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.


     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.


     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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Karl Kinkel - President
Karl Kinkel, President & Founder
Longsgap Services LLC
5262 Elk Creek Pkwy
Independence, VA  24348
(276) 773-3730
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