Battery question

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julians

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can a battery go from being able to start an engine just fine, to not being able to even turn it over 12 hours later, without anything draining it in those 12 hours? Ie is it possible for a battery to fail overnight?

Ive been out in majorca over the weekend, using the boat as usual. For the first 3 days the boat has been starting on the button no problem, but then on day 4 when i went to start the engine there was not enough power in the battery to turn it over, i had to link up to the service battery to start the engine.

Once started we ran for an hour or two,then turned off the engine, then immediately tried to restart using the engine starting battery only, and again it wouldnt turn over at all. Linking up to the service battery enabled me to start the engine. It seems the engine starting battery has just died overnight. Voltage from the alternator looks good.

For background the boat has a single engine,and two batteries,one is purely used for starting the engine, the other is used for powering the accesories (fridge etc) , i have a switch that enables me to link the batteries together to start the engine (or power the accessories) if one battery fails. Normally i keep the batteries separated. Both batteries are approx 5 years old, and are connected to a mastervolt charger when to boat is left for any period longer than a few days.
 
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simonfraser said:
'Once started we ran for an hour or two,then turned off the engine, then immediately tried to restart using the engine starting battery only, and again it wouldnt turn over at all'

you sure the engine starting battery is being charged ?
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Yeah thats the concern i have, hence the question - isit possible for a battery to fail over night? Or is it more likely that i have a charging problem?

i can see on the guages that the alt is putting out the correct voltage,but not sure if that voltage is reaching the engine battery.
 
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Got a full set of tools including multimeter on the boat for emergencies , this was not an emergency and i dont have the time to go diagnosing problems when on family holiday, especially when were only there for 4 days.

Anyone know the answer to my original question- do/can batteries fail over night?
 
julians said:
Got a full set of tools including multimeter on the boat for emergencies , this was not an emergency and i dont have the time to go diagnosing problems when on family holiday, especially when were only there for 4 days.

Anyone know the answer to my original question- do/can batteries fail over night?
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This sounds unlikely, although I suppose it’s possible that something broke internally to cause a short, or poor current delivery.
Could it be that something drained the battery overnight?
 
"Could it be that something drained the battery overnight?"

I switch off the batteries every night with the big red key, so they 'should' be completely disconnected , but who knows.
 
julians said:
Got a full set of tools including multimeter on the boat for emergencies , this was not an emergency and i dont have the time to go diagnosing problems when on family holiday, especially when were only there for 4 days.

Anyone know the answer to my original question- do/can batteries fail over night?
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Yes they can but in 50+ years of car ownership I have only had it happen once. Absolutely fine one evening. Dead as a Dodo next morning and no response to a mornings worth of charging.
 
VicS said:
Yes they can but in 50+ years of car ownership I have only had it happen once. Absolutely fine one evening. Dead as a Dodo next morning and no response to a mornings worth of charging.
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Thanks, Thats exactly what im seeing in this case. Hopefully its just a dead battery and nothing more serious.
 
Experienced a similar situation last week while in Netherlands. In our case all batteries ( 4x85 amphr in 2 banks) were fully charged and no loss found between the battery terminals or pos leads to the master switch. Swapped the master switch feeder leads over just in case one lead was only carrying a small current but not the cranking load. No problems indicated except the original issue.
By this time all electrics were exposed and on re-trying a start with the troublesome battery bank smoke was seen coming from the neg common block. Closer inspection revealed the terminal crimp on the battery bank neg to common neg block was poorly done and the copper cable could move in the terminal resulting in the cable only carrying light loads to and from that bank.
Happy to say swift application of the Mole grips and brute force seems to have solved the problem. Having stop\started our way back through south Holland canal system we have returned to the home mooring without further issues. However a new lead will be made ready and carried on board in case of a relapse before the end of season layup service.
Hope this may help.
 
Is it an "Off,1,2,Both" switch you use to select / link the batteries, they are know to go faulty.
You say you switch off overnight then no go next day, this could point to a faulty switch.
I assume you checked the level of the starter battery recently if its not a sealed type? A dry/low level battery is not going to hold much charge,
 
VicS said:
Yes they can but in 50+ years of car ownership I have only had it happen once. Absolutely fine one evening. Dead as a Dodo next morning and no response to a mornings worth of charging.
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Croftie said:
Is it an "Off,1,2,Both" switch you use to select / link the batteries, they are know to go faulty.
You say you switch off overnight then no go next day, this could point to a faulty switch.
I assume you checked the level of the starter battery recently if its not a sealed type? A dry/low level battery is not going to hold much charge,
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No,its not that type of switch , there are three seperate removable 'keys', first one switches on engine battery , second one switches on service battery, third one links them together.

Theyre sealed batteries.
 
As WFA infers before going into the why's and wherefores - you really need to check the connections.

They ( assuming proper connects ) normally decay slowly,
It turns over slower , takes just a tad longer to fire up .
Unless as JTB infers there’s been a drain ( bilge pumps ) - cos they weren’t,t on when you arrived how do you know they have not been reving there nuts off all night ?
Or alternatively some water shorting across the elecrodes ? Or as said a loose connect .

Having eliminated all the above the answer to your Q is YES .
Heat not being helpful in killing them off and @ 5 y - replace them as a service item .
Bentley and Ferrari replace @3 y as a service item ——— or what ? Wait until erh —- punters car arrives on a flat bed ? - ain’t gonna happen .
 
I would test the batteries first, check the voltage when the engine has run and they are fully charged, check the voltages an hour later and see if a battery had dropped, repeat this an hour later.

Check the isolators are actually switching off as it is not uncommon for them to arc across the contacts and keep a continual circuit and battery drain as the arcing between the terminals can actually do this.

Most likely a dodgy cell and once one goes it quickly becomes two or three cells as the others have to work so much harder.
 
VicS said:
Yes they can but in 50+ years of car ownership I have only had it happen once. Absolutely fine one evening. Dead as a Dodo next morning and no response to a mornings worth of charging.
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+1, but in just 30 years of ownership.

In my case it was just a few hours after starting the diesel car perfectly well in the morning, a few hours later, dead as a dodo.
I didn't believe the diagnosis until the new battery had been in a few days and was still starting without issue.
 
I have never had one go overnight. I have flattened one on a cruise and because it was on 10V the alternator would not excite to charge it...? Not 100% sure on that last... either way the battery was dead, not charging, and trying to fast charge it from a cheapo battery charger led from one fault to another and cost me a new alternator too. Still havent worked that one out either as both just got replaced. What killed it I believe was a slow shorting bilge pump +ve lead and a small amount of salt water in the bilge creating a circuit.

Edit: if not overnight at least in the couple days I was on anchor)
 
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