One Battery Solar System

7Hunter9

Hi folks

I've been using a 100 watt solar panel (Renogy 100 Watts 12 Volts Monocrystalline Foldable Solar Suitcase) with a Power Sonic PS 121000 U 12v 100ah battery to power my off grid refrigerator (Whynter FM-45G 45-Quart Portable Refrigerator/Freezer) for about a year. Basically I just hook up both the solar panel (it has a charge controller) and the fridge to the battery and its kept running for two weeks at a time without issue. 

I've read that the system should really have two batteries. Dumb question...Is this true? 

Marc Kurth

Are you saying that you have been doing this successfully for a year, but you want to know if it will work?

Marc 

7Hunter9

Hi Marc. No, my question was about having two batteries as opposed to one.

Estragon

Having two batteries would likely be too much for your panel. The panel would put out ~5a at best, which is already on the low side for 100ah of battery. If you got a second battery to reduce depth of discharge on cloudy days, you would probably want to increase charging capacity.

Marc Kurth

@Hunter79: Yes, Sir - understood.

I was nudging you toward telling us how you feel that it has been working for the last year. Are you asking because of a perceived problem?

It always (always) boils down to the relationship between power in, and power out. Operating hours under what conditions and time frames are.the basic pieces of the puzzle. My point was that because you have been doing this for a year already, you would have a feel for performance.

Theory and rules of thumb are great...... but experience is greater!

Marc

7Hunter9

Thanks Estragon and Marc. Sorry I misunderstood you Marc. I was just asking to learn more and, I'd read elsewhere that two batteries are better than one. Actually, the setup has been working great. Thanks Estragon for the info, that makes sense.

mcgivor

7Hunter9 said:

Hi folks


I've been using a 100 watt solar panel (Renogy 100 Watts 12 Volts Monocrystalline Foldable Solar Suitcase) with a Power Sonic PS 121000 U 12v 100ah battery to power my off grid refrigerator (Whynter FM-45G 45-Quart Portable Refrigerator/Freezer) for about a year. Basically I just hook up both the solar panel (it has a charge controller) and the fridge to the battery and its kept running for two weeks at a time without issue. 

I've read that the system should really have two batteries. Dumb question...Is this true? 

The question is a little ambiguous, you say it has been running for a year, then you state 2 weeks at a time.
Based on the specs for the refrigerator, it draws 65 watts, or 4.5 amps at 14.4 V,  the problem is the 100W panel can barely support the load, as the voltage drops when the sun sets, the current drawn will increase. Assuming a 50% duty cycle for the refrigerator it would need ~60Ah, but the solar is only depositing ~20Ah (based on 4 hours of peak sun), a 40Ah deficit, these are rough calculations by the way, but personally I'd be amazed if it worked for more than 2 days before killing the battery, adding more battery would only delay the demise, you need to seriously consider a larger PV array and battery bank based on a calculation. Just my opinion, for what it's worth.

7Hunter9

Thanks mcgivor. I can see how that statement confused you. What I meant to say was that over the course of a year I've used this setup a lot as I am an outdoors man. My longest time running the fridge with this setup was 2 weeks of continuous use. I'd also like to clarify that this was during the mild winter months in Arizona where the daytime temperatures are very mild (60-70) therefore the fridge does not have to work as hard as during the summer when temperatures are 100+. I mainly keep the fridge in my truck bed. The truck has a camper shell. Sounds like I've been very lucky with run time. 

mcgivor

Luck is the operative word, obviously you've had some good in that department but I would seriously consider improvements, start a new thread with the load and the operation duration, including location when used etcetera, there will be folks only happy to assist and it will only cost you your time, but you will get a better understanding of what is really required, before finding out the hard way. Good luck.