Batteries

The batteries are probably the single most critical component of any off-the-grid system. They store an awful lot of energy in a fairly compact package.

They are also the only element that really needs periodic maintenance if you expect to get any kind of life out of them.

At all times you should make sure that your batteries are kept above the freezing point of the electrolyte, a frozen battery is as good as destroyed.

Not all batteries are created equal, for an alternative energy installation you will need 'deep discharge' batteries. Normal car batteries will NOT last, they are made to start cars, not to be deep discharged.

We used 24 2 Volt Surrette KS 17 cells. These store about 48 KWh, about 50% of that is actually accessible if you use 50% as the lower discharge boundary. Each of these cells weighs a little more than 100 pounds, so the whole bank of 24 batteries weighs about 2400 pounds (excluding the box), or slightly over a metric ton.

TRIPLE CHECK your connections before you connect your brand new battery bank to your inverter, you will seriously regret any mistakes that you may have made at this point. Lay out a path from battery to battery as you connect them and make real sure that you know what you are doing before adding the next cable to the string. Shorting out a bank this size is no picnic... Wear safety glasses at all times when working on your batteries, and when working with acid add an apron and gloves.

To reduce the risk of causing a short between terminals of adjacent batteries you can tape up a 1/2 " wrench, all but the very last bit. That way if you drop it the metal of the wrench is not going to be in contact with the terminals in more than one spot.