PortaPow AA+AAA usb battery charger


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Portapow has usb chargers, cables, power banks, solar panels, usb meters, etc.. Here I have found a simple usb powered charger for AA/AAA batteries. I can charge from 1 to 4 NiMH batteries and is specified to use -dv/dt termination.


I got the charger in a plain white cardboard box.


The pack contains the charger, a A-A usb cable and a instruction sheet.

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The charger has a usb-A connector for power input, this do not fit the normal usb cables, but requires a special USB-A to USB-A cable (it is supplied). I would have preferred a micro usb input, then it could have used the same cables as most phones and other usb equipment.


At the back the charger has a red led to show when power is connected.


The display has four animated battery symbols when charging.
Pressing the refresh button will stop the animation and slowly discharge the cells. When the cells are empty they will be charged again.


The charger has a flip down spacer to select between AA/AAA batteries.


The other end is just normal connections, but not in very good quality. I had to bend them a bit to get enough tension on the batteries.


One AA and one AAA.


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The charge current is about 0.75A, termination looks to be -dv/dt with a low trickle charge.


The other slots looks the same.


The XX cell is old and the charger must have termination on time or voltage.


These two cells do also terminate early, i.e. they are not completely filled. It looks like the charger has a 2100mAh maximum charge?


The AAA cell is charged nicely with a -dv/dt termination. The current is a bit high at 0.75A (This is about the rated maximum charge speed for AAA cells).


As usual it takes some time to detect a full cell when using -dv/dt.


With four cells the charge current is reduced to about 0.3A and termination is a bit slow (Maybe it was on a 2100mAh limit, but the charger is rated for 3000mAh cells).


And it uses about 0.7A from usb.


M1: 31,0C, HS1: 37,7C


M1: 36,3C, M2: 37,6C, M3: 35,9C, M4: 34,2C, M5: 38,1C, HS1: 45,1C
Even when charging with the lid on the battery temperature is fine (I only opened the lid when taking IR photos).


When power is turned on the charge need about 5 seconds to initialize. It has one 1.5A charge circuit and will time shared it between the slots. One or two slots will get 50% of the time.


With 3 cells it adds one phase to the time sharing, i.e. about 30% to each slots.


And for four cells it is below 25% of the time for each slot.


The trickle charger is a 15 millisecond pulse every 1.65 second at 1.5A, this is about 13mA


A press on the refresh/charge button will start a refresh cycle, a second press will cancel the refresh and continue with charging.


The refresh is done at a rather moderate speed with about 200mA discharge current.


The discharge speed is the same with four cells, but the charge speed is reduced, making the total time a few hours longer.


HS1: 30,7C


M1: 34,0C, M2: 35,4C, M3: 34,9C, M4: 33,6C, HS1: 43,2C
The discharge is at a fairly low current and do not generate much heat in the charger.

This discharge is with constant current, for that reason I did not do any scope images (It would just be a straight line).


The charger do a good job on 2000mAh batteries with a nice low trickle charger, but it cannot charge larger cells.
As is often the case with chargers it will reduce the charge current when it has to charge many cell simultaneous.
Because it did not charge any of my high capacity cells fully I will only rate it acceptable.


Here is an explanation on how I did the above charge curves: How do I test a charger
Index of all tested chargers