Keeps on dying

[BB']

I'm having an issue with my cranking/electronics battery not holding a charge. At first I thought the battery was undersized for the load I was putting on it so I upgraded from a group 24 to a group 31 battery and had the same issue (battery would not last a day on the water running electronics and starting motor). So I decided to dedicate the group 31 battery for my cranking battery and add another for my electronics. Electronics are running like a champ with no issues but cranking battery continues to die? I have something on my motor draining my battery while on the water and while stored. What could be pulling power on my motor causing the battery to drain? I have a 2014 Nitro Z7 Sport with a Mercury 150 fourstroke. The batteries are both brand new Interstate group 31's. Any thoughts, comments, or suggestions would be greatly appreciated. Thanks and God bless!

[2500]

Do you have battery disconnect? When off water, ECM stays live. On water it sounds like a trim motor ground. And pulling voltage

Make sure the cranking is fully or true charged up. Then run it. It could be your battery is half or less charged and the running time is not enough to charge back full. And when off water it drains to a low voltage and is enough to crank boat.

Make sure all connections are tight and also make sure the ignition switch is not going bad

Look at auto bilge and bilge pump to make sure not on and lights courtesy and such can drain quickly

[BB']

Thanks for the info! I'm away for work now but I will definitely take a look at the things you mentioned and hopefully come find a solution!

[rickdb1]

Are you sure your motor is charging the starting battery?

[BB']

according to the volt meter at the helm it is charging (while running) at 13 volts give or take a little......but even if i fully charge the battery at home it will die in a matter of days with no use just being stored. I ordered a battery disconnect and will be installing that to help but was just trying see if i could find the actual problem causing it to drain

[tdt91]

It's nice to have the disconnect switch but that is a band aid. You are correct, you need to find the problem. Try charging the battery and check it to make sure it's charged. Then disconnect it completely and check after a few days to see if it has drained a bunch like you say it does. Remember that NEMA is always drawing too unless it's switched. Even so I don't think it would drain it that much.
It could be your charger. I have a portable charger that will tell me what percent it's charged or at what volts it's at just by pushing a button. I use it when I'm trying to figure this kind of stuff out. Did you put the new battery on the motor or did you keep the older one on the motor. Check the water level in the batteries too if they are not sealed.

[BB']

Thanks for the info.....I just installed a Genius mini on board charger a couple of months ago. i haven't had any issues with the other batteries not charging and when i pulled it off of charge last time the charger showed battery was full and volt meter reading of 12.8 confirmed. i tried both batteries on the motor and had the same results....thats why i assume it is something with the motor drawing the battery down but wasnt sure where to start. They batteries are not sealed and water level is about 3/4 full on both.

[tdt91]

What Amps for each bank does that charger put out. Generally a good fully charged battery will show over 13 volts when freshly charged.
3/4 full don't mean much, your plates need to be covered with water.

[BB']

Each bank puts out 4 amps. Sorry for the poor description for the water level in the battery....the water is over the plates...when you pop the cap off the water level is about 3/4 from the opening at the top.

[2500]

Each bank puts out 4 amps. Sorry for the poor description for the water level in the battery....the water is over the plates...when you pop the cap off the water level is about 3/4 from the opening at the top.

Go to a Napa or automotive parts place get the 1/2 gallon wet cell battery fill jug, get couple gallons of distilled water, and its quick automatically fills and stops correct level. If you have wet cells

[Justfishing]

Take a multimeter/volt ohm meter. Set it for 12 volt amperage. Disconnect one post of the battery and touch it to the battery and cable. See how much draw you have. From there start pulling fuses or disconnecting accessories and note the change in the draw. Hopefully you have everything set up that you can have the engine isolated from all the other draws.

[EuropeanAM]

Lots of info above, some better than others.

A couple notes and suggestions:

- ECM/PCM does NOT stay live overnight. It has a time-out and powers down completely.

- LOAD TEST CRANKING BATTERY. Provide results.

- TEST VOLTAGE AT THE BATTERY: Before Starting, and 5 Minutes after starting engine. Provide Results.