My old backup car, an E320 wagon, 95..had a low battery and I took it for charging and they tell me its bad..

They did that before but I charged it myself and it was fine for months, not bad..But it died again and now when I installed with it reading 11.5 and yes, low...NOTHING..I did not notice it was REVERSE POLARITY Charged..Holdng 11 volts from negative to positive..

I just hope there is no damage to systems from connecting the reverse charged battery. I looked it up and indeed this happens. Now I must totally discharge it and begin chargign the proper polarity..Taking it slow because its pulling 50 amps and getting pretty warm!!

Just a who knew this was even possible!! And praying I dont need new relays all through the system..

Any comments always much appreciated!

What specifically did they say was the failure type? Open cell , shorted cell, weak overall, won't hold a load test?

Fine for months as in the car was running and driving? Or was this just the battery sitting not being used?

Well apparently something is wrong with the battery or the car. Have you checked the car's charging voltage?

So the reverse charged battery was connected to the car with + to + ? Did you get a large spark when you connected the battery to the car?

Was your voltage test performed after the battery was sitting for 8 + hours or was this shortly after a charge?

A fully charged lead acid battery that has been sitting for 8 hr will read 12.66 fully charged. I don't know what voltage a reverse charged battery will attain.

Based on your voltage readings, you might have a shorted cell in the battery in addition to the possible reverse charge. I recently tested a battery that had a shorted cell ( an actual short not " it is shorted " some apply to every electrical fault. ) that would crank slightly slow and not die off like a discharged battery would. A shorted cell 12 volt battery results in a 10 volt battery with the same amp capacity as a 12 v battery.

Did you make sure your test instrument reads proper polarity on a known good battery? Even a flashlight battery would be a good test.

none of these questions showed you read the post..simply a dead battery. Im not going to say how it was connected because its all normal..No my meter is not bad. Stop it..

They charged it and said it was bad, IT WASNT..I charged it myself and it was fine..Fine means fine, you dont need details.

But after sitting months it was dead again. No surprise..its usual for a car sitting without driving to go dead..Then they charge it IN REVERSE and Yes this is possible and it held 11 volts with negative as positive..

I installed it not knowing!! Then when I went to charge it myself because of course the car did not start!! I discovered the reversed charge..

Ive totally discharged it and now have it charged properly and it holds charge..And you need no fault designation such as bad cell or whatever..these auto parts shops are not capable of this diagnostic..They just hope to sell batteries. Doesnt matter..

We could discuss potential faults in the electrical system but thats not my question and I can research that in known information..And the battery may not be prime but it holds a strong charge for weeks, but not for months in a stored car..I think its actually been a full year! It should have and could have been charged but they charge it BACKWARDS and it held 11 volts with negative positive..No it goes without saying I did not connect it in reverse, thats impossible given the battery box and cables..no aliens and no way to test each cell and this is all just irrelevant..bad questions because you clearly know nothing about this, as I did!

If someone KNOWS anything about this or the potential damage to the car from putting a reverese charge into the electrical system, THAT would be apprecicated..(you forgot to ask what brand of battery or other irrelevant nonsense) Dont you want the make of my meter and year of the car?? What color it is??

Anyway its a fascinating potential this is even possible..for anyone really interested..Hope it helps someone who is curious and interested..

I have bought a battery from a warehouse that was backwards, - I never installed it as I have a habit to check the battery in its isolated state before I install it.

The only way I know that can happen is if the battery has been activated backwards because to charge it backwards your battery should be having close to only 2V when applying the charger. Most chargers will shut down when connected backwards on a depleted battery (11V)

In any case if you connected it to the car, a lot of fuses would have popped.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Do you have another battery you can use to check out the car? Do you have another car you can check the re-polarized battery in? I’d want to confirm both are good before putting them together. Otherwise you’re chasing two variables.

Sixto
98 E320s sedan and wagon
02 C320 wagon

Long story short, the battery is reversed back again and started right up, no problem and apparently no damage to relays..Yes thanks Sixto, Ive got tons of batteries but none of them will fit the box and easiest is to just charge the battery properly with positive on positive!! It got very hot in the reversing but held charge of 12.79 overnight and we will see if it holds long term..But who knew you could reverse the polarity by charging backwards!! The local ORiely is getting a major lesson in battery work..and thank god theyre not getting sued for system damage! Ive been through A LOT of electrical training and have NEVER seen this information..

