What is the best rechargeable battery charger??I am asked this question several times a week. My answer, it depends. What are you going to use the charger for??
Let me share some information that should help you pick a good charger for you needs.
Ground rules. This discussion will deal only with NiMH batteries and chargers.
First let me talk a bit about charge rates. In order to have a well defined knee in the charge so that full charge can be detected by a -dV algorithm it is best to charge NiMH batteries at a sufficient rate. When battery people talk about charge rates they usually throw around a bunch of "C" numbers like .2C or .5C or even 1C. So what is "C" and what does that have to do with the charger you select.
In simple terms you can get "C" by taking the battery capacity in Ah or mAh (explained in a moment) and divide out the time or hours (h). So if we have an AA cell that is rated at 2700 mAh in order to find the 1C rate we divide the mAh by h and get mA (miliamps or thousandths of an amp) So the 1C rate for that cell is 2700 mA or 2.7 A. In theory if you charged that cell at the 1C rate for an hour it would be close to fully charged.
I do not recommend charging at such a high rates for consumer AA and AAA cells. The problem is heat. When the cells are charged at high rates such as 1C or more it is very easy to get too much heat build up in the cell. If it gets so hot that the cell vents gas then it is now on it's way to premature failure. It is possible to charge at those rates but only with the right charger that monitors the batteries for all parameters to prevent any damage to the cells. It would also be best to use active cooling for the cells being charged.
Having said those negative things about fast charging at 1C or higher rates I also have to say that it there is a problem with charging at very low rates. As mentioned above very low rates may not give the indications needed in the charge curve to show when full charge has been reached and the charger will fail to terminate charge properly. In short the charger can miss the -dV charge termination point.
So what is the best charge rate?? I recommend chargers that slow charge in the .2C range and fast charge in the .3C to .5C range. Those are rates of charge that are high enough for the charger to work well and not so high as to cause undo heating in the cell being charged. Here is an example. Suppose you have some NiMH AA cells rated at 2500 mAh. The 1C rate for those cells is 2500 mA or 2.5A. The normal charge rate .1C to .2C would be 250 mA to 500 mA. The fast charge rate .3C to .5C would be 750 mA to 1250 mA. In that case a charger that charges at 500 mA would be perfect for normal charging. It would charge those 2500 mAh cells in a little over 5 hours.
Let me summarize. The best charger is one that is computer controlled and has independent channels for each battery being charged. It detects full charge with a -dV algorithm. I has temperature monitors for each battery being charged. It slow charges at .1C to .2C rate or it fast charges at .3C to .5C rate. It should set appropriate rates for AA or AAA batteries automatically.
Here are some chargers that meet those criteria.
Tenergy TN157. Good low cost charger with refresh function.
PowerEx MH-C800S. Very good consumer grade charger.
PowerEx MH-C801D. Good professional grade charger, higher rates faster charge times.
PowerEx MH-C808M. Professional grade charges AA, AAA, C, D.
AccuPower AP2010. Good all around AA AAA charger.
AccuPower AP2020. Charges AA AAA C D and 9V.
Chargers that can test batteries.Say you purchase some batteries that are billed as the latest and greatest AA 3000 mAh batteries. How do you know?? Most major brands are very good about rating their batteries, they supply standard data sheets on their web site. However there are manufacturers and retailers that flat out lie about the capacity of batteries. So how can you tell if you are getting ripped off. Get a charger that can actually test batteries for capacity.
First a bit about battery capacity. Capacity rating is usually given in Ah or mAh (Ah - amp hours or mAh - miliamp hours) and is an indication of how much energy is usable from the battery. An example, if we have an AA cell rated at 2500 mAh it means that battery could supply a 2.5 Amp load (2500 mA) for a time of one hour. Or it could supply a 500 mA load for a time of 5 hours. Approximately. So capacity is an indication of how much work you can do with your batteries.
There are chargers that can test your batteries for the actual capacity, as opposed to what is claimed by the manufacturer or retailer. To do this all of these chargers perform the following cycle; put a full charge on the batteries, then perform a controlled discharge while measuring how much energy is obtained from the battery, then perform a full charge again. At the end of the cycle the tested capacity is displayed on the control panel of the charger. If you are serious about getting the best performance from your batteries then this kind of charger is a must have. It is the only way you will know for sure the state of your batteries.
These kind of chargers usually have other functions that are useful such as break-in and recondition cycles. Names and details differ but the ability to test is the same in all of them. Some have better capability and controls than others but the ones listed here will all do the basic job of testing batteries for actual capacity.
Shown in table form with basic parameters.
