Winter camping in the FLX

[jrg3170]

We're thinking about buying the FLX (2100BH) to camp at our local ski area during the winter (mid 30s during the day, teens overnight but sometimes as low as 0F). I'm interested to hear what experiences FLX owners have had with winter camping? We would be dry camping, but generators are allowed. My main concern is whether the tanks will be useable.

A few questions:

1. Does the FLX furnace ducting vent into/pass thru the underbelly, as with the regular model?
2. How many amps do the tank heaters draw? Somewhere I saw 5 amps each, 15 amps total?
3. Has anyone run the tank heaters off of the battery? How long can you run them for?

Lastly, a non-winter question - how long does it take to recharge the 320ah battery with a typical quiet generator, say 1800 running watts? Which I guess is really asking how many amps the battery charger will take...?

[RocknRoll]

Bring a lot of fuel because under those conditions, you'll be most likely running that generator 24/7.

MM's including the FLX are not 4 season trailers. Very few are.

[jrg3170]

To power the tank heaters you mean? My math shows I'd only need to run the generator a few hours a day, maybe less? Looking for validation of my assumptions, tell me if I'm wrong:

3x tank heaters draw 5 amps each, 15 amps total
80% depth of discharge on the 320ah battery = 256ah

Runtime = availability capacity / amp draw
256ah/15amps = ~17 hours

Given the tank heaters are 12V the inverter doesn't need to be on overnight. And of course some of the battery will go to lights, fridge, pump, etc... so the 17 hours is more of a theoretical maximum.

During the day, the battery will recharge some from the solar panels. But, let's just assume no solar for now.

The next question is how long the generator has to run to recharge the 320ah battery. This is the part I'm more unsure on. There's two parts to this:
1) How much power the battery can take / charging rate
2) How much power the generator can make

I think the limitation is #1? Most of the quieter RV type generators max out at 30amps, but that's at 120V (so 3600W). The Xantrex takes 150A (!) at 12V (?), or 1800W? So the generator can produce more power than the battery can take?

So to replenish the 256ah at 12V is 256/150 = 1.5 hours. There will be some charging losses and such, and the charging rate won't be 100% through the full curve, etc...

But, where this napkin math gets me to is:

1) I can run the tank heaters off the battery overnight, at least for a few hours
2) I can top off the battery at the end of the day with the generator as needed, for probably 1-3 hours

Am I thinking about this the right way?

[RocknRoll]

If it was me, I would be ultra-conservative so you wouldn't have to constantly worry about power management. Maybe perform a real time test with the generator powering everything you want it to do and then throw in a 20% fudge factor.

Remember, batteries do not hold a charge nor charge well in the cold, especially at freezing temps.

At best case, solar may give you 50% what you get in the summer. That does not include cloud cover and/or precipitation.

Another factor is the trailer heater itself. Not sure what the fan draws, but it can be substantial.

Insulation is your best friend. Plan on covering the windows, vents and possibly insulating the pass-thru for additional comfort. Good luck!

[Marine359]

We’ve camped in freezing weather in our plain vanilla 2108ds for up to a week with hookups, and 2 days with no hookups. There’s not a lot of volume inside, so it doesn’t take much to keep it warm, and it’s pretty well insulated; better than most TTs I think. However, when we boondocked we were too close to running out of power during the night. We’ve since added a 2Kwh powerstation, so, I think we’ll be ok now.

Micro Minnie’s have two tank heaters. Each one draws about 65 watts when they are on. So by my calculation, if you leave your tank heaters on for 10 hours, you will consume about 1,300wh. The Lithionics 300ah LFP in the FLX stores 3,600wh at 100% SOC. I don’t know exactly what the furnace uses, but it’s a lot. And don’t forget the 600wh/day the compressor fridge will use. We have 300w solar on the roof, 100w portable, and 170ah LFP, and when boondocking in ambients in the teens, with 100% SOC we could make it through the night with furnace on, tank heaters on, and fridge turned off. But we had to fire up the generator first thing in the morning. So during the night we went through over 1,800wh. The solar was enough to recharge, but not enough to service daytime loads of furnace, fridge, and tank heaters during daytime ambients in the thirties. We also have a thermostatically controlled tank heater on our battery, so that’s another load that can’t be dropped if we want to be able to recharge.

If you set the furnace thermostat to 65F at night, when you get up in the morning to make coffee with your kettle and French press, the range (with fan on) heats the interior to 70F before the dw gets out of bed. Biggest issue is getting moisture out. Opening windows and running a roof fan or the A/C fan makes cools down interior again.

[Marine359]

An add on how we managed to get through the night: turned off inverter, turned on tank heaters just before going to bed at 11pm, set thermostat to 65F. Up at 6:30am, battery SOC 5%, turned off tank heaters, started truck and hooked up 7-pin, started battery heater. Waited til battery heater turned itself off (40F) then started generator. Next night we turned thermostat down to 60F and added more blankets. Didn’t want to nearly run dry again, and not be able to heat the battery.

So to figure furnace consumption,
Tank heaters running for 7.5 hours = 975wh
Subtract from the 1,860wh we used overnight means furnace used somewhere in the neighborhood of 850Wh allowing for some lighting, and phantom loads.

[Marine359]

Re: Battery charging. Math is simple.
Assuming your charger can be programmed via Bluetooth for charge amperage:
Charging at 50 amps for one hour, puts 50amphrs into the battery.
So, if you charge a 300ah LFP at 50amps, it will take 6 hours to charge fro zero to 100% SOC. Or, 3 hours charging at 100 amps.
Make sure you don’t exceed the max amperage input for your battery, and it’s not a good idea to charge at or near the battery’s max input all the time. My battery has a max input of 80amps. But I charge at 50 amps when using generator (to conserve gen run time), and 20amps when on a pedestal. Only charge at 80amps when we’re in a hurry to leave.