Adding Extra Battery Power to FFE

[Anti_Climax]

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

 

[TheChickenTendy]

If you could draw up what you are talking about that would be greatly appreciated.

 

[Anti_Climax]

If you could draw up what you are talking about that would be greatly appreciated.

 

[triangles]

How much power does the Focus motor draw? What discharge rating should I be looking for with an external pack? Also any leads on where I can get Li-ion packs? I can only find LiFePO4 packs in large sizes.

batteryhookup.com has an assortment of new, used, and salvage batteries.

 

[TheChickenTendy]

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.

 

[Heima]

Might be because the BMS of the original battery is telling the SOBDM that the battery is full, and charging is unneeded.

 

[Anti_Climax]

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.

 

[TheChickenTendy]

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.

 

[TheChickenTendy]

So I have been running the extra battery for couple weeks after getting an external charger. I was only able to get a 3kw charger for the secondary pack but it sits around at home long enough to charge it. My longest commute is Tuesdays and I cannot charge at that location so getting there and back with the heat blasting going a total of ~65 miles is great. The guess-o-meter is very confused and not accurate. I had a 35 mile budget when I left and got there with 18 left. I then proceeded to get home with 10 remaining. So it seems to figure out it can go further when it gets to around 1/3 on the battery graphic.

On the charging front I did try all sorts of tricks to get the battery to charge with the car. I tried starting with the extra pack at a 5v over, 5v under, and matched. I also tried letting it charge for 5min before switching the extra pack back on. If the extra pack is connected it is instant wrench and flashing charge ring. So my solution is the external charger and I split my 50A 14-50r in 2 and put a 14-50P on the other charger. Combined its 40A so I'm not going to pop my breaker.

Now I just need stronger shocks. It rides a bit low in the back.