How important is it to use the right ampere-hour charger for the ampere-hour of the battery?What is the min. and max ampere-hour charger you would use for a 600 ampere-hour battery and a 840 ampere-hour battery?
Well you will need a 10 Amp or 14 Amp charger for your two batteries. I would make sure the transformer in the charger can handle at least 20 Amps and then it will never fail. Well maybe if the battery is almost flat. The higher the current that you need to charge the battery the higher the rated current of your transformer. If you draw more Amps than the transformer is rated for it will overhead and the transformer will fail. I make sure that there is always plenty extra power available and then it lasts for years.
