Here you have a view of the external battery of Energizer (XP18000A) of 18 000 mAh. Image

Energizer allows DC 19V, 3.5A in output : 19*3.5 = 67W

There are 2 batteries, so 2*3.7 = 7.4V then batteries allow almost 18A ... (9A for each battery)

The boost converter doesn't have heat sink !

How is it possible ?! I found this picture on a russian website so I can to read components.

Moreover, it contains regulator of li polymer/ion charge, 5v - 16v - 19v converter in the small PCB.

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  • \$\begingroup\$ where is that 3.7V coming from? These packs are probably quite higer in voltage. \$\endgroup\$ – Vladimir Cravero Aug 10 '14 at 9:43
  • \$\begingroup\$ On the top right of the first barcode, you can see 3,7V \$\endgroup\$ – Alexis_FR_JP Aug 10 '14 at 16:35

It's not only important the battery size in terms of capacity: the charge/discharge rate is also very important. For instance, you could charge a 20Ah battery with a 1A rate, so a full charge from depleted would take 20 hours. That would let you skip the heat sinks if your charger is efficient enough (i.e. switching vs. linear).

When you put batteries in series you add voltages, but not the capacity. Two 3.7V 9Ah batteries in series will give you 7.4V 9Ah, not 18Ah for sure!

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  • \$\begingroup\$ Oh yes yes, my reference to heat sink was for the use. (discharge) Yes of course, but I spoke about current not the capacity. (67W / 3.7V = 18A) but I've even so made a mistake. (9A for 2 batteries, without heat sink...) Thank you for your answer, I'm not able to put "useful" cause my reputation is < 15pts. \$\endgroup\$ – Alexis_FR_JP Aug 12 '14 at 9:44

It is hard to see in the photo, but there are three balancing wires. That would suggest a 4S configuration instead of 2S, and a battery current of 5 A.

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  • \$\begingroup\$ Thank you, What is 4S and 2S ? \$\endgroup\$ – Alexis_FR_JP Aug 10 '14 at 16:38
  • \$\begingroup\$ 2S = 2 cells in series; 4S = 4 cells in series \$\endgroup\$ – Turbo J Aug 10 '14 at 19:39

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