WRT Lithuim Ion, bad advice. Comsumer lithium Ion has average of ~300 cycle, costs more, takes even more complex chargers, limits the devices due to less standardization, etc. Look at my bob and gear pack now, I'd need to carry about 10 different chargers if I switched everything from AA to lithium Ion. CPF loves Lithuim Ion because they tend to use their gear every day, puts run time as the top priority, and had a flashlight centric view of batteries. If you include radios, GPS, etc then lithium ion becomes a poor choice.

Now with NiMH you don't want to treat them like NiCad so don't fully discharge them every use, every 20 is the recommended number now (according to CPF and other sources).

Remember also that even though a charger may be multi channel, smart, etc that it still may not be a good charger. There are various methods used to determine a full charge and better chargers will combine two or more. Also charge within the recommended .5 to 1C, charging too fast generates heat which shortens the life, charging too slow makes the end of charge harder to detect and tends to result in overcharging. So stay away from "fast" or the "slow gentle" chargers.

Thanks.



I think you are misunderstanding. I didn't say lithium ion was perfect for every situation. In fact, *rechargeables* are not optimal for every situation.

But I also think you are professing a somewhat slanted view of the technology as well. Lithium ion is light, good power density, fairly easy to charge, holds its charge and works well in the cold.

When it comes to lithium ion I exclusively use 18650s and the neither charger nor the batteries were overly expensive.

I haven't burned a 123A in my flashlight for years now with this method, but I also have a 2x123A battery pack as a backup.

And it isn't flashlight specific. My Yaesu VX-5 uses a lithium ion pack by default, and it would probably be pretty darn heavy if it had enough rechargeable AA cells to do the job.



These sound like good things. Of course, lithium ion is also good for devices you don't use often because of the almost nil self-discharge.

Yes, I understand there are cases where the duty cycle of NiMH is an advantage.

I mentioned I use NiMH too. I also use primary lithium AA and AAA and 123A cells.

Everything has trade offs. Pick the right tool for the job.



Yep, not all chargers are designed equally. This is why I pointed to an actual empirical test of chargers.

-john

> I have a few NiMH batteries 4 to 5 years old, they may have about a hundred
> cycles behind them at most but their capacity is now much less than what it
> used to be.
>SNIP<
> It's so bad that sometimes a freshly recharged pair of NiMH's will last just
> about 10 minutes in my camera or barely suffice to power up a flashlight.

A hundred cycles over 48 months is at the lower end of battery life, but we all know better than to expect the thousands promised on the box. I'd also expect NiMHs to expire on their own after the passage of 4 or 5 years.

Another issue is that NiMHs are 1.2V; alkalines are 1.5V. I've got some devices that expect 1.5V from each cell and they won't operate with rechargeables at 1.2V. I would expect a flashlight to run on 1.2V cells unless it's a high output lamp instead of regular filament. I don't know what LEDs require.

Additionally, high recharge voltages damage cells. If you're using a quick recharger (minutes instead of hours), you're cooking the chemistry, destroying the cells' ability to take and hold a charge.

If all your stuff is four or five years old, I'd considering buying all new high-capacity batteries and a new, modern charger that does not promise 60-minute charging. I think you've gotten all the life out of your old ones.

The self discharge of NiMH is about the same as low self discharge NiMH so no advantage there. They do weigh less but in anything that uses them in a pack such as GPS or radio you still need a special charger so the weight savings is lost there. Then figure in the cost of replacing the battery pack or cells about twice as often as NiMH even if they are not used since they deteriorate with age.

I don't understand what you are saying here. The self discharge rate of NiMH is much higher than lithium ion.



Again, I don't understand. If you use any type of rechargeable battery, you need to make provisions for charging in the field, or providing spares. This would be the same for NiMH or lithium ion.

Lithium ion doesn't work for many devices due to the difference in voltage (witness GPS) and I'm not suggesting you go crazy trying to make it work.

