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how many watts of solar panels do I need to maintain 200ah of LiFEPO4 batteries (12v system)?

eurotrash

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how many watts of solar panels do I need to maintain 200ah of LiFEPO4 batteries (12v system)?
 
You need to produce as many watts as you are using. I use about 6kWh of power each day. I have 4kW worth of panels. as long as I get 1.5 hours of sun I am good. The best plan is to have enough panels to provide your minimum requirements on a cloudy day and a strategy for putting extra power to use. In the Winter I use extra power to heat the concrete slab to save firewood. In the summer I use excess power to run dehumidifiers in the lower level.
 
with my 200ah battery i use a 50 watt panel to just maintain it , but my battery is for emergency back up for my furnace so there is little or no draw , its just there so it always topped off , now if lose power and run down the battery i have to put on my charger as it would take weeks to recharge battery by solar alone
 
Thanks guys. This is very helpful. For further clarification this is for a van build.
 
I have a 2600w array for a 460ah bank at 24v. I'm pretty sure it's not big enough... At least that's what I'm telling the wife.
 
Thanks guys. This is very helpful. For further clarification this is for a van build.
i would think in a van build , the question could be how much solar can i fit on the van safely , since i would thing this would be a limiting factor
 
Thanks guys. This is very helpful. For further clarification this is for a van build.
The more important information is how much of the battery’s capacity do you use each day.

A 12V 200Ah battery is 2560Wh.

If you were to use 50% each day then you’d need to replace 2560Wh x 0.5 = 1280Wh. Assume 5 hours of sun on average per day. That would be 1280Wh / 5h = 256W of solar. But since these will be mounted flat on a van roof I’d add 33% to be sure. So you are looking at about 340W of solar. If you use more of your battery each day then you need more solar. Use less, need less.
 
i would think in a van build , the question could be how much solar can i fit on the van safely , since i would thing this would be a limiting factor
As roof space on the van roof is at a premium I'm leaning towards this design https://www.mobile-solarpower.com/simplified-400-watt-fewer-wires-and-alternator-charging.html (from this web site). The only thing I would change is to substitute two Rich 200 watt 12V panels https://richsolar.com/products/200-watt-solar-panel for the four 100w panels illustrated. Does this seem to be balanced? I'll be doing mostly touring allowing the alternator charger to do most of the heavy lifting? Thank you
 
I'll be doing mostly touring allowing the alternator charger to do most of the heavy lifting?

If the alternator is doing most of the charging I'd think you might need only 200w of panel. That would save $220, and go a long way to paying for the DC-DC. And free up some roof space.
 
The big questions for panel sizing is how you spend power at night (when the engine is off), and how many nights you will stay in one place without driving the van for more touring. You could always use the van as an inefficient generator if you get into battery trouble - but most vans do not like to be idled for more than a few minutes without motion. Actual driving, in comparison to idling, creates airflow around the exhaust components - and mere idling can overheat those things (manifolds, mufflers, catalytic converters, and so on).

I have a Trailer RV which charges at about 450 watts from the TV, but we tend to stay in one place for multiple days when we reach a gorgeous destination. So my Solar has to do all the recharging - except in "emergency" situations when several cloudy and rainy days have happened in a row. My 4Runner is pretty good about extended idling, and Toyota has no particular warning to avoid it. (Although, per above, your van might NOT like doing that). I have 500W of panels overhead, flat on the roof with no angle into the sun. In relatively sunny days in late summer, we're usually fully recharged (from Solar alone) before 2 PM daylight time.

So I'm a bit "over-paneled" for my actual electrical use. Your 400W pan sounds pretty good to me. If you don't go for drives every single day, or you extend your travels into fall or early spring, then I "feel" that only 200W of panels would be marginal at best, and maybe inadequate.
 
just got back from 3 months of full-timing in my truck camper. I switched to a single 100 Ah lithium and upped my solar array to 225w. I don't have any high power devices (microwave, coffee maker etc). A typical day results in a low of 90% and back up to 100% in a few hours. Lowest I got was 70% after 4 days in a very shady spot on Labor Day weekend. The only charging came from my solar. Never used my DC-DC charger.
 
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