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For rechargeable devices that get their voltage from a USB adaptor or port I highly recommend the "AboveTEK AUT-39C Dual Port Portable USB 2.0 Power Monitor with Built-in Real Time Charging Display" for $11.99 (Amazon Prime) as it gives you a good idea of the DC current being used through both of the USB ports. (Output I allows for data communication with USB port it is plugged into while Output II is strictly for charging.)
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
This meter has proved to be very helpful in the following situations:
#1. Determining that a USB cable was defective. Some cables were completely dead, some would draw current intermittently when wiggling microUSB plug and one was drawing significant current when not plugged into anything.
#2. Determining that a tablet bought used on eBay was not charging properly. It would draw some current initially but would stop after a second or two. At one point it drew excessive current (like 2.7A and body of tablet got hot near USB jack.)
#3. Some mobile devices do not charge as fast (if at all!) when powered down. If charging current remain the same when switching the device is OFF it should charge faster if you leave the device off since there is no current drawn to power the operating system or display.
#4. Determine relative current output of different USB adaptors (switch one device from one adaptor to another and compare readings.)
#5. This is strictly my own observation but if you have monitored the current draw periodically throughout the life of a tablet it drops considerably when Li-Ion battery pack is reaching the end of its useful life. So not only does such a battery pack not hold its charge as well as it did when new but it also takes considerably longer to recharge.)
BTW I had purchased a less expensive single port AboveTEK AUT-38S a month earlier but thought that the readings were way too low and was going to return it. However the readings of both meters were similar so my conclusion was that mobile devices will usually set the charging current based on several factors which might include temperature and current mAh capacity of battery pack.
https://www.amazon.com/gp/product/B00ICR1UB6/
Steve Ahola
P.S. From the manual emailed by customer service:
Mode 1 : Display Charging Volt & Amp (Power On Default) - 4.79V 0.95A means currently charging Volt is 4.79V and charging current is 0.95A
Mode 2 : Display Capacity in Ah - C0.V 865A means in total charged capacity is 0.865Ah since last reset ( read from first line to second line please ).
Note: the meter alternates display automatically.
From a more in-depth explanation provided in a user review at Amazon:
>>> There isn't much to this device. Top number shows Volts, bottom number shows Amps.
It also alternates between another display showing capacity: the numbers indicate energy in miliamp-hours, updated every minute. "C 0." on top and "032" on bottom indicates 32 milliamp-hours (mAh), or 0.032 amp-hours (Ah). Multiply that by 5 volts and you get 0.160 watt-hours (Wh), a unit by which many battery packs are rated.
Just to be clear, the top number is the left part of the decimal, and the bottom number is the right part of the decimal. So if the top number showed "C 2." in this example, the number would mean 2.032 Ah. This is the best and most economical USB charge meter/display I have seen. see less
By Paul on December 27, 2014<<<
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
This meter has proved to be very helpful in the following situations:
#1. Determining that a USB cable was defective. Some cables were completely dead, some would draw current intermittently when wiggling microUSB plug and one was drawing significant current when not plugged into anything.
#2. Determining that a tablet bought used on eBay was not charging properly. It would draw some current initially but would stop after a second or two. At one point it drew excessive current (like 2.7A and body of tablet got hot near USB jack.)
#3. Some mobile devices do not charge as fast (if at all!) when powered down. If charging current remain the same when switching the device is OFF it should charge faster if you leave the device off since there is no current drawn to power the operating system or display.
#4. Determine relative current output of different USB adaptors (switch one device from one adaptor to another and compare readings.)
#5. This is strictly my own observation but if you have monitored the current draw periodically throughout the life of a tablet it drops considerably when Li-Ion battery pack is reaching the end of its useful life. So not only does such a battery pack not hold its charge as well as it did when new but it also takes considerably longer to recharge.)
BTW I had purchased a less expensive single port AboveTEK AUT-38S a month earlier but thought that the readings were way too low and was going to return it. However the readings of both meters were similar so my conclusion was that mobile devices will usually set the charging current based on several factors which might include temperature and current mAh capacity of battery pack.
https://www.amazon.com/gp/product/B00ICR1UB6/
Steve Ahola
P.S. From the manual emailed by customer service:
Mode 1 : Display Charging Volt & Amp (Power On Default) - 4.79V 0.95A means currently charging Volt is 4.79V and charging current is 0.95A
Mode 2 : Display Capacity in Ah - C0.V 865A means in total charged capacity is 0.865Ah since last reset ( read from first line to second line please ).
Note: the meter alternates display automatically.
From a more in-depth explanation provided in a user review at Amazon:
>>> There isn't much to this device. Top number shows Volts, bottom number shows Amps.
It also alternates between another display showing capacity: the numbers indicate energy in miliamp-hours, updated every minute. "C 0." on top and "032" on bottom indicates 32 milliamp-hours (mAh), or 0.032 amp-hours (Ah). Multiply that by 5 volts and you get 0.160 watt-hours (Wh), a unit by which many battery packs are rated.
Just to be clear, the top number is the left part of the decimal, and the bottom number is the right part of the decimal. So if the top number showed "C 2." in this example, the number would mean 2.032 Ah. This is the best and most economical USB charge meter/display I have seen. see less
By Paul on December 27, 2014<<<