UM25C USB tester instructions pdf, very good

Pete7874 · 2018-06-08T15:17:32.000Z

Who has the best price on UM25C currently? Any coupons out there?

Thanks!

klrman · 2018-06-08T18:42:07.000Z

Pete7874:

Who has the best price on UM25C currently? Any coupons out there? Thanks!

$20.88 at banggood right now for the um25c. I couldn't find a coupon so went with their sale price when I ordered. Mine was $5 cheaper as I did not get the bluetooth version.

d_t_a · 2018-06-09T01:23:13.000Z

Official RuiDeng AliExpress store:

https://www.aliexpress.com/item/RD-UM25-UM25C-for-APP-USB-2-0-Type-C-LCD-Voltmeter-ammeter-voltage-current-meter/32855845265.html

The price there is $21.50, but ordering 2pcs drops it to $20.86/pc.

dodge_911 · 2018-06-17T18:25:14.000Z

dodge_911:

d_t_a:

I also notice there are 3rd-party USB meter being released right now that look like the UM24, but has some differences (notably this “A3 USB meter” has type-C port), but the display screens look almost exactly like the UM24.

If all goes well, I'm getting that A3 in for a video...

No news yet on that A3, but I am getting the UM25C and UM34C from RuiDeng themselves :)

DB_Custom · 2018-08-28T14:49:19.000Z

Hi guys, I just got the UM25 without bluetooth and am a bit confused at what I’m seeing. (This is my first one of these devices)

It’s using 5V from the computer to the device plugged in, lets say a NiMH/Li-ion charger from O-Light with magnetic leads and auto-sensing polarity. With an Eneloop in the circuit the UM25 is showing 4.969V and 0.1954A. This is showing me how much power is being pulled from the computer’s USB port, but not how much the charger is using. I used my clamp meter on the negative lead and it shows 0.51A going into the cell.

So how do I figure out the conversion? Or is it not about that, merely about what the charger is pulling not what it’s putting out? But of course it’s advertised to be able to check the accuracy of your phone battery, but if it’s giving a reading of the charger current you really don’t know what the battery itself is doing, do you?

Sorry, random pic off the net… not my device plugged in.

Also, last night I was using it with my battery bank, this is a 12,000mAh bank that was down to the 25% indicator, but it charged up showing a bit less than 2000mAh used through the tester, I’m assuming this was because of the 5V use at the computer USB port, so what do these numbers do for me exactly?

maukka · 2018-08-28T15:54:59.000Z

It’s a USB meter. It has no way of knowing anything outside of that.

klrman · 2018-08-28T16:07:55.000Z

DB Custom:

Hi guys, I just got the UM25 without bluetooth and am a bit confused at what I’m seeing. (This is my first one of these devices) It’s using 5V from the computer to the device plugged in, lets say a NiMH/Li-ion charger from O-Light with magnetic leads and auto-sensing polarity. With an Eneloop in the circuit the UM25 is showing 4.969V and 0.1954A. This is showing me how much power is being pulled from the computer’s USB port, but not how much the charger is using. I used my clamp meter on the negative lead and it shows 0.51A going into the cell. So how do I figure out the conversion? Or is it not about that, merely about what the charger is pulling not what it’s putting out? But of course it’s advertised to be able to check the accuracy of your phone battery, but if it’s giving a reading of the charger current you really don’t know what the battery itself is doing, do you? !{width:40%}https://i.ytimg.com/vi/gP89sSzcoo8/maxresdefault.jpg!:https://i.ytimg.com/vi/gP89sSzcoo8/maxresdefault.jpg Sorry, random pic off the net… not my device plugged in. Also, last night I was using it with my battery bank, this is a 12,000mAh bank that was down to the 25% indicator, but it charged up showing a bit less than 2000mAh used through the tester, I’m assuming this was because of the 5V use at the computer USB port, so what do these numbers do for me exactly?

I don't think the numbers add up, maybe you have a faulty UM25. How can the meter show 0.1954A and the clamp meter show 0.51A? My UM25C shows what the charger is using. If my flashlight has a 2A fast charger built in, the meter is displaying 2A or 2.1A until the saturation phase near the end charge cycle slows down and the meter displays that accurately too.

DB_Custom · 2018-08-28T16:17:27.000Z

But the USB port is outputting 5V, where the cells charge at 4.2V, so there is a conversion factor for what the USB is using as compared to what the charger is putting into the cell, with some losses as no charger is 100% efficient, right?

d_t_a · 2018-08-28T16:23:51.000Z

DB Custom:

Hi guys, I just got the UM25 without bluetooth and am a bit confused at what I’m seeing. (This is my first one of these devices)

Also, last night I was using it with my battery bank, this is a 12,000mAh bank that was down to the 25% indicator, but it charged up showing a bit less than 2000mAh used through the tester, I’m assuming this was because of the 5V use at the computer USB port, so what do these numbers do for me exactly?

