Weather Report and Battery Charging

Weather Report and Battery Charging

Postby Coulomb on Thu Jun 11, 2015 12:02 pm

The weather report calls for sunshine after morning fog. Highs in the mid-70s with low humidity.

Sounds like a good forecast. Too bad it's meaningless without a location specified.

Float voltage is 13.15. That may be a fact, but it's meaning stops at that. Without knowing battery temperature that fact is meaningless.

Here's a charging specification with real meaning:

"For 12-volt batteries, charge to at least 13.8 volts but no more than 14.6 volts at 77°F (25°C)".

The source for the above is:

MK Battery is a division of East Penn Manufacturing which makes gel batteries.

Now read this:

Some years after Ample Power published the above information, a report from Sandia Labs "discovered" that the guidelines published by East Penn at the time led to undercharged batteries.

A little history might explain it. Florida and points south were a great market for sealed gel batteries in the 1980's. Most of them were installed in boats with the typical ferro-resonant charger of the era. That was a death sentence in the usual temperatures encountered. Soon the gel batteries were coming back in volume, still under warranty.

In returned batteries the gel was dry as sand since all the electrolyte vented through gassing.

Soon the terms of use were changed with a very low charge voltage specified -- a voltage that would be appropriate at about 95F.

Temperature compensation was the real answer.
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