Help please - battery 1 shows 12.5 V but won't turn engine.

[Danny Jo]

Help please - battery 1 shows 12.5 V but won\'t turn engine.

Someone will no doubt tell me I did it wrong, but I drained my engine oil while the engine (Perkins Perama 29 hp) was still hot, but before I had secured a supply of fresh oil. So I went back a fortnight later, fitted new oil filter, added the necessary amount of oil, and turned the engine over (without starting it) on the service batteries (actually both battery 2 and battery 1), to pump the oil around. So far so good.

Then I thought, perhaps I ought to check that battery 1 was capable of doing what it was installed to do, act as an emergency starter battery. Battery 1 was showing 12.5 V (Mastervolt battery management system) but would not turn the engine. I noticed as I turned the key to first position (normal running) the ignition and oil pressure warning lights came on nice and bright, but they faded a little at the next, pre-heat position, and died altogether in the start position. At the same time the Mastervolt reading flashed "E".

My conclusion is that I must have a dodgy connection which can handle only a very low current. Has anyone got any thoughts on the most efficient way to troubleshoot this? The photo (edit - higher resolution version) below shows battery 1 fitted forward of, and slightly lower than the three batteries that make up battery 2. The back of the main switch is somewhere in the region of the bottom right of the photo. The batteries are gel type, dating from 2002, I think. I did a partial drop test of "battery 2" in April, aborting it at 160 Ah by which time the voltage had dropped to 11.5 V.

 

[fireball]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

The simple test would be to take off the connections, clean up and reconnect - test again.
If that still doesn't work then you can place another known good battery in it's place - that will test the battery1 wiring.
If it is the wiring then it is a case of tracing the wiring to the various locations (probably just switch 1 in this case), first reseating the connections and then bypassing them.
It is also possible that the switch for battery1 is duff - you could prove this by bypassing the switch.

 

[Pye_End]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

Voltage testing is not always a reliable way of knowing whether a battery is alive or not. It is a useful initial indicator only.

If you can get at the cells (can't quite make out from the photo) then always worth a go with a hydrometer before you start resorting to load tests etc.

Drop test - if you mean flatten the battery and seeing how long it lasts - not a good idea unless you only drop it by 50% from a fully charged battery as you can destroy it just by testing it.

 

[StanFolds]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

From the picture it looks to me as if the cable to battery 1 is much thinner than those to battery 2, it could well be that the thin wires aren't capable of taking the current to the starter. I would change them to the same size that you have on battery 2.
Edit, I have just noticed the cables running to the bottom of the picture so please ignore the above. /forums/images/graemlins/blush.gif. You can test the switches by swapping the connections between batteries but cleaning the connections including the battery posts is the most probable cause.
Stan

 

[VicS]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

I agree clean up all the connections, on the heavy wiring that carries the starter current at least, negatives and engine "earth" included

12.5volts would not be a particularly good reading for a conventional battery after resting for say 12 hours and I would not expect a very lively performance by the starter at that. but i am not sure what to expect with gels. It certainly would be useless if the battrey had just come off charging.

To otherwise check the connections, and it could be one or more of the crimps or the battery isolating switch itself, you really need to put a fair sized load on the system and then check along the system with a sensitive voltmeter looking for voltage drops across connections or components. Less tedious IMO to clean up and tighten all the connections first and only resort to checking for volts drops if that fails.

BUT before you go much further connect the voltmeter directly to the battery posts and see just how far the reading falls when you try to operate the starter. If it falls below about 9.5 then get the battery charged and tested.

TIP clean battery posts etc with a nylon Scotchbrite type of pot scourer. it removes the crud without taking off metal. Lightly coat with Vaseline after re-making the connections

 

[FullCircle]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

Sounds very like you have a corroded cable which will carry the voltage but not the current.
Check the cables to see if they have corroded under the insulation, as they may not be tinned marine grade. It will be black and 'orrid looking. Only need to strip a bit back to know.

I had this last year on a Fulmar Nav light. Showing 12.5v at the multimeter, but would not light the bulb. Changed the cable, end of story.