What is the configuration?

5v USB port < USB meter < power bank

The power bank was 25% full based on its indicator.
Was the USB meter’s capacity reset to Zero when you plugged it in (capacity reading needs to be reset to zero first if measuring capacity)?
Assuming the USB meter’s capacity display was reset to zero, and the capacity charged reads 2000mAh, and the powerbank became full (display reads 100%), right?

Then that means 75% capacity is 2000mAh, so total capacity of the powerbank would calculate to something like 2667mAh.

However, my guess is the capacity readout (25%) of the powerbank is a “guess” [not that accurate] based on the voltage of the lithium-ion battery inside the powerbank, and not the actual capacity. Another thing is the power bank may have degraded in capacity (if this is not a “new” powerbank).

I recall testing a 10000mAh powerbank when it was relatively new (I didn’t have a USB meter yet when it was brand-new), but when I got that powerbank it had several cycles of usage, and I measured something like 8000+ mAh capacity. But right now (after 2 or so years), when I do another capacity test (it now takes a very longer time to “fill up” the last capacity, and it’s just something like 3000+ mAh capacity (from empty, charge to full, measuring capacity with the USB meter in between). Seems like a big degradation…

Yup, USB 5v vs lithium-ion nominally 3.7v so there would also be an efficiency factored in the equation…

klrman · 2018-08-28T16:25:06.000Z

I think it's different for Voltage. The USB port is always putting out 5V, but until a device is plugged in, it should display 0A until something is pulling current from it. That's how mine works, it always displays 0A until I connect something to it, but always displays 5V.

DB_Custom · 2018-08-28T16:28:17.000Z

So the only thing that really gives any indication to the health of my cell phone battery is the mA put in, would this be fair to assume? (It lists mAh for some reason, which is capacity not active voltage if I understand it right)

Ok, so here is a pic I just took with the meter plugged into the 2A output of my USB3.0 hub, feeding a 10,000mAh Bank through a type C Kevlar braided cable…. this is a MI power bank rated at 5.0V 2A charge rate with the Type C inlet.

The display is upside down, sorry.

klrman · 2018-08-28T16:36:12.000Z

here is the full eng manual in pdf

The first link I posted in the OP is not displaying the full manual

I never checked mAh, but I think the meter displays it but I need to try it out myself to make sure

Barkuti · 2018-08-28T16:36:54.000Z

DB Custom:

…

It’s using 5V from the computer to the device plugged in, lets say a NiMH/Li-ion charger from O-Light with magnetic leads and auto-sensing polarity. With an Eneloop in the circuit the UM25 is showing 4.969V and 0.1954A. This is showing me how much power is being pulled from the computer’s USB port, but not how much the charger is using. I used my clamp meter on the negative lead and it shows 0.51A going into the cell.

So how do I figure out the conversion? Or is it not about that, merely about what the charger is pulling not what it's putting out? …

The figures match well, the USB meter sensed power in is P_in = V_in × I_in = 4.969A × 0.1954A = 0.9709426W. Power going into the cell is P_cell = V_cell × I_cell, you did not measured cell rail voltage but anyway I am going to presume ≈1.4V, thus P_cell = 1.4V × 0.51V = 0.714W. This would be about 73.54% overall efficiency, not bad for a small low voltage device.

DB Custom:

… But of course it’s advertised to be able to check the accuracy of your phone battery, but if it’s giving a reading of the charger current you really don’t know what the battery itself is doing, do you?

…

Bollocks. Your phone/tablet/laptop battery is totally under the control of its battery management circuitry. Get a proper application for the task. In Android, I recommend 3C Battery Monitor Widget.

DB_Custom · 2018-08-28T16:43:09.000Z

New to smart phones as well, recently got the Apple i8. The charger that came with it sucked, I got the Apple 12W charger that supposedly charges at 5V/2.4A then I heard about the bigger chargers working on this new phone so I got a 29W that says it charges at 14.5V/2.0A (this i8 has the wireless charging capability, it’s supposed to be compatible and indeed does charge considerably faster with this 29W charger)

TheOnlyDocc · 2018-08-28T17:06:20.000Z

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.

DB_Custom · 2018-08-28T17:19:48.000Z

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.

klrman · 2018-08-28T18:50:08.000Z

TheOnlyDocc:

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.

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

DB_Custom · 2018-08-28T22:29:47.000Z

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.

TheOnlyDocc · 2018-09-02T14:43:49.000Z

@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)

DB_Custom · 2018-09-02T14:55:31.000Z

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…