"Michael A. Terrell" wrote in message
...
Arfa Daily wrote:

"Michael A. Terrell" wrote in message
...
David Brodbeck wrote:

Homer J Simpson wrote:
"David Brodbeck" wrote in message
t...

Had one explode on a travel trailer once, too. The battery was in
a
plastic battery box on the front A-frame and had been on trickle
charge
for about three months. This was in the middle of winter. It
threw
shrapnel a foot or two on either side.

Froze up?

Probably. To say that the battery chargers in RV power converters are
often poorly designed would be, perhaps, too kind.


All of the RV power converters I've had were nothing more than the
transformer, a pair of diodes and a power switch. The were intended to
run 12 VDC motors and lights, so they had no filter capacitors They
were not intended to charge a battery.


All of the 'off-vehicle' battery chargers that I've seen here in the UK,
are
just a transformer, couple of diodes and a fuse and meter. I've never
even
thought about them having filter caps.


Some people try to use the "Power Converter" top power electronics,
then complain when the smoke pours out. The high ripple and high peak
voltages destroy cheap stuff.


I don't actually see why they would
need them. The battery being charged represents a very low impedance cap
(electrically) anyway, doesn't it ? For this reason, all of the
electronic
circuitry in modern cars, runs quite happily, with not a sign of a big
cap
anywhere, including on the alternator output, to where the battery is
glued
pretty much directly.


These devices are used while parked, to keep the load off the
vehicles battery and electrical system.


I've also read somewhere I think, that charging with a
'pulsy' waveform is good for breaking down inter-plate sulphation. Could
be
wrong on any of this - auto electrics not really my subject, but have
owned
and maintained cars for more years than I care to remember.


I have seen a lot of conflicting views on the subject but a quality
car battery should last five years or more, with proper use and care.


Interesting about the exploding batteries. I'm sure that temperature must
be
a big factor in this. I've been in Florida when there has been sustained
heat. The UK does get that hot, but only for a day or so at a time. I
have
never had a car battery explode on me, and I can't think of ever having
heard of any friends or colleagues that have either. On the other hand,
we
do get sustained periods of cold ( or at least we used to ) in the
winter,
and I don't recall ever having heard of a battery freezing. Looking
around
on the net, the freezing point of sulphuric acid, seems to be around
the -20C mark depending on concentration, so that might be why batteries
don't typically freeze here, but what happens when these things are in
use
up in the north of Canada or wherever ? Do freeze inhibitors have to be
added ? Does a frozen battery cease to produce any current at all, and
does
it recover if left to unfreeze ?


I spent a year in Alaska back in the '70s. We had small electric
heaters that wrapped around the battery to prevent freezing. We also had
dipstick heaters to keep the oil thin enough to start, and a lower
heater hose heater that kept the coolant above its freezing point. You
were limited to a single 20 amp, 120 volt circuit to protect your
vehicle, and you needed a permit to use the outdoor outlets on the Army
base. It dropped below -20 F quite often, and sometimes low enough that
the battery would still freeze.

If the electrolyte does a full, hard freeze the battery case cracks.
A little less than that can distort the plates and short them out, or
break the connections at the top where the connect between cells. I
have autopsied a number of damaged batteries before turning in the scrap
lead. Its amazing the damage a little frozen electrolyte can do to a
lead acid battery.



Thanks all. Very informative stuff. Sorry to cause the teeth sucking Dave
( don't do it too much - you might get mistaken for Gordon Brown and we
wouldn't want that ... ;~} ). I must admit that I've had my Halfords'
charger since I was a kid with my first Moggy Minor, and it's still going
strong. Haven't looked inside one for years, so I'll take your word for it
that we now have to charge brute force lead acid batteries with an
electronically controlled feather touch. But how does that stack up against
charging it on the vehicle with an alternator ? That hasn't got much more in
it than it ever had, has it ? Three phase bridge, pretty basic voltage
regulator, yes ?? Still fundamentally a brute force charging device, relying
on the battery to self smooth the charging voltage, without help from caps,
and to stop drawing charging current when it's had enough, much like in the
old days. There are plenty of 10 or more year old vehicles out there with
very conventional alternators on them. Is there supposedly an issue then,
when a new generation sealed maintenance free battery is fitted to one of
these cars ?

Arfa