18650 power bank

[bella-headlight]

Paypal has refunded me in full.

 

[TinderBox (UK)]

Great result, now what are you going to buy to replace it.

John.

Paypal has refunded me in full.

 

[bella-headlight]

Great result, now what are you going to buy to replace it.

John.

Believe it or not another one the same from a different seller or the black Tomo version.
I really liked this power bank.

 

[TinderBox (UK)]

Do the new 2 cell versions show the ma being draw from the usb ports like the new 4 cell version do?

I have the 4 cell Soshine that shows the ma.

EDIT: Also have a look at the Soshine E4S

John.

 

[bella-headlight]

I have already just ordered a Tomo V8.
I like the capacity of the 4 x 18650 form power bank.

 

[TinderBox (UK)]

I put 4 x 18650 3400mah (NCR18650B) in my Soshine E3, that`s 13600mah and put an connected an usb power meter, and then connected an 1amp resistor load.

Once the Soshine E3 shut down due to low battery i checked the usb power meter, It only showed 7750mah had been pulled from the power band, that has a capacity of 13600mah, that means only 57% of the power banks capacity is available with an 1amp load, that`s not very good.

I checked the no-load voltage of the 4x18650 when i removed them from the power bank, 3.25v, 3.22v, 3.24v, 3.26v , I will charge the 18650 back up in the Soshine E3 and see what the full termination voltage is.


John.

 

[kreisl]

thanks for the 1amp load test.

i had several v8 4 tomos for testing, great price , white, black

~10h30min for charging 4x NCR18650B from 2.858V each,
total "13791mAh" (usb doctor) transferred between USB adapter output 5V (mains) and USB port input 5V (tomo),
termination voltage on my current unit is like:
slot1 4.205V (after overnight and with older cell: 4.197V)
slot2 4.216v (after overnight and with older cell: 4.214V)
slot3 4.184V (after overnight and with older cell: 4.180V)
slot4 4.214v (after overnight and with older cell: 4.210V)
measured removed from tray, with ut61e

initial tomo USB input current was "1.65A" (usb doctor) and this number decreased slowly during the CC-phase and decreased faster, as expected, during the CV-phase. basically the tomo USB input current did not exhibit perfect CC-CV behavior, since the CC-phase was not constant 1.65A.

edit: single cell 18650 powerbank 1.56us$ rofl
http://m.gearbest.com/chargers/pp_187287.html

 

[HKJ]

Once the Soshine E3 shut down due to low battery i checked the usb power meter, It only showed 7750mah had been pulled from the power band, that has a capacity of 13600mah, that means only 57% of the power banks capacity is available with an 1amp load, that`s not very good.

That means about 80% efficiency in the boost converter, not bad and not not very good either.

 

[TinderBox (UK)]

Well that termination voltage looks good, so the E3 must be really inefficient, My Nitecore F1 specs say it`s 90% efficient, I will have to put this to the test next.

John.

thanks for the 1amp load test.

i had several v8 4 tomos for testing, great price , white, black

termination boltage on my current unit is like
slot1 4.19v
slot2 4.18v
slot3 4.22v
slot4 4.21v
measured removed from tray, with ut61e

 

[kreisl]

Well that termination voltage looks good, so the E3 must be really inefficient,

tomo technical details were reviewed years ago, for example on a blog. i like the concept of exchangeable 18650's. but the technology inside is outdated, of course. there are now a bunch of QC3.0, Qualcomm's QuickCharge v3.0 technology, enabled powerbanks on the market. already tons of them on taobao/alibaba, and a few better of them like BlitzWolf also available for the Western market.

HKJ reviewed the massive Ravpower QC3.0 enabled 18650 powerbank not long ago. And afaik TOMO is developing a QC3.0 powerbank, maybe similar in function to the V8-4, these days too. For the most compact portable QC3.0 powerbanks i'd choose BlitzWolf or Xiaomi or alike, for 18650 exchangeability i'd hope for the new TOMO which is hopefully more efficient than our old unit.

Btw, for fair comparison or evaluation of efficiency, in my opinion imo one should refer to the energy (stored energy in 18650's vs. delivered energy to 1amp load), not to the capacity.

If you take the capacity as point of reference, then yes, the Tomo has efficiency of ~50%. A number which is typical for 18650 powerbanks.

 

[TinderBox (UK)]

Ok, I just tested the Nitecore F1, I fully charged an new 18650 an 3400mah (NCR18650B) different cell to last test, I connected my usb power meter, and added an 1amp resistor load, my usb meter only showed 1630mah when the battery power died.

So from an 3400mah cell, you only get approx 1630mah of power, and then the device you are charging has an charging efficiency as well, so there is a lot of wasted energy.

John.

 

[kreisl]

see? again around 50%
really typical number because you reference capacity instead of energy.

 

[TinderBox (UK)]

Nitecore rate the F1 with an 90% efficiency in the specs, but i suppose that`s at 500ma load or lower??

John.

see? again around 50%
really typical number because you reference capacity instead of energy.

 

[HKJ]

So from an 3400mah cell, you only get approx 1630mah of power, and then the device you are charging has an charging efficiency as well, so there is a lot of wasted energy.

Not that much, efficiency is about 80% at 1A if you do the match correctly (Based on my measurements).

