# Boost /step up converter efficient and very small for high current ? (with example)

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

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.

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