Battery question from sailing novice

[Boxhamster]

Hi,


Was on a sailing trip with a mate, it's his boat. (70s "Mallorquina").


Did a whole day of sailing+motor, then spent a night in a bay. Next day late afternoon got ready, pulled out the anchor, got the motor running, but after a minute got a rope tangled into the propeller. After I got it free after a good 15min of cutting we wanted to get the motor running again, but it wouldn't start any more.
Checked everything, but the starter had no power and just cranked for a weak half second with very little output. The batteries were on 100% (engine) and 80% (auxiliary).

After a lot of troubleshooting, calling some of his friends and trying both batteries individually we figured out that the switch allows you to also combine the batteries and the motor started. (no idea why my mate didn't think of that earlier since it's his boat...).


Anyway, I've been doing some research on batteries today. The batteries he tells me are 2.5yrs old and this type: https://www.eurobateria.es/epages/63...ucts%2FBTVARG3


Below a picture also:



Is what I described normal? Is it to be expected after only 2.5yrs that batteries give out? He was on this sailing trip for a week already, so they had some use. Or are they the wrong type? From what I see they're for cranking anyway, so should do that good at least.

Thanks for any input.

[Stu Jackson]

A friend of mine just told me a similar story.


He wouldn't listen to my simple advice, so he spent a week going down rabbit holes with no success.


When he final cleaned the terminals on his battery posts, his engine started, right away!!!

[George_SD]

1) Batteries can degrade, especially if not maintained properly
2) this appears to be a car batter, which is OK for starting the engine, but not ideal for "house" loads (electronics, fridge, etc).
3) This looks pretty messy and is potentially not up to regulations. More importantly, you may have parasitic draw from loads connected directly to the battery and bypassing switches/fuses.


Good luck

[Be Free]

Looking at the picture I'd suspect a bad connection on the engine battery. I can see the negative cable on the engine battery and it looks like the clamp has been over-tightened (perhaps they used a positive clamp) and that style adds an additional connection that could easily loosen or develop corrosion. The positive connection is not visible but it is likely the same type.


There is definitely at least one load on the engine battery regardless of the switch position. The power for the shut (on the positive house terminal??) is wired directly to the engine battery. It's not much of a load but it is there.


The OP states that the engine battery was "100%" and the house battery was "80%". Since I don't see a shunt on the engine battery I suspect that its state was determined by voltage and the house battery via a battery monitor connected to the shunt.



I can't really see if the negative cables are connected to a common bus but they would have to be to combine the batteries for starting. Is that cable coming off the engine battery going to a bus or is going back to the engine?



Too many questions to diagnose exactly, but my money is on a bad connection on either of the engine battery terminals. One of them is loose or corroded. If I had to guess, I'd go for the negative post.

[Tetepare]

What’s the water level in the batteries?

That’s a rats nest.

[Boxhamster]

Thank you all for the input! This is highly appreciated.
I'd also say that the auxiliary battery should be a different type of battery for deep charging and not the same type. That I had noticed.
We'll do some figuring out once the boat is back from the trip and will get back here.