DF 70 electrical charging problem

I been having an on going problem for about the last 5 or 6 trips now. I have a 2 battery system and after a days or even half days fishing the batteries are almost drained when I return to dock. I've checked the batteries before I start the outboard (both at 12.7v) and after I start (both at 14.7v) after I throttle up a little in neutral, they test at 14.4v. When I return to dock one battery is so low it will not turn the engine over. I have little to no other electronics on the boat, fm radio, running light, bilge pump which I did not even use the last trip out. Could this be an open ground problem? My main wire from the outboard engine, a 70 hp Suzuki has a splice in it before it goes under and thru the bilge on its way to the center console where the battery selector and batteries are located. Could this splice or a bad spot in the negative leg of this cable be causing the problem? It seems like an intermittent problem when compared with the test readings I am getting at the dock. Driving me crazy!

Re: DF 70 electrical charging problem

Where are you getting the voltage readings?
At the batteries them selves?
or some where else?
Sounds like motor charging system is doing its thing but batteries are not receiving it

Re: DF 70 electrical charging problem

I am getting the reading at both batteries themselves, and both batteries are brand new as I purchased them when this problem first appeared, to take them out of the equation. My question is can a corroded ground line alone cause this problem. If that is the case I will try and replace the entire line.

Re: DF 70 electrical charging problem

If you are measuring the voltage at the batteries and you get 14+ volts then the batteries should be charging. You can test voltage drop at different spots and connections on system to see if there is a high resistance connection or cable.