Batteries & Charging
A brief overview of the different types of batteries that may be used in solar electric and backup power systems. The common automobile batteries in which the electrodes are grids of metallic lead-containing lead oxides that change in composition during charging and discharging.
An MPPT, or maximum power point tracker is an electronic DC to DC converter that optimizes the match between the solar array (PV panels), and the battery bank or utility grid. To put it simply, they convert a higher voltage DC output from solar panels (and a few wind generators) down to the lower voltage needed to charge batteries.
A charge controller or charge regulator is basically a voltage and/or current regulator to keep batteries from overcharging. It regulates the voltage and current coming from the solar panels going to the battery. Most "12 volt" panels put out about 16 to 20 volts, so if there is no regulation the batteries will be damaged from overcharging.
Lithium batteries stand apart from other battery chemistries due to their high energy density and low cost per cycle. However, "lithium battery" is an ambiguous term. There are about six common chemistries of lithium batteries, all with their own unique advantages and disadvantages.
Absorbed Glass Mat batteries are constructed differently than the traditional flooded battery. This write-up covers mainly the Concorde Sun-Xtender AGM's, but also applies to most other brands of deep cycle AGM batteries.
There is more to comparing batteries than just cost or amp-hour ratings. For example, based only on cost, the Concorde AGM's do not look so good. On the other hand, you probably would not want to store a flooded battery in your computer room. There is no one best battery for all applications.
An extensive dictionary of battery terms and usage. Also, see our glossary of solar terms and usage.