Solar Power (part 1) Battery Bank

My previous series was on understanding batteries and different ways to connect them. This series is a continuation, but moves into solar power set ups.

How do you know how much power you will need to generate and store for your RV needs? All appliances are rated in AC watts or amps. You can use the following formula to determine the DC amp hour draw for a 12 volt DC system:

(AC amps X 10) X 1.1 X hours of operation = DC amp-hours
(AC watts / 12) X 1.1 X hours of operation = DC amp-hours

This formula should be used to calculate the number of amp hours used between recharges for each appliance. Although a deep cycle can be discharged 80% without permanent damage it is best practice to allow for 50% cycling to improve battery longevity.  Do this by calculating the amp hour usage between charging cycles and then use a battery bank twice that capacity.


Sample Power Consumption in 12 volt DC Amp hours

Appliance Wattage 15min 30min 1hr 3hrs
light 100   2 4 8 24
blender 300 6 12 . .
coffeemaker 1000 20 40 80 .
Refrigerator 750 . 21 42 126
microwave 1500 30 60 120 360
vacuum 1100 22 44 88 264

How many batteries do you have in your battery bank?




Some of the information contained in this post is from the Bob Livingston RV Repair & Maintenance Manual 1998