USB 'Power Banks'

[JohnW2]

Hi. This probably isn't the best of forums for this, but I am 'amongst friends, so ...

I'm used to, often mis-described, imported 'electronic/electrical tat' but this one has even me a bit confused.

I've been looking around at USB-charged 'power banks' (for running mobile phones etc.) for a Christmas present. There are a few well known/reputable manufacturers (e.g. Belkin, Energizer) plus a good few other branded ones which seem quite similar (and seem to get good reviews), and what one generally sees are ones with capacities of 5,000, 10,000 and 20,000 mAh, at prices (for 'standard'/'budget' products) generally in the range of about £15 - £30 or so (although one can pay much more for allegedly 'fancy' ones).

However, if one looks at the likes of eBay, the great majority of what one finds are unbranded ones (from Chinese suppliers, although 'sold in UK') with claimed capacities ranging from 50,000 mA up to 500,000 mA and beyond, often at prices that wouldn't even get many of the 5,000 mAh branded ones. These claimed capacities are clearly ridiculous, and they presumably can't all simply be 'typing errors', so I wonder what is actually going on?

Even Amazon has mainly 'sensible sounding' ones.

Kind Regards, John

 

[ericmark]

My worry is it catching fire, we read about aircraft, car, and phone fires either caused by batteries or made worse by batteries, like the Richard Hammond crash. I am not really that worried about a battery large enough to recharge a phone, but as you get to large enough to jump start a car, then I want to buy from a well known UK supplier.

We hope be it Argos, Asda, Tesco, Aldi or Lidi that their buyers test the units before putting them on sale, and even if they don't, should one go faulty there will likely be a national recall. As to Amazon not so sure, it says

When we are notified of a product recall by a retailer or a national or European authority, we stop selling the product as quickly as possible. We will also contact customers who have already purchased the item from us, by e-mail, to advise them of the measures put in place by the manufacturer or the authorities.

which seems to say they don't test anything themselves, so when you buy some thing you really don't know where it has come from, for all you know it is arranged in UK but comes direct from China and no one every checks what is being sold.

In the main I use the packs when I have been playing games on my phone, and once I have reached a point where I have to use it, I stop playing games, so a 5000 mAh pack at £15 from likes of Curries PC World is ample. My jump start pack is still lead acid 12 Ah.

 

[JohnW2]

My worry is it catching fire, we read about aircraft, car, and phone fires either caused by batteries or made worse by batteries ... I am not really that worried about a battery large enough to recharge a phone, but as you get to large enough to jump start a car, then I want to buy from a well known UK supplier.

I wouldn't argue with any of that, but it's not really my point/question.

It's clearly impossible to get a battery 50Ah, let alone 500Ah or more, into a space usually smaller than a mobile phone (otherwise 'a thousand Christmases' woul have come for EV manufacturers), so the descriptions are obviously ridiculous, but it seems so strange that there are so many of them.

A search on eBay for "power bank 100000mAh" (WITH the quotes) gets 235 hits, the first three of which are:

.. and the text of the listings continues to talk about 100,000 mAh - so it's not just a one-off typo in the listing title. For example, the spec of the first one above includes ...

... I can but presume that they don't understand what "mAh" mans, and are all copying one another! If they are, as I would guess they probably are, 10,000 Ah, then they are still 'too cheap', but probably no more so than one expects of "Chinese imports". Mind you, whilst I can guess that "100,000 mAh" may actually mean 10,000 mAh, what on earth can 500,000 mAh (aka 500 Ah - but again about the same physical size!) mean - and there are 267 hits for that, of which the first three are ...

... and, maybe 'the record' ....

Kind Regards, John

 

[bernardgreen]

John, have you not heard of the Flux Capacitor Energy Storage system developed by Doctor ( of Science ) Emmett Brown

 

[bernardgreen]

There is a possible explanation

Both a comma and a period are generally accepted decimal separators for international use. ... 2) Period (spoken as point), the thousands separator in many non-English speaking countries. 3) Comma, the thousands separator used in most English-speaking countries.

50,000 mAh could be in reality be 50 mAh with 3 decimal places

 

[Mottie]

If it seems too good to be true......

 

[bernardgreen]

If it seems too good to be true......

then it was made in China

 

[sparxxxx]

Along the same lines, I have NOCO Genius Boost Sport GB40, portable jump starter which has rave reviews ie it works. This thing is charged from a usb port for 3 hours and this gives enough power to start numerous cars. How is that possible?

 

[bernardgreen]

How is that possible?

Typing as I think about it......

