Re: sealing battery posts

[Ken Lange <lange@SONIC.NET>]

I apologize if my EV buddy Dave Luiz has already posted this
information.  Between the two of us, we have 62 of the pre-
production (read that as leaky) Optima Yellow Tops.  Here's
our sealing experience.

When we got the batteries, we cycled them all once; the discharge
was nominally 100 amps with a constant resistance load box that
Dave designed and built.  The batteries showed a wide variation
in leak rates;  however, all of the leaking occurred at the negative
terminal only.

Dave designed a sealing method.  He crafted a tool using an
inexpensive soldering iron which he filed to make a special tip.
It looks like a cylinder (diameter is the original body, about
1/2 inch or so) which has on the end a little nub of a cylinder
which is about .080" in diameter, and about the same length.  He
heated this up and ran it around the negative lead terminal, resting
the larger diameter on the lead surface.  This made a channel
about .080" wide.  We then cleaned away the residual flash of
yellow plastic using an Exacto knife.  After cleaning the channel
with acetone, it was filled with JB Weld epoxy.  When cured, the
epoxy can be filed or sanded flush with the lead at the base of the
post.   It's almost the same color as oxidized lead, so it looks
pretty nice.

After doing this to all the batteries, we cycled them again to check
for improvements.  On the basis of this one cycle, none of the
batteries leaked, even a tiny drop, except for several batteries
where there was a bubble in the JB Weld.  The bubbles tended to
be invisible when the epoxy was applied, and SLOWLY rose to
the surface without popping, leaving a hole.  Treating these holes
with a second epoxy application fixes this problem.

We did only a short evaluation of JB Weld's resistance to sulfuric
acid; we soaked cured epoxy for several days in battery electrolyte
with no noticable degradation.  Longer term effects are unknown.

It was a bit of work, and Dave did the major part.  It is comforting
for me to have made a stab at fixing the leaking, since several of the
batteries in my car will be less than readily accessible.  This should
be one of the advantages of 'sealed' batteries.

We also recorded the voltage and current every 10 seconds
when we discharged the batteries.  There's quite a variation of
capacity, but conclusions are tough because it reflects both battery
capacity and self-discharge rates in one number.  If anyone is
interested, I can email the data.  It's in a Lotus 1-2-3 spreadsheet
at the moment.

Ken Lange
Re: sealing battery posts