Napa 85-5000 battery charger manual

SkiMore wrote:


Step 1) Solar panel.

Step 2) Bring batteries home and hopefully recover them
If the batteries are shot I'll drop down to 2 x 12V * 100A (2400watt) which will give me 1200 usable watts which is still way more than I need. I could probably use 1 battery and get a nice small sinewave inverter and be ok also. On the rare times I need more power I could fire up the generator.

Based on 1200WH(notice the H as it is important)

1) Solar: Have you decided between 12V and 24V battery banks?

The 30A charger is a good match for a 24V 100AH bank. 30% is an optimal rate that balances fuel, charge time and battery life. For a 12V 200AH bank, 60A would be your target. However, with solar, the 30A should be fine. I bulk charge a 110AH bank with a 12A(10+%) charger and then let the solar take over for absorption and float. Together, the charger + solar works very well.

2) Watt-Hours;
a. 2 * 12V 100AH in series is 24V * 100AH = 2400WH
b. 2 * 12V 100AH in parallel is 12V * 200AH = 2400WH

At a rate of 120W you will reach 50% in 10 hours, that is, you have used 1200WH. 120W is approximately the 20hr rating of 10A for 12V, 5A for 24V.

Above or below 120W draws, the AHs taken will vary. In the extreme, you will not get 1200W for an hour, but maybe 30min. Under 120W you will get extra time. This is how batteries work with inverter draws.

This is important to consider because to size solar, you need to know how many bank AHs need to replaced. You can't simply size solar arrays on Watts alone.

Using your 1200WH projection we can SWAG your solar Watts. Do you intend to recharge daily by solar and use the genny for inclement weather? If so, divide 1200 by the daily insolation for you location. Say you get 3.5hrs of daily solar insolation, 1200/3.5 = 360W array. Insolation will vary by season.

HTH;
John