I have the UM25C for a few month. Nice device and paired with a 1A load good for checking USB cable resistance (good to show people why their 2 or 3m long ultra light and thin cables double or tripple their charging time). Overall a usefull little tool. And with the option to stop charging when the current goes below a threshold you can preset, is also nice.
Only thing i do not like is, that you can not change the divisions in the Current-Voltage Graph (app). If you have something that pulls 1A the current and voltage lines are ontop of each other.
Ah, thanks for the reminder d_t_a, my wife has been using this MI quite a lot so it’s probably got a lowered capacity. It reads sort of strange, at one place it says 6250mAh, another it states 9510/10000 as min/typ. This one has Texas Instruments components and is supposed to have very high efficiency, well over the 90% mark, but it’s 3 18650’s may be getting worn.
The other, the USB C one, is 10,000mAh with Li-Polymer pack, it’s about the same size as my wife’s phone. Also with TI components and high efficiency. (this is the one the meter is hooked up to, in the picture and still charging)
As it works out, the i8 has a pretty good break-down of what is using the battery and to what percentage, so it’s pretty easy to configure my new phone to conserve power. Except I talk to a friend from BLF using speakerphone and we build lights while talking for hours so my phone gets run down easily when we are doing that. lol 50% of my battery usage in the past week has been on speakerphone.
I should read the whole manual as I didn't know about that option to preset the cut off for charging. That is a real bonus for me, thanks 
My phone is supposed to have an 1821mAh battery pack. It was showing 50% when I put it on the 12W charger, rated for a 2A charge rate. The USB meter showed a 1.74A charge rate and the phone is now full, showing 100, with the meter saying it has put in 874mAh. In my battery health area it says my battery is at 96 of a new cell. So, this looks to be pretty close or accurate. 
Edit: Actually, now that I check it closer, while the phone shows 100% it also still shows the charging icon and the USB meter shows a 0.06A rate still being applied. It’s been charging for 1:27:55 and now shows 879mAh put in. So it’s pretty neat to be able to see the slow ramp down to a really full cell, like my big chargers do. I really never noticed the charging icon still on with 100% visible, may have been unplugging it before it was completely done.
@klrman
I use the charge cut off for my QI charger. It will not turn off complete (trickel charge) when the phone is full. So i use the samsung charger then the UM25 and then the QI charger. When the battery is full the current will drop below the treshold and the um25 will cut off the power to the QI charger.
But i will have to set new parameters for my new QI charger (with fan to reduce the temp that will hopefully give my battery a longer life). But the fan will draw also a bit of current so i will have to check how much current the package is deawing when the battery is full. (https://www.aliexpress.com/item/New-Fast-Charging-Pad-For-iPhone-X-8-8-Plus-Qi-Wireless-Charger-with-Cooling-Fan/32909679667.html?spm=a2g0s.9042311.0.0.3fa34c4dtVxFs1)
When I bought this UM25 I saw a different model first and picked it up for $9.95. Then shortly after placing that order I saw this UM25 and really liked the display so I splurged and ordered it as well. The UM25 came in first and got me spoiled, the other unit has a smaller LCD display that is difficult to read, not able to rotate the screen to optimize viewing angle for odd USB port placement, just really a waste of $10.
I still don’t understand how this ultimately helps me keep an eye on my phone’s battery, like right now I started the charge at 32% on an 1821mAh cell, showing 95% done on the phone’s screen the meter shows it’s used 2011 mAh of power and has gone from a 2.A charge rate down to 0.3A. I know the meter is showing me total power used from the port, but it’s still misleading to me as to how that directly relates to the actual charge rate and capacity of the internal battery of my phone. Oh well. I’ll figure it out eventually and may even connect the dots at some point…
UM25 only monitors the amount of energy goint to the smartphone, including the loss before converted to the 3,7V for the battery.