Charging with 5 volts ( USB ) at 2.1 Amp is 10.5 watts

Charging at 10.5 watts for 3 hours will put 31.5 Watt-Hours or 340,200 Watt-Seconds ( 3 x 60 x 60 x 31.5 ) into the battery in the GB40

Assume an average cranking time of 10 seconds to start a car and from the data sheet up to 20 jump starts on a single charge

340,200 Watt-Seconds spread over 200 seconds is a supply of 1,701 Watts

Assume the cranking voltage is 12 volts

1,701 Watts at 12 volts is a current of 141.75 Amps

140 Amps could start a car in 10 seconds providing the car's ( flat ) battery did not take most of that current.,

So yes it is possible in theory

 

[sparxxxx]

Thanks for that excellent explanation, I wonder what will be possible in 10 or 20 years time.

 

[DetlefSchmitz]

I guess that this has become an issue because of the convention used to describe the 'capacity' of a power bank. No-one has mentioned that mAh is not a measure of energy, which it needs to be, if it's going to be useful as a means of comparison. If you don't know the voltage then it becomes a number you can play as you wish. The more respectable ones refer to the mAh capacity of the battery inside, which goes part way but still ignores the voltage. Bear in mind that the voltage coming from a power bank can be anything from 3.3V up to 21V (at the moment) so it makes a significant difference to the energy available.
But if internally there are, say, 2 cells with X mAh: if they are in series they would have a 'capacity' of 2X, if in parallel the 'capacity' would be X. I would expect there to be many more cells involved.
Airlines impose a carry on limit of 100Wh, which is clearly a meaningful way to express it.
But answer to real question is that vendors on eBay lie, and it is made easier by the use of a meaningless parameter.

 

[JohnW2]

Thanks for that excellent explanation, I wonder what will be possible in 10 or 20 years time.

If the UK governments had its way, I suppose there would be no vehicles with internal combustion engines that needed a batter-operated starter motor in "10 or 20 years time"!

It obviously is all a question of charging time. A tiny tiny charger could charge a batter enough to work a car's starter motor iof one was prepared to wait a few days for the charging to happen.

Kind Regards, John

 

[JohnW2]

There is a possible explanation ... Both a comma and a period are generally accepted decimal separators for international use. ... 2) Period (spoken as point), the thousands separator in many non-English speaking countries. 3) Comma, the thousands separator used in most English-speaking countries. 50,000 mAh could be in reality be 50 mAh with 3 decimal places

I consdiered lots of such possibilities, but to little avail ...

(a)... although I included (comma) thousands separators in what I typed in my post, none of the eBay listings (including all those I posted) had any separators (comma or period/point) at all.

(b)... whilst 50,000 mAh, let alone 500,000 mAh are not credible (given the physical size and prices), nor would be 50 mAh or 100 mAh (which would be far too little, at 5V, to be of any use).

(c)... even if they had intended 50 mAh, it would be very unusual/unlikely that they would express that to three decimal places (i.e. "50.000", usiing our normal conventions).

As I said suggested before, I can but presume that one person in China original 'got it wrong' and that most/all of his/her fellow countrmen subsequently copied that mistake.

Kind Regards, John

 

[flameport]

The claims on battery capacity are not mistakes - they are just outright lies.

One vendor has power banks of a certain capacity, so the next one will claim theirs has more so it appears better value. Repeat forever.

Same applies with other devices - a random example:

 

[JohnW2]

I guess that this has become an issue because of the convention used to describe the 'capacity' of a power bank. No-one has mentioned that mAh is not a measure of energy, which it needs to be, if it's going to be useful as a means of comparison. If you don't know the voltage then it becomes a number you can play as you wish. The more respectable ones refer to the mAh capacity of the battery inside, which goes part way but still ignores the voltage. Bear in mind that the voltage coming from a power bank can be anything from 3.3V up to 21V (at the moment) so it makes a significant difference to the energy available.

All theoretically true but I would say that is is only just about coming to "become an issue", because of what you write in your last sentence.

Traditionally always, and still in the vast majority of cases, "USB power banks" only had 5V outputs - so it has been immaterial as to whether capacity is quote in mAh or mWh (or Ah or Wh). It's the same with 'car batteries'. Since the vast majority of cars have 12V batters, their capacity could be specified either way, but the convention has arisen that they are always specified in Ah, not Wh. The same is true of virtually all other types of rechargeable battery (from button cells and AAA upwards) - I don't recall capacity ever having been expressed as mWh or Wh.

Whether it is (5V) USB 'power banks' (12V) car batteries or any other type of rechargeable batteries (any other voltage), since the conventional way of expressing capacity is very well-established, to change to doing things differently ('properly'?) would presumably just cause considerable confusion?

Airlines impose a carry on limit of 100Wh, which is clearly a meaningful way to express it.

It is certainly the meaningful way to express it in view of the nature of their concerns but, as above, it is of no real consequence to someone buying a device for use with nominal 5V or 12V output. In the specific instance under discussion, I suppose that it may become a much bigger issue (hence needing to be addressed) if/when there is an appreciable amount of usage of voltages other than 5V from, say, USB power banks.

Kind Regards, John