Battery reverse polarity?

[Downunder Bob]

I would discharge the battery and then charge it with some kind of limiting resistor in series with the charge leads. A car
tail light works well for this( #1157 comes to mind). That way it can reverse it's polarity without much danger. I often use
this method on smaller batteries that would be cooked with a regular car charger.

Thanks I have two small chargers the 1A one mentioned and another that I can set at two Amps, I think either of them will suffice I'll probably use the 1A one, but yes it won't charge a completely flat battery so I'll interrupt the discharge before it's completely flat.

 

[rgray]

A deep discharge can cause reverse polarity in a cell so it is possible for a small capacity battery it be possible.

Likely best to leave as is and remark posts

Remarking the posts gets my vote... Lead acid batteries do not like to be fully discharged. They will only survive it a very limited number of times. Even if they do survive it they are usually damaged (lessened capacity)

 

[cathead]

Thanks I have two small chargers the 1A one mentioned and another that I can set at two Amps, I think either of them will suffice I'll probably use the 1A one, but yes it won't charge a completely flat battery so I'll interrupt the discharge before it's completely flat.

I think you need to drain the battery completely. At that point you can charge it as it was intended. The positive and negative
battery plates are not the same so best to get the pos to be pos and the neg marked termianl to be neg. Also, it's not a bad
idea to know how many ampere-hours the battery is supposed to hold so you can charge it accordingly. For example:
a 10 ampere-hour battery could be charged at 1 ampere for 10 hours plus maybe 20% or so. This is self limiting to some
extent since as the battery voltage climbs, the difference between the battery voltage and the charge voltage decreases.
This probably won't happen but approaches it since if both battery voltage and charge voltage were the same, no current would flow.

 

[Scruffy]

I know this is a old post 30 years ago I left the key on of a jd riding mower. Put the charger on backwards. Got it all charged up and the starter would just spin. Scratch head. The starter was spinning backwards and the bendex wouldnot engage.
Left key and lights on for several days recharged battery, then threw it in the junk and replaced battery. All well.
Thanks ron

 

[Tim9]

Best bet is to TOTALLY DISCHARGE BATTERY and then properly charge it ....Positive to positive....Neg to neg.

I've had this happen a couple of times back when I had a service station. Sometimes new employees would screw up and hook the charger backwards. When the battery is totally dead, you don't even get a big spark when hooking up cables backwards. If the battery is partially charged, it's hard to make that mistake because it will really arch if you hook up backwards. In most cases, after proper charging all is good providing the battery isn't too old. But...discharge it first, then recharge.