 

[kreisl]

i just did a quick simple test myself with a single 1x Sanyo NCR18650GA 3500mAh nonimal (fully charged, condition Like New) in the tomo. i don't have a 1amp load, so i simply charged my depleted cr*ppy phone battery. what matters is that the system (=tomo+1xNCR18650GA) refused to continue charging after "1540mAh" (USB meter) had been transferred. I could restart the tomo with its ON/OFF switch and there'd be a ~0.9A current at the USB port, but after a few seconds the system would turn off automatically again. After taking out the warm Sanyo cell and letting it rest for a while, its offline voltage was ~3.40V. As we know from energy balance, the actual battery current draw must have been higher than the 0.9A, and at that high current draw the actual capacity of the Sanyo may be 3300mAh, not 3500mAh. Rough calculation, the Sanyo delivered ~3100mAh capacity (~200mAh difference because at 3.40V the Sanyo isn't fully depleted!) but only 1540mAh got delivered at the USB port. That's a capacitive efficiency of 49.7%, or 50% (rounded).

My USB meter does not measure energy, too bad, hmm. :thinking:

One could do the same simple test with other "powerbanks" like the USB chargers by Nietcore, Littokaala, Obus, Xstar, and you'd get about the same result, a capacitive efficiency of ~50%.

EDIT:
1670mAh at 0.65A USB port 3.4V offline battery
1720mAh at 0.16A CCCV USB port 3.2V offline battery
1410mAh at 1.05A USB port 3.5V offline battery

 

[sidecross]

Some of the confusion maybe because some people may be using an analogy of a 'power-bank' as a spare fuel tank in an automotive paradigm.

In the automotive paradigm, fuel can be taken from a fuel tank or reserve vessel until empty; this is not the same with current from a battery cell.

I plan on using 50% of the 'power-bank' capacity as my usable current.

 

[Lynx_Arc]

i just did a quick simple test myself with a single 1x Sanyo NCR18650GA 3500mAh nonimal (fully charged, condition Like New) in the tomo. i don't have a 1amp load, so i simply charged my depleted cr*ppy phone battery. what matters is that the system (=tomo+1xNCR18650GA) refused to continue charging after "1540mAh" (USB meter) had been transferred. I could restart the tomo with its ON/OFF switch and there'd be a ~0.9A current at the USB port, but after a few seconds the system would turn off automatically again. After taking out the warm Sanyo cell and letting it rest for a while, its offline voltage was ~3.40V. As we know from energy balance, the actual battery current draw must have been higher than the 0.9A, and at that high current draw the actual capacity of the Sanyo may be 3300mAh, not 3500mAh. Rough calculation, the Sanyo delivered ~3100mAh capacity (~200mAh difference because at 3.40V the Sanyo isn't fully depleted!) but only 1540mAh got delivered at the USB port. That's a capacitive efficiency of 49.7%, or 50% (rounded).

My USB meter does not measure energy, too bad, hmm. :thinking:

One could do the same simple test with other "powerbanks" like the USB chargers by Nietcore, Littokaala, Obus, Xstar, and you'd get about the same result, a capacitive efficiency of ~50%.

And if you calculate the actual energy at 3.7v nominal in 5.0v out you get 11470mw in 7700mw out or about 67% efficiency which is pretty close to the 70% figure I estimate power banks do that number probably goes down as current increases and goes up as it decreases.

 

[Gauss163]

I put 4 x 18650 3400mah (NCR18650B) in my Soshine E3, that`s 13600mah and put an connected an usb power meter, and then connected an 1amp resistor load.

Once the Soshine E3 shut down due to low battery i checked the usb power meter, It only showed 7750mah had been pulled from the power band, that has a capacity of 13600mah, that means only 57% of the power banks capacity is available with an 1amp load, that`s not very good... .

It's 82% efficient, not 57%. You were comparing apples and oranges since the cell's capacity is rated at 3.7V but the USB meter is reporting capacity at 5V. To compare you should compare the total energy. The meter measured 5V*7.75Ah = 38.75Wh. HKJ's discharge test shows the NCR18650B deliver about 11.856Wh at 0.5A. So 38.75/(4*11.856) = 0.817, so you got about 82% efficiency. That's typical for a cheap powerbank. Try it at 5V/0.5A to see if it gets much better.

Note that when you use the powerbank to charge a device that also includes another typically 80% efficient buck/boost regulator then they combine by multiplying to yield 66% efficiency in total, i.e. about 1/3 of the powerbank's energy is lost in the combined inefficiency of the step up/down voltage regulators on both ends.

For example, if you use the powerbank to charge a cellphone or tablet battery then typically at most 2/3 of the powerbank's energy can be transferred to the target battery. This double loss - combined with the above voltage mismatch in capacity ratings - are the source of much confusion.

 

[TinderBox (UK)]

Thanks, Gauss163 you are full of knowledge :bow:, There should be a better way for the average consumer to pick a power bank, The mah rating seems to be of little use as it is based on 3.7v, But that only 2/3 of the mah rating of an power bank will actually be transferred to the battery of your device is handy to know.

John.

 

[kreisl]

For the most compact portable QC3.0 powerbanks i'd choose BlitzWolf or Xiaomi or alike, for 18650 exchangeability i'd hope for the new TOMO which is hopefully more efficient than our old unit.

I checked amazon, looks like Anker has updated their flagship model of the powercore+ powerbank series from QC2.0 to QC3.0, good for them! Soon enough all other powerbank manufacturers will offer their products with QC3.0 compatibility, no doubt. As mentioned earlier, on toabao and alipapa there are already lots of noname powerbanks with QC3.0 technology. Maybe not certified by Qualcomm, i dunno.

Qualcomm has published a PDF list with all official QC3.0 certified products by trade names and makers all over the world. But Qualcomm isnt able to keep the list uptodate since every week there are more new QC3.0 powerbanks popping up on the market, especially those made in the Chinas.

As with flashlights, i stick with brand name products. Gives me a better feeling :duh2: