La Crosse Technology BC-900 AlphaPower Battery Charger

Why should you get this charger instead of some other charger?
5 words: CHARGE, DISCHARGE, TEST, REFRESH and LCD!
CHARGE
Choose the individual charging rate for each battery, (200/500/700/1000/1500*/1800*mA).
Why choose the charging rate?
If you're rushing, charge fast and hot. If you're charging overnight or over dinner, charge more slowly. Slow charging is almost always gentler on the batteries, giving you a longer useful life.
Why set the charging rate individually?
You want this ability in case you have batteries of different capacities, partially discharged batteries, mixed brand/quality or any number of other reasons.
* Note
1500/1800mAh only available in Charge mode and only when charging 1 or 2 batteries in terminals 1 and/or 4.
DISCHARGE
This mode discharges the battery down to 1 volt then recharges to full capacity using Delta V measurement, at a user-selectable charging level*, of course.
Why discharge then charge?
This is the older technique developed to avoid capacity-robbing memory effect encountered when recharging NiCad-based batteries (which by the way are compatible with this charger, unlike the Maha mentioned below).
Why Delta V?
This is the modern measurement adopted by most "fast/rapid" chargers. While not quite as accurate as simultaneously using Temperature measurement and/or detecting Zero Delta V, as the Maha/PowerEx C-204W can do, it should be enough to prevent battery damage and insure complete, consistent charging.
* Note
Discharge rates are 1/2 the selected charging rate (max 1000mAh charging in this and other modes). Some batteries can take discharge rates this high, others can't. Most electronics don't drain batteries this fast continuously, so most batteries won't be any "healthier" if discharged too fast. Since this mode will probably take several hours to complete, do it overnight at the gentler 200mAh or 500mAh charging modes (and corresponding 100mAh/250mAh discharge modes).
TEST
Did you think that those little power strips on alkaline batteries were a good idea? I did, who doesn't want to know how much juice is left in a battery. The problem is the indicator bars weren't very meaningful and couldn't measure voltage too accurately.
Now, this charger can tell you more accurately the voltage output of your batteries (which you may interpret as an indication if it's fully charged > 1.40V or discharged < 1.20V). Still, that's just an indication of charged capacity. Why not a direct measurement?
The Test mode does just that. It measures the capacity of each battery and reports it. It initially charges each battery, discharges it (simultaneously measuring the mAh) and then recharges it, leaving you with full batteries and a record of how much juice it discharged during the test.
Why Test?
You ever pull open a drawer, find a rechargeable, wonder if it's "still any good," recharge it and then use it just to find out? This baby will do it all for you, giving you the answer for each battery as it finishes.
Another good reason is to verify the capacity of newly bought batteries. I'm using it now to check each battery in a brand 24-pack of Lenmar 2000s. It's found some clunkers which I'm saving for the next mode, which is...
REFRESH
If you're thinking this mode refreshes batteries, you're right. I haven't had the chance to use it yet, but you know I will. I've got some great candidates too, brand new clunkers from Lenmar, some good old "state of the art 1400mAh" Sanyo and Nexcell NiMH's and even some older NiCads (it may be cheaper in the short term to return them to service than to dispose of them).
You can't use this charger on alkalines or rechargeable alkalines, so don't even think about "refreshing" those in this charger.
One thing about the Refresh mode. Refreshing NiCads manually may take several cycles of charging and discharging. Not only does this charger perform the charge/discharge cycle as many as 20 times, it measures the capacity of each discharge cycle and stops refreshing when the capacity of each battery isn't improving anymore. With other chargers, you're probably overcharging some of the batteries just to get the others back up to snuff.
LCD
One thing the Maha doesn't have is an LCD readout (though their C-777 model does, maybe next year?). The BC-900 has an individual LCD readout for each battery, which you can set to alternatively display any of 4 different measurements (hours, volts, mA charge/discharge, mAh), in addition to continuous displaying the particular mode each battery is in. The LCD readout retains it's reading (e.g. tested mAh) until the battery is pulled out, making overnight "tests" possible. The LCD makes all the other charger modes informative and practical.
Shame on those other chargers that have LCD indicator bars but no numerical display (some even cost more than the BC-900).
Understand, as great as all the different modes and options of this charger are, without an informative LCD display, they would be "shot's in the dark". With the individual displays, I'm happily recharging batteries, checking the quality of each, refreshing some while storing the "truly" fully charged ones.
With the LCD, I'm getting an idea of just how good a pack of batteries (and hence brand) is.
ROOM FOR IMPROVEMENT
Transformer
The current power brick is oriented so that it may block adjacent outlets, so put it on the end of a powerstrip or AVR/UPS unit. My Nokia phone charger has the plugs on the edge so it's really low profile on the outlet.
While the transformer is thankfully a bit slimmer than most external units, it is also a bit longer than most (about 1.75in by 3). It is however Autovolt from 100-240V, although another reviewer mentioned the 3V DC output was sort of a pain.
I wish this charger had a built-in power transformer and a retractable cord.
Cooling fan
Batteries get hot from charging, they'll read hot too. A built-in cooling fan would keep the batteries cooler during charging and probably give a more accurate "just-charged" reading on the LCDs. Some other high end chargers have fans built-in, so I'd hate to see this "ultimate" charger get upstaged by lacking such a common-sense $1 feature.
Free Bag
The unit comes with a free bag which is much roomier than necessary. I could fit my Casio Exilim camera, dock & transformer for the Casio, backup compact film camera along with the battery charger, C/D-cell adapters and 24-pack of batteries in the bag. While I feel sort of silly mentioning a quirk about a free item, the bag is hardly usable as a belt bag since it is so ... baggy.
CONCLUSION
If you ever invest in rechargeable AA/AAA technology, you'll multiply your investment by getting this charger.
UPDATE 7/6/2005:
I've REFRESHed about 8 clunkers so far, 2 NiCads an officemate brought for me to work on (about 2 years old) and 6 Lenmar 2000 batteries.
The results?
NiCad
1 rated at 700, first TESTed at 256, REFRESHed to 677.
2 rated at 700, first TESTed at 344, REFRESHed to 741.
NIMH - done REFRESHing.
1 rated at 2000, first TESTed at 448, REFRESHed to 1507.
2 rated at 2000, first TESTed at 527, REFRESHed to 1820.
3 rated at 2000, first TESTed at 680, REFRESHed to 1488.
NIMH - still REFRESHing.
4 rated at 2000, first TESTed at 435, REFRESHed to 1270+.
5 rated at 2000, first TESTed at 436, REFRESHed to 1713+.
6 rated at 2000, first TESTed at 349, REFRESHed to 1813+.
More Room for Improvement?
Charging Rate Limit (wrt Terminal 1)
The charging rate selected for Terminal 1 (1-4 left to right) is the highest rate you can select for each of the 4 Terminals. I didn't think this would be a big deal, but when you REFRESH batteries at the gentlest rate (200mah charging, 100mah discharging) and the cycle may repeat as many as 20 times ... well, you do the math. I know I didn't have to set it at the gentlest rate, but I figured I shouldn't stress already marginal batteries.
Now, when the battery in Terminal 2 read full (as in Fully Refreshed), I took it out to charge one of the other batteries I had already used up. Enter the Charging Rate Limit. I am limited to 200mah charging (the current setting for the still REFRESHing battery in Terminal 1) and it's driving me nuts! I wish each Terminal had it's full 200-1000mah charging rate available independent of the settings on the other Terminals.

