Mar 31 2015

choosing a solar battery

As the owner of a small solar installation company in Northeast GA, I constantly go through the design and decision making process with new customers.  Buying a solar system is in a lot of ways like buying a car.  You have lots of options, bells whistles, warranties, and reviews to wade through.  Unfortunately, there aren’t nearly as many off grid battery based solar system specialists as there are car salesman.  Few installers ever get the chance to work on battery systems.  Inevitably, the size of the battery and type of battery is always a big concern.  Choosing a solar battery is a big decision.  There is a lot of conflicting information out there about batteries.  When reading and researching you have to look at the date the article was written, solar technology changes constantly.  Here’s some simple facts from a solar installer who owns and services his own 400 amp hour 48v battery bank.

A battery based solar PV system at home amongst the clutter of the garage

A battery based solar PV system at home amongst the clutter of the garage

  • flooded lead acid (FLA) deep cycle batteries last twice as long in a situation where the battery gets used and can be maintained.  Don’t just take my word for it, look at the spec sheets. Still don’t believe me, show me a golf cart, forklift, zamboni, floor scrubber, or any other large battery operated vehicle with a sealed battery.
  • FLA are about half the price of sealed batteries
  • FLA batteries are actually pretty easy to take care.  Auto watering kits allow you to water a bank in less than 5 minutes.  You can check SG’s like a scientist or equalize routinely, charger settings are very important but that should be setup correctly at system commissioning by your installer.
  • A battery bank is not the only thing in your house that needs to be vented because of potentially explosive gases.  Gas dryers, septic tanks, toilets, water heaters, stoves, fireplaces.  C’mon folks, if it’s installed correctly it’s not a problem.
  • If a battery can survive in a motor, it can probably live in a box on your property.  Garages are a great place for a battery bank.
  • most battery banks we install are between 400 and 800 amp hrs.
  • We find most customers get through about 3 days before a 400 ah battery bank gets to 50%-60% SOC if there is no sun or charging source.
  • Most customers run the same loads off a battery charged by solar.  LED lights, fridge and freezer, well pump, electronics that plug in to an outlet, communication equipment, washing machine and dishwasher with no element.
  • A good rule of thumb is 200 amp hrs per person for luxury solar
  • battery worksheets are really confusing and stressfull
  • It’s often better to spend money on a generator for battery charging than a larger battery bank.
  • Opportunity loads are things you run when the solar has fully charged your battery and is passing directly through your system to your loads.  You battery loves this.
  • battery bank nonnie

    Johnny’s 400 amp hour battery bank with automatic watering kit quick connect in hand.

It’s April 2015, as Elon Musk touts weekly of his new Lithium battery technology, and salt water batteries begin to come on the scene, we excitedly await a new technology to replace the flooded lead acid battery.  Until, we see something that’s a better bang for your buck than the flooded lead acid deep cycle battery bank, we will keep doing what we know works for our customers and experimenting on ourselves and our family members.  J/K


Give us a call to talk battery. 770.843.3497

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Paul Franklin

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