charge level of the battery. That is also how it is displayed. According to a correlation between the battery capacity, the maximum possible regeneration is determined even before the brake pedal is pressed, which prevents ups and downs during braking.

MattsAwesomeStuff wrote: ↑Thu Aug 24, 2023 3:17 pm A better solution is perhaps to just not complicate things and accept that you will occasionally use your friction brakes for tiny, insignificant amounts of stopping only at the beginning of your journey.

He didnt expressed in quite the right way but i think he wants to know a way to limit regen in case voltage goes higher than safety margin for battery regen.
First you need to consider your safety margin. Is it 4.05V or 4.1V per cell. Then calculate your full voltage and set your pack voltage regen margin. In case of 96S that would be 389Vdc. Set this inside your OI web interface and your drive will release regen in case you go downhill first thing in the morning.
There is a thing about single cell voltage margin. This would have to be set inside BMS. Then there is an input inside OI that can reduce regen or set it to 0A. I use this pin in winter so regen wouldnt block my wheels on ice.

The BMS should send a maximum allowed current IN.
This can be either for charge or regen.
Them it is up to the charge controller or VCU to make this happen. So then “automatically” (almost) full battery = (almost) no regen.

larsrengersen wrote: ↑Thu Aug 24, 2023 9:44 pm The BMS should send a maximum allowed current IN.
This can be either for charge or regen.
Them it is up to the charge controller or VCU to make this happen. So then “automatically” (almost) full battery = (almost) no regen.

This is what i observe on our Ampera OEM EV.