"Huge" wrote in message
...
On 2007-03-09, wrote:
Huge wrote:

And I'm going to buy a second one for the (ride-on) lawnmower, whose
battery is dead as a door-nail, as we discovered yesterday.

Ride-on mowers and mini-tractors are really battery killers in my
experience, not because they work the battery hard or anything but
simply because they get left unused for long periods. As many others
have pointed out here it's leaving lead acid batteries uncharged (and
thus self-discharge) is what kills them.

Sadly, this has the opposite problem. It's been on a charger on a timer
all winter, on low charge for 15 minutes a day. Sadly, this is
still excessive, and it electrolysed all the acid away.

Surely not at just 15mins/day? A modern car alternator charges the battery
at about 14.8 volts, think how many hours a car battery spends at this
voltage without any problems. Would a little trickle charger (I assume this
is what you use) ever bring the battery voltage up to such levels.

(as an aside, I've overcome the problem with one of those little wall wart
chargers, Gunsons do a (IIRC) 500mA output one for just over a fiver. I've
added a few 10 Watt ceramic resistors into the circuit to cut charge current
down to vehicle parasitic losses + about 50mA. - stays on 24/7 in the
winter.)

Julian.