[T2] Battery overflow on charge

[Jamie]

From: "John Kolak" <jkolak at gmail.com>
>  after charging overnight all of the cells overflowed
> leaving a nice acid mess on the garage floor. Now all the cells are
> only about half an inch below the top of the filler holes.
>
> Anyone have any idea why this happened?

another reason... if you charge at a rate above the gassing point... the 
battery will "gas".. or boil... or bubble... and the bubbles burst at the 
cap,, the cap leaks.. and dribbles out the overflow

a 12v battery has 6 cells... if the charger exceedes 2.45v/cell , the 
battery will gas. which condensates,, and drips, and leaks..

this isn't always equal,,, so even if you charge at a total of 14.4 volts 
max,,, a couple cells could exceed 2.45 volts,,, the wet spots will indicate 
ALL cells are overflowing,, but "usually" the liquid level is NOT even 
after... depending...

it is soooo variable,,, a lot of numbers seem to be set in stone.. but the 
battery doesn't know this..
if you want to really understand... check out ....
http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

a short quote from that page,,,
The correct setting of the charge voltage is critical and ranges from 2.30 
to 2.45V per cell. Setting the voltage threshold is a compromise, and 
battery experts refer to this as "dancing on the head of a needle." On one 
hand, the battery wants to be fully charged to get maximum capacity and 
avoid sulfation on the negative plate; on the other hand, an over-saturated 
condition causes grid corrosion on the positive plate and induces gassing.

To make "dancing on the head of a needle" more difficult, the battery 
voltage shifts with temperature. Warmer surroundings require slightly lower 
voltage thresholds and a cold ambient prefers a higher level. Chargers 
exposed to temperature fluctuations should include temperature sensors to 
adjust the charge voltage for optimum charge efficiency. If this is not 
possible, it is better to choose a lower voltage for safety reasons. Table 
4-5 compares the advantages and limitations of various peak voltage 
settings.