Which Battery Pack Has More Capacity as a Power Bank?

[NW-Bound]

I like your threads. It shows you are not the type who gives up easily.

The one above that does not a color display is the one I have. Works fine for me.

 

[easysurfer]

I like your threads. It shows you are not the type who gives up easily.

The one above that does not a color display is the one I have. Works fine for me.

I used the one without color today. Simple to operate and can't beat the price. Only about $7.

The only thing with that one I'm not sure of is how do you know the nominal voltage for Wh calculation? Do you just assume USB powerbanks carry 3.6V?

For about $7 more, the color one does the calculations for you.

 

[NW-Bound]

I used the one without color today. Simple to operate and can't beat the price. Only about $7.

The only thing with that one I'm not sure of is how do you know the nominal voltage for Wh calculation? Do you just assume USB powerbanks carry 3.6V?

For about $7 more, the color one does the calculations for you.

The mAh that it displays is at the USB output, which is nominally 5V. This 5V is what put out by the DC-DC converter inside the battery pack, which steps up the 3.6V to 5V. This DC-DC converter has some loss, which may be 80%.

Suppose at the end, the battery runs out at 2200mAh. The energy delivered to the load is 2.2Ah x 5V = 11 Wh. Note the 5V, and not 3.6V.

What the battery actually delivered is higher, because of the loss of the DC-DC converter. So, the battery energy may be 11 Wh/0.80 = 13.75 Wh. And if the battery voltage is 3.6V, then its capacity is 13.75/3.6 = 3.82 Ah or 38200 mAh.

Note that there's no way any external device can know about the efficiency of the internal DC-DC converter. You need to measure what the battery puts out, vs. the power delivered at the 5V USB output.

For comparison between two packages that both put out 5V, you can just use the mAh reading of the dongle. The one with a higher mAh at 5V wins.

 

[easysurfer]

The mAh that it displays is at the USB output, which is nominally 5V. This 5V is what put out by the DC-DC converter inside the battery pack, which steps up the 3.6V to 5V. This DC-DC converter has some loss, which may be 80%.

Suppose at the end, the battery runs out at 2200mAh. The energy delivered to the load is 2.2Ah x 5V = 11 Wh. Note the 5V, and not 3.6V.

What the battery actually delivered is higher, because of the loss of the DC-DC converter. So, the battery energy may be 11 Wh/0.80 = 13.75 Wh. And if the battery voltage is 3.6V, then its capacity is 13.75/3.6 = 3.82 Ah or 38200 mAh.

Note that there's no way any external device can know about the efficiency of the internal DC-DC converter. You need to measure what the battery puts out, vs. the power delivered at the 5V USB output.

For comparison between two packages that both put out 5V, you can just use the mAh reading of the dongle. The one with a higher mAh at 5V wins.

Now I'm a bit confused . Here we are saying to use the 5v in the calculation. But on the RAVPower battery bank example from a previous post, we used the 3.6V. That's something different?

With this tester, just use the 5V and the mAh to calcualate to get Wh? If that simple, I will probably keep this tester for the cool factor. Otherwise, maybe I should just stick to the color one .

 

[NW-Bound]

The label of the RAVPower bank shows the mAh and Wh of the internal cell. If you divide the 38.4 Wh by the 10.4 Ah, it's 3.69V which is the internal cell voltage. That makes sense and agrees with the nominal 3.6V of a typical lithium cell.

But when you measure at the USB output, what you are getting is 5V and not the 3.6V because there's a DC-DC converter in between.

The converter ups the voltage from 3.6V to 5V. In return, the amperage in Ah is reduced (conservation of energy). And then, heat loss of the converter electronics probably costs you 20%.

 

[easysurfer]

The label of the RAVPower bank shows the mAh and Wh of the internal cell. If you divide the 38.4 Wh by the 10.4 Ah, it's 3.69V which is the internal cell voltage. That makes sense and agrees with the nominal 3.6V of a typical lithium cell.

But when you measure at the USB output, what you are getting is 5V and not the 3.6V because there's a DC-DC converter in between.

The converter ups the voltage from 3.6V to 5V. In return, the amperage in Ah is reduced (conservation of energy). And then, heat loss of the converter electronics probably costs you 20%.

Thanks, this sorta makes sense . But which V do we use to calculate the Wh? 3.6V or 5V?

 

[NW-Bound]

Thanks, this sorta makes sense . But which V do we use to calculate the Wh? 3.6V or 5V?

The measurement device sees the USB putting out 5.xxV, at so many mA, and counts up so many mAh. So, you use these numbers, meaning the 5V. These measurements go together.

 

[easysurfer]

The measurement device sees the USB putting out 5.xxV, at so many mA, and counts up so many mAh. So, you use these numbers, meaning the 5V. These measurements go together.

Got it now . Used the cheapo tester on a drill battery (with USB adapter) earlier. The Wh on battery label is about 24Wh. The test (after calculating) showed about 7.7 Wh. Either battery just old or performance not as stated.

Nice tool to use.

 

[easysurfer]

The dummy load arrived in mail today. I have to contraption set up for a Ryobi drill battery.

My goal is by end of weekend to compare the calculated Wh with this tester and the color one that does the Wh calculation for me to see how the compare.

 

[NW-Bound]

^^^ Cool.

You can cascade the two measurement devices on the same load test. I will be curious to see how the two measurements compare.

 

[NW-Bound]

By the way, I forgot about the display of the Klein tool that you returned.

See the 5.04V and the 1.815Ah? Multiply the two together, and you get 9.15Wh.

The Klein shows 9.235 Wh, which is close.

