Struggling with solar!

bfeeny

I have a new 95 amp hour Costco Deep Cycle battery, an All Powers 100W monocrystalline flexible solar panel and a CMG2420 charge controller. We recently returned from a 3 day boondocking camping trip and I am frustrated with the performance of my solar system. Our camp site was somewhat shaded and we certainly did not receive full sunlight but  felt that because of our limited use of power and having the solar panel that the battery should have lasted longer. We used the Alde for hot water and some heat for a total of about 1 hour per day, we used the water pump for about 15 minutes a day and one 12v light for about 10 minutes at night and that's it.
We arrived with a full charge of 12.6 and left 72 hours later with a12.1 volt reading. The battery according to the controller reached a maximum of 12.5 volts during the day but quickly dropped to 12.3 volts in the evening. Any suggestions or comments would be welcome.

4ncar

The true state of charge can only be determined with a battery monitor (shunt type). Were you using the Alde on propane or electric? 95 ah is not a lot, remember on 1/2 of that number is usable. The panel was problematic only generating 3 or 4 amps of charge in the shade, at best, coupled with the fact that you only got a few good hours of charge at that low amperage, so don’t think you can really blame the panel. Try it at home on a nice bright sunny day, see if it improves.

VictoriaP

Well, most panels do not perform well in even partial shade. I have a pretty highly rated and efficient Renogy 100w, and I’ve seen it drop to 10 watts with light cloud cover or in shaded areas. 10 watts is basically trickle charging, that won’t keep up with any usage at all. Depending on how far north you are, you may only have a few hours of maximum sunlight available to use as well. 

pthomas745

How were you monitoring your battery?  You don't tell us what trailer you have, so are you using a SeeLevel monitor?  A multimeter?  One of the plug in meters?  The solar controller?

If properly used, a multimeter type battery measurement can come pretty close to any of the "shunt type" meters.  You just have to use the proper technique to get an accurate measurement.

If you were using any of those types of monitors, and you hadn't "rested" the battery, it will always read a lower state of charge.  (Even a Victron voltage reading will be lower if the battery isn't rested). 

So, what were you using?  Even with your disappointment with your battery, you camped for three days and came back with "approximately" 50 percent of your battery remaining.  The trailer used about 4 amps a day in "parasitic drains",  (12 of your 45 available amps).  The Alde might have used a couple of amps.  You don't tell us what fridge you were using, because even the fridge on propane uses some power.

So....I would say......cloudy weekend, three days on the road, return home with 50-60 percent of your battery remaining...is not too bad.  With a little practice on how to rest your battery and use whatever you were using to monitor it, you should do much better next time.

This section of the Battery FAQ goes over the concept of "Rested Battery" and "Surface Charge."

https://www.solar-electric.com/learning-center/deep-cycle-battery-faq.html/#Battery Voltages

bfeeny

Thanks for the comments. I have a 2018 320CS S so was not using my fridge. I used a multi meter and the SeaLevel Monitor which seem to both read the same as the charge controller. The Alde was on propane.  Don't know anything about rested batteries so will do some research. I'm going to do some testing in my driveway in the sun to see if my results change

BirdieJane

““new 95 amp hour Costco Deep Cycle battery”
this is only 47 AMP hours of usable battery.” This is very few AMP hours of Battery to expect a stress free Boondocking experience in partial sun. I would recommend going to duel six volt battery’s and if parked in partial sun you will be able to go a few more days. You could add 1 more 100 watt panel would help. You did not see what type of solar controller you have MTTP would be best. 

pthomas745

Those of us with 70ah batteries would love to have 47 usable amp hours.   My 70AH battery, 100 watt panel, and propane fridge works just fine.  (PS: I will have a 100 ah battery in a month or so!)

ScottG

pthomas745 said:

...

So....I would say......cloudy weekend, three days on the road, return home with 50-60 percent of your battery remaining...is not too bad. 
...

+1!

DougH

@bfeeny FWIW, a Victron charge controller made a big difference for us.  Worth the extra money.

I used to have a pair of EFTE panels covered with tiny hemispheric lenses.  Both the physical surface and the wider frequency range of energy absorption made those panels fantastic in shade, clouds, and throughout the whole day from before sunrise to after sunset. They even registered moonlight on the controller. Sadly hail did them in, and they're no longer made.  But it makes me wish that all RV panels were like that, since we often park in partial shade or go through several cloudy days in a row.