Question on Number of Solar Panels

2OLDMAN is the only one that got it right. With NO sun shining directly on your panels for months at a time, even 400W of solar panels will not come close to replenishing your daily use of 75-90 AH per day.

You need to figure out how long you have to charge the batteries before losing high sun. A typical 120WATT solar panel will produce around 5-6AMPS DC current so you need to figure out how long 5-6AMPS DC will recharge a battery. Two panels will produce 10-12AMPS. It is a known fact that 14.4VDC with 17-20AMPS DC Current capacity will re-charge a 50% depleted battery back up to its 90% charge state in a three hour time period. That would need to be four panels in high sun for a good 3-4 hours time for one battery.

You can probably get around 6 hours of high sun here on the East side of the US and alot more on the West Side of the US.

For me here on the east side I would have to run my 2KW generator for the first hour to get past my 50-53AMPS battery demand when first hit with 14.4VDC and then perhaps I can allow the remaining time I have in the high sun using four solar panels to finish my re-charge when the batteries are being hit with 13.6VDC before the high sun goes away.

If you never deplete your batteries down to their 50% charge state then you won't need as much re-charge time to get them back up to their 90% charge state. The batteries will perform very well with only a 90% charge state on them. If you cannot get to the 90% charge state then the batteries will start falling off rather quickly when you use them. This will eventually harm your batteries.

I think you have to plan using something like this to get there...

I am just now starting to think Solar Panels after doing alot of camping off the power grid since 2009 with my 255AH battery bank which works out great for us running down our batteries to their 50% charge state by 8AM each morning and then running my trailer off my 2KW generator for three hours re-charging the battery bank back up to its 90% charge state so we can do all of this all over again the next day/night run off the batteries.

For me the solar panels would work great after I got past the initial 53AMP DC Current demand using the generator first.

Others get by ok with less charge time because they never run the batteries down to the 50% charge state over night...

Roy Ken

There's no overkill; a charge controller will just cut back production when the batteries get full.
However, 90 Ah per day is about 1080 watt hours. You would need to make close to 1200 watt hours to replace that taking loses into account. Given the conditions you describe I don't think 400 watts will be enough.

No solar is going to work with sunlight being blocked by a mountain.