Thoughts on FWC factory upgrade of electrical system to 135 AH Dakota Li battery and Redarc 25 A DC-DC charger

[rando]

One of the benefits to using a DC-DC charger is you can use smaller wire. I think even at 50A, Victron only calls for 6AWG, and will only physically accept 4AWG. I use a 30A DC-DC and it works fine with 8 AWG. Also, the limiting factor is typically the wiring in the camper (which I think is 10AWG, at least with FWC in 2016), so unless you plan on pulling out the cabinets to rewire, running a larger wire may be of limited value.

 

[bikeandski]

Thanks again all for the feedback.

- BFH4N: I have developed a wiring plan, HW is going to be tight in the battery box. I would be interested to see your diagram for reference.
- Truck to camper wiring: I plan to run 4 AWG from truck battery to the Victron 50 A DC-DC in the battery box, 80 Amp breakers at the truck and house batteries. This was proposed by the respected FWC aftermarket supplier. This is suitable for the max 50 Amp charging (and largest lead size for the Victron 50 Amp converter input), though I did consider 70 Amp breakers. Anderson SB120 between the truck bed and camper. I'm considering the aftermarket panel mount kit with dust cover from Amazon for the SB120 connector at the truck bed feedthrough. How are folks mounting/protecting the truck to camper plug?
- Wiring from Battery Box to camper loads: The factory wiring has red 10 AWG from the rear battery box to front ACR, with a 30 Amp inline fuse to the ACR terminal, along with 10 AWG white wire on the ACR terminal sending current to all camper loads. My inclination is to use the existing red 10 AWG wire from the battery box to the front under-seat cabinet, and replace the 30 Amp fuse with a 30 Amp breaker between the lead from the battery box to the white camper load wire. The 10 AWG here seems a tad light, but is consistent with the factory approach and 30 Amp fused camper load.
- Inverter/charging accessory plug and wiring: I'm planning on a SB175 accessory connector for occasional inverter use, and occasional shore charging with a LiFePO4 charger instead of the IOTA shore charger with AGM profile. This wiring from the batteries and high amp bus bar to a SB175 plug using 1/0 AWG wire, with a 200 Amp breaker for circuit protection, and also to depower the accessory plug when not in use.
- Definitely going with the BMV-712 monitor. The LiTime bluetooth app is limited and unreliable from what I have read.

And lastly, the dreaded LiTime 100 AH group 24 battery with heating and bluetooth: One arrived yesterday, the second is out for delivery today. I charged the battery up and am running my refrigerator today on the inverter as an option for short term power outages. The fridge is drawing about 10 Amps DC at 40% duty cycle, so the 100 AH will last over a day. The BMS cut off consistently above 100 Amps during bench tests, providing some assurance against a catastrophic failure. The bluetooth app is limited to SOC, estimated time remaining. voltage, power draw, current draw, heater settings, and an option to depower battery. I am cautiously optimistic the batteries will work together in parallel for the camper, despite the problems others have reported. If not, I may go with one 100 AH battery for awhile, or repurpose them and see if any higher capacity batteries are available with internal heating.

Enjoy your day,
Steve

 

[Jon R]

Regarding fuse location: you should locate your fuse protecting the 10 awg camper load wire as close as possible to the potential source of large fault current (the battery).

 

[bikeandski]

Regarding fuse location: you should locate your fuse protecting the 10 awg camper load wire as close as possible to the potential source of large fault current (the battery).

Thanks. This was a consideration I had as well. I was curious about the factory fuse location up front under the seat next to the ACR. I suppose the ACR could be considered a power source and justify the fuse there, but it's not capable of a "large fault current" given the wire size to the truck battery . This location was very attractive to me since the battery box is packed and the breaker provided two studs to connect the power lead to the load wire there. I may have to get creative mounting the breaker in the battery box, or repurpose one of the mini 30 Amp fuses from the factory wiring.

 

[Jon R]

I suspect the wire from your truck battery has a fuse right near that battery. It should anyway. The next question is whether that fuse is sized to protect the 10 awg wire.

 

[BFH4N]

Did you use two LiTime batteries?

Just one Dakota 135AH.

 

[BFH4N]

And why do you think #4 awg is overkill? I ran mine with #2 welding cable, and have seen 90A over that wire over extended periods of time. If I ever go bigger on my house battery bank (200AH BB now) I'll be glad I have enough wire in there already. I have used the house batteries to jumpstart the truck... instantaneous current flow was likely over 100A for that.

I think the Redarc charger is rated at 25 Amps, which wouldn't require 4 AWG wire but, like I said, it was already there.
I did install a big relay (salvaged from the original OEM battery isolator and rated, I think, at 200 Amps) which might allow jump-starting the truck from the camper battery. I haven't thought of a way to test this, other than intentionally discharging the truck battery, so who knows if it would work? The manual-reset circuit breaker for the camper wire is only 80 Amps, so I think it's a question of whether the truck would start before that trips.
Anyway, when the camper battery is really low, the Redarc charges at about 20 Amps when the truck is running, so I'm happly with this setup.

 

[BFH4N]

Thanks again all for the feedback.

- BFH4N: I have developed a wiring plan, HW is going to be tight in the battery box. I would be interested to see your diagram for reference.
- Truck to camper wiring: I plan to run 4 AWG from truck battery to the Victron 50 A DC-DC in the battery box, 80 Amp breakers at the truck and house batteries. This was proposed by the respected FWC aftermarket supplier. This is suitable for the max 50 Amp charging (and largest lead size for the Victron 50 Amp converter input), though I did consider 70 Amp breakers. Anderson SB120 between the truck bed and camper. I'm considering the aftermarket panel mount kit with dust cover from Amazon for the SB120 connector at the truck bed feedthrough. How are folks mounting/protecting the truck to camper plug?
- Wiring from Battery Box to camper loads: The factory wiring has red 10 AWG from the rear battery box to front ACR, with a 30 Amp inline fuse to the ACR terminal, along with 10 AWG white wire on the ACR terminal sending current to all camper loads. My inclination is to use the existing red 10 AWG wire from the battery box to the front under-seat cabinet, and replace the 30 Amp fuse with a 30 Amp breaker between the lead from the battery box to the white camper load wire. The 10 AWG here seems a tad light, but is consistent with the factory approach and 30 Amp fused camper load.
- Inverter/charging accessory plug and wiring: I'm planning on a SB175 accessory connector for occasional inverter use, and occasional shore charging with a LiFePO4 charger instead of the IOTA shore charger with AGM profile. This wiring from the batteries and high amp bus bar to a SB175 plug using 1/0 AWG wire, with a 200 Amp breaker for circuit protection, and also to depower the accessory plug when not in use.
- Definitely going with the BMV-712 monitor. The LiTime bluetooth app is limited and unreliable from what I have read.

And lastly, the dreaded LiTime 100 AH group 24 battery with heating and bluetooth: One arrived yesterday, the second is out for delivery today. I charged the battery up and am running my refrigerator today on the inverter as an option for short term power outages. The fridge is drawing about 10 Amps DC at 40% duty cycle, so the 100 AH will last over a day. The BMS cut off consistently above 100 Amps during bench tests, providing some assurance against a catastrophic failure. The bluetooth app is limited to SOC, estimated time remaining. voltage, power draw, current draw, heater settings, and an option to depower battery. I am cautiously optimistic the batteries will work together in parallel for the camper, despite the problems others have reported. If not, I may go with one 100 AH battery for awhile, or repurpose them and see if any higher capacity batteries are available with internal heating.

Enjoy your day,
Steve