Engine batt doesn't hold charge

[SeatoSky]

Maybe someone can help me resolve an engine battery issue that’s dogged me since buying my 2017 CB30: it’s never held a charge for more than a few hours at anchor so I always used parallel. The excellent Garrett at Port Boat House gave me a $250 credit towards a new battery I added another $150 to get a 1298Ah DEEP CYCLE 950 CCA – ROLLS, installed in Dec 2019. It was okay for about 6 months reading around 12.9 before starting, then began to weaken. Readings this summer were 12.4 then it dropped to 9.4 then 8.8. This last week it went up to 12.8 so I tried without parallel and after one failed turn I got an EVC warning with no code. Back to parallel. We absolutely minimize any use of house batts overnight and take a deep breath every time I press Start.

Any advice on this would be really appreciated.

 

[Bruce Moore]

Bumping post delayed in moderation queue.

 

[Levitation]

You have a parasitic drain on the engine battery. Voltage measurements will be of little/no help here.
You are going to need some help from someone with experience with boat/airplane/truck/tractor/whatever charging systems. (he does not need to be a boat mechanic specifically)
Some experienced help (necessary)

Isolate the engine battery from everything and charge it for 24 hours
Let it set, disconnected completely, and check the voltage 3 times a day for a day or three. (it may be toast by now from your description), and self discharging from a shorted cell(s)

Unhook the Blue Seas relay from the engine battery
Measure the resistance of the + alternator battery lead (to ground, this will be "back" through the alternator)
Measure the resistance of any lead that is connected to the engine battery (ignoring for now the connection to the house batteries) This will be "forward" through the loads the engine battery may be feeding when the engine is off.

I am not going to write some 10K plus words here on how to trace down any parasitic drain. Get some help.

GL

 

[knotflying]

Following up on Denny's post. Make sure the only connections to the battery are engine related. Hence you should not be getting any parasitic draw. The other thing is to remember to have your engine turned off. I am not sure of your ignition setup, key or FOB? With the switch on you will get a draw and that will definitely drain the battery. As Denny said, if you have done that several times you may have killed the battery. So charge it and let it rest and see what happens.

 

[Ralf H]

Hi Seatosky,

To back up the previous posts, you apparently have parasitic drain on your battery. The most obvious being if you leave the engine power switched on at the dash when not running the engine. That will draw down the battery over time. If this continues, the battery will lose effectiveness over time. Check that first, then move on to other issues as mentioned earlier. Hope this helps.

Cheers,

Ralf

 

[Bobby P.]

I have a 2017 31 RT. Had the same problem. I realized that the solenoid for the propane stove was linked to the starter battery and I didn't know to shut that off when not in use. When on, it draws a lot of juice.
Hope that this easy fix fits your situation.
Bobby

 

[SeatoSky]

Thanks everyone, this really helps narrow the issue down. I always switch engine power off at the dash when not running so that's the first one crossed off. Next to your solenoid suggestion Bobby - fingers crossed - and if that doesn't fix it at least I'll be able to ask for professional assistance with a more sophisticated idea of what's going on.
Will post the upshot and meanwhile appreciate all the suggestions.