Zulfigar..Interesting..

I did install the reversed battery, it was showing 11.5 and I didnt notice because who would think?? but the meter showed a - sign..11.5 IN REVERSE..

I shorted it to drain, intermittently so as not to burn up the cables..or melt the posts..then when dead I charged from a charger capable of 50 plus amps..again intermittent because of heat..Got it holding a nice 12.75 and then charged again just a little and it all seems good!! No evidence of bad fuses but we will see..

how did you drain it? - I hope not a dead short because I have seen a real bad accident like this happen - the battery literally popped the cell caps and blew electrolyte. (baking soda takes care of the burns though but not for eyes).

If your battery was bubbling nice when charging and now has correct charge and polarity - its all good.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

maybe the most confusing paragraph ever posted...

"it died again and now when i installed it...."

where was it when it died if you 'then installed' it.....

"i did not not notice it was REVERSE POLARITY Charged..."

how did you eventually "notice'" it?

"I took it for charging and they tell me its bad..."

if you had the capability to charge it yourself, why did you 'take it for charging'?


"Any comments always much appreciated!"

Apparently not....only posting this because you kind of flamed 97320 for posting question to help understand your not-all-that-clear post.

__________________
0o==o0

James 4:8

"...let us put aside the blindness of mind of those who can conceive of nothing higher than what is known through the senses"
-Saint Gregory Palamas, ---Discourse on the Holy Transfiguration of Our Lord God and Savior Jesus Christ


Centrally located in North East Central Pa.

I guess we can all stand to be a bit more civil to each other on the forum.

To whom and what post(s) are you directing this towards?

Your posts are all over the place and difficult to follow. If you want help from actual professionals, you need to be clear on the details.

So you want help but won't give details?. ? . . ?

Make me, report my posts to the mod and have me docked points. I'll be waiting. . . . . I'm only working through this post in case someone else has a similar problem and is looking for help.

Your first post didn't say " they " charged it, your post stated " they " said it was bad and you charged it.

They way your first post reads, you are the one that reverse charged the battery.

If you really had a reverse charged battery, there would have been a very large spark when you hooked up the battery cable. If you did get such a large spark, why didn't you stop there and investigate rather than trying to start the car?

There is a vast difference between a depleted battery ( like an empty gas tank ) and a failed battery ( tank with a hole in it. ) Details matter. . . .And given you are having continuous battery issues, there is an underlying fault. Regardless, when a battery is run below what is considered full discharge of 11.7 V , it is damaged. Do this enough time and the battery will fail.

Open circuit voltage and loaded voltage will determine if there is a shorted cell. A shorted cell in a multi cell battery will have low but steady loaded voltage. ( Remember, with a shorted cell it will act like a 10 v battery as the shorted cell effectively isn't there any longer ) A weak or discharged battery will have a rapidly falling voltage under load.

I've got 40 + years in and around the auto repair business in parallel with 20 in industrial machinery ( as in computer controlled systems, CNC equipment , robotics and such ). I've also been known to dig into board level repairs on electronics here and there ( that is testing and replacing parts on a circuit board not just changing the board ) . Still want to go a few rounds?

I thought Post #3 was unusually harsh and not reflective of the forum in general. We are all friends here.

Youre reading all sorts of possibilities into the post which is a simple dead battery in a car not being driven which is not repeated failure but the usual, for a car sitting. Had it charge and they said it was bad (previously) but it was not and charged easily HOLDING A CHARGE for months..then after sitting a year, of course it went bad..as so often will happen..

Then when it was charged by this shop again, they charged it backwards and yes, when I discovered this, I discharged totally and recharged it properly and its fine..

YOure the dominant silverback who wants to obviously "go rounds" with guys who happen to have learned something very little known and so you harass with irrelevant questions and picking the comment apart for having said too much or too little..

Either way its just harassment and I shared more useful information than you with all your expereince..

I wont be back and Im not here for help but to offer useful information unlike some of these old pros who are just here to demonstrate authoritative knowledge.

I got my moneys worth and just hope I shared very little known information about something potentially damaging..

me too

__________________
0o==o0

James 4:8

"...let us put aside the blindness of mind of those who can conceive of nothing higher than what is known through the senses"
-Saint Gregory Palamas, ---Discourse on the Holy Transfiguration of Our Lord God and Savior Jesus Christ


Centrally located in North East Central Pa.