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How to Choose a Battery or
Batteries to Match
Your Solar -Wind System
Energy Storage
Battery voltage and storage capacity matters.
That's the
inverter's
input that determines the number of hours you can continue to remain up
and running in the event of a power failure.
Deep Cycle
Batteries are designed to deliver constant voltage output as
they are discharged.
Your battery bank provides DC power to the
alternator.
Which in turn supplies
AC house voltage power to run your life style.
So really how are you going to use that power?
1.
Power when the sun doesn't shine and the wind is calm.
2. Power to net meter into the
electric grid and lower your peak power
demands.
3. Power when the electric grid is
down.
4. Power to supplement your backup
generator when the electric grid is
down.
Voltage
What
battery bank voltage is required to drive your alternator? 12, 24, 48
volts? Batteries are available in 12 and 24 volt sizes. Battery
banks can be wired to meet your need.
Amp
Hours
Amp
hours is a rating given to batteries so you can calculate how long a
battery will deliver power. Perhaps you want to have enough energy
storage
to last five days and your
average usage is 3.45 kw per hour. If you chose a 12 volt
deep cycle battery for your bank with a 7300 amp hour rating, you
would only have 80% of the power of a fully charged battery available
for your use.
12volts x 7300 amp hrs x 0.80 =70080
VI hrs -- that's 70.08 kwh per battery
3.45kwh x 24 hrs x 5 days = 414 kwh to last 5 days of normal usage
414 kwh / 70.08 kwh per battery = 5.91 batteries -- round up to 6
batteries in your
bank
Charge -- Discharge Rate
All the batteries in your battery bank need to be similar in type and
rating so they will charge and discharge at the same rate. If they are
not the same, the battery with the lowest amp hour rating will limit
the capability of the others in the bank and may in fact result in
damage
to the others.
Automobile
-vs- Marine
Automobile batteries are designed to give
sporatic bursts of energy to start the engine. Marine deep cycle
batteries are designed to deliver constant voltage over an extended
period of time. Your alternator needs constant voltage power over an
extended period of time to work efficiently.
Care and Maintenance
Most of the batteries I've
looked at have only a one or two year guarantee. If you use lead acid
batteries they are prone to collect crystals on the plates. The
crystals need to be removed periodically to maintain the battery's
efficiency. There are special devices that will remove them.
Safety
High current, acid and hydrogen are the main dangers. High current
gives
you heat. Acid can burn your skin and eyes. Hydrogen, given off at one
of the plates can be explosive and needs to be safely vented so it
doesn't
collect and become a hazard.
Batteries are heavy. You'll need equipment to
safely lift and move them. You'll need safety glasses, a rubber apron
and
rubber gloves to handle them safely. Be safe, don't be sorry.
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