Battery Charging

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areFish

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Apr 11, 2018
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I have 2 new 6V batteries for my travel trailer.  After a boondocking trip I started charged them in tandem with a 3.5A charger on 12V mode.  When the charging started it was flashing 25% and about 27 hours later it was flashing 100%, which means it is not yet finished charging. 

I could hear what sounded like water boiling or bubbles rising inside the batteries.  The batteries were cool to the touch and prior to charging, the acid level seemed good.  I?ve unplugged the charger until I get this figured out.  Is the sound of bubbles during charging normal? 
 
Something is not right.  Bubbling may indicate the battery is releasing hydrogen which is an explosion hazard.
Not sure what you mean by "in tandem."  6v batteries have to be connected in series to add to 12v.  Be sure your charger is not applying 12v to a single 6v battery.

Also, if a battery has a dead cell it can outgas this way.  Some auto stores offer free testing.
 
MikeNNRV said:
Something is not right.  Bubbling may indicate the battery is releasing hydrogen which is an explosion hazard.
Not sure what you mean by "in tandem."  6v batteries have to be connected in series to add to 12v.  Be sure your charger is not applying 12v to a single 6v battery.

Also, if a battery has a dead cell it can outgas this way.  Some auto stores offer free testing.
Click to expand...

They are connected in a series.  Both batteries were emitting this sound.  It would be odd both new batteries would have a dead cell.  Thank you for the free testing idea.
 
Every battery I ever charge bubbles after it has been plugged in a while. RV, or Motorcycle.  Even smell a faint sulfur smell.  You seem to be charging at a low amperage, I say you are fine.
 
If the batteries remain cool and you aren't seeing a lot of wetness on the top, I'd say the bubbling is well within normal range.  Besides, if the only charging is the 3.5A gadget, it's not applying  enough power to cause a problem. a 3.5A max applied to a pair of 6v's (210-230 AH) isn't gonna overwhelm anything, even with a shrted cell.

 
Two things can happen that cause batteries to "Boil"

One is over charging.. Your charger was flashing 100% but still charging so it may have been "Equalizing" which is a controlled over charge.

The other is rapid charging. I DO NOT THINK this was your problem.

My "External" charger (A Deltran Battery Tender) only goes up to 20 amps in "Bulk" mode (70 in jump start and about 2 or 3 in "Maintain")
 
Thank you for the info. I emailed the manufacture of the charger. Looks like the fizzing or bubbling sound was normal however the charger wasn?t the right charger for my batteries. The charger was for batteries up to 120 AH and mine are 243 AH.

Lots to learn.
 
The "right charger" is a judgement of the time to reach full charger. Your little 3.5A charger will take many, many hours, but it will eventually reach full charge. A more capable (higher amp) charger will get there somewhat quicker, but they all get to the same place eventually.

A 7-10 amp charger will probably reduce the charge time by 30-40%, but a 20A charger probably won't decrease it a whole lot more. Batteries can only accept amps at a certain rate, so huge chargers aren't always a benefit.

If you would like to learn more about how batteries charge and what a charger needs to do, see http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery/subscribe_thx
 
Arch Hoagland said:
"it was flashing 100%, which means it is not yet finished charging."


I'm confused. Isn't 100% full?
Click to expand...

In this charger?s case the 100% flashing means over 75% and solid 100% indicator light means 100%.
 
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