nicd vs. nimh chargers (for 90 min 9N batts)

Last night (this morning??) I offered to post some photos of a comparison between NICD charging circuits and NIMH circuits.
The nicd circuit is inside the 9N charging base and can be seen at
www.hmmwv.net/charge.jpg

the components ( from left to right ) are the idiot diode (for the idiot who connects the polarity wrong) - the voltage regulator - the power resistor to make it look like a constant current source, and two resistors/leds to tell you it's working. Pretty simple. No rocket science here. No rocket science funding either.

Now take a look at the NIMH counterpart.
www.hmmwv.net/c2.jpg

this is an evaluation board by benchmarq that handles nimh chemisitry and treats it with respect. As you might expect, it is substantially higher in cost to manufacture than the simple constant current nicd charger used in the 9N charger. The spec sheet alone for the BQ2004E chip is larger than the surefire catalog.

Trust me - switching to nimh chemistry batteries is a pain. it's your pain threshold that determines if you're going to do it or not.

BTW - tonight the 3000 mah pack after resting, charging overnight, and starting again today ran bright for 75 minutes, then suddenly (i.e. 30 seconds or less) went to nothing. This was cycle #2 for prototype #1. Cycle 3 should increase even more.

This *IS* a learning experience.

All that for an additional 45 min of run time To be honest I didn't think it would be as hard as it sounds. Now I understand why Surefire has stuck with NiCad. I think for most people it would be easier and cheaper to carry spare NiCad batteries.

It is the thought of knowing that a "better" battery is avaiable. Have you looked in to LiIon at all? Do they make any in standard sizes yet? Or they an odd voltage that wouldn't be compatable?

Brock

Keep up the good work hmmwv. Keep the reports comming.

Brock -

RE: Li-ion --- YES! -- and i'm wondering why there isn't a 3.6P model out there (3.6V Lithium) - To make a long story simple, there are two types of lithiums being made - the sony type - and the other type. The difference is in the center electrode. I have lots of Sony-type lithiums that are within .020" of fitting down the barrel of a 6p, and they are 4/3A size (i.e. 2x2/3 A, get it???)

That project involved pealing off the protective outter film on the li-ion, using a much thinner, more natural, latex, form of protection to replace it, and shoving the 3.6 V cell up the 6P barrel. I hope that last paragraph made it through the censor.


A 3P lamp assembly worked great because the li-ions voltage drops pretty fast with current. The sony li-ions are all over the place thanks to laptop manfuacturers. It's a very popular battery - probably rivals the DL123 above it in this photo:


What the result ended up being a was a lithium ion 3P in a 6P body, with a separate dedicated charger for the cells (which weighed next to nothing)

SF could mass-produce it by making the barrel size just slightly larger on the 6P (to accommodate the sony safety film - blue in the picture above) - and then putting the 3P lamp and a custom charger with it. They could also use the body of the 12Z, fatten it a bit, use the P60 series lamps, and put a standard head on it and have a lithium-ion powered 6P in a 12Z body. (the .6 V difference goes away as soon as the current starts)

Once again, though, this would have delayed the development of the 10 series, which we are all waiting for, and would only appeal to a limited market. Plus lithium-polymer is right around the corner (charing ICs are already available for the batteries!) - so Lithium Ion is last years model.

Lithium Polymer - oh.

Maybe I need to do some reading cos I've only heard of it in passing!

That's a mighty photo you took there!

Great ideas!

Al

OK,I just got to step in here,
Alistar,I agree,where`s the 6 volt size,65 lumen Li,Lp..re-chargable??!!,The battery technology is there!!!
Hmmwv,your post`s are very informative,,but I gotta tell you,I think your over-complicating the 9N NiMh project,
I`ve used an SF-9N daily for about 2 years now.I alternate 3 SF Nicad pack`s.,.1200-1400ma`s I believe,,around 40 minute`e run-time..as advertised....
I have also constructed some 3000mah Nimh (panasonic) sub-c pack`s....2 hour run-time ++,..Ive charged these pack`s with the standard SF slow-carger,Novak Digital-plus,and an IQ re-flex charger..no differance in heat build-up..or run-time,,as of yet..,,For the first couple of cycle`s I was treating them VERY gently..Charged at a low rate,with thermal probe.etc,,Iv`e found these current NiMh cell`s to be quite "Robust"..,,Take`s "abuse" quite well,,I don`t "quick" charge them ,...as i have 3-4 spare`s available...but the option is there,if required..
RGDS,Bill

Bill -

I'm going to assume you are talking about the 140 lm. bulb in the 9N and not the 20 lm. bulb.

There's a couple problems with what you've said in your post - first - if you're getting "2 hours + +" of runtime from the 3000 mah batteries, then something is wrong. Your battery voltage may be low on the panasonics, resulting in lower currents through the bulb and a substantially reduced light output. My 9N using the sanyo 3000 mah cells draws 2.5A - your 2+ hour runtime would suggest that your flashlight is using 1.5A - so to begin with, I think we're comparing apples to oranges here. Reasons for that later. Personally, I prefer the higher light output - but you may prefer the lower voltage and longer runtime (your bulbs will certainly last longer than mine).

As for charging your cells - I'd advise you to read www.panasonic.com/industrial_oem/battery/battery_oem/images/pdf/nimhchar.pdf which clearly states that some of the charging methods you indicated you are using can damage the cells (which also may explain why you are running for "2 + + hours") - I quote from the document

The overcharging of nickel-metal hydride batteries, even by trickle charging, causes a deterioration in the characteristics of the batteries...

Your 2 hour runtime is most likely evidence of the damage done by your haphazard charging methods. You should be getting close to 90 minutes of runtime if the cells are "above average" meaning they exceed the stamped ratings, or about 75 minutes of runtime if they are truly 3000 mah cells.

Have you measured your current draw through the bulb to determine how many mah you are actually getting from the panasonics?

Hmmwv, Have you tried powering a P60 lamp with two of the Li-Ion cells in series? How do you think that would work? The P60 pulls 4.8v at 1.1 amps. Maybe the P61 would drop it enough with the larger load, 3.75v at 2.3 amps. They don't make those cells shorter do they? Where did you get yours from and what charger are you using on them? Now I want to try it in my 12PM. I put a P60 head on it and it fit's and looks pretty sharp also like a little club.

Brock

Brock -

The Li-ion have the current capacity to do this (just barely, for the p60) - but for some reason my 12Z had a smaller interior diameter than my 6P did, which meant I'd have to chuck it up in the lathe and put a boaring bar down it to make room for the Li-Ion cells. - before I could make it to the machine shop, a friend borrowed my 12Z to use on his ride-along trip with the boarder patrol down in LA. They confirmed the blinding effects of the 12Z on multiple suspeccts. By the time I got it back, I'd cleaned up the shop and was off to other projects. Now I'm thinking of selling my 12Z since I got the M6, so I'm not anxious to have an "oversized" bore on it.

Electrically, what you are suggesting works fine - and if I recall, the runtime is pretty spectacular.

I was just re-designing the 9N charger when I recalled Bill's immoratal words, "I think you're overcomplicating this" -- He was right.

I've now milled slots in the 9N plastic and installed these little miniature fans to get cooling air over the flashlight while it's stuffed in there for charging. At 3A charging current - the sanyo 3000RC cells get HOT HOT HOT. So add a fan or two or threee... or.. well... Not sure how many I can cram in there and still get a charger in the same box, but you get the idea.

Anyways Bill -thanks for the in-sanity check. I think I need it once in a while. Gotta go wire up the fans now.