2Big2B
Free Wheeler
I am building an 8S 24v 100AH battery pack with an Overkill 8S 24v 100AH BMS for a "Bounder" model power wheelchair. The pack will replace a pair of 100AH 12v Gel cells in series.
The power wheelchair uses two massive 30A (?) electric motors. I just found a mention in the wheelchair's service manual that it can draw up to a 140A load from a stall (motionless) state to a Start (putting it into motion). Otherwise at full throttle the load will be under 60A.
Obviously the original 24v 100A SLA Gel Cell battery configuration didn't need a BMS - just circuit breaker/fuse protection.
My question is, if I am pulling a momentary 140A load through the Overkill 100A BMS, will it see that as a dead short and shut down? Will that be a problem I had not considered? If so, what would be the best work around - bypass the BMS and draw the load directly from the battery pack? Get a bigger BMS?
Naturally I have emailed this question into Overkill support - which is probably overwhelmed, so I am asking here too. I hope is not just a newbie stupid question. So what does a BMS do with a current greater than it is spec'd for - and/or is there a programable parameter I can set to define the maximum current draw as an over ride.
With the power switch on but the chair not moving, the chair should draw less than 120mA. Next, drive the chair on flat level hard terrain. The BOUNDER should draw between 12A and 20A from the batteries at full speed. Chairs geared for slower speeds and with lighter users will tend towards the lower readings. When accelerating, climbing hills or on soft surfaces such as carpets, the power consumption will increase. At stall, the current from the batteries can exceed 150A. When going downhill, current should be less than 10A except when the joystick is released, currents can increase as the chair slows to a stop. When turning on a hard level surface, less than 15A should be required, and less than 25A on indoor/outdoor carpets
The power wheelchair uses two massive 30A (?) electric motors. I just found a mention in the wheelchair's service manual that it can draw up to a 140A load from a stall (motionless) state to a Start (putting it into motion). Otherwise at full throttle the load will be under 60A.
Obviously the original 24v 100A SLA Gel Cell battery configuration didn't need a BMS - just circuit breaker/fuse protection.
My question is, if I am pulling a momentary 140A load through the Overkill 100A BMS, will it see that as a dead short and shut down? Will that be a problem I had not considered? If so, what would be the best work around - bypass the BMS and draw the load directly from the battery pack? Get a bigger BMS?
Naturally I have emailed this question into Overkill support - which is probably overwhelmed, so I am asking here too. I hope is not just a newbie stupid question. So what does a BMS do with a current greater than it is spec'd for - and/or is there a programable parameter I can set to define the maximum current draw as an over ride.
With the power switch on but the chair not moving, the chair should draw less than 120mA. Next, drive the chair on flat level hard terrain. The BOUNDER should draw between 12A and 20A from the batteries at full speed. Chairs geared for slower speeds and with lighter users will tend towards the lower readings. When accelerating, climbing hills or on soft surfaces such as carpets, the power consumption will increase. At stall, the current from the batteries can exceed 150A. When going downhill, current should be less than 10A except when the joystick is released, currents can increase as the chair slows to a stop. When turning on a hard level surface, less than 15A should be required, and less than 25A on indoor/outdoor carpets
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