PDA-Based ETDs

[Farrell]

Voltage Depression ("memory") occurs primarily in NiCad batteries 
(nickel-cadmium). NiMH batteries are almost never affected and Li-Ion 
batteries are NEVER affected. I have used numerous NiMH battery packs that I 
have made up extensively on my bicycles for powering lighting systems with 
consistently excellent results. I have tried Li-Ion and have had problems 
with the electronics involved (not to say that Li-Ion is bad, but I've just 
had problems with the technology). I have also used NiCad batteries in the 
distant past - nothing short of a nightmare. NiMH for small packs are about 
the same size as Li-Ion, seem to be bullet-proof, last forever (zillions of 
recharge cycles) and cost half that of Li-Ion.

I already have a 12V smart battery charger for NiMH, so that won't cost me 
anything. And the voltage indicator, which is only $17 is an add-on - the 
other $139 packs don't have one, so it is an upgrade and not comparable. 
Truth be told, I do also have to incorporate a voltage reducer and current 
limiter for proper charging and that cost me $13. So the pack and 
electronics will cost me $26 plus the voltage monitor. Even if I had to buy 
the charger, I can get a smart charger for that pack for $17. No battery 
holder needed - the pack will be a pad for my PDA. So total cost if I had to 
buy all the parts - batteries, charger and needed electronics - would be $13 
+ $13 + $17 = $43 and I chose to upgrade the pack with a battery monitor, so 
add $17 for a total cost of $60.

We're still talking less than 50% the cost of the other - and I get to have 
all the fun of building it! And I do enjoy building battery packs. It's 
kinda like doing key bushings - can't explain why I enjoy doing them so 
much, but I do. So building the pack is just icing on the cake. The pack 
will also likely have a Sitka Spruce panel to hold its shape!

YMMV.

Terry Farrell

----- Original Message ----- 
From: "Don" <pianotuna at accesscomm.ca>
> And the cost of the battery holder, and the cost of the voltage indicator,
> and the cost of a charger, and what is your labor rate per hour? Lots more
> than $13.00 I suspect. Plus LI vs Nickle Metal Hydride--no memory effect 
> on
> the LI, but there is for the Nickle.
>
> At 06:08 AM 5/1/2008 -0400, you wrote:
>>Well, for one, I already ordered batteries to make up an external pack. 
>>The
>>pack I'm making is half the size of the Zap pack (and half the capacity -
>>but still way plenty, I'm quite sure), and the batteries only cost $13
>>compared to $139.
>>
>>Terry Farrell