I work with large scale hybrid electric systems using inverters, PV
solar, wind turbines, batteries and diesel gensets for small remote
villages.  Our batteries are usually large systems that take up a large
room, in one instant we have a Trace Technologies 90 Kw inverter that
is programmed to equalize every 30 days.  These batteries get a
constant workout much more than what you would experience in an RV,
thus you may not need to equalize as often.   I would defer to the
inverter manufacturers recomendation regarding frequency as they have
many hours of research invested to maximize the system.

A little more about battery equalization that may or may not be of
interest.
As batteries are exercised the individual cells react a little
different in their rate of charge & discharge due to the minute
difference in internal cell resistance.  Thus when a battery or series
of batteries are charged, the charger charges to a set voltage of 14.5
volts assuming 2.4volt/cell on a 12-volt system.  Since each individual
cell has taken a different charge rate due to this internal resistance,
the total battery voltage is correct, but each cell voltage is
different, some higher and some lower than 2.4volts/cell, which results
in some of the cells not reaching a full charge.   The battery loses
it's full charge potential over time, thus the equalization.  What the
equalization does is to temporarily overcharge the battery so that each
and every cell is overcharged thus guaranteeing a minimum desired
volts/cell.

However there is a draw back, anytime a battery is worked either charge
or discharge, heat is generated proportional to the rate of current
flow.   Hence when equalizing the batteries the temperature often rises
higher than normal.  There are many things that can decrease the life
of a battery and one of them is heat.  Many large inverters actually
have a thermocouple connected to the battery to charge to a specific
volts/cell per battery temperature and controll maximum charge rate
without overheating.  The typical setting is 40 degrees C (105F)
maximum battery temperature, manufacturers usually don't warn you over
overtemp, only over charge.  But over temperature rapidly decreases the
life of the batteries.  I can't overemphasize monitoring your battery
temperature.

Recently a hybrid system in a remote village using 8o T105 golf cart
batteries in four paralelled banks of 20 in series for 240volts DC.
This system was designed for a seven year life failed after only one
year.   When the manufacturer analyzed the batteries, the failure was
determined to be from overheating.  We went to the site and found that
the operator had disconnected the thermocouple during routine
maintenance and forgot to reconnect thinking it was not that important!

JerryB

On Fri, 17 Jun 2005 12:57:20 -0400, birch999 wrote:

Har- yes, indeed, though I do believe it cut short the life of my Sony TV-
fried the flyback transformer.

Yabut- they are different animals. The power supply is often meant to
accept anything between 100 (Japan) and 240 (EU) volts, and output the
required voltage to the computer. If the power supply put 20 volts on the
+12 volt line (or 6 volts on the 3.3 volt line)- I doubt the computer
would last long.

Well- yes and no. They basically just regulate the power on board the
circuit board. Making the regulator capable of dealing with 25 volts would
add significant heat sink requirements.
Actually, most new refrigerator boards will take up to 17 volts, but they
have to because of "dirty power"- when they filter dc power with a large
ripple, the end voltage will often be 15-17 volts.
I'm sure Dinosaur boards would probably survive- though they use 7812
regulators on board, which are not heat sinked, and I know that Sunbeam
tests their florescent ballasts to 24 volts.

You would be amazed (or probably not) at the cost cutting that goes on. A
couple of examples- The older Norcold 6XX models- the oem's wanted to save
money, so Norcold built a model with no interior light- probably saving
less than $5 at the oem level. Some oem's delete the start kit option on
air conditioners- the customer complains the A/C won't start- Coleman adds
a start kit under warranty. Dohh!