12 volt battery help please?

Thread Starter


Joined Jan 15, 2015
I just bought a new Die hard 12 volt 2 amp battery charger for my Lead sealed 1.3ah and 8ah batteries and when plugged in and charging there is a noise as if it is boiling inside, yet there is not a lot of heat at all... is this bad? any suggestions? should i return the charger and get a smaller amperage charger or what should i do?


Joined Oct 2, 2009
Post a link to the battery data sheet(s).

Post a link to the specifications for the battery charger.

Usually, chargers for flooded automotive batteries are not suitable for SLAs, and vice versa.


Joined Oct 2, 2009
What's making the boiling noise, the charger or the battery?

Get a proper SLAB (sealed lead-acid battery) staged charger.
Don't let the battery voltage run down.
Don't overcharge the battery.

Here is what happens when you overcharge a SLAB or when the charger fails to go to STAGE 3 (float charge):



Joined Mar 14, 2008
I think generally you should not charge a battery at a rate more that about 1/10 of its AH rating. On that basis 2A is way to much for your batteries and that's why they are gassing (boiling).


Joined Nov 30, 2010
My Sears lawn mower came with a battery charger that was guaranteed to destroy the battery in a few weeks. Being a wise guy, I added a regulator to it and saved myself a lot of aggravation. Imagine, expecting the parts that come all in one box to be compatible with each other!

Anyway..the right answer is to get the right charger.


Joined Nov 30, 2010
Not a chance.
You need to feed the battery with the right amount of current in one stage and the right amount of voltage in other stages. I just did a single voltage regulator with a 0.1 amp limit at all times. It's been working for 2 years, so far. I'm sure there is a more, "right" way to do it, but I'm not maintaining hundred dollar batteries. I'm working with (1) 3 or 4 amp-hours worth of battery. It's AGM. Absorbent Glass Mat. Read your label to find what kind you have then go to batteryuniversity.com to read all about it.


Joined Mar 14, 2008
could i just add an inline 500ma fuse or something and it work? or too simple?
A fuse would just blow and the battery thus wouldn't charge.
A suitable resistor in series with the battery may work but you would need to experiment to see what value gives the proper charging current.
The correct value likely would be in the neighborhood of a few ohms with a 5W rating.


Joined Nov 18, 2012
gel cells are not completely sealed, they would preasure up and explode if they were.
Gel cell batteries are recombinant batteries and are sealed. They are not made to be boiled and that is why they have special chargers which usually regulate the battery at 14.1 VDC maximum. If they are charged at a higher rate, they will boil and trip the pressure sensitive vents allowing the gas to escape. If done enough, the electrolyte dries up and then you end yo with the picture that Mr. Chips provided. Any gassing is made to recombine with the electrolyte in a special housing in the case.