The point is, I've logged full throttle pulls with the Sevcon's battery discharge current limit turned off. The log still shows the limit the BMS is trying to apply.
I had thought the battery limit was based on voltage sag - presumably it then calculates what amount of current draw is acceptable.
In cold conditions, my '14 SR sometimes hits some kind of battery limit under WOT conditions and the controller seems to cut power almost completely.
How easy is it to disable the Sevcon battery limit? I don't care about battery life now and would rather punish as many electrons from it as possible. I assume the Sevcon DVT software and a supervisor level password?
I'm sure your correct in that some aspect of the limitation the BMS imparts on the motor controller is based on protecting the weakest cells in the battery. That said, my cell balance has always been under 10mV, and I have seen the BMS pulling current when the voltage sag was still north of 90 volts at full throttle. Unfortunately, I can't see the cell balance whilst at full throttle, but I'll probably add a sniffer for that at some point as well.
In answer to your question, it is a simple matter to turn off the BMS' control of the battery discharge current. You will need the DVT software and IXXAT cable. The login passwords are built into it though; you don't have to worry about it. The following is according to a 2021 bike. I'm sure other years are similar if not nearly identical.
There are several ways to do it depending on what you want to do. By default, 0x2870,1 (battery current limit data source) is already set to 0 (disabled). But to actually disable current limit control, you have to set 0x4623,3 (cutback range) to 0. The controller will then pull every amp it can get its hands on based on the available current, motor map, MOSFET limitation, and your right wrist. If you'd like to maintain some cutbacks, you can set 0x2870,1 to 1 (use max currents only) and adjust the thresholds and cutbacks to your preferences. If you do that latter, you only have to update the max discharge current under 0x2870,2. You'll find another one at 0x4623,2, but with the battery current limit data source set to use max currents, the latter value is overwritten by 0x2870,2. You should also replace the first variable of RPDO1 with a dummy 16-bit value.
It's a similar operation to override the BMS control of regen current. In that case, you replace the second variable of RPDO1 with a dummy 16-bit value.
Keep in mind, the BMS will still protect itself by telling the MBB to shut down the bike and open its contactor if voltages get too far out of wack. If you keep an eye on your cell balances and don't do stupid stuff at the bottom of charge, the likelihood of hurting the battery that wasn't already destined for a short life is probably pretty low. That said, proceed at your own risk.
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Topic: 2021 SR/S 0-60 0-100 4.3s something wrong? (Read 1822 times)