As an engineer, the first thing to do is open it up and take a look. What I found was a decently built product with large cells. A rather complex circuit board to control the charging. You can leave the charger and your device connected for a backup power configuration. The magic behind the device is that the DC power plug module outputs 12.6 volts which is just high enough to charge the batteries without providing excess voltage to your devices. The charged unit itself output 12.48 volts with no load. This product will not likely work well with any other power plug module.One drawback is that it is too easy for the switch to be accidentally pressed off. Since it extends beyond the case, any pressure, such as a bump against a surface will turn it off (or on). They should design in a ridge around the switch to help prevent turn-off (or have it recessed). The plastic case is good, but not waterproof in any way. What I found counter intuitive is that the red LED on the case never turns green. It makes the unit seem like it never gets fully charged. The LED on the power module does change color however. Instructions are typical ambiguous Chinese to English translations.
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