The Klein Wh number is more accurate, because the Volt and Amp vary slightly during the 4 hours of the test. We take the current snapshot voltage of 5.04V, but it could vary a bit during the 4 hours.

 

[easysurfer]

^^^ Cool.

You can cascade the two measurement devices on the same load test. I will be curious to see how the two measurements compare.

The color tester doesn't arrive til Sunday.

But that's something I can do when I have them both.

 

[easysurfer]

By the way, I forgot about the display of the Klein tool that you returned.

See the 5.04V and the 1.815Ah? Multiply the two together, and you get 9.15Wh.

The Klein shows 9.235 Wh, which is close.

The Klein Wh number is more accurate, because the Volt and Amp vary slightly during the 4 hours of the test. We take the current snapshot voltage of 5.04V, but it could vary a bit during the 4 hours.

Yes, I do the how the numbers relate now.

If only the Klein retained the readings at power off, I'd be quite happy. Plus, I'd trust their calculations the most due to reputation. But the not retaining readings is a deal breaker.

 

[Jerry1]

I can’t wait for the color one to come - i.e. - I can’t wait to see which one you recommend and that I’m going to buy.

 

[easysurfer]

Got some numbers back. Nice having the dummy load.

According to this tester, the Ryobi battery I'm testing, spec of 45Wh now only has 18.531 Wh. Good to know .

 

[easysurfer]

Just started running a test with the colored one . Should have comparable results in about 2 hrs.

Gonna run alone then cascaded two testers in the next run.

 

[NW-Bound]

Got some numbers back. Nice having the dummy load.

According to this tester, the Ryobi battery I'm testing, spec of 45Wh now only has 18.531 Wh. Good to know .

How old is your Ryobi battery? I suspect that it is fairly aged, and has lost much of its original capacity.

Do new batteries test up to their capacity? Yes.

I have tested literally hundreds of cells that I bought on the surplus market. Depending on how long they have been in use, or perhaps just liquidated because of a design change, they may test anywhere from 90% to 100%.

Not all Chinese cell makers lie. Often it is the vendor who lies, not the manufacturer.

Now, the aging rate of the cells is a different story. Some age faster than others, and this is something you only know after owning and using them.

 

[easysurfer]

How old is your Ryobi battery? I suspect that it is fairly aged, and has lost much of its original capacity.

Do new batteries test up to their capacity? Yes.

I have tested literally hundreds of cells that I bought on the surplus market. Depending on how long they have been in use, or perhaps just liquidated because of a design change, they may test anywhere from 90% to 100%.

Not all Chinese cell makers lie. Often it is the vendor who lies, not the manufacturer.

Now, the aging rate of the cells is a different story. Some age faster than others, and this is something you only know after owning and using them.

The Ryobi battery is quite old. I say over 10 years old. In fact, I bought another some time ago because this one seemed to not last as long as when new. The measuring kind of confirms this.

I did notice that the non-color tested did shut off before the battery is totally drained, so that too may be why the Wh result is lower than the specs. The tester shut off, but I have a plain battery tester (especially for the Ryobi) that shows 1 bar of energy left.

I'm curious too see with the color tester how much if any juice if left in the Ryobi batter when that tester shuts off.

 

[easysurfer]

Got a result to compare. Ran color tester alone. The color tester did drain the battery a little more but the numbers are close.

non-color: 3550 mAh, 18.531 Wh

color: 3654 mAh, 18.035 Wh

As for which one to choose? A personal preference.

Color calculates Wh automatically and probably a bit more precise. Also can turn off display during running.

I think (to my surprise) non-color display easier to read. Larger text.

The numbers I'm most interested in (mAh, Wh) are tiny on color.

Color about 2X as much is cost.

p.s. when the battery charges up, I'll run them both cascaded.

 

[easysurfer]

Oh, I also like that the non-color shows elapsed time, color does not.

 

[NW-Bound]

The Ryobi battery is quite old. I say over 10 years old...

45Wh down to 18.5Wh, or 41% of original capacity.

If it were a lead-acid or NiCad, would you expect it to work at all at 10 year old?

Yes, lithium cells last a long time, but not forever. They usually age fairly gracefully too, but a few go "kaput" suddenly.

 

[easysurfer]

Here's the numbers running both the color and non-color tester at the same time.

I've decided to keep the cheap one and return the color and the unopened Klein.

I prefer the very simplicity and display of the cheap one (despite having to calculate the Wh).

 

[easysurfer]

Thought I'd revive this thread as today I saw a USB tester on Amazon which might be exactly what I want. I just had to buy . Looks simple to operate and automatically calculates the Wh.

I could just as well use the one I have at the moment and calculate the Wh on my own. But the lazy in me thinks would be nice to not even have to use that brain cell.

Looks like the tester has to make the trip from China so may take a few weeks to arrive.

In the meantime, here is a picture.

 

[ERD50]

Thought I'd revive this thread as today I saw a USB tester on Amazon which might be exactly what I want. I just had to buy . Looks simple to operate and automatically calculates the Wh.

I could just as well use the one I have at the moment and calculate the Wh on my own. But the lazy in me thinks would be nice to not even have to use that brain cell.

Looks like the tester has to make the trip from China so may take a few weeks to arrive.

In the meantime, here is a picture.

Got a link the the device?


-ERD50

 

[easysurfer]

My Uonlytech (brand name) USB Tester arrived today.

It works .

The button serves several functions like zeroing different measurements one a a time depending on how many rapid clicks.

It does function the way I want. Captures measurements when measured battery bank runs out of juice and long press on button resets all measurements.