servers.net>
>Remember you cannot jump gel batteries. You will "short" a cell, which
>may not be the technical description but is the effective description.
>
>I paid for three gel batteries before a Roseburg, Oregon welding supply
>dealer answered my question:
> "How do I treat this gel battery?"
> "Just like any other battery," he answered.
> "So it is OK to jump it?"
> "Hell no, you can't jump a gel battery."
I'd be interested in talking to this giver of advice to see
if he understands what a "gel" battery is.
A long time ago, in a galaxy not too far away, someone
wondered if flooded batteries could be a little less sloppy
by turning the water/acid mixture into a bad tasting
imitation of Jello.
The idea worked . . . sorta. The batteries were indeed
less sloppy but they still leaked if turned upside down
or if you poked a hole in the side. Further, their low
temperature performance wasn't as good as a flooded battery.
Some years later, another thinker in the ways of batteries
was probably watching a TV commercial for Brawny paper
towels and wondered if a lead-acid battery wouldn't perform
better if the electrolyte remained liquid. Instead of slowing
it down in jello, suppose the liquid were completely contained
in a high surface area medium like paper towel, or perhaps
fiberglas.
(As an aside, consider fabricating a cube of .001"
diameter glass beads. That means 1000 beads along
each edge. The number of beads required to build
the cube would be 1000 x 1000 x 1000 or 1 billion beads.
The surface area of a sphere is 4 x pi x radius squared.
This calculates out to 3.14 x 10 to the minus 6 square
inches/sphere. Multiply this times 1 billion spheres
and we get a total surface area of 3140 square inches of
INTERNAL surface area! This gives you some idea of the
magic that makes an RG battery work. We know that liquids
have a certain affinity for cling to a surface . . . the
above exercise shows how easy it is to get a lot of surface
area in a small volume. Try the excercise again using
1/2 mil diameter beads.)
Further, if the liquid WERE totally contained in a
partially saturated, glass mat . . . what would, or
should happen to bubbles that are driven out of the
water by charging the battery?
This thinking was the birth experience of the gas recombinant,
starved electrolyte, vented yet sealed lead acid battery.
This is NOT a gel-cell device, yet the majority of people
who sell these things don't know it. Gel cells are still
around but RARE. They are popular in some deep-discharge
configurations for wheelchairs, etc.
>I have forgotten to turn off the master switch a couple times since, but
>never had to buy another gel battery after I started disconnecting the two
>battery cables, jumped the starter directly, and after the engine was
>running, reconnected the two cables.
Now, let's consider the physics of "jumpering" any battery
to deal with a totally flat battery. A dead battery will
draw a lot of current from a constant voltage source like
a hefty alternator . . . it doesn't matter what kind of
battery it is. A gel-cell had a higher internal impedance
than this flooded cousins . . . much higher than a modern
RG battery. This means that ANY current, charge or discharge,
results in higher internal losses due to heating. It is
conceivable that a totally dead, gel-cell battery might
suffer ill consequences for having been jumpered to a
vehicle with a fully charged battery and the engine running.
The question for the moment is, what is the true nature of
the battery that started this conversation? You have to go
out of your way to FIND a true gel-cell battery manufactured
by Sonnenschein or Johnson Controls. There may be other
sources but they are not the Panasonics, Powersonics,
Hawker, or Yuasas of the battery marketing world. Irrespective
of what any battery seller might say about sealed
lead-acid products, it is most unlikely that the battery is
really a gel-cell. RG batteries are quite tolerant of
high recharge rates and the few seconds of connection needed
to crank an engine are not likely to heat things up even in
a relatively tired battery.
>I have not seen this advice in print, but it was a costly lesson to
>learn buying new gel batteries.
>
>As Ben Franklin said, "Learn from other's mistakes; you do not have time
>to learn them all yourself."
Ben was a critical thinker and he would want to know more
about the conditions that precipitated his unhappy
experience with batteries. I can tell you that
multi-million dollar biz-jets get their batteries (Ni-cad,
RG and flooded) jumpered to ground power carts capable of
thousands of amp output with no ill effects. We don't have
enough data to deduce the cause of our friend's battery
failures. It is insufficient and erroneous to put out a blanket
statement about "jumpering a gel-cell battery" . . . especially
when the product in question probably wasn't a gel-cell device.
Bob . . .
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( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
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