Ideal Battery Amp Hours (Ah) for a 370 Watt Solar System

AZ_JOE

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Hi All -

My new Reflection TT has a 370W solar system. That said, will two 100Ah batteries suffice for dry camping? I arrived at two 100Ah batteries using the following formula: (8 hours of sunshine X 370 Watts) / 13 Volts (LiFePO4 Battery) = 228Ah.

228Ah from the 370W in a day is ideal. In the real world, I suspect the the amount will be <228Ah. As you may know, 8 hours of sunshine may not be possible every day and there are probably losses in the solar system (panel, charger, wiring, etc.). BTW, my solar charger is 60A.

Your insight is appreciated -

Joe
 
The ideal battery is more of a function of how much electricity you'll use in a day than the size of your solar array. Since you have a newer coach I'm going to assume you have a 12-volt frig. Allow about 100 Ah per day for that. You don't mention an inverter, but those can quickly eat up a lot of battery. Yes, 2 100 Ah batteries would minimally serve your needs. In my coach I have 800 Ah, there are days when I don't get enough sun for my 900 watts of solar to recharge the batteries.
 
@soundsailer is right on. Solar is only going to help in as much as it will offset the wattage you use. Until you determine your usage, you won't know if 2 100AH batteries and 370W of solar are enough. Another big factor will be how long you dry camp. If your solar won't recharge your batteries to 100% every day, it will be a question of how long you can go before the capacity is fully depleted. If you plan to do overnights without shore power while traveling between destinations, you'll likely be okay for a couple days on the road, depending on weather and usage. Otherwise, assume a 12V fridge alone will use one battery in a 24 hour period, less what you get from solar during that day.

Best to just use it for a while and see how it goes. Then you'll know if you should get more solar, more battery capacity, or both. If yours came with a battery monitor, learn to use that. It's a great way to see how much power various devices use, or how much total capacity you use in a day. Congrats on the new camper!
 
The ideal battery is more of a function of how much electricity you'll use in a day than the size of your solar array. Since you have a newer coach I'm going to assume you have a 12-volt frig. Allow about 100 Ah per day for that. You don't mention an inverter, but those can quickly eat up a lot of battery. Yes, 2 100 Ah batteries would minimally serve your needs. In my coach I have 800 Ah, there are days when I don't get enough sun for my 900 watts of solar to recharge the batteries.
Thank you SoundSailor
 
@soundsailer is right on. Solar is only going to help in as much as it will offset the wattage you use. Until you determine your usage, you won't know if 2 100AH batteries and 370W of solar are enough. Another big factor will be how long you dry camp. If your solar won't recharge your batteries to 100% every day, it will be a question of how long you can go before the capacity is fully depleted. If you plan to do overnights without shore power while traveling between destinations, you'll likely be okay for a couple days on the road, depending on weather and usage. Otherwise, assume a 12V fridge alone will use one battery in a 24 hour period, less what you get from solar during that day.

Best to just use it for a while and see how it goes. Then you'll know if you should get more solar, more battery capacity, or both. If yours came with a battery monitor, learn to use that. It's a great way to see how much power various devices use, or how much total capacity you use in a day. Congrats on the new camper!
Thank you Riverbug
 
I have 800 watts of solar and have NEVER seen 800 watts going into my 810Ah of Lithium batteries. 600 watts on a good day. Have been told that 75% is about the max you'll see the panels do.
 
I have the same 370w panel but 600ah of lithium. As others have said figure out what your usage is to determine the ah and/or more solar. I do not do much boondocking may a night or two. I do have 3 nights planned in May and feel confident I can go that long, but I also have a generator just in case.
 
The only way to get full use of the panels is to tilt them. I have 970 watts on the roof of my fifth wheel and today in Quartzsite Arizona got a peak of 1007 watts (tilted) with the magic of MPPT. If they weren't tilted I would only get in the 700s.
JK
 
@AZ_JOE That 370 watt system is capable of around 18 amps on a sunny day mid summer. Your 60 amp solar charge controller has a lot more capacity so if you need to add more panels, you can give those batteries a bigger boost. Fyi, I am also using a 60 amp charge controller but with 1000 watts of solar and the most amps charge I've seen was 52 on a sunny day, end of May when the batteries were low. Of course if your batteries are close to being fully charged you won't see much charging from your solar.
 
All of the comments you have received are good.

I will offer another way to think about batteries [amp hours, ah) and Solar charging.

Let's say, your camper uses 100ah per day and you have 500ah of battery storage, you could boondock for 5 days. However, you also have 370 watts of Solar on your camper, and each day of your trip is partly to mostly cloudy and your Solar brings in 30 to 40 amp hours worth of energy to charge your batteries. After 3 days you could extend your trip by a day, if you get another 30 to 40 amp hours of battery charging from the next 3 days you get another day.

What I am saying with the above example is that battery storage capacity and Solar charging are both combined to determine how many days you can boondock without plugging in somewhere for an overnight charge.

If you want a more complete understanding of Solar and batteries, check out the pinned thread on the Solar and Generators forum, titled: Affordable Solar... there is a lot of information in that thread and it will really help you understand how your Solar and batteries work together.
 
All of the comments you have received are good.

I will offer another way to think about batteries [amp hours, ah) and Solar charging.

Let's say, your camper uses 100ah per day and you have 500ah of battery storage, you could boondock for 5 days. However, you also have 370 watts of Solar on your camper, and each day of your trip is partly to mostly cloudy and your Solar brings in 30 to 40 amp hours worth of energy to charge your batteries. After 3 days you could extend your trip by a day, if you get another 30 to 40 amp hours of battery charging from the next 3 days you get another day.

What I am saying with the above example is that battery storage capacity and Solar charging are both combined to determine how many days you can boondock without plugging in somewhere for an overnight charge.

If you want a more complete understanding of Solar and batteries, check out the pinned thread on the Solar and Generators forum, titled: Affordable Solar... there is a lot of information in that thread and it will really help you understand how your Solar and batteries work together.
I appreciate the insight. Thank you!
 
I've always contributed as your capacity as a gas tank. The more you have, the longer you can run before fill ups.

The charging is how fast you can fill it up. As mentioned by SolarPoweredRV, if you cannot fill it up fast enough, you will extend your time, but still run out.

If you can fill it up as fast as you are using it, then you can last a very long time.
 

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