[Kayak fisherman]

I have a question.
I have a friend who has a boat with two Exide Nautilus Gold NG24 batteries. The batteries have always worked properly. My friend bought a new Black and Decker Smart Charger (40 amp, fully automatic) and charged one of the batteries, but the other battery was not isolated. So, I think both batteries were being charged. After about 6 hours my friend checked his batteries and they were making bubbling sounds and they were very warm to touch. The charger still read "40 amps". These batteries were nearly charged to begin with.

There hasn't been a problem before. However, on previous occasions my friend remembered to charge one battery at a time with the other isolated. During these previous charging sessions, the charger knew when to shut off and gave a "fully charged" message. Also, there was no battery bubbling/warmth.

Are these batteries now toast?

Another question. If it's been about 3 wks (winter time) since last topping off a battery, what is the lowest "healthy" voltage it should read PRIOR TO topping it off? Is < 12v bad news?

 

[Capt.Nick]

Get a Hydrometer at an auto/marine store.
some have exact readings while others havv good/bad indicating colors on te float.Check the specific gravity in each cell.Each cell should read around 1280 or higher,or good,indicating a fully charged & good battery.Older batteries may not get this high of a reading.No reading or a weak reading in any cell indicates a weak or bad cell.i personally have rarely gotten more than 2 "good'years out of any marine batteries.I usually scrap them after 2/3 years of regular service.

 

[Kayak fisherman]

My batteries are ok. However, I bought some AGM-type batteries with alot more juice. They should be alot better.

 

[pescador26]

battery chargin

Your batteries should be OK as long as you did not boil the electrolyte out of them
and expose the grids