As you can see the PowerEx C9000 is by far the most capable charger/analyzer in this group. It also has the best build quality and provides the best cooling situation for the batteries under test. The charge and discharge functions are programmable in 100 mA increments. It also has the highest testable capacity limit. It is simply the best.
Next in line the BM200 is a capable charger. It has good space for cooling the batteries under test. The charge rate is programmable in 200 mA increments. However the discharge rate is fixed at half the charge rate. Same testable capacity as the C9000. This charger also has a test for battery internal resistance. This can be a useful test for some applications.
The AccuPower IQ328 is more compact, gives less cooling air to the batteries. The charge rate has 4 settings, 200 mA, 500 mA, 700 mA and 1000 mA. The discharge current is fixed at half the charge current. Maximum testable capacity is 3500 mAh. A capable charger and good value.
The La Crosse BC-1000 and BC-9009 are identical, except for the color of the case. Take off the case and the circuits boards are identical, as is the firmware revision. La Crosse just put a new case on the BC-9009 and changed the name. These two chargers have the same electrical specifications as the AccuPower IQ328. Four charge current settings, 200 mA, 500 mA, 700 mA and 1000 mA. Discharge current is fixed at half the charge current. However firmware restricts testable capacity to 3000 mAh.
The La Crosse BC-700 is just like the BC-1000 except it has only three current setting, 200 mA, 500 mA and 700 mA. Discharge current is fixed at half the charge current. 3000 mAh max testable capacity.
The La Crosse BC-500 is the most limited. The display is limited in the information it can display and charge current is 200 mA or 500 mA. It has only one function button and is a bit harder to program and use for test purposes. If is a fine charger but not a good choice for testing batteries.
Battery test information
What are the best batteries??
How do batteries compare??The first column displays test results from battery analyzer tests. This device allows testing at selected current load. Time, Voltage and Current are logged. Results are battery discharged capacity (mAh) and discharged energy (mWh). For all NiMH cells the test termination voltage is 0.90V. The test current for AAA and AA cells is 500 mA. Test current for C and D cells is specified in the test results. This allows comparison of the cells with no other factors influencing the results as may be the case in the testing charger results. This can be compared to the results from the individual charger tests to see how the chargers perform. Note; only the C9000 and BM200 are capable of testing the C and D cells with adapters. This is due to firmware restrictions in the La Crosse Techology and AccuPower chargers.
I use the chargers available with a test function. This function displays the actual capacity of the cells under test. All of the chargers perform this test basically the same way. First the test parameters are set. Then the test cycle begins. The cells are charged to full using a -dV algorithm to detect full charge. Then the cells are discharged at the test rate while timing the discharge. When a predetermined voltage is reached (0.9V) then discharge is terminated. Then the cells are charged again. At the end of test cycle the capacity measured during the discharge is displayed.
All cells are retail new and are run through 2 recondition cycle before capacity testing is performed. In all tests 4 cells are tested and results averaged. Please note that due to variations in manufacturing and testing any results within several percent of value should be considered identical for these tests. This chart will grow as I get more batteries to test. Enjoy the results.
Note; the BC-9009 and BC-1000 are identical except for the color of the case. Both have same circuit board revision and firmware revision.
Batteries are ranked from results of the Battery Analyzer tests.
Click on the above link to purchase on ebay.
(LSD) = Low Self Discharge type, ie. Imedion, Eneloop, AccuLoop
Four cells are tested on each charger.
The average of the four tested cells for each charger is displayed.
Charge 1000 mA
Discharge 500 mA
La Crosse BC-700.
