I should of had the Battery Tender on the MB like I did with the others.

I'll charge overnight @ 10amps and see where it gets me. If dead I'll replace the MB battery with an Interstate.

Maybe it's just me, but I'd be wary of leaving a suspect battery unattended on a charger overnight.

Reading this thread is confusing.

If as I understand it, Rick put 50 amps through the electrical system with reversed polarity, the damaged components are likely to be the alternator, voltage regulator and possibly, some instruments (ask me how I know). It's also possible some wires had the insulation melted off them.

This car needs a thorough electrical assessment.

Tech, The polarity was correct. The rumor started as a guess.

FWIU, reversing polarity will likely only damage the battery or charger. Sounds like you you've experienced worse...sorry to hear.

I will look at some of my cars owners manuals...I could swear that I've read that jumping (certain cars?) could fry the electronics. Then again I'm getting old.

You're not as old as me, but you're correct. Jumping a car is a trickier proceture with alternators, and lots of us learned with generators. Hooking up in the wrong sequence can blow the diodes in the alternator. your car's manual will have a hook-up sequence to follow.

Arrrgh.
The sequence now described to hook up jumper cables is to prevent battery explosion from a spark. i.e., Pos (running) to Pos (dead) Neg (running) to Neg metal grounding point away from battery (dead)
Nothing to do with diodes.
What Rick did was correct. Maybe just didn't let the battery charge enough, as Wayne said.
I use a 225A start setting on my charger if I have to start a car in a hurry. No negative effect on any electronics unless they are defective in the first place and will draw that much current.

Hot, humid, rushed...yup, should have been more patient. Had to push the heavy bastard out to the driveway. I'l have to go back tonite to retrieve.

If the battery is shorted internally, all the juice from the charger-starter is going through the path of lowest resistance, which is the battery. You should disconnect one lead from the battery, connect it to the charger, and try to crank. Like that, the battery is out of the circuit. Let me know if it works.

Aurel

"Dead Car Battery Starting Method # 1: Preferred method of starting the dead battery
Try this method before you try Method #2. A guy named Doug from Canada sent in this tip. He's boosted cars a lot in winter and has found that it's critically important to shut off the boosting car’s engine during the moments of actual cranking of the car with the dead battery. This does however reduce available power to the dead car because the boosting car's alternator isn't running, Doug has had a number of "live" boosts make the boosting car's alternator diodes either fail outright or die very prematurely from the extreme current draw on the alternator while cranking the engine on the bad car. So the safest method is to have the good engine running a few minutes to charge the dead battery. Then shut off the good car's engine and disconnect the cables and start the bad car's engine...."

This way if the car with the dead battery won't start you can have two cars that won't start :)

Seems to me if you hook a dead battery up to a running car the alternator will already be maxed out.

Doug is a wiener.
I'll continue jumping cars the way I always have.
No diode problems. Ever.

:D SmileWavy

Rick: I recently had a problem with what I thought was a fried system on my `85 380SL. Turned out that there is "Overload Protection Relay". The cute little critter is the last thing in line before the brain blows up.

Rick, if you're worried about the health of the SL's electronics, why don't you just pull the battery from one of your other cars and plug it into the Benz? If the car starts right up, then you know it's a simple case of a dead battery in the MB.

I agree.!
Jump started more cars than I can ever remember the standard way.

Have fun, boys. I've got the receipts here somewhere for a couple of rebuilt alternators with blown diodes caused by similar situations to Rick's. YMMV

Yupp. Company I work at burned down perfectly nice Alfa Romeo shop + 10 customer cars this way. Don't trust the unattended charger.

If it's going to be charged overnight, take the battery out, put it into battery corner (with proper ventilation etc.) and charge it. If it blows, it won't take the house down.

i spent 3 days hooked up ot the charger, while cranking my 944 after i had put in the enginge back in with new rings...

no problem whatsoever, although i must admit it was a professional charger, one you can wheel around, big bugger... not a tiny one...

but either way , it shouldn't frie anything on the car
at worst you would blow a fuse on the charger if there is something pulling much current

Just so long as though hast not f*cked thy neighbors wife - your'e fine. Nothing that can't be exchanged for your soul. (Or ~$30 for a new battery)

Then possibly the diodes were already blown, resulting in the need to charge the battery in the first place.
;)

My wife's Mercedes is like this. The manual is clear, no jump starting and no charging with the battery in car. Don't know why.