I use this to estimate the condition of my vape batteries as relative reference among other things. I first let the battery "lock" in the mod, then I fully charge (mod off) and record the time and mAh taken. This is my initial reference and with a fresh good new battery, the time will be the lowest and mAh the maximum. After than, from time to time I perform the same chargin process (full discharge in the mod, full charge with mod off) and compare the results. High increase in charge time, compared to the initial recorded charge time, indicates a big increase in the internal resistance (since the mod will enter CV charge mode) and of course lower mAh put in will also indicate that. This USB device is a very cheap and easy way to check your batteries and it is very cool too!
Verified purchase: Yes | Condition: New
I'll preface with this, I ordered two of these - one for myself, and one for my grandfather - to use to sort through USB power leads and wall warts. Initial first test was using my Samsung Galaxy S8+, OEM USB-C cable and OEM 2 amp charger, and that did not turn out well. My device was at 80% charge - which would take normally 30 minutes to complete to full. With the "Charger Doctor" plugged in series between the charger and the device, sapped some of the power for itself and providing a readout of 4.96 volts and a measly 0.46 amps. My phone reading 1 hour 20 minutes until full. That can't be right. So I tested the same setup with several other wall warts, getting similar or same results unless it was a 1 amp charger - which read out 0.86 amp on screen. The label on the product says that it supports from 0 amp to 3 amp chargers, while it's not "wrong", it doesn't output numbers to support their claim when a 2 amp charger is showing that my device is apparently only getting 0.46 amps. For the heck of it, i decided to plug in the two charger doctors I had in series to each other from the wall wart. The top one reading "5.06 volts / 0.10 amp" and the bottom one reading "4.86v / 0.54 amp." This was tested with each one being swapped around to confirm it wasn't just one unit. It was both units. Upon further inspection of other listings and other websites, the current draw to just run the device appears to be between 0.30 and 0.50 amp. Just. For. The. Charger Doctor? Well, that supports my theory that - at least this variant (which was supposed to be a clear unit, instead was both blue) of the Charger Doctor is not reliable, and I cannot recommend the unit to anyone, even if the load is under 1 amp - as the Charger Doctor will still produce erroneous results due to the power requirements of the Charger Doctor itself. At least the refund process was quick and painless. Read full review
Verified purchase: Yes | Condition: New
This item gives you an idea on what condition is your item. For example if your item has a battery that is rated 2600 mah (ex. galaxy s4) then you turn off your phone while is totally empty and you plug in a USB in series with your phone. You must be sure that your phone (or what else) is empty and turned off. Then you have to do some maths. Lets say that your phone is 2600mah at 4.2V full and 3.3V empty. So this battery is more or less (4.2+3.3=7.5V/2=3.75V mid voltage). So 3.75V*2.6A=9.75W. Lets say that you install it all night for charge and you get 2300mah on this usb charger tester. If your supply was good then this power supply delivered 5V*2.2A=11W. Assume that there is a loss (most of switching regulators never convert at higher than 80-85%) at the convertion inside phone from 5V to 3.75V(mid voltage), and a loss from the convertion of electric energy to chemical energy that is stored inside the battey lets say total 20% losses. So we get that 11W-20% loss =8,8W. So from a theoretical 9.75W that is our battery we gave it 8.8W our battery is still in good condition. If our battery is less than 30-35% less than the manufacturer declares then we must replace it.Read full review
Verified purchase: Yes | Condition: New
THIS is "THE BEST" USB Monitor you can find for the money! THIS displays both USB VOLTAGE and USB CURRENT ~ "constantly". SEE your Current as your USB Cell or other rechargeable to full charge! Also instantly see if any USB item overloads your supply! I have purchased more than 10 of these to for 'surprise gifts' to my friends... EVERYONE Loves them! Other monitors 'actually flash' from one screen and back again ~ this is VERY ANNOING!
Verified purchase: Yes | Condition: New
I found out by using this product that one of my adapters was faulty. I almost threw awY a perfectly good battery. Instead I threw awayy the adapter
Verified purchase: Yes | Condition: New
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