alexyoung91:
@PeterH - how can i limit the current going to the batteries? If this motor is spinning fast enough to achieve a charging voltage of say 15v again, surely a fixed current will be produced thats charging them? Do you know the maximum voltage you can charge lead-acids at? Also is it possible to charge them at lower voltages, i assume that because its still electrons flowing into the battery, what difference does the charging voltage make?O_o
If it's a 12V lead acid battery battery it'll be happy for you to hold it indefinitely at 13-14V. The amount of current needed to achieve that will vary depending on the state of charge. I suggest you also control the discharge to prevent the battery from being fully discharged below around 11V to prevent damaging the plates, this will also avoid it taking a massive current when you connect the charger. It will still take a high current, though, easily 100A for a single battery and correspondingly more if it's in a bank, so in practical terms the current will probably be limited by your generator being dragged down by the load of the battery.