When shopping for nickel-metal hydride (NiMH) chargers it is important to find a charger that will do three things: 1. Charge the cells independently instead of in pairs (this is important in case one battery is bad, which happens frequently), 2. Charge at an appropriate rate --taking at least 1-2 hours (no 15-minute fast chargers!), and 3. Correctly stop charging when the battery is full (rather than charge for some number of hours regardless of the charge currently in the battery). Very few chargers you see in stores will do all of these.
NiMH cells will last more cycles if they are charged at an appropriate rate. The ideal charging rate is 0.5C, where C is the capacity of the battery in mah. For example, a 2700 mah cell (C=2700) should be charged at about 1350 mA (there is some debate about whether lower rates or a rate up to 1.0C is better). Therefore chargers with a charge rate that can be selected by the user are preferred. For capacity testing, the discharge rate is usually 0.20 to 0.25C.
AA/AAA Chargers
The Powerex Maha-C9000 AA/AAA battery charger and conditioner
Maha Powerex MH-C9000 WizardOne Charger-Analyzer charges 4 AA or AAA NiMH batteries. It charges cells individually at a user-selectable rate and cuts off when the battery is full (actually it has a small topping off charge and a very slight trickle charge to keep the battery full). It can also discharge batteries to determine their capacity (has LCD display), or apply a "break-in" charge. It is often recommended in the CPF forums. About $50. ManualReview by Silverfox
La Crosse Technology BC-9009 AlphaPower Battery Charger is similar to the Maha MH-C9000, is smaller, cheaper, and usually comes packaged with 4 AA and 4 AAA NiMH batteries (see caveat later). It lacks the "break-in" charge and can not discharge a battery without subsequently recharging it. It is usually about $40. It was formerly called the BC-900. The BC-700 charger is a less powerful version. A number of Amazon reviewers have reported problems with these chargers melting, summarized in this CPF thread. Manual
Sony BCG-34HRE4KN A 4xAA charger with charge indicators for each battery. Includes 4 2100mAh LSD batteries. It has a refresh button to discharge the battery before charging it and costs about $25. Manual. This charger is a successor to the Sony BCG-34HRMF4 Battery ChargerCPF threadManual
Sony BCG-34HLD2RNSony Cycle Energy BCG-34HLD AA/AAA NiMH chargerOlder versions of the silver 34HLD may have been based on timer, but the newer white version is a smart charger that charges cell individually and cuts off when each cell is full (only one indicator light which goes off after the last battery is complete). AA's are charged at 360mA (a pulse charge of up to 1400mA that averages to 360mA) while AAA's are charged at 140mA. The 2RN comes with 2 1000mAh batteries, the 4KN comes with 4 2100mAh batteries, and the 4EN comes with 4 2500mAh batteries. This is a very inexpensive ($5-$12) basic charger. Manual, CPF thread, review.
Sanyo Eneloop MQN05U (NC-TGR01 in Japan) - Charges 1-4 AAA or AA cells and usually comes with 4 AA eneloops. Note that this charger has a single indicator light which comes on after all of the cells are charged. It should not be confused with the very similar MQN06x which has two indicator lights and charges in pairs. Any NiMH charger can be used to charge Eneloop cells. CPF thread
Maha MH-C800S - 8-cell smart charger with LCD display. Has fast (1000mA) or gentle (500mA) charging mode (lower rates for AAA cells), conditioning cycle, 100-240V power. $57. MH-C801D is similar but has twice the charging rate (2000 mA default rate is too high for most batteries) and costs a little more. CPF threadManual
Titanium M-8800 Smart Fast 8 Bay AA/AAA charger - 8-cell smart charger with individual channels, LCD indicators, 500 mA charging rate (for 5-8 cells, otherwise seems to be 1000mA which is high for AAA batteries), and ability to discharge cells. $30. Helpful post on CPF. Includes AC (100-240V) and car adapter.
AAA/AA/C/D 9V Chargers
Ansmann Energy 8 - A consistent award winner in Photography magazines. 1-6 AAA/AA, 1-4 C/D, 1-2 9V. Ni-Cd or NiMH. Ansmann Energy 16 is similar but has twice as many bays. Auto discharges to avoid memory effect. Charges each battery individually, based upon readings taken once each minute. Charge rate is not user-selectable, but rates are appropriate (300 mA for AAA, 700 mA for AA, and 1000 mA for C or D). Manual
Maha MH-C808M - 8-cell for AAA, AA, C, or D (no 9V). Has fast (2000mA for AA, 700mA for AAA) or gentle (1000mA for AA, 350 mA for AAA) charging cycle. This could be too fast for some batteries. Sanyo recommend a maximum charge rate of 950mA for their Eneloop AA cells for example. Can condition batteries and has LCD display. $90. Review: CPF threadManual
Rayovac PS3 Rechargeable Battery Universal Charger - Has four bays with independent charging, but you can put two AA or AAA batteries in one bay (which you would want to avoid). As long as batteries are charged individually, this should work. It is a very old model charger (introduced no later than 2001). $22. CPF threadmanual
Energizer Family Charger (CHFC) - Like the Rayovac, has 4 independent bays. As long as you charge one battery per bay, you are charging independently. Though it uses smart termination, it also automatically cuts off after a few hours, so high capacity D cells will take multiple charging cycles to actually get full from empty. It is available online but also bricks and mortar stores like Walmart. CPF threadmanual
Vanson BC1-HU. Available rebadged by several vendors. Can condition cells.
