Battery Charging

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DITTRICH

MB Enthusiast
Joined
Apr 16, 2004
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1,940
Location
London
Car
S205 C200SE & W202 C230K
My car battery is deeply discharged and I need to convince my RING RSC808 smart charger to do the job because the battery cannot convince the charger to start charging at 0.0 volts. The dead battery is out of the car as there is nowhere to charge from in the underground car park. I am thinking I need a charged battery wired in parallel to convince the charger to work. I am going to see if my local garage have a charger that can work from 0.0 volts (plan B). But, am I on the right track? I don't have a spare 12v battery lying around. These smart chargers leave a lot to be desired.
 
If the battery is discharged too much, a smart charger like the Ring or CTek wont do it.
It needs a few hours on a 4 - 6 amp mains charger before the smart charger can take over.

Can you borrow a mains charger to get it charging first?
There is a chance the battery will need replacing if its been completely discharged for too long
 
If it's been at zero volts for any sort of time you will never get it back.... if you can get it to take a charge it will have a noticeably reduced capacity and be permanently damaged. Nothing kills and sulphates a battery faster than letting it go/leaving it flat.
Zero volts is rare and often means the battery has suffered an internal short.
 
My car battery is deeply discharged and I need to convince my RING RSC808 smart charger to do the job because the battery cannot convince the charger to start charging at 0.0 volts. The dead battery is out of the car as there is nowhere to charge from in the underground car park. I am thinking I need a charged battery wired in parallel to convince the charger to work. I am going to see if my local garage have a charger that can work from 0.0 volts (plan B). But, am I on the right track? I don't have a spare 12v battery lying around. These smart chargers leave a lot to be desired.

You are on the right track with the charged battery in parallel method which is effectively like jump starting. Connecting up a parallel battery will begin charging the dead battery on it own without your Ring connected up. A hefty current may flow so you will need jump cables. I would connect them up and stand well back for a while before trying the Ring.

If the battery you are trying to charge is truly 0.0 volts then it may be too damaged to recover. A battery is considered fully discharged at 10.5 volts.

Edit: ALFAitalia makes a valid point about the possibility of an internal short which could make charging attempts dangerous.
 
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Connect two batteries together in parallel.

This will fool the charger, as it will see the average voltage, which will be higher than zero, and it will start charging both batteries. Once the dead battery has some charge, you can charge it on its own.

But you'll obviously need a second good battery to do this.

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If it's at 0V I think you're wasting your time. The battery will never recover. Yes you may eventually get it to read something like 12V but it's going to be ruined and have very little capacity.
 
If it's at 0V I think you're wasting your time. The battery will never recover. Yes you may eventually get it to read something like 12V but it's going to be ruined and have very little capacity.
Yes but its only to get the car started and onto a trailer to the big scrapyard in the sky. So it only needs to start the engine. If all else fails, reconnect the battery (goes in the w202 boot) and wire across from the s205 good battery.
 
Connect two batteries together in parallel.

This will fool the charger, as it will see the average voltage, which will be higher than zero, and it will start charging both batteries. Once the dead battery has some charge, you can charge it on its own.

But you'll obviously need a second good battery to do this.

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For more detailed information, see our cookies page.
Thanks, I kind of reached the same conclusion myself and just wanted some confirmation. It is vaguely possible there may be an old style dumb battery charger at my Mum's house and I will give this a go first. Its kind of like a one off problem and long life of battery is not a concern as the w202 is about to take its final journey.
 
Thanks, I kind of reached the same conclusion myself and just wanted some confirmation. It is vaguely possible there may be an old style dumb battery charger at my Mum's house and I will give this a go first. Its kind of like a one off problem and long life of battery is not a concern as the w202 is about to take its final journey.

What are you doing with the plate? :)
 
What are you doing with the plate? :)
MBC230K and MBE300D will be put up for sale at some point. MBC200SE is not a valid number unfortunately. I had grown very attached to both these plates but of the two, MBE 300D (MBE 3000) is probably more marketable. Someone tried to buy it from me in a traffic jam on Southwark Bridge once.
 
One of the reasons I changed from CTek chargers to the Noco Genius 5, is it claims it can charge batteries from 0v.
Apart from that is also charges lithium batteries too which none of my Cteks did.

 

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