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Mobilesport's avatar
Mobilesport
Explorer
Mar 26, 2020

Would solar be effective in the midwest?

Would a 200 watt solar panel keep a single 100ah lifepo4 charged during a midwest Iowa winter/December ?
I use about 50 ah per day , I found a online calculator that said 50ah is about .65kwh

I believe my 100ah lifepo4 is like 1kwh or 1.2 kwh
.65kwh is about 20kwh per month so maybe a 300watt panel would work??


  • Lwiddis wrote:
    "I use just solar to charge my GC2's. I have never used a generator to charge my 8 year old batteries and they are still going strong. I boondock 99% of the time."

    I get tired of exercising my generator every other Wednesday since I too don't need it for recharging. Solar is fantastic!


    Solar probably is fantastic if you live in a nice climate like California, probably won't work good in the midwest.
  • Mobilesport wrote:
    Lwiddis wrote:
    "I use just solar to charge my GC2's. I have never used a generator to charge my 8 year old batteries and they are still going strong. I boondock 99% of the time."

    I get tired of exercising my generator every other Wednesday since I too don't need it for recharging. Solar is fantastic!


    Solar probably is fantastic if you live in a nice climate like California, probably won't work good in the midwest.


    I live in the mid west. I'll have to tell my solar that it has been bad. After all, it has not cost me a dime since I installed it and still works fabulously.
  • 50 amp-hr at 12v is 600w-hr (actual voltage may modify the results a bit but not enough to drastically change the answer).

    General assumption is you get 4-5 times the rated wattage in watt-hours...ie: 200w panel will get you 800-1000w-hr in a day.

    On the surface sounds great. Problem is there are several mitigating factors.
    - Winter in the north, the angle of the sun and shorter days will reduce panel output.
    - Cloudy days (more common in winter) will reduce panel output.
    - Snow on the panels will kill most of the output.
    - Charging systems are not 100% efficient, so even in ideal conditions, expect to lose some.

    Unlike Lead-Acid batteries which are typically kept above 50% discharge to avoid damage, Lithium can run down to around 20% with little risk, so 100amp-hr translates to around 960w-hr of usable power if you start fully charged. Depending on age and abuse, you may no longer have 100amp-hr batteries.

    For your usage, I would want at least 50% more solar to make up for the losses from the theoretical output (maybe 100% more...300-400w of panels). Then I would want to double the battery bank as you will get multiple cloudy days from time to time. 1920w-hr will give you 3 days in a row of cloud cover before you run out.

    Alternatively, you can keep a small generator and an eye on the charge state. If the bank gets too low, crank up the generator for an hour or two and give them a boost (preferable to go thru the onboard AC to DC charger as most generator 12v outlets don't put out a lot of amps).

    PS: Be careful reading the replies as many people are mixing up units.

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