Accessory Power Revive Charger Performance of this budget charger is unknown, but it claims to charge cells individually and use smart termination. The charge rate is too high when charging one cell, but is acceptable for 2 cells or more. It also has an unknown rate of trickle charge, so it is not good to leave it in the charger. They also have a cheaper version but at 1200mA is too high for most batteries.
Not Recommended
The following chargers either charge cells in pairs(¹), use too high a charging rate (²), or use a timer (³).
Any 15 or 30 minute charger. These cook cells and dramatically shorten cell life.
Lithium Ion Chargers
Li-ion chargers aren't as commercially widespread as NiMH chargers. Precautions must be taken to avoid overheating cells and they should be monitored while charging. Some people only charge li-ion cells in their fireplace or in a steel bucket! For tips on safely using Li-ion cells refer to this post. The important thing for li-ion chargers is to correctly stop charging when the battery voltage reaches 4.2 volts (for a typical 3.7 volt cell) and not to charge at a rate exceeding the capacity of the cell (e.g. "1C" for an 800 mAh battery is 800 mA). See this article from Battery University for information about properly charging li-ion cells. A good charger will slow the charge rate as the battery gets closer to being fully charged.
Pila IBC 4-Stage Charger - Has 2 independent bays and will charge batteries 65-67mm long batteries by default and 50mm long using the included adapters. It charges batteries at up to 600 mA and correctly terminates at 4.2 volts. This charger is often recommended in the forums. Because of the 600 ma charging rate, it is not appropriate for 10440 cells which often are 500 mAh. Note that Pila only recommends this charger be used with Pila cells, but it will work fine with any li-ion cells, but will require your own adapters for 16340's. About $45. CPF thread
Ultrafire WF-139 - Rarely recommended, but this two-bay charger seems to be used often and is less expensive than the Pila. Some models seem to charge batteries over 4.2 volts, while others seem to terminate correctly. It can do various sizes of batteries up to 18650, but the charge rate is too high for 10440's. It has two independent bays. In addition to DealExtreme, it is available from AW, Lighthound, and some other online dealers. Less than $20.
DX 18650 charger (US) or DX 18650 charger (EU) are dedicated chargers for 18650 batteries and have two independent bays. Very inexpensive but seem to charge correctly by using a higher rate at the beginning and then tapering off as a battery nears completion. Seems to correctly terminate at 4.2V. $8.
Universal Smart Charger - A single bay charger with a charge rate low enough to safely charge 10440 cells, but can also charge up to 18650 (though it will take a while). Seems to safely terminate at or below 4.2 volts (discussion). Has no switches or controls, but automatically adjusts to 110 or 220 volt power (has folding US type folding power prongs) and will charge either li-ion or NiMH batteries (for NiMH batteries, terminates at 1.4 volts). It is very, very cheap: less than $6.
Hobby Chargers
Turnigy Accucell 6 hobby charger
Hobby chargers are built to charge battery packs that are often used with remote control cars, planes, boats, etc. They will charge packs of multiple cells and therefore must have higher power and typically have 12V input (RC users will charge from their car or a battery in the field). Due to the variety of cells they charge, they do not usually include battery holders, however most users will use strong neodymium magnets to hold the alligator clips to the ends of a battery as shown here. They can be used to charge a wide variety of battery chemistries and combinations of cells. Here is a good introduction to hobby chargers.
Turnigy Accucel-6 60W 5A Balancer/Charger. Very popular and not as expensive as the Bantam charger that it copies. Seems to work well with this power supply though it can also be found on eBay for less. ManualReview.
Turnigy Accucel-8 150W 7A Balancer/Charger. More power than you really need for charging flashlight batteries and requires a heavier duty power supply.
The iCharger 106B+ supports the "Open Format" data of the LogView software and can display, plot and analyze the charge and discharge data by it. (See detail information about logview on the following website: LogView Shows Your Serial Data...)
The iCharger 1010B+ supports the "Open Format" data of the LogView software and can display, plot and analyze the charge and discharge data by it. (See detail information about logview on the following website: LogView Shows Your Serial Data...)
