Andy wrote:
On Sep 12, 5:39 pm, Jack wrote:
Float chargers are attached to the 12v in the generator, and also to
two 12v that provide back-up for the sump-pump. Neither of these
units is used every day; in fact, the sump-pump batteries have never
been used in seven yrs. So, presumably, the chargers main function in
these applications is to keep the 12v from discharging due to lack of
use.

But beyond that, do chargers, theoretically, keep batteries ready and
able to run indefinitely? Or will the cells eventually die of old age
despite the chargers, much like a well-preserved, fit old person: Bob
Hope, Geo. Burns, Jack LaLanne?

Andy comments:

Float chargers, such as the one from Harbor Freight, do a pretty
good job of maintaining the charge, but that doesn't mean that
it can keep things going for long periods of time without checking.
Much like planting flowers --- they need to be weeded...
When working with chemical reactions over a wide temperature
range, there is no such thing as "hook it up and forget it "....

Every month, check the water level in each cell. Top them up with
distilled water if is low. Depending on the temperature variations,
the float charger can't compensate for every single variable, and
occasionally will feed in a little bit too much and boil off a little
water..... I'm not aware of ANY device which will compensate
exactly for the changes that occur with the electrolyte which
require minor changes in the float voltage.....

I've used the Harbor Freight float charger for years, and easily
double
the battery life in my lawn tractor.... but it won't give the battery
immortality, and you have to check up on it......

Remember, it is a FLOAT charger, not a BATTERY CHARGER....
A real charger, with a hydrometer, should be used to charge the
battery... Then the float charger is attached to compensate for
internal leakage..... A FLOAT CHARGER will not "charge up"
the battery by itself.... That is a mistake that many people
make. If you use the Harbor Freight float charger, read the
manual.....

Andy in Eureka, Texas , P.E.

I harbored my datsun last winter. It started ok. That's all I know about
that.
I know from floating NASA equipment, you have to be well under 100 ma to
keep bubbling down. 10 ma is good, if it enough to keep it above a certain
minimum voltage. Batteries are best overcharged occasionally to above 14
volts, to extend life. They might also need balanced, by discharging.

Greg