Sunday, May 09, 2010

AA Battery Chargers Fully Compared (4 Models)



This time I compare four battery chargers of mine. They are all portable compact ones that are ideal for travelling. First, their actual characteristics and designs are compared:-

Features and Characteristics
Panasonic BQ-395TH
Camelion BC-0905C
Energizer CHCC-UK
Maha Energy PowerEX MH-C401FS
Made in
China
China
China
Taiwan
(Number of) Batteries that can be charged
4 AAs / 2 AAAs
4 AAs / 4 AAAs
4 AAs / 4 AAAs / 2 9Vs
4 AAs / 4 AAAs
Intelligent Charger?
Yes No, Timer
No, TimerYes
Number of Charging Channels 1
4
2
4
4
Number of Detection Channel(s) 21
2
4
4
What is Detected? 3Negative Delta VBattery InsertionBattery Insertion
Negative Delta V
Charging Current and Voltage (for AA) 42200 mA @ 1.5V (Maximum 6)
250 mA @ 2.8V
360 mA @ 1.4V
1000 mA / 300 mA Selectable @ 1.6V
Trickle Charge 5No, Not Specified
No, Not SpecifiedYes, 50 mA
Yes, 50 mA
Extended Power Plug
Yes
No
No
Yes
Car Adaptor
No
No
No
Yes

Next, I compare the actual performance of them, according to my practical experiences:-

Actual Performance
Panasonic BQ-395TH
Camelion BC-0905C
Energizer CHCC-UK
Maha PowerEX MH-C401FS
Practical Charging Time Required for a Set of 4 x 2650 mAh Energizer NiMH
~ 3 Hours
~ 10 Hours
~ 8 Hours
Fast Charge: ~ 2 Hours
Slow Charge: ~ 7 Hours
Practical Charging Time for 2 x AAs
~ 1.5 Hours 6No Difference
No Difference
No Difference
Cut-off Accuracy 7Average
Not Applicable
Not ApplicableGood
Fullness of Batteries 7Average
Not Good
Good
Very Good
Self Discharge Rate of Charged Batteries 8 Average
Low
Low
Fast Charge: Average
Slow Charge: Low
Cancellation of Memory Effect 9 Average
Poor
Average
Fast Charge: Good
Slow Charge: Average

Well, let me explain some of the terminologies and performance aspects I have mentioned above in the following:-

1. Number of Charging Channels: That means the number of individual batter(ies) that can be charged independently at the same time. For example, the Camelion charger can adopt four batteries but it has only two charging channels, which means that batteries must be charged in pair, i.e., at least two at a time.

2. Number of Detection Channels: It is referred to the detection ability and indication that the charger provides to show the battery status. The Panasonic charge has only one indicator with a Green LED, either not lit on (no battery), flashing (during charging) or lit on (charging completed).

3. Detection Method: The intelligent chargers can detect the "Negative Delta V", which is simply the change in voltage of the battery that is being charged and when there is a negative change in the voltage, the charger will believe that the battery has been fully charged or almost fully charged. As for "Battery Detection", the charger just detects if a rechargeable battery is inserted and also if it is properly inserted or if it is defective.

4. Charging Current: The higher the charging current, the shorter the charging time will be. The simplified maths for calculating the total charging time required is indeed easy. Assuming everything is linear, it is simply to divide the rated mAH capacity of the battery by the charging current. For example, a 2200 mAH battery charged in the Panasonic charger at 2200 mA rate will require 1 hour to complete.

5. Trickle Charging: It means to continuously charge in small current after the battery has been fully charged, so as to maintain its full charged status.

6. The Panasonic Charger has an interesting design. Its *total* maximum charging current seems to be limited at what is rated. Just say if you charge one battery it can be completed in one hour, but two will then be two hours and then four requires four hours! So, this "fast" charger is not always a fast one, especially when the user has to charge four batteries at a time and everytime (case of charging batteries for the Pentax "AA" DSLRs).

7. Cut-off Accuracy and Fullness of Batteries: When the cut-off accuracy is good, the batteries are almost full per charge. If premature cut-off of charging takes place, the batteries can still be charged until they will reach their full capacity, ultimately. To check, just take out the freshly charged batteries after cut off and re-insert them into the charger to see if charging starts again but without cut-off again within a short period.

8. Self Discharge Rate of Charged Batteries:-

I think this is self-explanatory. But one thing interesting to point out. With those LSD (Low Self Discharge) NiMH like the Eneloop and AlwaysReady etc., the discharge rate could be lower, comparatively. However, I found that those LSD batteries seem to have more memory effect than traditional ones. Moreover, all LSD batteries do have lower mAh capacities than traditional ones, too. So, I now end up with using Energizer non-LSD high-capacity NiMH batteries (8 nos.) for my K-x, which seem to be the best compromise.

9. Cancellation of Memory Effect:-

Theoretically, NiMH batteries have no or little memory effect. Memory Effect refers to the rechargeable battery's capacity is being limited only to the difference in capacity between the last time when it was re-charged and to what it has just been charged again. So this delta is really small, resulting in low capacity of the battery as there is a memory developed and stored in it already.

NiMH used in K-x suffers very much from this phenomenon as the K-x actually requires high power and with just lower voltage, the camera will show battery depleted and the camera is cut off. Actually, there is still a lot of charge left inside those "depleted" batteries as believed by the K-xes (they are not enough to drive the K-x, anyway). When the user takes those "depleted" batteries for recharge (actually the batteries can still be used in a lot of other devices (or even for previous Pentax DSLRs like the K-m!), memory effect will still be developed after some time.

Some battery charger manufacturers claim their designed charge pulse patterns can help to eliminate the memory effect and erase the stored memory. They do this by discharging the batteries while the batteries are charged. Maha Energy actually is one of them who claims this feature of their PowerEX chargers. I verify that it works for the fast charge mode better but in slow charge mode, I don't see a clear advantage there. The weakest charger in eliminating the memory effect is the Camelion, from what I experienced, which even cannot recharge the batteries used in my K-m well, I think.

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In fact, the K-x camera is just the most demanding electronics device that I have ever used and owned that push the limits of NiMH batteries and maybe even more on the chargers! For my K-m and K100D etc., the situation is not that worst and critical actually! Same rechargeable batteries charged using the same chargers yet produces very different results and instability in my K-x bodies! The K-x is really so power hungry, especially when LiveView or Movie Recording are used. In fact, I would still insist it should have adopted rechargeable Lithium as its power source (as on Day One I "complained" about it) but unfortunately Pentax hadn't! :-(


Read Also:-

Better K-x Rechargable Solution? Is the NiZn Safe?

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