Charge 700 mA
Discharge 350 mA
Charge 1000 mA
Discharge 500 mA
La Crosse BC-9009/BC-1000
Charge 1000 mA
Discharge 500 mA
Charge 1000 mA
Discharge 500 mA
500 mA rate
1000 mA rate
500 mA rate
1000 mA rate
500 mA rate
||10290 mAh||10020 mAh||10290
|Tenergy Premium D 10000
||8952 mAh||8138 mAh||10130
Imedion D 9500 (LSD)
||8338 mAh||8187 mAh||8714
|AccuLoop D 10000 (LSD)
||8324 mAh||8338 mAh||8440
|Tenergy Centura D 8000 (LSD)
||8440 mAh||8282 mAh||8246
|Duracell AA 2550||46 mΩ||46 mΩ||45 mΩ||48 mΩ|
|Eneloop XX AA (LSD)||47 mΩ
||50 mΩ||44 mΩ||48 mΩ|
|Energizer Rechargeable AA 2300 (LSD)||48 mΩ||52 mΩ||41 mΩ||52 mΩ|
|Eneloop AA White (LSD)||50 mΩ||52 mΩ||48 mΩ||49 mΩ|
|PowerEx AA 2700||55 mΩ||68 mΩ||49 mΩ||48 mΩ|
|AccuPower AccuLoop AA 2300 (LSD)||56 mΩ||64 mΩ||52 mΩ||53 mΩ|
|Tenergy Centura AA 2000 (LSD)||60 mΩ||66 mΩ||56 mΩ||58 mΩ|
|PowerEx Imdeion AA 2400 (LSD)||62 mΩ||50 mΩ||69 mΩ||66 mΩ|
|Tenergy Premium AA 2500||62 mΩ||68 mΩ||60 mΩ||57 mΩ|
|Tenergy (Blue) AA 2600||66 mΩ||56 mΩ||73 mΩ||69 mΩ|
|truCELL Precharged AA (LSD)||68 mΩ||78 mΩ||65 mΩ||61 mΩ|
|AccuPower AA 2900||71 mΩ||72 mΩ||69 mΩ||71 mΩ|
|La Crosse AA 2600||74 mΩ||90 mΩ||68 mΩ||63 mΩ|
|Amazon Basics AA 2000 (LSD)||81 mΩ||82 mΩ||94 mΩ||68 mΩ|
|Rayovac Platinum AA (LSD)||86 mΩ||82 mΩ||87 mΩ||90 mΩ|
|Delkin Devices AA 2900
||97 mΩ||98 mΩ||94 mΩ||100 mΩ|
|Ansman AA 2850
||105 mΩ||98 mΩ||111 mΩ||106 mΩ|
|CFL AA 3800
||115 mΩ||125 mΩ||110 mΩ||109 mΩ|
|BTY AA 3000
||119 mΩ||140 mΩ||114 mΩ||105 mΩ|
|AccuPower AAA 1200||71 mΩ||72 mΩ||69 mΩ||71 mΩ|
|Duracell AAA 1000||84 mΩ||80 mΩ||87 mΩ||84 mΩ|
|PowerEx AAA 1000||86 mΩ||80 mΩ||98 mΩ||81 mΩ|
|Tenergy Premium AAA 1000||86 mΩ||88 mΩ||87 mΩ||84 mΩ|
|PowerEx Imedion AAA 950 (LSD)||96 mΩ||108 mΩ||87 mΩ||92 mΩ|
|Eneloop AAA White (LSD)||96 mΩ||98 mΩ||101 mΩ||90 mΩ|
|Rayovac Platinum AAA (LSD)||98 mΩ||99 mΩ||102 mΩ||94 mΩ|
|Tenergy (Blue) AAA 1000||104 mΩ||104 mΩ||115 mΩ||92 mΩ|
|AccuPower AccuLoop AAA 950 (LSD)||113 mΩ||106 mΩ||126 mΩ||106 mΩ|
|Tenergy Centura AAA 800 (LSD)||113 mΩ||122 mΩ||113 mΩ||103 mΩ|
|Amazon Basics AAA 800 (LSD)||126 mΩ||124 mΩ||111 mΩ||143 mΩ|
|La Crosse AAA 1000||141 mΩ||152 mΩ||140 mΩ||131 mΩ|
Brand and Type
|Tenergy Premium C 5000||18 mΩ||18 mΩ||18 mΩ||18 mΩ||19 mΩ|
|Tenergy Centura C 4000 (LSD)||24 mΩ||34 mΩ||13 mΩ||24 mΩ||24 mΩ|
|AccuLoop C 4500 (LSD)
||25 mΩ||24 mΩ||26 mΩ||26 mΩ||23 mΩ|
|AccuPower C AP6000
||27 mΩ||32 mΩ||28 mΩ||25 mΩ||24 mΩ|
||28 mΩ||20 mΩ||42 mΩ||27 mΩ||26 mΩ|
|PowerEx Imedion C 5000 (LSD)
||55 mΩ||80 mΩ||40 mΩ||42 mΩ||60 mΩ|
|Tenergy Centura D 8000 (LSD)||15 mΩ||12 mΩ||14 mΩ||15 mΩ||17 mΩ|
Premium D 10000
||17 mΩ||20 mΩ||15 mΩ||16 mΩ||16 mΩ|
|AccuLoop D 10000 (LSD)||19 mΩ||30 mΩ||15 mΩ||16 mΩ||15 mΩ|
|AccuPower D 11500
||20 mΩ||28 mΩ||14 mΩ||22 mΩ||16 mΩ|
|PowerEx Imedion D 9500 (LSD)
||33 mΩ||44 mΩ||28 mΩ||25 mΩ||37 mΩ|