More grist for the battle of the battery

Bill Daniels wrote:
Lithium Ion rechargeables seem to have recently seen a 50% or so price drop.
A 4-cell, 14.8V, 8AH with charger and mounting plate can be had for $169.99
(USD).

Can you supply a URL? While I strongly discourage people from making up
their own Li-ion battery packs for their glider due to potential safety
problems, a _production_ battery pack with it's dedicated charger would
likely alleviate most of the concerns I have about using a large Li-ion
battery in a glider. I don't worry about the little ones in my PDA, cell
phone, or camera.

These are basically long endurance laptop batteries.

What would be the advantage of this battery over the 12 volt, 7 to 9
amphour SLA for your application? Neither size nor weight seem important
in a battery of only 8 amphours, whether SLA or Li-ion. That's a Nimbus
you fly, right?


This is still too much for me given that a SLA with the same capacity is
around $25 but the downward price trend is hopeful. Someone contemplating a
transponder, electric T&B and other juice hungry gadgets in a $100,000+
glider might see Li-Ion as a possibility now.

Unless it allows the pilot to mount significantly more capacity in the
original battery box, eliminating the need to find a place to mount more
batteries, I don't see any benefit. Saving a few pounds seems pointless
in most gliders, even a SparrowHawk.


Beyond price, my concern is voltage. 4-cell Li-Ion packs produce 14.8V and
a detail in the spec sheet admits that a new, fully charged pack might
produce 16.2V into a high resistance load. My avionics manuals say 16V max.
Is that 0.2V overvoltage likely to be a problem?

"Probably not", but I don't know how much margin is built into that
specification. Routinely operating at the high end of the voltage range
might be a different situation than the specification addresses. Ask the
manufacturer, I think.

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Eric Greenwell
Washington State
USA