Is my battery goosed ?

superheat6k

superheat6k

Well-Known Member
Joined
10 Jan 2012
Messages
6,798
Location
South Coast
Visit site
Last week when returning from a weekend trip I forgot to plug in the shore power, but as normal left the fridge running on the domestic and port engine battery.

Today when I discovered my error the port was completely flat, the starboard was low but would still turn the engine.

After an hour or so on charge the battery had recovered sufficiently to start the engine.

How do I tell if I have goosed the the battery or if it will be OK the than waiting for it to go flat when least convenient ?
 
Fully charge it and do the usual checks.

There is no reason for it to be knackered just because it was flattened though. I've had a zillion batteries run flat on various things over the years, mostly with no ill effects, occasionally one refused to take a charge. Modern chargers will usually recover a flat battery now though.
 
Someone wil come alone and give you better advise then me , but till then , I would charge it fully and disconnect it from everything and leave it for some days five is good and check it , if it still holding the charge it's prob still good .
Other then that take it some where they can check it
 
Cross fingers, recharge fully and check if it holds a charge.
Generally, if you reduce a battery voltage to 10.5 or less it will have been terminally damaged.
The only way to find out is to recharge @ 13.5-14.4 volts until fully charged, leave it standing for 5-10 hrs then check the standing volts - if above 12.5v any damage is not terminal.
Without knowledge of battery/charger sizes it's difficult to give any times, but recharge is unlikely to take less than 4-6 hours.
 
superheat6k said:
Last week when returning from a weekend trip I forgot to plug in the shore power, but as normal left the fridge running on the domestic and port engine battery.

Today when I discovered my error the port was completely flat, the starboard was low but would still turn the engine.

After an hour or so on charge the battery had recovered sufficiently to start the engine.

How do I tell if I have goosed the the battery or if it will be OK the than waiting for it to go flat when least convenient ?
Click to expand...

It seems unusual to have appliances running off a start battery. Is it always like that or had you left a 12 both type switch in the wrong position?

Richard
 
charge fully. leave 12 hours. then connect a small load, such as a light bulb from a car. measure voltage with load connected. compare to soc vs volatge curves freely available on tinternetweb. (soc = state of charge). this is a fairly accurate method

or do same, but leave load on for several hours. then calculate the difference, and you can work out the battery's capacity now. it was a 100ah, but now its a 30ah. again, info available freely. try battery university.
 
RichardS said:
It seems unusual to have appliances running off a start battery. Is it always like that or had you left a 12 both type switch in the wrong position?

Richard
Click to expand...
As mentioned in reply 7, this is quite normal for twin engine boats to run the domestics from engine one bank. There is a starter solenoid used to parallel the batteries from the lone dedicated engine battery so it is still possible to start the second engine if you over do the power consumption.

I don't think the fridge has been off since I bought the boat, the charger simply floats the load from the shore supply, as long as you plug the lead in, of course.
 
RichardS said:
It seems unusual to have appliances running off a start battery. Is it always like that or had you left a 12 both type switch in the wrong position?

Richard
Click to expand...

Common, albeit less than ideal, practice with twin engined mobos Richard, one engine (typically Stb) has it's own battery and the port engine shares the domestic bank, usually with an emergency start parallel switch.

EDIT: must type faster :)
 
PaulRainbow said:
Common, albeit less than ideal, practice with twin engined mobos Richard, one engine (typically Stb) has it's own battery and the port engine shares the domestic bank, usually with an emergency start parallel switch.
Click to expand...

Why less than ideal?
 
I presume like most boats you have a battery bank. Which is only as good as its weakest link. Charge the batteries then disconnect all the batteries and occasionaly monitor their voltage of each battery over a few hours. You will probably find one weak battery, that would drag down the others, and that needs changing. I have eight batteries (2port eng, 2 stbd eng, 4 servises) and usualy end up changing one a year. The problem is that one failing battery drags down the others and can ruin them unles you issolate it early.
 
You must log in or register to reply here.

Share this page

Top