This is a review of the DX Deal Extreme, dx.com, power inverter supply
SKU 256305 @ dx.com.
I will describe what I have found as far as how well it works.
This little board is supposed to supply USB 5 Volts at up to 600 mA from AA batteries.
"Convert 0.9V~5V input voltage to 5V stable output. Produce 200~300mA current with one AA battery or 500~600mA with two AA batteries to charge your" USB device.
First, all tests were run with a 3A power supply.
Test 1: This test was run with the power supply at 1.30 Volts.
When I measured the output voltage without any load it measured 4.97 Volts.
With a small load of around 30 mA the output voltage went up to 4.99 - 5.00V.
With a load of about 150 mA the voltage was up at 5.10V.
With a load taking about 600 mA the voltage was 4.68V. This does not meet the specification or the USB standard.
I then tried a load taking ~ 500 mA and the voltage was, 4.85V which meets the USB standard but is still not within their specification.
Last I tested it with a load of 800 mA and the voltage dropped to around 2.86V. Since the device is only supposed to source up to 600mA I think that value is understandable.
Being curious I decided to try a few more tests.
Test 2: This test was with the power supply running at 1.57 Volts which is in the fully charged range of an Alkaline battery.
Sourcing 400mA the voltage dropped to 4.87V so increasing the source voltage did not help.
Test 3: This test was running two boards together to supply more current and the supply voltage was set back to 1.30V.
With the two boards attached for the inputs and outputs tied together the input voltage was 1.30V and the output voltage was 5.00V when sourcing 600mA.
Sourcing 800mA the voltage was down to 2.86V so one of the boards was obviously sourcing almost all of the current and this will not work to source more current if needed. At least, not in this simple method.
Since the information says the input voltage can be up to 5 Volts I tried a few more things.
Test 4: At an input of 4.45V and supplying 600mA the board was down to 4.73V but the interesting thing was the longer I waited the higher the output voltage got. I was able to lower the input voltage to 4.20V with the current still at 600mA and the output voltage was still 4.73V. This is still not quite at the USB standard of 4.75 - 5.25V but it might work.
The problem with this is, if we have a source of 4.75 - 5.25 Volts then we do not need this board to supply USB 5V power. Also, keeping an input source of 4.25 - 4.70 is going to be difficult with three AA batteries in series when they are supplying 600mA to charge a cell phone.
Conclusion: These boards will source up to at most 500mA with an acceptable USB voltage but will not source the maximum of 600mA when using 1.5 to 3V input from two AA batteries either in parallel or in series.
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