Golf Cart Charger

Looks like fun stuff.
Now, using car batteries is gonna continue to be a problem. Not only are you putting loads on them they are not designed for, but you are actually charging them wrong. Lead acid batteries are 2.2 volts per cell. They are charged at 2.4 volts per cell and their charge current varies depending on the design. Car batteries are actually designed to be hard charged at high current for a short time. Similar to the way they are discharged. with what you are doing, you are putting a varying load on them for longer intervals and discharging them beyond their design. A car battery should never be discharged below 2.0 volts per cell. When you do this, you loose up to 20% of the capacity of the battery. The 20% part happens when you get it down below 1.85 volts i believe, but you can look it up. Now, this applies to deep cycle batteries as well. Hence the reason that they run 6 volt batteries. Because each cell has it's own capacity it the cells in a 6 volt (3 cells instead of 6 cells) each cell has greater individual capacity. This means it takes longer at the same current draw to drop the cell voltage down to a discharged state. Now of course as mentioned above, over charging is as bad as under charging. What overcharging does is creates sulfides in the battery. The sulfides which are mildly conductive leach to the bottom of the battery and short out the individual cells. This is one way that you can get a battery to suddenly have 10 or 11 volts coming out of it and no way to get it to charge beyond that voltage. And once it occurs, the other cells in the battery now have additional charge voltage across them because one cell is shorted out and the rest of the battery quickly sulfides up and dies.

So as far as the car battery being cheaper. Not really. If you have to replace the batteries every 6 months and it costs 150 to do it. And the proper batteries cost $500 but you only need to replace them every 5 years, it's not really cheaper.
 
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