Powerchimp 4.I mentioned above that a few days ago I ordered a Powerchimp 4. I received it on Monday, quite earlier than I expected since I only ordered it the previous Friday. I tried to charge the four AA batteries that came with it. When you use a power source that can deliver a lot of amperage, it seems to work quite well. With four batteries in it, it consumed about 0.8 amps (or 800 milliamps) at above 5 volts from the USB supply.
When charging four batteries, the unit got pretty warm, I suspect part of the circuit is consuming a lot of power instead of putting it all into the batteries. I did not measure how many amps are actually going into each battery, I only measured how much power was coming out of the USB port. Thus, I can't comment on the efficiency of the unit.
But when I tried it on a lower power USB source (a really cheap USB charger on 110 volt source), I found that it choked. It would go through a cycle where it initiates charging, but once charging starts it draws too much power, voltage drops and it stops charging. And then the cycle repeats itself. (I knew that it was not charging because the lack of LED indicator lights.) That is pretty much the same problem I had with my Eneloop chargers, which I noted above did not play happy with a low power source. I found that my low power USB source would charge two batteries at 4.4 volts, 0.33 amps input to the Powerchimp and that was just barely working, thus I concluded that was the bare minimum. I tried AAA batteries and they appeared to draw the same power as AA batteries. Thus, my low power USB charger would only charge two AAA batteries, not more.
I tried it on a dynohub today with the AXA Luxx 70 Plus for USB supply. The AXA Luxx 70 Plus is a headlamp and USB charger combination, it puts out about 5 volts and about 0.5 amps (500 milliamps) at normal riding speeds to the USB port. My Sinewave Revolution USB charger puts out maybe 20 percent more power than the AXA, but for around home use I have the AXA on the bike, not the Sinewave.
On the AXA the Powerchimp would charge two AA batteries, but not three or four. There are individual LEDs for each charging circuit for each battery, and with two AA batteries those two LEDs lit up, but with three or four batteries in it none of the LEDs that indicate a charge to each cell lit up. The Sinewave might charge three because it puts out a bit more power, but certainly not four. Thus, the dynohub is the limiting factor if you want to charge lots of AA batteries. I was generally in the 10 to 14 mph (~15 to 20 km/hr) range of speeds for my monitoring of the charger.
And I had a big surprise. When I slowed to below about 6 mph (~9 km/hr) it stopped charging, but continued to draw about 110 milliamps from the USB port. But here was the surprise, when I speeded up again it did not start charging again. Perhaps the circuitry at low voltage erroneously thought that the AA batteries were fully charged? It was easy to reach down and turn my light on and off again, that stopped and restarted power to the USB port and then the Powerchimp started to charge again. I have not used a cache battery on my USB port to keep power on when I stopped or slowed down for a steep hill. But it is clear that if I want to power the Powerchimp from a USB port powered by a dynohub, I need to have a cache battery in the circuit to keep voltage up into the Powerchimp. Otherwise it will stop and will not restart unless I come to a complete halt to reset the power to it, or notice it and use other measures to rectify the situation. I learned this by having an ammeter on my USB port which I could check while riding. I think most people do not use such a meter, so most people if they use the Powerchimp on a dynohub without cache battery might wonder why it does not consistently charge.
If you planned to supply your AA/AAA charger from a USB port on a Li Ion battery powerbank, it probably would charge four batteries just fine as long as your power bank had enough power to completely charge them. It would have to deliver at least 800 milliamps for a long enough period of time to charge them, which likely is for several hours.
That said, my next tour, I am not sure which I will bring, the Powerchimp for AA/AAA and another charger (Lenmar) for my camera batteries, or the Pixo C-USB charger for both. But the powerchimp is in the competition in part because when I have a outlet for power, I can charge four batteries and the Pixo C-USB only two. But I know with certainty that I will have a small cache battery in the circuit when charging from the hub. (I already own one, don't bother to make recommendations.)
The Powerchimp 4 comes with two cables, one to charge the AA or AAA batteries, the other cord is if you want to use the device as a powerbank, but I never expect to use it as a powerbank so I did not try it in that mode.
If you can find a Powerchimp for $20 USD like I found on the USA Ebay site, I think it is a very good buy. The four included NiMH batteries were low capacity, but were a nice addition when a lot of chargers do not include any.
I am not giving a full review of the device, for more detail, see this link:
http://www.produktinfo.conrad.com/datenblaetter/550000-574999/556189-an-01-en-POWERTRAVELLER_POWERCHIMP_4A.pdf
