Marine battery with reverse polarity.

[Geo-TH,In]

A few weeks ago I posted about a friend in Florida that 2 12v batteries in series for trolling motor.

Well I got my late mother's electric wheel chair. It too has 2 12v lead acid batteries. One battery good the other battery is bad. I charged each battery with a 12v charger. Then I connected a 12v seal beam to the bad battery and drained it all the way. When the good and bad battery are in series I then connected the seal beam to where you would get 24 v.

Mystery solved. The good battery back feeds through the bad/dead 12v battery putting a reverse polarity on the terminals.

I conclude, friend has a charger with 2 12v outputs. He drained his batteries with trolling motor. The sick battery drained first, it had a reverse polarity on it and no smart charger will charger it.

old post

 

[JD Seller]

George this would be only true if the boat had something wired in 24 volt. His batteries would normally be hooked in parallel not series.

 

[Geo-TH,In]

JD
Trolling motor is a 24v, 2 batteries are in series. Speical boat charger is made with 2 12 v out.

I figured out how the bad battery got the polarity reversed with mom's 2 batteries which are also wired in series, however her charger is a 24v.
George

 

[Texasmark1]

High thrust TMs are usually 24 volt and use 2ea deep cycle Size 27 12v batteries for that power wired in series. Additionally there is a center wire to the series that provides 12v which is switched in to run the TM when you don't want or need the high thrust operation. Makes the foot pedal less sensitive for sneaking around looking for the "Lunkers".

And yes you can discharge and recharge a battery the other way to some extent. You are talking about a chemical solution of Sulphuric acid, water, and lead (H2SO4 + H20 + Pb). Nothing magic about reversing just what happens when you do.

Will tell you this. If you have adequate charging capability or a thick iron bar, if you discharge too rapidly you had not be in the area when the discharge to reverse recharge commences.

Mark