I'm not sure...I don't know if the pair is charged with two individual channels...?
....so that means it charges two in series.
Well, if it can't charge a single battery on the right, then it doesn't charge two batteries independently (and not to mention the fact that it doesn't have two LEDs).
The number of LEDs could tell you if is an independent channel but not necessarily. The Sanyos chargers are examples of independent channel chargers that share one LED. Based upon the electical configuration(see configuration below), the unit charges two cells in series. It would mean that the sensing circuit alters it's connection when the second battery is added.
....bang for the buck charger out there today providing it can reliably terminate at low currents...tests are forthcoming
Looking forward to the resultsif the results are good I might look for one or two on ebay.
...For a small, portable charger, I bought the Duracell Mobile Charger CEF23DX4 ...Terminates better than the CEF20.
I've done some tests and measurements on the charger...it is an interesting design. While it does seem to take a while to terminate, this may be deliberate and the result of the low currents involved. Higher charging currents will result in faster/larger changes in voltage in a given time and allow decisions to made earlier. Slower charging is gentler and allows for more time margin before overheating occurs.
With batteries removed, the open circuit measurements (~9V) indicate a current source design (good) on both positive terminals. When a single battery is placed on the left, the right (empty) terminal drops to about 4.3V (???).
AA Configuration: The left postiive charge terminal seems to be electrically connected to the negative terminal of the right bay. This indicates that the circuits do charge in series for two cells.
Update:
I ran a definitive test (by isolating nodes) to prove that all the current for the left bay came from (and through) the right bay when charging two cells. It also showed that the electrical topology (where current came from for the left bay) altered when charging just one battery. Despite the marketing claims, this charger is not truly a indepedent channel charger when charging two batteries. It is only true for one battery operation and in that case, you lose the ability to balance the cells simultaneously.
Termination Experiment: I performed a number of tests using some batteries that terminated well with a 2 hour fast charger (i.e. about 1A charging current) using
- two 600mAH NiCads
- two older 16000 mAH Rayovac NiMH batteries
These batteries were discharged of 33mAH of charge that I'll refer to as the
partial amount. Based upon the 280mA charge rate and charge inefficiency (0.66), the batteries would have ideally terminated in about 10 minutes.
Single Channel Results:
- Alkaline battery: detected within 15 seconds
- Both Nicads termninate in about 20 minutes (100% overcharge of partial amout). Relative to the capacity, this is a 5.5% excess.
- One Nimh cell(sample B) was found not to terminate after six hours when charged fresh from storage. Battery was barely warm.
Afterconditioning the battery with a few charge/discharge cycles using the fast charger and resting overnight, it terminated after 40 minutes. Results is 300% overcharge of partial amout). Relative to the capacity, this is a 6.1% excess charge. Battery was barely warm.
- Second NiMH battery had similar results without need for discharge cycles.
The results indicate that charger is smart in being able stop the charging early for an nearly full battery...some of them that are not very vibrant and that are known to need higher charge rates to generate the stopping signal.
One of things that I dislike most is a missed termination. It causes the battery to get pretty hot and (I think) lose it's vibrancy. It alters the nature of the battery forever and can be termed a destructive cycle.
One of the nice things about the mini charger is the gentleness on the unit as the batteries are at worst slightly warm. If the NiMh can tolerate this condition, then this provides an opportunity for batteries charged in series to "equalize" the fullness of charge....providing they started out unequally discharged.
The following have not been looked at in detail:
AAA batteries: Preliminary results with the lower current (110mA) AAA charging circuit using eneloop (vibrant) batteries need to be re-run before I can comment.
Two channel/batttery results have not yet been run but the paired voltage of 3.1V seems to be critical to termination.
The mini charger with AA batteries should prove to be a good overnight charger that is gentle on batteries. Unlike the timed chargers, it has the ability to top up batteries smartly. Due to the low current, it has a dead time zone of about twenty minutes that it needs to evaluate the charging trend prior to making decisions to terminate a charging cycle. It is a great example of technology filtering down to entry level...now if only it had another LED!