 

[Birdseye]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

Try the battery and then with some care feel along the wiring circuit to see if any particular point has got hot. If it has, then thats where your bad conncetion is.

If nowhere is getting hot, then the battery may well have developed a high internal resistance.

 

[Danny Jo]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

Thanks everyone. I'm off to the boat to have a go with the Scotchbrite and Vaseline. Now where the hell's my multimeter?

 

[TheBoatman]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

Not sure if this will help but I had a similar problem just recently and it turned out to be a bad "internal" connection in the battery switch. The switch was capable of carrying 12.5v at low amps but as soon as it had to carry starting amperage it quit.
I intend to change the switch this winter but to overcome the immediate problem I sprayed some WD40 down the key hole and operated the switch a good few times - that did the trick and the engine started OK.

I would advise checking all the connections and then finally check the battery itself.

Peter.

 

[duncan]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

as others have said it could be a number of things so it's important to isolate the area first then the exact cause as Fireball and others highlight.

whilst I don't think it's related to the recent oil change I wouldn't rule out possible loose connection caused when removing the oil filter too............ie most problems are caused rather than occur! however my money would be on the battery switch

 

[Danny Jo]

Sorted - embarrassingly simply

I think I must have been intimidated by all those wires. With confidence boosted by your advice, I started with the battery connections. The very first one I tried was loose. The nut holding the three leads on the positive terminal was no more than finger tight, in spite of a split lock washer. I don't think the nut had worked loose, just that the terminals on the two smaller leads had worked their way down into the larger hole of the terminal on the main lead - there was no suitable washer to prevent that. With the benefit of hindsight, you might be able to persuade yourself that you can see what I mean in a blow-up of the original of the picture I posted, which was taken in October 2005.

Thanks again for the help.

 

[mikejames]

Re: Help please - battery 1 shows 12.5 V but won\'t turn engine.

Did you leave the battery bank discharged recently ?
Once a gel battery goes flat it has to be recharged pretty instantly or it will get sulphated up. This effect is quicker than with wet cells and certainly more financially distressing.

As you have three batteries in parallel you might only have been seeing only one working one with a correct voltage : this also may be somewhat knackered and unable to start the engine : this was how my last killing of a gel battery went : left the VHF on on a small two battery system with a 1-2-both switch in the wrong place and came back too late. Recharged the flat battery back to over 12 volts but it couldnt deliver any current any more.

 

[VicS]

Re: Sorted - embarrassingly simply

[ QUOTE ]

[/ QUOTE ] That is just the sort of bodge that is going to give you troubles.
The terminal on the big lead is the wrong size for the stud it is fitted on, That terminal sholud be changed so that it is the correct size for the stud .

 

[TheBoatman]

Re: Sorted - embarrassingly simply

[ QUOTE ]
That is just the sort of bodge that is going to give you troubles.

[/ QUOTE ]

Vic I do hate it when posters mince there words /forums/images/graemlins/wink.gif

Peter.

 

[Danny Jo]

Re: Sorted - embarrassingly simply

[ QUOTE ]
The terminal on the big lead is the wrong size for the stud it is fitted on, That terminal sholud be changed so that it is the correct size for the stud.

[/ QUOTE ]
The base onto which it's clamped is big enough, so I settled for a big fat washer that was the right size for the stud. But there is much the same setup on the other 7 heavy duty terminals, so maybe I should pursue your suggestion. Is it difficult to get new terminals fitted to the leads?

 

[VicS]

Re: Sorted - embarrassingly simply

[ QUOTE ]
Is it difficult to get new terminals fitted to the leads?

[/ QUOTE ] Should be possible to get them done by a good Auto electrician and many others as well. It'll need a heavy duty crimping tool but if you can beg, borrow, steal or even hire one you could do it yourself.

Personally I would crimp and solder but there are strong arguments against soldering.

[ QUOTE ]
Vic I do hate it when posters mince there words

[/ QUOTE ] You mean "their words".

You have a dig at me and I'll have one back! /forums/images/graemlins/grin.gif