Forum Discussion

adamis's avatar
adamis
Nomad II
Dec 19, 2020

Moving LiFePo4, Rewire or run Long Extensions?

On my Bigfoot Camper my battery compartment is on the outside compartment of the camper. The door is just a lightweight metal door with vents in it (no insulation). There are no heater vents to the compartment either. On a recent camping trip in early Fall we were up near Lake Tahoe at high elevation. The temps at night got into the low 30s / high 20s. We had to run the heat all night to keep our twin babies warm (can't smother then in blankets) and my 100ah Battle Born LiFePo4 couldn't make it through the night running the furnace (another upgrade project). We had to run the truck in the early morning to start charging the battery and I noticed that it was charging really slowly at about 3 amps (I have a 20 amp DC to DC Renogy charger installed). It took me a while to realize the slow charging was because the BMS was likely limiting the current while the battery was so cold. Later it charged around 15 amps. Although we don't camp in the off season often, it is something I would like to be prepared for. Moving the battery to keep the temperature maintained better seems like a worthwhile endeavor.

I'm considering moving the battery inside the camper, under the dinette seat right next to the onboard charger / inverter. The conundrum I face is, I currently have appropriately sized wire for a 2000w inverter, my 20 amp charge controller, 200w (soon to be 400w) of solar plus my genset all wired to the current battery compartment. I can rerun all of these to the new compartment at extensive time and effort. It would shorten the run for the solar but lengthen the run for the inverter / genset.

The alternative is to just run some heavy gauge wire to bridge between the old compartment and the new compartment. Less work overall but running thicker cable (thing 4awg or suggestions...) can be more difficult in the tight spaces. I will do the work if it really is necessary but I'm thinking about taking the easy route on this one.

Thoughts?
Truck Campers
  • Grit_dog's avatar
    Grit_dog
    Navigator
    Dec 20, 2020
    If you’re only using half the capacity of the inverter, then #4 wire is fine, but a bit small if running it to its capacity.
    In mild weather like +20 F like you were camping in, your lifepo4 will work fine if you keep it “warm” through use/load. At least my bike battery does. But yes they’re a poor choice in general for cold conditions.
    Biggest issue is you have a very expensive battery and not much reserve capacity compared to the $ invested. And only 100ah doesn’t really cut it if you’re actually using more than nominal power usage. But buying another one is another $900 expense and you still only have “average” reserve capacity.
    Why not just run your genset in conditions like this? That is the actual easy solution for occasional use. It solves all your problem with no additional expense or effort.
  • okan-star's avatar
    okan-star
    Explorer
    Dec 20, 2020
    In the summer when I need to run the AC at night I run the Honda , it will run for over 8 hrs at eco mode with my AC , not in a campground of course . The times I`ve camped in 0 to 30 degree nights I run the Honda and use a small cube ceramic electric heater on a low setting and the propane heater will cycle on and off every hour or so , so the grey and black tanks still get heat . While boondocking you can chain the Honda up away so its quieter .
  • adamis's avatar
    adamis
    Nomad II
    Dec 20, 2020
    2oldman wrote:
    Going to a higher voltage like 24 would make the long cabling less of a problem, but I assume your inverter is 12v. Is your inverter due for replacing?


    No, inverter is good. I currently have it very close to the current battery compartment but on the inside so cable length is fairly short, maybe 18". I probably could move the inverter closer to the new location for the battery but haven't really decided if it is worth the effort. Currently we use the inverter for baby warmers and the wife's coffee maker which pulls ~700 watts. I don't think we would have any higher wattage use other than these items. Not going to run the AC or microwave off of it.
  • 2oldman's avatar
    2oldman
    Explorer II
    Dec 19, 2020
    Going to a higher voltage like 24 would make the long cabling less of a problem, but I assume your inverter is 12v. Is your inverter due for replacing?
  • 2oldman's avatar
    2oldman
    Explorer II
    Dec 19, 2020
    KD4UPL wrote:
    Ever felt the air coming out the furnace vent? It's sometimes hotter than the air coming out the ducts inside. Seems like a terrible design that hasn't changed since the 1950s.
    I believe that's so your coach doesn't get loaded up with moisture, the by product of burning gas. Yeah, furnaces are hogs but they do the job.
  • time2roll's avatar
    time2roll
    Nomad
    Dec 19, 2020
    Single battery seems small to support a 2000 watt inverter. I think I would want at least 2 and I would recommend 3+

    Not sure I get the whole rewire issue. If the inverter/charger is under the dinette seat and you put the battery(s) in with it the wire should be minimal. If you have connections to the battery compartment the existing wire should be fine. The only big wire needed would be from battery to inverter and they would be very close.
  • RickW's avatar
    RickW
    Explorer III
    Dec 19, 2020
    Not my core competence but, if you move your Li batteries inside AND buy another 2000 watt inverter just for use in the new location, the bridge wire gauge should be more reasonable.

    This could be your winter configuration and the space used for storage in the other three seasons.

    Also a setup to double battery capacity and inverter power in the future.
  • KD4UPL's avatar
    KD4UPL
    Explorer
    Dec 19, 2020
    Yep, a furnace eats up a ton of power. The old saying is "one battery, one night." I really don't understand why they can't put a more efficient heating appliance in an RV. Not only is the standard gas furnace an electricity hog it also seems like it's wastes a lot of heat. Ever felt the air coming out the furnace vent? It's sometimes hotter than the air coming out the ducts inside. Seems like a terrible design that hasn't changed since the 1950s.

    I'd probably just run large wires from your current battery compartment to the new location but #4 isn't nearly large enough for a 2,000 watt inverter. You would want something like 2/0 for that load; it's likely to be around 200 amps when making 2,000 watts.
    If you decide to put the batteries back in the exterior compartment then it's really easy to put them back. I know space is tight on a TC, you could put them back outside all summer and they would probably do quite well.
    Really, I'd probably just try to get a second battery in the same compartment and keep in mind that you will need run the generator every winter morning.

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