90 Minute 9N batteries have arrived

hmmwv

Newly Enlightened
Joined
Oct 27, 2000
Messages
155
Location
Santa Clara, CA USA
Well - At 1AM this morning (PST) the first 90 minute 9N battery PROTOTYPE was turned on and allowed to run continuously. Here we are at 1:55 and it's still bright white.
For those of you who haven't been following my ventures here, I **WANTED** nimh batteries in the surefire 9N, because the factory rating of 40-45 minutes is just not enough sometimes. I've always had to carry at least 1 spare battery with my 9N.

The 9N usese 3 sub-c NiCDs in series for 3.6 V, paired with a 3.5V carley lamp. It's an excellent design - and I'm not sure if my changes are going to be backwards-compatible with the design.

A while back, panasonic and sanyo entered into a race - who could get the biggest capacity in a sub-c NIMH cell - panasonic had the early lead, but sanyo's technology was superior, often yielding 3200 mah or more. They are only spec'ing 3000 mah, but the 3200s are expected soon, and the 3000s delivered in this lot "may be a little underrated"

For a picture - www.uwave.com/bat.jpg - left is the negative terminal, which on sanyo's will have "HR" stamped into it - center shows the 3000 MAH designation, right is the positive terminal and insulator. If these batteries don't look cheap - it's because they aren't - about $8 EACH, plus taxes, shipping, minimum order quantities, trip from japan, etc. For what I've spent on this project so far, I could have bought another 4 M6's.

But the thought of having twice the capacity of a standard 9N battery pack just drove me to the point of obsession. And so was born the idea to purchase the hard-to-find SC3000 batteries and make a surefire pack out of them.

Tonight is the burn-in phase - all NIMH cells need to be charged/discharged about 4 times before they actually DELIVER their rated capacity. It's now 0205 (65 minutes) and the pack has begun to dim - time to shut it off - but this is to be expected - it is the first use of the pack, and 2/3 of rated capacity is not unusual in this case. The pack will be charged, and discharged again.
I expect the runtime to increase with each of the first 4 charge/discharge cycles.

Again - if you haven't been following the discussion on the nimh vs nicd controversy - nimh does require a different charger design than nicd, in fact, nimh cells can be damaged by nicd chargers, although the reverse is not generally true. So part of this experiment is to develop a charger specifically taylored to the 3000 mah cell - which means a charge current of 3A, followed by a "top off" period, followed by a "maintenance" period - not your standard 9N charger by any means. This is perhaps the stickiest point of all - between the cost of the cells and the design of the charger, the additional cost to the product would make the 9N a VERY expensive light. By using NiCDs, the design cost has been minimized - they are about 1/8th the cost of the NIMH cells, and the charger has 3 components inside it (I'll post a photo of a NIMH charger tomorrow and compare it with the 9N charger - you'll see why the charger is sooo expensive!)

In summary - for me a 90 minute battery on my 9N means I can quit carrying my SL-35x (1.5 hour runtime as well) when I need a constant-on light that runs a LOOOONG time. In fact, I can carry 2 battery packs for 180 minutes (3 hours!) of light with less weight than the SL-35x. The only reason I bought the SL-35x is because I needed the runtime and I was waiting for these cells to arrive (they had to be imported from japan) - my tired old 9N NiCDs are now giving about 5 minutes of runtime, so the 9N was not usable without new batteries.

All information in this letter is preliminary - I have only engineering calculations that suggest 90 minutes of runtime - factual data wll be presented along with more photographs in the next few days.

Oh yes - the Nimh cells are slightly higher in voltage than my tired old NICDs - an open circuit nicd was (fully charged, still hot) about 4.05V - A similar NIMH was 4.45V - 10% higher - also the light is "whiter" during the discharge phase, indicating higher voltages, and shortened bulb life. There may be risks associated with the use of these cells and the 3.5V carley lamp - but I have spare lamp assemblies where the low beam burned out first, leaving a perfectly good high beam lamp to use.
 
Top