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 > How is this for a power system? Solar vs battery balance?

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Los Angeles, CA

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Posted: 02/17/19 12:05am Link  |  Quote  |  Print  |  Notify Moderator

How is this for a power system? Solar vs battery balance?

Hi all

Have owned a couple RVs, and now designing (with Hallmark) a 9.5’ Everest pop up truck camper.

How is this for the balance of 200 watts of solar and 200 amp hours of (probably Lithium) batteries?

I’m aware that the Lithium are very expensive, but they can be run down to 90% depleted without any damage….. plus they last many times longer than wet cells, so in the really long run, probably (hopefully) no more expensive. The Battleborn batteries (likely get these) have a built in battery management system that makes sure the battery can be used (or discharged) at temperatures as low as -4°F. However, the battery will not accept a charge below 25°F. The BMS also makes sure they dont over charge or under charge.

Planned system:

Propane for stove…. and Truma Combi. (hot water and air.)
(of course 12v needed to run the Truma Combi too)

7.2 CU side by side. 2 way compressor. Novacool RFS7501 fridge.

Maxx fan.

Interior LED lights.

Solar System: 2 X 100 Watt Soft Panels on roof.

Xantrex 817-2080 Freedom XC 2000, 2000 Watt Pure Sine Wave 12 Volt Inverter/Charger

Victron BMV 712 Battery Monitor w/ Bluetooth Lifepo4 Ready

2 (two) x Battleborn 100 amp hour (each) Lithium

Other occasional loads:
Small microwave. Blender. computer maybe.

We camp 4 seasons…. sometimes below freezing. Sometimes higher altitudes. Sometimes in cloudy Pacific NorthWest. So the ability to discharge the Lithuim 90% with smaller bulk and weight has advantages.

We mostly boondock. We prefer the quiet.
Occasionally we stay someplace for 2 nights, but often drive around a bit, to explore, each day (so the F350 would also help charge up the batteries)

Thanks for any and all thoughts.




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Posted: 02/17/19 03:30am Link  |  Quote  |  Print  |  Notify Moderator

I’m not an expert on anything. With that said, depending on how you use your power you may need an extra solar panel or two to keep your battery charged! But like I said I’m not an expert!


Cape Cod

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Posted: 02/17/19 05:27am Link  |  Quote  |  Print  |  Notify Moderator

That would work for summer camping, but I would double the batteries and solar for four seasons. I think the Combi will suck those 2 Li batteries down on just moderately cold nights. That would also cut down on the genny time to recharge.

That's just a quick look. Get the amp draw off the specs for the Combi and figure it'll run 50% on freezing nights.

This topic might get more replies over in Tech Issues. Let me know if you want it moved.

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Lynchburg, VA

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Posted: 02/17/19 06:30am Link  |  Quote  |  Print  |  Notify Moderator

This guy would suggest that you would likely want more solar for that much battery.


Traveling. Always.

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Posted: 02/17/19 06:36am Link  |  Quote  |  Print  |  Notify Moderator

You need a lot more solar.

Why spend all that money on the batteries and have a weak charging system?

You should have more like a single 350 watt or a pair of 350 watt panels.

The charge acceptance is pretty high on those lithium batteries. Find out the charge acceptance rate on them in amps per hour and size the panels to match that output.


New Hope, MN

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Posted: 02/17/19 07:01am Link  |  Quote  |  Print  |  Notify Moderator

"Solar System: 2 X 100 Watt Soft Panels on roof."

If by 'Soft Panels' you mean the flexible type, I would not recommend these for a permanent install. I have one 180 watt flexible panel that I use as a portable. The plastic has fogged and it is cupped in several spots. As others have mentioned, you need more solar. The compressor fridge is quite economical but will draw a lot more power than a propane one.

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Goose Creek, SC

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Posted: 02/17/19 07:11am Link  |  Quote  |  Print  |  Notify Moderator

Can't really answer your question without knowing more about the Truma system. Can't find any power consumption specs nor BTU output. Only info I could find is that it runs about $1500.

Other thing I would need to know is how much aux power you need for computers, tv, etc. If you are light on those (say 1hr/day) and assuming the Truma consumes the same power as a regular furnace, you should be able to get two possibly three days of boondocking in clear weather with that system before you need alt source.

Usual rule of thumb is 100 watts solar per 100 amps of storage for short term. Idea is that 100 watts will average about 60A/hrs per day while a battery drained to 50% will require 50A/hr. However, those numbers assume you don't have a large requirement during the day. With the compressor fridge, you should consider a 3rd solar panel so it will provide the necessary power for the fridge during the day which is usually it's highesst demand period since that is when it's the warmest. With the lithium batteries which you may drain deeper than a standard battery, it will also help recovery. Of course, this assume you are in a sunny environment.

In regards to the batteries, since you are going lithium, make sure you put them inside where they are in the climate controlled space for better performance along with one less leak and insulation hole in the outside wall.

Edit: Finally found a few specs for the Truma 4E version but they should all be about the same. While the power consumption is less, the heat output is less so it's going to run longer than a standard furnace. The assumption to use the same power consumption above as a standard furnace is valid and on the safe side.

* This post was edited 02/17/19 07:19am by kohldad *

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E. Washington

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Posted: 02/17/19 07:30am Link  |  Quote  |  Print  |  Notify Moderator

2 100W solar panels on the roof won't get you much charging current except in the summer with the sun overhead.

I suggest you consider two things:

-portable solar panels you can orient towards the sun for maximum charge current.

-A MPPT solar controller.

I realize using portable panels more work (set up, storage, cable, etc).

I use one 110W panel on the roof and one portable 110W panel that I can move with the sun, and especially, put OUT in the sun when the TC is parked in the shade.....and a Morningstar MPPT solar controller. Yes, the MPPT controllers get more out of the solar panel than conventional controllers.

If it were me, I'd put my money into solar panels and an MPPT charger than LiFePo batteries. And definitely NOT flexible panels.

Hope this helps.

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Coldstream, BC

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Posted: 02/17/19 07:39am Link  |  Quote  |  Print  |  Notify Moderator

We dry camped with a compressor fridge for 5 years. 7.5 cuft NovaKool, great unit but we found 200w solar, 200AH batteries just for the fridge was required for 100% dry camping. The rest of our electrical needs were minor. Good luck.


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Regina, SK, Canada

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Posted: 02/17/19 09:18am Link  |  Quote  |  Print  |  Notify Moderator

Li batteries do not wish to be topped off, nor trickle charged. More solar (400 to 600 watts) and a charge controller designed for Li would be my choice.

Victron has a 2000 watt inverter that is cheaper and better than the Xantrex. The biggest difference is, that after warranty runs out, the Victron can be repaired. Xantrex won't sell the parts.

I suggest staying with one "family" for components--so go Victron for the solar charge controller, too!

600 watts may obviate the need for a generator, except for running the roof air.

Battleborn has some "packages". I suggest following their recommendations.

Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

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