Battery's or altenator?

My challenge truck has 3 optima yellow battery's, befor I bought it, it had been left stood for 2 years,

I charged the battery's and I thought they were ok, used it once, left it for 2 weeks and they had dropped to 7 volts,

Jump started it and was ok loaded it up and it started when we got there ( was slow to crank tho)

Went to use my winch in anger and it just stopped, (8274 with ep9 motor) but the 1st outing I used it and it worked fine dragged me up a very steep hill after they had been charged,

How can I tell if there dead or if it a small output altenator ? It's running a split charge and last time I checked it was working,

If the batteries had been left 2 years without recharging, they are cream crackered.

Peter

I agree batterys are probobly fubar but best way to tell would be to test what the alternator is putting out with the engine running ,should be around 13.5 volts or slightly more

The alternator is charging but I'm not sure it's restoring the amps in the battery, amps and volts are to different things

If the battery is sulphated then the charging voltage will come up fairly quickly but the battery capacity will be low and it will not support the load from the starter.

Electrically the battery goes from being a low-impedance source to a high impedance source.

Peter

Optima yellow tops are a AGM battery of that makes a diffrence can be hard to charge when been dead I've read on Google

No difference, it's still a lead-acid battery and more susceptible to sulphation than a wet type.

I've got 225AH AGM batteries in the Mercedes conversion, 450AH worth, they are sitting on the solar panels on float charge until we need them.

Personally I wouldn't use a VRLA battery in a road vehicle, but can see the advantages for off-roading.

Peter

Peter

chrisstdt said:

I agree batterys are probobly fubar but best way to tell would be to test what the alternator is putting out with the engine running ,should be around 13.5 volts or slightly more

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13.5 volts is not enough for most modern batteries, 14.2 to 14.8 volts is the norm. The alternator would take days to fully charge those batteries whatever size of output. Alternators are constant voltage devices, the charge current drops off rapidly after the first few minutes.
There is a small chance you may recover those batteries with a decent charger. I've had Yuasa batteries that have not been touched for 2 years that recharged with no problem.

when you say it had dropped to 7 volts after two weeks, was that the starter battery or the batteries the other side of the split charge system.
It just seems unlikely to me that all three go at the same time, it seems more likely that one has gone and is dragging the others down with it.
Have you checked that there is no current draw when everything is switched off?

I've going to test to see if I have a draw,

Both the starting one and the aux's were flat, I've been abit busy and not had chance to look at it again yet,