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[Doctor Gollum]

Just dug the battery out of the boot.

Showing less than 5v. Genuine Merc/Varta AGM battery, apparently made in December '22

I presume 7 months isn't a normal battery life expectancy.

I also presume that there's no point trying to charge it with a regular Helfrods battery charger...

[Sir Tigger KC]

Yeh give it a go!  What can possibly go wrong? 

[Marks DTM Calib]

Always go for a charge, nothing to lose, that said lead acid sulphates fast when discharged.

Might be a quiescent drain somewhere

[johnnydog]

I'd use a smart battery charger, not a traditional type, and set it to the reconditioning / repair setting which goes through a staged reconditioning cycle, rather than just blasting charge into it regardless. Depending on the reason for the low voltage, or how long it has been left in that condition, you may (possibly) recover it, but standing with a low state of charge doesn't do a battery any good.
But you must know this..
Depending obviously on where you sourced the car from, is there no redress from them?

[Andy B]

I'd use a smart battery charger, not a traditional type, and set it to the reconditioning / repair setting which goes through a staged reconditioning cycle, rather than just blasting charge into it regardless. Depending on the reason for the low voltage, or how long it has been left in that condition, you may (possibly) recover it, but standing with a low state of charge doesn't do a battery any good.
But you must know this..
Depending obviously on where you sourced the car from, is there no redress from them?

5 volts might be a bit too low for a smart charger to start charging, smart chargers generally need to 'see' a bit more voltage first.

[Doctor Gollum]

Always go for a charge, nothing to lose, that said lead acid sulphates fast when discharged.

Might be a quiescent drain somewhere

One thing at a time Car has barely done a whole 2,000 miles since January.

[Doctor Gollum]

I'd use a smart battery charger, not a traditional type, and set it to the reconditioning / repair setting which goes through a staged reconditioning cycle, rather than just blasting charge into it regardless. Depending on the reason for the low voltage, or how long it has been left in that condition, you may (possibly) recover it, but standing with a low state of charge doesn't do a battery any good.
But you must know this..
Depending obviously on where you sourced the car from, is there no redress from them?

I asked the question as it's the first AGM battery I have come across. Technically,it shouldn't have one fitted as it isn't a stop/start equipped car. And if I need to buy a smart charger to charge the incorrect battery in the car, I may as well buy the correct size/capacity battery.

Car was purchased in the knowledge that it might need a consumer battery, the surprise was what was fitted.

I know full well what sitting does to batteries having been through that with my Omegas and the newer Mercs have a reputation for higher current draws than might be expected, especially if left sat

[TheBoy]

IME, AGM batteries when well looked after do not last as long as non AGM, but you still expect 5+ years from them (if looked after)

As you know, any battery allowed to be deep discharged, or kept for long periods in semi discharged state will suffer permement damage that reduces their capacity.

Its rare to see these magical conditioners fix these issues, but if you already have a good charger with the function, and the batt is shagged anyway....

[Doctor Gollum]

IME, AGM batteries when well looked after do not last as long as non AGM, but you still expect 5+ years from them (if looked after)

As you know, any battery allowed to be deep discharged, or kept for long periods in semi discharged state will suffer permement damage that reduces their capacity.

Its rare to see these magical conditioners fix these issues, but if you already have a good charger with the function, and the batt is shagged anyway....

I don't and I presume it is

Will start with the correct battery and work through any gremlins from there

[johnnydog]

I'd use a smart battery charger, not a traditional type, and set it to the reconditioning / repair setting which goes through a staged reconditioning cycle, rather than just blasting charge into it regardless. Depending on the reason for the low voltage, or how long it has been left in that condition, you may (possibly) recover it, but standing with a low state of charge doesn't do a battery any good.
But you must know this..
Depending obviously on where you sourced the car from, is there no redress from them?

5 volts might be a bit too low for a smart charger to start charging, smart chargers generally need to 'see' a bit more voltage first.

That's true of smart chargers in a normal charge mode, but the recon / repair mode enables them to 'attempt' to go through the repair cycle on a very low voltage or a flat battery, unless of course it is totally goosed. Although in my experience once you have to start using this mode it is knackered anyway and needs replacing.

[Doctor Gollum]

Alternator is showing 14.56v across the front battery and 14.48 across the rear, so can only conclude that the battery is done.

[TheBoy]

Alternator is showing 14.56v across the front battery and 14.48 across the rear, so can only conclude that the battery is done.

Do you have facility to full charge the batt off the car?  Before you do the honourable thing and condem it completely.

[Doctor Gollum]

Alternator is showing 14.56v across the front battery and 14.48 across the rear, so can only conclude that the battery is done.

Do you have facility to full charge the batt off the car?  Before you do the honourable thing and condem it completely.

I do now

The Bosch S3013 currently fitted seems to have done the job

[Doctor Gollum]

Currently boiling away...

[Doctor Gollum]

Turned it off for the night, but has got it up to 11.4V.

See what it says in the morning