Although, I will point out that *if* you try to take a generic external battery pack, lithium ion is going to be a big win if you are carrying it due to the lighter weight.

example



I suppose. It hasn't been my experience, FWIW. Even with a decent, independent cell charger and effort doing charge management, NiMH has always been a bit of work, and I've always had cells go bad in what seems like a short period of time. Contrast that with the handful of 18650s I swap out in my EDC light which I use all the time which have never been problematic and I have yet to have one go bad.

It has been charge, use, repeat.

The original poster talked about use in a flashlight, so as a random comparison here are two total flashlight solutions (light + two sets of batteries + charger):

Example AA Solution


Example Lithium Ion solution


(source for both lights - fenix-store.com)

Pretty close price-wise IMO.

I'm not saying lithium ion is the answer for everything, but I think it has compelling cases. And actually, it pretty well excels in flashlights (use specifically mentioned by the original poster).

-john

Comparing lithuim ion and traditional NiMH then yes NiMH self discharges faster but the newer low self discharge NiMh are about even with lithium ion.

The problem with your example solution is your listing one top of the line charger for one device. You can use that same Maha c9000 for a dozen different gadgets so the price gets divided between all of them as well as the pack weight. With lithium ion devices you need a charger per unless in the race case of a flashlight you can charge individual cells.

So look for example:

AA Solution
$50 Maha C9000
$50 AA Powered flashlight
$200 handleld GPS
$200 two way radio
$200 digital camera
$50 couple dozen Sanyo eneloops for each and spares for each

Lithium Ion solution
$15 lithium ion cell charger
$50 lithium ion powered light
$20 LG 18650 3.7V 2600MAH
$200 handheld GPS
$20 Power supply/charger for GPS
$30 Spare battery pack for GPS
$200 two way radio
$20 power supply/charger for radio
$30 Spare battery pack for radio
$200 digital camera
$20 power supply/charger for camera
$30 Spare battery pack for camera

remember the maha comes with a wall and car charger so to get the equivalent with the lithium ion solution each device usually comes with a wall charger but then you need the vehicle charger or an inverter. The bateries are all different, the one from the gps won't fit the camera, the one from the camera won't fit the gps, the one from the gps won't fit the radio, etc.
Even if you eliminate the second chargers you still have 4 instead of 1. Ok sure its nice you can charge everything at once but you can buy 8 bay nimh chargers or buy a pair of c401fs, etc.
You still can't share the lithium ion batteries between devices.
Again, your solution does look best if you only look at flashlights, as I said before, but looking at a bigger real world picture, newer technology (low self discharge nimh), ability to share the spares, and the ability to supplement with a $10 bulk pack of 30 AA's if needed the advantages of lithium ion are quickly outweighed by standard AA's

Actually, you *need* a top of the line charger to effectively manage NiMH batteries, IMO.



I won't bother responding to the rest since we are obviously not communicating. I've never said using AA technology wasn't flexible, etc.

-john

Perhaps a universal charger that charges Lithium Ion and NiMh and NiCd AA and AAA might be useful such as the Ansmann Digicharger Plus

http://www.adorama.com/ANDGP.html

A lot of gadgets with dedicated Lithium Ion cells usually have the recharging circuit built into the device and many of those gadgets just need a DC-DC universal regulator i.e. 12V cigar connector to whatever the DC Voltage requirement of the gadget is designed for. Many of these gadgets are also more compact and lighter than their AA or AAA NiMh equivalents.

Is there such a thing as an AA powered mobile phone?

That's where this type of device comes in handy.

-john

OK, so I just bought a pretty darn smart charger as far as the specs go. Will see how it works in practice but I've already determined most of my older NiMH batteries are basically shot. Maybe I'll be able to revive a few with the refresh function but I got another pack of Sanyo 2700mAh plus I see some Eneloops on the way.

BTW, what has been said above re: Lithium being ideal for flashlights. It may well be true but I'm more than willing to sacrifice what marginal improvement Lithium can offer for the versatility of AA batteries. There are some very high-performance LED lights that run on AA's. Having all your portable gear run on standard AA's, flashlight included, is a huge benefit IMO. Especially for a relatively sporadic, preparedness-minded user.