Quote Originally Posted by IBNFSHN View Post
Well you are partially right. You don't get a spike from a battery. The trolling motor can cause surges in the way of start current and stall current. (and there is a difference between a spike and a surge) A battery doesn't produce anything, it stores it. A marine battery that measure 12.5 volts is 90% discharged. 12.6-12.7 volts, depending on the temperature, is fully charged. These are not my theories, its what the manufactures tell me.
Thats pretty much what I was saying. As far as the voltage of a fully charged battery that will up for debate. The industry standard is 12.5 (not much difference in that and 12.7) whereas some think a battery that has 12.1 volts in fully charged when it is partially discharged. I don't agree that 12.5 volts of a 12.6 volts battery is 90 percent charged. .1 volt being 10 percent???? That would mean a battery that has 11.6 volts would be dead and deep cycle batteries are meant to be depleated to a point. I have run deep cycle batteries down to 5 volts just about everytime fishing so with that percentage standard I should have already been back home. The percentage should be left out of it as every battery will be different in terms of reserve. I just wouldn't assign a deep cycle battery voltage a percentage. It would be better to keep up with your battery voltage and know how long you can run your equipment.