I'm working a new job 75 miles away, and can get there with one DCFC stop, but would of course prefer not to, and I happen to have my original battery pack just hanging around, with probably 10 good kWh available in it...
I recall but am not finding the thread on a European college project that placed a second battery pack inside the car and ran both together. My desire is much simpler, to place the old pack on a trailer and use it for part-time range extension, without messing up the BMS, capacity calculations, etc...,
SO, discussion please on how to accomplish this. Most lokelyly, I could charge the battery trailer with an external charger and then connect in parallel where the DC feeds into the inverter (via a pigtail with an Anderson connector). However, the ideal solution would be to recharge in parallel with the OBC or/and DCFC.
Just like getting extra regen (and range) with a pusher trailer, once the batteries are hooked up in parallel, the car may not be any the wiser if the external battery is hooked in downstream of the point at which coulombs are counted/ amp-hrs are measured. BUT, unlike a pusher trailer, I won't simply be unloading the motor so the car has to do less work and gets more regen, as if I'm always driving downhill. In the case of a battery trailer, the motor will be working harder, pulling more amps and amp-hrs, while the battery mysteriously delivers more energy than expected, and the cell voltages stay healthier for longer.... Since the BMS is very slow to change AH measurements and turtle mode is based on the lowest V cell measurement in the onboard pack, I expect that part-time use of a range trailer wouldn't cause overcharging or overdischarge problems for the onboard pack (especially if one employs common sense and doesn't try to drive 80 miles with the optomistic RR numbers shown after disconnecting the trailer!).
Any good links or ideas on where to connect in the offboard pack, and how to energize the offboard BMS?
2012 i-SE "MR BEAN" 110,300 miles
2016 KIA SOUL EV, 90 kW, 27 kWh, 34k miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh