What's the Best Battery Charger?

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DougPaul said:
The MH-C777 looks fine for battery packs, but looks like it can charge only one item at a time. The ability to charge cells individually is desirable, so if you have a bunch of AA or AAA cells you are probably better off with a charger that simultaneously charges several cells individually (eg MH-C401 or MH-C801).

I have several "lost" battery packs where one cell appears to be weak, but since the pack is sealed the entire pack must be replaced. If I could get at the cells individually, I might be able to fix (rejuvenate) or replace the weak cell... High quality battery packs (eg laptop batteries) often have external connections to each cell and internal temperature sensors to allow one to maximize the useful lifetime.

Doug
Click to expand...

Well actually like I was saying Doug. If you buy a 4 pack or 8 pack battery holders from radio shack.

4 battery pack AA holder

or like this

8 battery pack AA holder

You can charge anything you want including D, C or AAA cells or actually anything with the charger up to battery packs providing 25 Volts. Like I said it has a pair of alligator clips so you can just hook on and it does have the overtemp sensor as well. If you only ever need to do AA or AAA then I agree those others are a great choice. This is a really remarkably versatile system though if you ever need to do other types of odd batteries or battery packs. I have actually made a connector that re-charges/conditions many laptop batteries also. Like I said it will handle NiCd, NiMH and Lion batteries and battery packs.

Regards,
Keith
 
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SAR-EMT40 said:
Well actually like I was saying Doug. If you buy a 4 pack or 8 pack battery holders from radio shack.
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As I stated earlier, it is better for the NiMH cells to charge them individually if possible. Thus if you have a bunch of individual cells (eg AA or AAA) an MH-C401 (or similar) is a better choice than an MH-C777 (or similar) and a 4-cell battery holder. The MH-C777 looks like a fine charger for sealed packs.

I think we are mostly in agreement on this tangent...

FWIW, I think charging bunches of AA or AAA NiMH cells are the primary topic here.

Doug
 
DougPaul said:
As I stated earlier, it is better for the NiMH cells to charge them individually if possible. Thus if you have a bunch of individual cells (eg AA or AAA) an MH-C401 (or similar) is a better choice than an MH-C777 (or similar) and a 4-cell battery holder. The MH-C777 looks like a fine charger for sealed packs.

I think we are mostly in agreement on this tangent...

FWIW, I think charging bunches of AA or AAA NiMH cells are the primary topic here.

Doug
Click to expand...

OK, gotcha now. So you think that each cell on those units has it own charger or at least they are charged in parallel. I wasn't aware of that.

I have been using mine in this fashion for quite a while but I do make sure they are worn down to (about) the same level and have had some good results over the years but I get what you are saying. Granted that is anecdotal but I have had good luck with it. I understand your point though.

Regards,
Keith
 
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SAR-EMT40 said:
OK, gotcha now. So you think that each cell on those units has it own charger or at least they are charged in parallel. I wasn't aware of that.
Click to expand...
Yes--chargers such as the CF-401 have four independent charging circuits so if the cells are mismatched or have different initial charge levels, each cell gets treated according to its individual needs.

I have been using mine in this fashion for quite a while but I do make sure they are worn down to (about) the same level and have had some good results over the years but I get what you are saying. Granted that is anecdotal but I have had good luck with it. I understand your point though.
Click to expand...
Charging a group of cells connected in series (ie a battery) with a single circuit generally works, but is not the best for the cells. This forces the same amount of energy into all cells and as a result some may get overcharged and some undercharged. As you charge a cell, the energy first goes into desirable chemical changes (ie the charge) but once the cell is full, it must dissipate the energy in other ways. This excess energy can overheat the cell, generally damage the cell, cause gas formation, pressure build-up, and force the pressure seal to open and vent electrolyte. NiMH cells are pretty delicate with respect to overcharging--the max allowable overcharge current is ~.05C. (C is the capacity in amp-hours.) NiCads are more robust to overcharge current: the limit is ~.1C. (In fact, the standard trickle charge for NiCads is .1C for 14 hours.) A good smart charger charges at a good rate (2-3 hour (ie .5C to .3C charging current) is optimum for NiMH) and shuts down to a safe low trickle rate when the cell is fully charged or close to fully charged. (A smart charger can detect a fully charged cell because the its temp starts to rise and its voltage, which has been rising during the charge, levels off and begins to to drop.)

The above is for NiMH cells. Lion (lithium ion rechargeable) cells are far more delicate and dangerous. If you discharge them to zero or overcharge them, they are destroyed. And if you overheat them or short circuit them, they are likely to catch fire and/or explode*. (Lion cells and equipment which uses them contain protective circuits to prevent such events...) There are several different chemistries of Lion cells with different safety factors. See http://www.batteryuniversity.com/partone-5B.htm for more info.

* This is why higher quality Lion batteries bring out connections for all cells--so each cell can be watched individually.

Doug
 
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A touch off topic but Doug gave me the following reference Battery University. They state, and I have found out the hard way, that batteries (Alkaline, NiMH, and Lion) all tend to fail at about -20C (-4F) I have gotten around that with my GPS and camera by placing a handwarmer in the respective cases. On a long hike a few weeks ago to do the Twins and Galehead where the temps were as low as minus13F. my GPS worked fine and the camera's lens never fogged.
 
Yesterday I ordered one of the chargers recommended on this thread along with 4 low-discharge AA batteries. When it arrives I'm going to chuck my Energizer battery charger, aka "battery cooker".

I'm no longer plugged into the tech-toy market (a good thing), and until this thread I hadn't heard of low-discharge batteries.

Am going to wait on the rechargeable lion batteries ... ;)
 
I was going to ask why rechargeable Lion AA batteries are not available, but instead did some quick research. According to the Greenbatteries.com site:

Are Lithium Ion batteries available in standard sizes like AA , C or D cell size?

No, Lithium-ion batteries are not available in standard sizes. We believe this is because it would be too easy for users to inadvertently put them in a charger not designed for Lithium-ion batteries creating a potentially dangerous situation. (If an alkaline battery is put into the wrong charger it might leak or even burst, but a lithium-ion battery put into a NiCd or NiMH charger not designed for lithium-ion, might ignite. Also, because Li-ion batteries operate at much higher voltage (typically 3.7V per cell) than the 1.2 to 1.5V of most cell batteries, designing a 1.5V lithium-ion cell would be expensive.

I did find These batteries, but they do clearly state that they are not a direct replacement for 1.5v AA's.
 
Paradox said:
A touch off topic but Doug gave me the following reference Battery University. They state, and I have found out the hard way, that batteries (Alkaline, NiMH, and Lion) all tend to fail at about -20C (-4F) I have gotten around that with my GPS and camera by placing a handwarmer in the respective cases. On a long hike a few weeks ago to do the Twins and Galehead where the temps were as low as minus13F. my GPS worked fine and the camera's lens never fogged.
Click to expand...
Lithium primary (non-rechargeable) cells work down to ~-40 (take your choice--F or C :) ). NiCads will also work to temps below the limits of NiMH, around -40, IIRC.

Doug
 
Quietman said:
I was going to ask why rechargeable Lion AA batteries are not available,
Click to expand...
As you noted, the voltages are different and improper management of Lion cells can destroy them or cause fires/explosions.

Are Lithium Ion batteries available in standard sizes like AA , C or D cell size?
Click to expand...
CR123 cells are a standard size that comes in Lithium primary (3V*) and Lion (3.3v rechargable) technologies.

Lion (Or Li-Ion) cells seem to come in standard sizes that are different from the usual consumer sizes (AAA, AA, C, D, etc). http://www.batteryuniversity.com/ refers to the 18650 cylindrical size in a number of places and a search on "18650 lithium ion" brings up a number of suppliers including http://www.onlybatteries.com/cat_featured_items.asp?cat1=27&cat=2&id=162&uid=1106 which lists a number of sizes.

Camera manufacturers, unfortunately, have steadfastly resisted the use of standard size Lion cells in their cameras. (And every other new camera seems to require a different size/form factor battery.) All the better to keep prices high...

* There are two different chemistries for lithium primary cells--one produces 1.5v and the other 3V.

Doug
 
Warning about Energizer Duo USB charger

No, it won't burn your house down or supercharge your battery. It just turns over control of your computer to unknown hands. From the manufacturer's notice to users:

"ST. LOUIS, March 5, 2010 /PRNewswire via COMTEX/ -- Energizer has been informed by the CERT Coordination Center (CERT) that the Windows software that was referenced and made available via a download with its Duo Charger, Model CHUSB, contains a vulnerability. Energizer introduced the Duo Charger in the United States and the USB Charger in Latin America, Europe and Asia in 2007. Both products charge Nickel Metal Hydride batteries from both a wall outlet and a USB connection. The product included a feature that would allow the user to view the battery charging status on a computer if associated software was installed. The Duo Charger product documentation referenced www.energizer.com/usbcharger to download the software. The site offered downloadable software in both Windows and Apple(R) versions; however only the Windows version contained the vulnerability.
Energizer has discontinued sale of this product and has removed the site to download the software. In addition, the company is directing consumers that downloaded the Windows version of the software to uninstall or otherwise remove the software from your computer. This will eliminate the vulnerability. In addition CERT and Energizer recommend that users remove a file that may remain after the software has been removed. The file name is Arucer.dll, which can be found in the Window system32 directory."
 
My new toy arrived today, along with a pack of Eneloop batteries - thank you Amazon. Am running a discharge/refresh cycle on 4 at the moment.

One interesting note - this "smart charger" cannot recharge a battery if it's totally flat, so I guess I'll keep the old charger around just in case.
 
Kevin Rooney said:
One interesting note - this "smart charger" cannot recharge a battery if it's totally flat, so I guess I'll keep the old charger around just in case.
Click to expand...
Most smart chargers perform some tests on the cell to determine the type and health before starting the charge. Totally flat or weak (worn down or damaged) cells can fail and the charger will refuse to charge them. Different chargers can have different thresholds, so if you have several chargers, one may accept the flat/weak cell.

I have a simple (dumb, non-smart, no automatic shutoff) trickle charger (MH-C126S) which applies a 60 mA charge current. If all else fails, I can use this to put an initial charge in a flat/weak cell and finish the charge with a smart charger.

Note: a trickle charge of greater than about .05C for NiMH and .1C for NiCad can damage the cells. (60 mA is .03C for a 2000 mAh cell.) C=the cell capacity in amp-hours.

Doug
 
One interesting note - this "smart charger" cannot recharge a battery if it's totally flat, so I guess I'll keep the old charger around just in case.
Click to expand...

My Maha chargers will start charging a totally flat battery within 30 minutes. I have put a dead cell in and nothing happened immediately. After some time, the charge light came on.

When the maha charger has a problem with a cell-- unable to charge or inserted into the charger backwards-- the red charging light flashes.

Kevin- I suggest you get a totally dead cell and convince yourself that charging will start after enough charge has entered the battery so that the charger can see "something".
 
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