Choosing an external battery (powerbank) for a smartphone, tablet, laptop | We advise, we share experience



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Powerbank - Selecting an external battery for your smartphone, tablet, laptop

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Mini FaQ
1. Manufacturers indicate the capacity of banks in accordance with the capacity of batteries installed in the device. This technique is generally accepted.
2. When assessing the capacity of a bank, losses must be taken into account. For example, for the most common use case of a bank for charging a device’s battery, the following losses occur:
- loss when converting from 3.7 V battery to 5 V output voltage in the bank;
- loss when converting from 5 V input voltage to 4.2 V charging voltage in the charged device;
- losses in the rechargeable battery.
Assuming the efficiency of each portion of 0.9 obtain the overall efficiency of 0.9 * 0.9 * 0.9 = 0.73. This figure is approximate and depends on many factors, in particular, the charging regime. Manufacturer of this figure can not indicate fundamentally - because 2 of the 3 phases are not poverbanke and load. And nowhere stated that the measure is necessary in view of the losses in the user - for example, if poverbanku connected to LED lamp - leaving only the conversion loss is 5 V, and accordingly, the overall efficiency is 0.9, and even more.
3. Sometimes another value of capacity is written on the banks - capacity in terms of an output voltage of 5 V. Theoretically, this is more correct - after all, the device produces most often 5 V, but in practice it only causes confusion.
Firstly, because this figure is obtained by formal multiplication of the battery capacity by the voltage difference 3.7 / 5 = 0.74 without taking into account the efficiency, which can vary.
Secondly, the fact that the coefficient obtained is close to that obtained in Section 2 is nothing more than a coincidence, and the output voltage may not be 5 V ...
It is easier to explain with an example: Pipo and Cube tablets have batteries of the same capacity, but Cube charges from 5 V, and Pipo charges from 9 V (my bank gives 5, 9 and 12 volts).
So, when charging Pipo, the capacity of a bank must be multiplied by 3.7 / 9 = 0.41 and, accordingly, will the bank be enough for a smaller number of charges? No, 5 and 9 volts are just intermediate values, but energy is still described in item 2 - both at Cube and Pipo, the bank will provide the same number of charges (at Pipo, even slightly more - 9 V loss less)
4. All these figures are approximate - the parameters and conversion efficiency depend on the mode, and even when charging devices, the output capacity will be different depending on whether the tablet is charged with a 2A charge current or a phone with a 0.5A charge current. other devices - not the only use !!!
5. Unforgettable about the temperature mode of operation - from 0 to +40 РЎ0.
At low temperatures, even lower than 0 РЎ0, the battery self-discharge increases by several times, i.e. If you carry it in the cold in a bag, then at the most crucial moment you can get a discharged battery. Also, when cooled, the battery capacity and its life are very significantly reduced. If it is possible, do not freeze the battery !!!

Real capacity of banks.




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Topics Curatorslava_ussr

Post has been editedslava_ussr - 08.11.19, 09:05
Reason for editing: reversed the words in the topic title



Rep: (108)
Since I collect such charges, my personal opinion is that the charger is certainly not worth the 2500
No charge gives out the claimed capacity, because manufacturers do not indicate the inevitable loss of efficiency of the electrical circuit and batteries

Lithium battery efficiency = 3.7 / 4.2 = 0.88, where
3.7 - average voltage at the battery output
4.2 - input battery charge voltage

1 stage conversion
energy of the internal battery of the device with a voltage of 3.7 volts (average)
converted to USB port voltage - 5 volts
The efficiency of the power electronics is at best 0.9

2 stage conversion
Voltage supplied to the phone 5 Volts
converted to 4.2 volts needed to charge the phone battery
The efficiency of power electronics (already placed in the phone) is also, at best, 0.9

total total efficiency of external battery
0.88 x 0.9 x 0.9 = 0.71 or 71%

so boldly multiply the declared capacity of any device by 0.7



Rep: (241)
I ordered a coolook pb-2000, and there one usb is sharpened for an android, another for an apple. I saw the info that you can get the apple slot to work with android devices, but I did not find how to do it. Maybe someone knows?
Sorry, if oftop, a more suitable topic is not dug, but create a new one

Post has been editedlehachuev - 09.06.13, 18:50



Rep: (108)
Apple port has a limiter 1 Ampere - port A, as I recall
port B - no current limit, up to 2.4 amperes
Android devices work fine with both ports, I do not understand what your problem is



Rep: (241)
I haven’t received any charge yet, I read reviews from users ... Sorry for the noobiness and thanks for the reply)



Rep: (108)
But for how much I ordered, if not a secret? And what kind of batteries did you buy for it?



