Adding Extra Battery Power to FFE

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So, you'll want to tap the output that will be powering the vehicle contactor and run that to another small relay. Then use that relay to switch your additional contactors with a new fused 12V circuit.

Chances are good that the relay will not handle driving 2x the normal load, but a small relay should be a marginal increase over the stock contactor load.

Let me know if you need/want a diagram
 
So Motorscm1 is correct that the car doesn't seem to care about an extra battery being plugged in when driving. I took a 20 mile drive and the budget went down but the status kept going up. Unfortunately the car refuses to charge the extra pack. When I plug the charger in the light ring does its normal thing and then it flashes a few times and turns off. I guess I'll have to rig a separate charger to the extra pack.
 
Might be because the BMS of the original battery is telling the SOBDM that the battery is full, and charging is unneeded.
 
So Motorscm1 is correct that the car doesn't seem to care about an extra battery being plugged in when driving. I took a 20 mile drive and the budget went down but the status kept going up. Unfortunately the car refuses to charge the extra pack. When I plug the charger in the light ring does its normal thing and then it flashes a few times and turns off. I guess I'll have to rig a separate charger to the extra pack.
Is the extra battery off the bus before charging starts? Part of the charging process involves checking for voltage with the contactors open and closed. If it's present before the contactors trigger, it's seen as a fault.
 
Is the extra battery off the bus before charging starts? Part of the charging process involves checking for voltage with the contactors open and closed. If it's present before the contactors trigger, it's seen as a fault.
Hmm... I might have to do some more testing with that. I believe I tried connecting the extra battery after the charging started. Maybe if I wait a bit longer. It was doing a thing where I heard the contactors cycle and then the ring would flash.
 
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