[Snip]

The problem is the volts vs amps curve. At lower charge voltage, batteries
can take a whopping amp load... consider it sort of like the jolt they
endure when kicking over a starter for a big engine, only in reverse.
However, as the battery approaches full charge, the voltage rises and the
amperage drops. To continue trying to charge at a fixed amperage will
damage the battery as the voltage climbs towards 15 or even 16V.

A 3-stage "smart" charger will actually taper off the amperage at a fixed
voltage, and then trickle a lower voltage to maintain the full charge. It
takes a fairly sophisticated controller to do this. But it's very well
worth the extra money IMHO because the batteries will have about 25% more
electricity available (when new, if you get a smart charger and hook it up
to an old battery it could be much much more) and they will last longer.

If you are going to plug in a charger and leave the battery for a few
days, absolutely use the lowest setting. At 2A it is getting almost
50amp-hours a day, which means that in two days a big Group 31 will be
fully charged, in three or four days it will be trying to soak up a
damaging overcharge. A smaller battery will fare worse.

Fresh Breezes- Doug King


I have a question I've pondered for a while ..........

On a trickle charger, if you were to connect an IC
that limits the voltage to 12 Volts only ( LM12 ) could you
leave the charger on indefinately without damage to the battery?

12V is not the right trickle voltage. I forget what it is, but it's a little
above a fully-charged battery, which will actually register something just a
touch higher than 12.6 V at rest - and having rested a while since being on
the charger.

I have several battery links posted at
www.ctlow.ca/Trojan26/index.html#battery. One of them is www.batteryfaq.org.
It's a complicated topic.

Charles

====

Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

"Joe Here" wrote in message
...
I have a question I've pondered for a while ..........

On a trickle charger, if you were to connect an IC
that limits the voltage to 12 Volts only ( LM12 ) could you
leave the charger on indefinately without damage to the battery?

On Thu, 09 Oct 2003 01:18:52 -0400, Joe Here wrote:

On a trickle charger, if you were to connect an IC
that limits the voltage to 12 Volts only ( LM12 ) could you
leave the charger on indefinately without damage to the battery?

================================================

What we are really talking about here is the so called "float" voltage
where a battery can be kept at full charge while under no load. Float
voltage is normally specified in the range of 13.2 to 13.4 volts
depending on temperature and battery type. Anything higher will boil
off the battery over time.