Insufficient Solar?!

[ShuttlePilot]

I agree with what Greg suggests ^^^^.

But just for some back of the envelope math. Lets assume your system is working great to see if your experience is close.

Your battery bank is 400Amp hours (Ah) to dead. Lets assume your batteries are 100% by late afternoon and you have used 20% of that by next morning.

400 Ah x 0.2 = 80 Ah removed from batteries by morning.
or
80Ah x 12.7 volts = 1,016 Watt hours that need to be replaced by solar. In addition to what is used through the day like refrigerator running.

Now for solar generation. Again let's assume everything is working great including full sunny day. Which is where solar installers, manufacturers, and many owners greatly exaggerate the math. Here is just a ball park calculation.

200 watts of solar, averaging 70% efficiency (maybe a stretch), between 10 am and 2 pm, add an additional hour for the cumulative morning and afternoon off peak time. So 5 hours of generation.

200 Watts x 70% = 140 watts average
140 watts x 5 hours = 700 watt hours for the day.

So in this dirty calculation the solar isn't keeping up with the energy used by 316 Watt Hours. Don't forget this is on top of the energy used during the day like refrigerator so the deficit would be what ever that is too.

So my suggestion is that if your seeing a gradual decrease over several days your set up is probably working as designed. I believe your full timing out of your van. I would suggest what some off grid folks do that just can't add any more solar but have a large battery bank. A small Generator. They run their generator after a few days when the bank gets to around 60%. But here is the smart part. They only use the generator for a Bulk charge and in the morning. Then, letting the solar on "Charge Day" finish the Absorb charge. This is a more efficient way of using the generator time and when the noise is OK.

There is often ways to improve the efficiency of a solar system. Watts made by the panels to watts stuffed into the batteries and appliances. These will improve your system but I don't think it will make your setup meet your expectation.

-Eric