Ready to get my feet wet with Solar power

pianotuna wrote:
Hi lc,

From a battery charging approach for 464 amp-hours of bank the range of wattage needed is between about 280 to 700 watts. (based on between 60 and 150 watts per 100 amp-hours).

On a worst case basis, I draw 72AH daily from a 110AH bank. I need more that 150% of 110AH to replenish the AH drawn. I fall short every day with 170W of panels non-tilted. The bank is used for 12V compressor fridges and the worst case occurs during hotter weather when more solar is available anyway. In my driveway tests last summer, I was drawing 72AH daily from a single 79AH battery.

Now, it can be said that either bank is too small, but I find that I don't need to run the genny until the 4th day with the 110AH bank. I increased the bank from 79 to 110AH due to adding a second fridge.

Making the bank larger won't really change the daily draw. A bigger bank would only extend the days between recharges with genny help. Further, a larger bank would only serve to indicate a larger solar system.

In fact, this 110AH bank is a balanced setup for a weekend camper that needs to have the bank recharged between weekends without shore power.

With the genny, the fridges can switch to 110VAC and all the excess genny Watts can be used for charging. The fridges draw about 45W each on AC if running. In the long term case, it is just a matter of how many days I can do this before I need to worry about sulfation.

Perhaps we need a rule that gives more recognition to daily draws, days of autonomy, and time available to recharge as opposed to bank size. Comments?

HTH;
John