Battery Types

In this post I'm only going to talk about lead-acid batteries. These are the big heavy batteries you'd typically find in your car.

There are a few different types of lead acid batteries which I'll discuss, however there are other types of batteries like LiFePo4 which I'm going to ignore because they are super expensive in South Africa at the moment. Hopefully in a couple years they will become viable, or let me know if you beg to differ.

So... Of the lead acids you firstly get high cycle and deep cycle batteries. High cycle would be a car battery where you want to draw a lot of power in short bursts with long intervals in between. Deep cycle batteries are used with inverters, where you want to draw a moderate amount of power for extended periods of time.

The next thing to choose is between flooded and sealed batteries. Lead acid batteries can be charged quite quickly at a high voltage, but this has a side effect of releasing hydrogen gas, which isn't a great thing to have in your garage. If gassing occurs you will need to top up the battery 'water', which is only possible in a flooded battery. Sealed batteries tend to last longer but only if you're careful not to overcharge them.

There are then two common types of sealed lead acids
AGM stands for absorbent glass mat: The battery acid lives in a fibreglass mat between the battery electrode plates. This keeps the electrodes covered in electrolyte nicely, but the whole thing is still pretty similar to a flooded lead acid battery.

Gel: The acid is a thick paste instead of a liquid. These batteries can't deliver as much current in one go, but they perform better under deep cycle, ie when most of the power is drained out. These batteries are more expensive, and last a bit longer before the electrodes wear out.