Rep: (241)
Charging here
http://www.aliexpress.com/item/High-Qualit.../694501083.html
Batteries here

Ordered and that, and more after reading these reviews here
http://lygte-info.dk/review/Review%20USB%2...-2000%20UK.html
http://lygte-info.dk/review/batteries2012/...me%29%20UK.html
I hope the links are not criminal
Shl. BIKOVskie links forum does not like. Batteries 2 X 3.7V TrustFire TF 18650 3000mAh Rechargeable Camera Flashlight Torch Battery, 8.79 per pair.

Post has been editedlehachuev - 09.06.13, 20:14



Rep: (4)
Going to buy an external battery.
Tell me, can an external battery charge ipad 2 with a current of 2 amps?
Can he charge him 1-2 times? How much capacity should there be for this?
Can I buy a capacious battery without additional charging (charge by charging for Ipad, is there a regular USB input)?



Rep: (3)
Good afternoon, and what opinions about gigabytes of the company? At 5000 capacity is 1500 rubles worth taking?



Rep: (108)
cerijvolk,
Firm Gigabyte batteries do not, neither external nor internal. Many models frankly resemble Chinese DIY kits on which they can write the name of any company.
Probably the quality of the finish of the case will be at the height, it can also put quite good batteries (again, strangers).
But I don’t think it’s worth overpaying for the brand, so for me let it be done with scratched plywood with traces of fat stains from pies and herring, nobody sees it anyway most of the time, but it must fulfill its main function.

P.S. To find out the effective capacity of any bank turn, the declared capacity should be multiplied by 0.7 - this is the total efficiency.
Charging cost of 5200 mAh = 400 rubles, even with a very small-scale assembly (more-cheaper)
I for 1500r. I sell charging on 10400 mAh


LAG_LAGbI4,
Ipad is already charged with current 2A from the native charging, almost any “thick” external battery can deliver such a current.
Regarding the number of times of total charges:
ipad 2 capacity = 25 Wh / 6700 mAh
to charge it once you need an external battery with a capacity of 6700 / 0.7 = 9500 mAh ~ 10000 mAh

Most external batteries have an input microUSB port for charging themselves, and there are no separate power supplies included with them; Initially, the creators conceived so that the user used the same power supply that charges his phone



Rep: (7)
I was looking for a new battery in smart, I found an officeStrongpowerThe reviews are very decent, both on batteries to phones, and to external batteries. They write no worse than kraftman for mobile phones, and as external akb, it’s like fire in general.



Rep: (99)
What kind of normal external battery can I buy in Moscow? Approximately so that the net 6500mAh would give out (3 Nexus4 charges), right now there is a Yoobao YB-642 (11200mAh). So I only charge the phone 2.5 times



Rep: (66)
Good evening everyone, tell me, is it possible to take batteries for Coolook PB-2000 without overdischarge protection or is it better with protection?
P.S. Hey :) No one know? It seems that many people have this box ... Yesterday I wanted to order, but I just can not figure out how to be with batteries.
UPD . In general, I ordered it with protection, let's see what happens.

Post has been editedRadagest - 10.07.13, 15:27



Rep: (4)
And there are quality boxes, such as Coolook PB-2000, only for 2 batteries?



Rep: (0)
Greetings. There is no time to wait for a coolbook with rechargeable batteriesGP GL301 .



Rep: (41)
The people, and what external batteries you will advise from compact, which you can safely carry in your pocket. Not less than 3mach. Something like ritmix rpb4400

Post has been editedDenton13 - 16.07.13, 00:59



Rep: (241)
Radagest @ 07/08/2013, 21:18*
Good evening everyone, tell me, is it possible to take batteries for Coolook PB-2000 without overdischarge protection or is it better with protection?

Above, I gave a link to the review of this device, people wrote that you can perfectly do without batteries protection (if I correctly understood the English. Text). But I, too, took with protection - just for everyone ...)))



Rep: (66)
Greetings. There is no time to wait for a coolbook with rechargeable batteries, so I’ll suggest the GP GL301 from China.

I think there are honest no more than 7 moves. And so, like GP ... I think the rules will be.



Rep: (0)
I think there are honest no more than 7 moves. And so, like GP ... I think the rules will be.

I bought it, it was discharged by 25% (1 LED went out), Huawei accend p1 xl was charging. I will continue to torment.

Post has been editedanotherusername - 18.07.13, 18:33



Rep: (6)
Are there any external batteries on Ali, which will work normally. I do not speak about the full compliance of the written capacity to the real, but at least about the sane work and several battery charges 2600Ma. For example, here is an optionhttp://www.aliexpress.com/item/2-Usb-Port-.../993737489.html
What advise you to order it with Ali?



Rep: (41)
People, did anyone buy the Satechi Portable Energy Station? What can you say about him? It seems to be powerful (10000 mAh), cheap ($ 50), light (210 g) and therefore there must be pitfalls. And yet - where it can be ordered not from abroad?


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