Alkaline, Nimh, Lithium, Lithium-ion Batteries

[ardfarkle]

llkylej wrote:

 

The alkaline and nimh graphs have a different scale to them (alkaline y-axis is between 4 and 6.5, while nimh is between 4 and 6) and since, if i am reading the graph correctly, the nimh batteries completely drop below 4 volts after the graph passes ~1800, whereas every single alkaline is still well above 4 volts even up to 2600 for the rayovac.

 

First off, only the voltages are important here. The 'number of samples' scale is nothing more than a time line to show that no long pauses existed during the testing procedure. The alkaline and NiMH tests used a different sample rate (alkaline=every 1 second, NiMH=every 6 seconds) hence the count discrepancy. 71 copies took ~170 minutes. If I had used a 1 second sample rate my DVM would have run out of sample memory. In addition, the sample towards the end of the test include failure information. This is why you see the voltage dropping below 4vdc on the NiMH chart. This information is normally edited out, but I left it there for an example that will made in the PD70X review. If you remove the error information and extrapolate the remaining values, you would have:

 

Last successful copy and time per copy:

Durcell - (((1842 samples * 1 seconds)) / 15 copies) = 123.33... seconds = 2.06 minutes per copy

Energizer - (((1689 samples * 1 seconds)) / 15 copies) = 120.64 seconds = 2.01 minutes per copy

Ray-O-Vac - (((2338 samples * 1 seconds)) / 19 copies) = 123.05 seconds = 2.05 minutes per copy

Panasonic - (((1692 samples * 6 seconds)) / 71 copies) = 142.99 seconds = 2.38 minutes per copy

 

Keep in mind the primary purpose of the charts are to show various aspects of battery performance for my PD70X review. However, they also demonstrate the performance advantages of NiMH cells over alkaline cells in higher current applications which is relevant to this thread.

 

i guess that means the graphs were entirely meaningless ...

 

Not at all. They show that empirical testing was performed.

 

It's one thing to mention how long your alkaline cells lasted last month while eating a cheeseburger, and later while at the beach with your kids you noticed the NiMH cells didn't last as long. There are too many distractions and variables to take casual testing at face value. It all depends on the tester and test conditions. By using empirical testing techniques under controlled/repeatable conditions, such variables are laid to rest.

 

In other words, these charts show I tested and documented what I am claiming.

Edited January 18, 2006 by ardfarkle

[OGBO]

A lot of interesting, amusing, and contradictory "information" posted so far in this thread, but not much authoritative or dependable (ummm, well, there are several self-declared Authoritative posts). During my time in the aerospace industry, I had occasion to talk to genuine battery experts, people who were working on developing and evaluating existing and new technologies. There are several considerations that have not appeared in the thread so far.

 

A quick way to get a summary of the real information is to go to Energizer's website and refer to the technical and application manuals. You will note there that such things as voltage required for operation, load, time cycling, etc. make a big difference in which battery you use for a given application, even for a given chemistry (internal battery design makes a difference!). One way of putting it is that a AA alkaline does not trade directly for an AA lithium iron (NOT lithium ion - different chemistry, different cell voltage), does not trade directly for AA NiCd does not trade directly for AA NiMH. For one thing, each of those chemistries has a slightly different cell voltage - not all are the nominal 1.5 volts. Something I found with some of the electronic gear I have is that NiCd (rechargables) will not power some gear (the cell voltage is slightly too low, and output under load may not be sufficient), where an alkaline or alkaline rechargeable works just fine. In other cases, the alkaline in the adapter case that plugs in to substitute for the normal Li-ion rechargeable pack gives far too short a lifetime and/or will not provide sufficient power (ham radio handhelds are a good example of this). In a low-drain application (some but not all GPSRs), the alkaline may give more life than a NiCd (one charge, not talking about long term cost here), with the result that you might have to carry a pocket full of fully-charged NiCd that a single set of alkalines would have sufficed for.

 

Basic point is - your mileage WILL vary with your particular piece of gear (whether flashlight, GPSR, cellphone, ham handytalky). Know your application, test it in the field under the weather/temperature/humidity conditions you will encounter (not someone else). Much of my usage is in the field for 3-4 weeks at a time, no store/outlet/solar panel nearby (have to keep the weight down), extreme temperatures (by some people's standards, but -20 to -40F is just fine by me), high potential for condensation (when carrying the gear inside the parka to keep it warm). Turns out that AA Li-iron works very well for much of the gear (except that the LCDs die when they get cold). OTOH, I use NiMH rechargeables for most of my local hikes when home in the SFBay area or summer Sierra. And then there are the 9volt applications - so far only 1 particular 9v rechargeable has proven reliable.

 

Final comment - there is NO single battery that is "best" for all applications. Match your power source to your electronic widget and particular application.

[+GOT GPS?]

I looked at several NiMH battery charging units:

POWEREX MH-C801D Deluxe Professional

POWEREX MH-C808M Ultimate Professional Battery Charger

MAHA MH-C204W Battery Charger

La Crosse BC-900 Battery Charger w/ LCD Display

 

I bought the La Crosse BC-900 today at amazon dot com, but did the

research at Thomas-distributing dot com.

 

Will be interesting to compare the BC-900 to my cheap Energizer Quick Charger

 

-

Geoff

[ardfarkle]

MAHA Energy/Powerex make very good chargers, but I have seen quite a few posts about the La Crosse recently. I think I'll need to buy one for testing. Like I don't have enough NiMH chargers already

[MagicTogether]

ardfarkle,

 

The charger I use is:

 

http://www.thomas-distributing.com/ap-accupower20.htm

 

If you are considering a charger review article maybe you'll want one of these accumanager 20 units also. Six separate charging channels, but fewer user selectable options that the La Crosse, no 240v. support.

 

And... maybe after your evaluation and comparison of the La Crosse I'll need something else too... but I have no outlet for writing about them, hence the task falls to you!

 

Jim

MagicTogether - Alaska

[+GOT GPS?]

I found this Thread down on the 4th page.

 

I just got the La Crosse BC-900 Battery Charger w/ LCD Display

Last nite, and I ordered it via Amazon.com on the 17th, so it was fast.

 

Very interesting unit.

Trying some Energizer 2500mah batteries in it.

Will take some time to figure it out, how it works.

 

-

Geoff