Complete Off-Grid Solar Kit Manual
Revision 1.0
Page 12 of 21
Windy
Nation
08/09/2012
4.1
F
REQUENTLY
A
SKED
Q
UESTIONS
1. What size battery should I use?
Each 100 Watt solar panel is capable of charging up to a 125 amp hour 12 volt battery bank under normal
conditions. Two 100 Watt solar panels wired for 24 volt battery charging are capable of charging up to a 125
amp hour 24 volt battery bank.
Examples:
Three 100 Watt solar panels wired for 12 volt battery charging
: A 12 volt battery that has an amp hour
capacity of up to 375 amps hours is recommended. Note that a smaller amp hour battery could be used (e.g.
150 amp hour) if desired.
Four 100 Watt solar panels wired for 24 volt battery charging
: A 24 volt battery that has an amp hour
capacity of up to 250 amps hours is recommended. Note that a smaller amp hour battery could be used (e.g.
100 amp hour) if desired.
2. What type of battery should I use?
A deep cycle battery should be used for an alternative energy (solar) system. Automotive and marine
batteries are not designed to be discharged and recharged over and over. Deep cycle batteries are designed
to be discharged time after time and can be discharged down to 20% capacity. Most battery manufacturers
say that a deep cycle battery
’s life-span can be greatly increased by not discharging it more than 50%.
Deep cycle batteries do cost more money than regular automotive batteries but they are well worth the
investment when used on an alternative energy system.
3. What size inverter should I use with my solar panels?
Inverter size has almost nothing to do with the power output of the solar panels. The DC to AC inverter is
connected directly to the battery and, therefore, is powered by the battery bank (the solar panels charge the
battery). Any size inverter can be connected to the battery bank as long as the battery bank is suitably sized
for the inverter.
You could have 1000 Watts of solar connected to your battery bank and only use a 100 Watt inverter. Or you
could have only 100 Watts of solar connected to the battery bank and have a 1000 Watt inverter.
Inverter size depends on the power requirements of the loads you will run. For example, if you are only going
to use a 100 Watt light bulb, then a 150 Watt inverter will easily provide the power. But, if you want to run a
1500 Watt vacuum cleaner, then you should get a 2000 Watt inverter.
4. Are the solar panels included in my kit 12 volt, 18 volt, or 24 volt solar panels?
Without going into detail, the Maximum Power Voltage (abbreviated V
pm
) of a solar panel should be rated at
about 1.5 times the nominal battery voltage. For example, a solar panel used for 12 volt battery charging
needs to have a V
pm
of about 18 (1.5 x 12 = 18).
The Windy Nation 100 Watt Solar Panels included in these kits have a V
pm
of 18. Therefore, these solar
panels are typically referred to in the solar industry as “12 volt solar panels” because they are designed for
12 volt battery bank charging.
A solar panel designed for 24 volt battery bank charging needs to have a V
pm
of about 36 (24 x 1.5 = 36).
When two solar panels with a V
pm
of 18 are wired in series, the two V
pm
‘s of each solar panel add together.
Therefore, two Windy Nation 100 Watt Solar Panels wired in series have a V
pm
of 36. The 24 volt wiring
diagrams shown in Appendix A show how to wire two solar panels in series for 24 volt battery charging.
Therefore, we can say that two Windy Nation 100 Watt Solar Panels wired in series is a “24 volt solar panel”.
