What chance does a stone dead battery have

[baldsparky]

Sorry for all these questions guys.
As you may be aware I'm having battery drain problems which appeasr to relate to the alarm horn (other posts cover that)
The battery is dated 24-03-13 so not very old.
My problem is that the offending electrical drain took the battery down to a point where it wont unlock doors or bring up the dash lights.
The alarm led on the dash switch was flashing but that was it.
So can a stone dead battery revive and how long should i leave it charging. Its an OEM Merc battery 100 ah.
Many thanks

 

[Ted]

It should revive even if it was totally flat.
You may find that some modern chargers will not start charging at this level, as they need a small voltage to 'kickstart' them - I think that it may be to determine if the polarity is correct - you can get over this by connecting another battery in parallel for a minute.
Personally I would trickle charge it at around an amp - this will take over four days to fully charge but I think you would regain most, if not all of its capacity.
If this isn't feasible, whack it on charge at around four amps for a day and refit it. Over time, much of the capacity will be recovered.

 

[Spinal]

How long has it been discharged? That will play a crucial role.

I've brought back batteries from "dead" many times, the worst having been "flat" for almost a year and badly sulphated. I checked the water was full, added some battery conditioning tablets and put it on an optimate charger (which has a desulphate option).

Left it a few weeks (didn't really need it, was more of a "let's see what happens") before checking it again. Optimate by that point said it was charged and maintaining... so I popped it into the car and it worked quite well.

M.

 

[baldsparky]

Discharged overnight only Spinal so not long before I put it on charge again. The battery is only 8 months old and genuine 100ah mercedes unit so hopefully all will be ok.
My car has every toy going, and I was wondering how long under no fault conditions the car can stand without use before any normal battery drain becomes an issue. ie weeks or months ??

 

[nigel cross]

Get the dealers involved, they should do all the work for you as its that new.

 

[SilverSaloon]

is it not still under atleast a 1 year new warrantly?!

 

[baldsparky]

Sorry guys, the battery is 8 months old NOT the car. At the moment there seems to be an alarm related drain on the battery, so dont think the battery is to blame.
I picked up a new alarm horn today as that seems to coincide with the rapid flashing indicators when i locked the car a couple of nights ago. And probably has caused the battery to go dead

 

[Spinal]

8 month old battery should have a warranty with it (regardless of car age).

If bought from a dealership, they should take car of charging and reconditioning the battery...

 

[baldsparky]

Your right of course but to be fair its just as easy for me to charge it and then get on with the task at hand.
Why it went flat in the first place ?? Thats the big one.

 

[yorkshiregit]

You'd normally get 3+ year guarantee on a battery, if it doesn't hold charge take it back

 

[Dieselman]

Why would the dealer or a warranty be responsible for charging a discharged battery?

 

[baldsparky]

Its the reason a perfectly good almost new battery discharged overnight that needed investigation. Not the batterys fault.
It was the horn alarm and now thats been replaced all is good.
Thanks for your help guys.