Canon NB-2LH Rechargeable Battery Pack for Digital Rebel XT/XTi, PowerShot S30/40/45/50/60/70/80, G7 & G9 Digital Cameras

I have been using my Canon PowerShot S30 camera for a couple of years now. When I purchased it, I also purchased an extra generic rechargeable battery pack to go with it. At the time I figured I would save the money and name brands are not always better. Looking back on it, I wish I sould have spent the extra $25 and gotten a Canon battery. The generic battery only lasts about a 1/4 of the time that my Canon battery does. Also after a couple of years of use my Canon is still running strong while my generic battery barely lasts at all. I am now getting ready to purchase a second battery for my Canon for a family trip in September and I will only be purchasing a Canon brand battery.
THE BOTTOM LINE: If you are going to be cheap and a penny pincher, then you are going to get a cheap worthless battery. If you want a battery that will keep its charge and that you can count on, buy a Canon battery.

GE/SANYO eneloop 4 Pack AA NiMH Pre-Charged Rechargeable Batteries

I was really excited when I first heard about the Sanyo eneloop LSD (low self-discharge] NiMH batteries. The promise to "maintain 85% of original charge after one year" sounds amazing. However, after reading Sanyo's Nov 2005 press release carefully, I learned that the claim is actually based on "simulation test when stored at room temperature of 20 degree C".
The rechargeable battery is an electrochemical device. Since most chemical reactions happen faster at elevated temperature, it is reasonable to expect the self-discharge rate of the eneloop to be also faster at higher tempeature. The question is: by how much? The following is my experiment:
I purchased two eneloop AA 4-pack on Jan 3rd. The packages were dated "2006-07", which means they were probably last charged in the factor nearly six months ago. The initial voltage is 1.31V for all cells. I then tested a total of five AA cells using the "Discharge/Refresh" mode on my LaCrosse BC-900 charger.
The first discharge cycle (at 250mA) yields the residue charge in those cells. The average of five cells came out to be 1476mAh. The spread is between 1388mAh and 1531mAh.
Next, the cells were fully recharged (at 500mA) and discharged again. The second discharge cycle yields the freshly charged capacity. Amazingly, the numbers all came out to be within 1-2% of rated capacity of 2000mAh.
Therefore on average, those five eneloop AA cells I tested have lost 26% of their original charge after nearly 6 months of storage. This rate of energy loss is about three times higher than what Sanyo advertised. However, it is important to point out that a typical NiMH cells will lose around 30% of is original charge within one month (Some brands, such as the Energizer 2500mAh, will loss 30% in one week). So the self-discharge rate of eneloop is still 6-7 times slower. Just remeber that they are best stored at temperature of 20 degree C or lower, if you hope to get the advertised self-discharge rate.
[Update on June 3, 2007]
In my 2-month self-discharge test using four different brands of NiMH cells. Hybrid and eneloop came up neck-and-neck!
Room temperature: 60-62 degree F (16-17 degree C). All capacities measured are average of 2-cells.
- Sanyo eneloop 2000, purchased Jan 2007.
Initial capacity measured: 2070mAh
Capacity after 62 days: 1796mAh (-13.2%)
(Note: my previous result for eneloop showed -18%, but I repeated the test and it did better this time)
- Rayovac Hybrid 2100, purchased Jan 2007.
Initial capacity measured: 2155mAh
Capacity after 62 days: 1859mAh (-13.8%)
- LaCrosse 2000, purchased Jan 2006.
Initial capacity measured: 1902mAh
Capacity after 62 days: 1417mAh (-26%)
- SONY 2300, purchased Sep 2004.
Initial capacity measured: 2210mAh
Capacity after 62 days: 1309mAh (-41%)
So neither eneloop nor Hybrid did as well as advertised, but they are still significantly better than previous generation of NiMH cells. So you can't go wrong with either brand.

Sony 2500 mAh AA Rechargeable Nimh Batteries, 4-pack

These are my first rechargeable batteries, so all I can say is that in comparison to alkaline, these are WAY better and longer losting. Alkalines stop working in digital cameras long before they are actually used up, because they can't supply the required current for high-demand devices. These Sonys last much more than 4x as long because alkalines only work for a few minutes. These Sonys maintain their voltage at a stable level. I am using them in an Olympus C-755 digital camera, and I charge them using the Sony BCG-34HE4 charger. I can't say exactly how many pictures you can take on one charge, because they last for so long I lose track. If you have a digital camera, you absolutely must use rechargeable Nimh batteries. Don't waste your money on the expensive "high-end" alkalines or non-rechargeable lithium, etc. Also, you are doing the environment a favor by not using toxic landfill filler.

Sony Quick Battery Charger with 4 AA Ni-MH Rechargeable Batteries

It doesn't say so in the product description page here anywhere (and I can't even find this charger on the Sony website), so here you go: it takes about 4.5 hours to fully charge the four 2300mAh batteries that come with the charger. Which I kinda like--I like that it's not a dumb charger (timed charger w/o regard for existing charge or overcharge) like the cheaper Sony charger here on Amazon.com (BCG-34HLD4), nor does it take inordinately long (some others I checked out take as long as 8-12 hours), but it's not a superfast 1-hour charger that super-heats up the batteries during the charge (and potentially reduce the battery service life).
The charger has the outlet plugs built-in, so there is no separate AC adapter. Be sure to keep the charger bay door open during charging to help dissipate the heat.
The batteries are Sanyo-brand ("HR" imprint on them) marketed under the Sony label.