Battery selection is key for any electric car conversion, in order to get the most efficiency. You can’t use just ordinary starter batteries, like what’s in your gas powered car right now. They are not designed for long high current discharges. Deep cycle batteries are the type you will need to use,as they can put out high current for an extended amount of time. The most used battery for an electric car is the lead acid battery, which breaks down into three major types.
The Flooded or “wet” cell is by far the most available lead acid battery. If they are the type with removable caps, then you have to periodically check and refill the cells. All batteries will produce hydrogen and oxygen when recharging, and you will lose a certain amount of water during this process unless the battery is of the sealed type ( maintenance free) The benefits of using this type of battery is usually the cost, they are the least expensive. They are also less sensitive to overcharging as compared to the other types of cells. However they can also be prone to collecting deposits on the plates if they are left in a discharged state for extended periods. This is called sulphanation, due to the sulphate crystal deposits that can form on the plates. There are devices known as”desulphators” which as their name implies can eliminate the deposits and basically rejuvenate an old battery back to usable condition. The flooded battery must also be kept charged up. A deep discharge without a quick recharge will cause the battery to lose its capacity. Flooded cells will perform best if the discharge is kept to only about 50 saturation. Sometimes called “starved electrolyte” since the mat is not fully saturated, these batteries will not leak even if the case is broken. This is particularly good because of their non-hazardous status, the cost to ship them is lower. Also since there is no liquid electrolyte to freeze and expand, they are immune from being damaged due to freezing weather. Most all AGM batteries are 99 to 3% per month) so they can sit idle with no charging for extended periods, unlike typical flooded batteries. the only downside to this type of battery is the cost. They will typically cost 2-3 times more than your conventional flooded type.
Your choice of the electric car conversion whether it is DC or AC, is going to be the deciding factor in your battery choice. If you choose to do a DC conversion you will want to use the 6 volt battery to make up your battery pack, simply because they provide the most amps for the size and weight. If you go with an AC conversion, you will want to use the 12 volt battery, as you need the extra voltage to make up the higher voltage requirement of the
controller. Which ever voltage type you choose, the flooded lead acid is the best choice from a cost/power ratio. As battery technology continues to
progress however, you could soon see the day when AGM batteries becomes as cost effective as the traditional flooded lead acid battery.