Would solar be effective in the midwest?

[Mobilesport]

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??

[valhalla360]

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.

[pianotuna]

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.

[Mobilesport]

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.

[Lwiddis]

"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!

[Lwiddis]

Getting many RVers to read the basics of battery charging is nearly impossible, Steve. They would rather complain than learn.

[BFL13]

I got in three days early last week where I would have had to use the gen and charger every day, but got in some solar so didn't have to use the gen until the second day. So solar extended my time between gen charging by a day. Or by 100% if you want to make that look good.

A couple days after getting home they closed the provincial parks for camping because of the Covid-19 thing, so am stuck on the computer at home getting in trouble. They are letting the local dog-walkers in the park (Rathtrevor) all day same as usual, so I don't see how camping overnight can spread the virus particularly. Phooey.

[Boon_Docker]

BFL13 wrote:

Boon Docker wrote:

BFL13 wrote:
Solar is just a way to extend the time between generator/charger recharging.

I highly doubt that statement.

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.

Right, so your time with solar between gen/charger charging is long enough so you don't have to use the gen before getting to shore power again.
That can be all summer or for several days in winter, whatever the scenario is. Including how many batteries in the bank, and your daily usage.

The last time my batteries were on shore power was 4 summers ago for one week. That is a pretty long extended time. 🙂

[BFL13]

Seattle Steve wrote:

BFL13 wrote:

2oldman wrote:

BFL13 wrote:
I don't understand what possible settings you can have on a solar controller that would alter that..

You talking to me?

No, the guy who thinks the controller sets the battery acceptance rate instead of the battery doing that for itself.

The fact that you don't understand only means that you don't understand; not that you have a valid point. 😉

You are invited to explain or link to an explanation of what you mean about solar controllers so the rest of us can try to understand it.

Otherwise you are saying something against what is well known about battery acceptance rates and charging profiles.

[BFL13]

Boon Docker wrote:

BFL13 wrote:
Solar is just a way to extend the time between generator/charger recharging.

I highly doubt that statement.

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.

Right, so your time with solar between gen/charger charging is long enough so you don't have to use the gen before getting to shore power again.
That can be all summer or for several days in winter, whatever the scenario is. Including how many batteries in the bank, and your daily usage.

[Seattle_Steve]

BFL13 wrote:

2oldman wrote:

BFL13 wrote:
I don't understand what possible settings you can have on a solar controller that would alter that..

You talking to me?

No, the guy who thinks the controller sets the battery acceptance rate instead of the battery doing that for itself.

The fact that you don't understand only means that you don't understand; not that you have a valid point. 😉

[BFL13]

2oldman wrote:

BFL13 wrote:
I don't understand what possible settings you can have on a solar controller that would alter that..

You talking to me?

No, the guy who thinks the controller sets the battery acceptance rate instead of the battery doing that for itself.

[Boon_Docker]

BFL13 wrote:
Solar is just a way to extend the time between generator/charger recharging.

I highly doubt that statement.

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.

[2oldman]

BFL13 wrote:
I don't understand what possible settings you can have on a solar controller that would alter that..

You talking to me?

[BFL13]

Lead acid batteries can accept "full charge" well past 80% SOC

It is all about the "charging rate", which is the amps/AH of battery bank. At any charging voltage, the lower the charging rate, the higher the SOC before amps taper at the end of Bulk and VV.

Solar often has lower max amps wrt the size of the battery bank, so that makes for a low charging rate, and so the end of Bulk in the 90s for SOC.

I don't understand what possible settings you can have on a solar controller that would alter that. The battery type settings usually only change the high voltage set point, which can change the amps being accepted. Higher voltage can mean more amps at any given SOC if the solar can provide more amps. Not going to change the charging rate very much between 14.4 and 14.8 eg.