Solar Primer continued...
Batteries - Which ones are right for me?
Batteries are the one component of an alternative energy system
which require diligent maintenance. Each cell in a battery supplies
2 volts, so a 6 volt battery has 3 cells, a 12 volt has 6 cells.
The battery's capacity is rated in Amp-Hours (or amps at the 20 hour
discharge rate in some literature).
Soltek recommends the use of 6 volt deep-cycle batteries (ie. GOLF
CART) for most small to medium sized residential/cottage/cabin applications
for the following reasons:
- each cell in a 6 volt battery is larger than each cell in a
12 volt battery - thereby providing more capacity, better cycling
performance (charging/discharging) and longer life.
- are relatively inexpensive and easy to find
- are more easily replaced if a bad cell develops
Flooded batteries
- Typical wet batteries with caps on each cell for topping up
with distilled water.
- The least expensive form of battery.
Sealed batteries
- Slightly different internal construction and acid requiring
a lower charging voltage
- Will not gas as much as flooded batteries
- Marketed as maintenance-free as they do not require watering
or new acid
- Much more expensive than flooded batteries
NiCd (Nickel Cadmium)
- Good for small systems (ie emergency lighting)
- Very expensive compared to other batteries
Battery Maintenance
All batteries should be tested every 3 - 6 months to ensure proper
charging and operation. This is done by testing with an accurate
volt meter while no loads are attached (open circuit), or with a
hydrometer which measures the specific gravity of the acid (a more
exact method for flooded batteries only). A full battery will measure
12.60 volts at rest. A battery at 20% will have a voltage of 12.00
volts at rest.
Do not add new batteries to an existing set which is more than 1
year old as the older cells will bring the new cells down to their
current performance level. An older set which has been well used
should ideally be replaced when increasing the size of the system.
Do not discharge a battery below 50% of its rated capacity in order
to ensure long life. The less a battery is worked, the longer it
will last.
Equalize battery bank every 1- 6 months depending on use to preserve
performance.
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