Comments on: How to properly charge a dead car battery

By: Rodolfo Cadilla

Rodolfo Cadilla — Thu, 14 Dec 2017 01:51:56 +0000

Hello, thanks for the great advice. My car is a Mercedes 1999 SLK 230, and the charger is a 3A 12V Battery Tender. The car manual advises to disconnect the battery from electrical circuit before charging the battery. In one of your responses you mentioned that if the negative battery terminal is disconnected, no damage will occur to the electronics. Even if no damage occurs, do you know if some of the electronics would have to be reset?
Thanks again 🙂

By: Mick O'Toole

Mick O'Toole — Thu, 23 Nov 2017 15:40:24 +0000

There is a fault with my boot/trunk and its not opening, so I can’t access the battery. Is it possible to charge from the front compartment without disconnecting the negative on the battery itself? Thanks in advance!

By: Mercedes Medic

Mercedes Medic — Mon, 23 Oct 2017 11:15:39 +0000

In reply to Mario Tello. If you disconnect the negative, the car has no power. It doesn't matter if the positive remains connected. You need both + and - to get power (current) to the car electronics.

By: Darleen

Darleen — Sat, 14 Oct 2017 22:55:50 +0000

I’m having a trouble with my battery I bought this 2000 Mercedes Benz S430 over 200,000 miles at auction for $900 and so far it has not given me any trouble except that now is not starting I’m having trouble getting the battery to start the cigarette lighter doesn’t even work but those are mechanical things a few things are outdated on it because it’s 17 years old but I just need some guidance on what I need to do about the battery because it’s been frustrating trying to get it started I cannot afford a new battery I like to be able to get a reconditioned battery I can’t afford to go to Chesterfield Auto Parts to get a reconditioned battery for $75 and I’d like to be able to find out exactly what’s wrong with it I can’t afford to have somebody come here to look at it or I can’t even afford to have it towed somewhere for someone to look at it if there’s any way someone could help me figure out what’s going on I’m out here now feverishly trying to get it to start I’ve got a jumper box which seems to be doing okay it tries to start and then it stops and just can’t get there I’m wondering if the starter needs replacing or what’s really going on at this point

By: Roland

Roland — Wed, 20 Sep 2017 00:04:56 +0000

Very good Website
I’ve got Mercedes w221 s500 2011 model I’ve got issues coz I drive for 3-4 days and then stays in garage for 2-3 weeks when I try to start the battery isn’t strong enough to turn the engine over is it any charger that keeps the battery charged up or to recommend which one so I can leave in slow charge

By: Mario Tello

Mario Tello — Fri, 15 Sep 2017 19:50:25 +0000

You say the battery can be charged while in the car, just disconnect negative side cable. What about positive side, does leaving the positive side connected while charging the battery not potentially harm the electronics in any way?

By: Greg

Greg — Mon, 03 Jul 2017 16:31:44 +0000

Thanks for the information. I performed the trickle charge for about 36 hrs on an 07 E350. Reinstalled the battery and so far seems to be working fine. I am sure a new battery is in the future but it was great to not have to buy it today.

By: Mercedes Medic

Mercedes Medic — Thu, 16 Mar 2017 17:50:30 +0000

In reply to dave williams. It may not have been charged fully in the first place. Try charging it with a 2A or 4A 12 volt charger. If it still gives you problems then you need a new battery. Also if the battery has any damaged cells it won't charge and may be the reason why you are having the problems described.