How to test remaining battery life?

[spagatti]

I was wondering if there is a way to test how much battery life you have left on a 36 volt system after a day on the water? I have a 12 volt smart charger that does tell me how much battery life is left on a single 12 volt battery. But my on board 3 battery charger does not indicate how much life is left after a day on the water.
Could I just hook the smart charger to one of the batteries in the 36 volt system and since those batteries all draw at the same level, my reading on one battery will be for all three? Wasn't sure if this would be accurate or damage something since the batteries are all connected...although the on board charger does charge this way.
Any advice would be appreciated. I would like to know how much juice I have left...have not had an issue yet, but seeing an actual percentage of life left is knowledge I would not mind having.

 

[fish devil]

:twisted: I would check them individually to get the most accurate reading.

 

[JMichael]

If all 3 batteries in your system are the same age and size, the method you listed would give you a good idea about how much was left in them but like Fish Devil said, checking each one individually will be more accurate. And checking them individually, could help spot any potential problems with one of your batteries before it ruins a day of fishing.

 

[spagatti]

Thanks guys. I will check them all individually...wanted to make sure I didn't harm them or get an inaccurate reading since they are all connected. But the on board charger is rigged this way so I should have figured it would work.