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Sunday, August 24, 2014

Testing a solar power-bank with raspberry pi -[ fake ebay specifications]

In this post i will explain my experiments with a solar power-bank from ebay. There are several of them on ebay with specification ranging from 20,000 mAh (20Ah) to 30Ah. It is really difficult to predict in advance what we get in them!

I got one which i intended to use as a backup for some portable raspberry pi projects. The power-bank is shown in the figure below.

Power-bank advertised as 30,000mAh  

So i charged it in to its full capacity (overnight!) and then connected to my raspbmc running on the pi. As i expected (size and weight of the bank vs the 30Ah ), the pi was running fine for barely 2.25 hours.

Before the last breath, uptime showed

17:24:06 up  2:23,  1 user,  load average: 0.57, 0.51, 0.45

So, if you are planning to run your pi's on power-banks,  beware of these super banks which comes at cheaper rates. But it was still a good deal as i got a small solar panel and couple of electronics at a that price plus a lot of learning.

So i started ripping the case and the findings were surprising! See figure below

Internals of 30,000mAh ebay powerbank with solar

There is a single battery with the markings spoiled by the glue (seems like a 3.7v 2400mah or so) and an extra battery which is connected to nothing! Lipo has just two red wires :) going to the charging circuits. It seems that there is a micro-controller on the charging circuit (cum buck converter). More on that later.

A bit late, i found a wonderful video review on this product by julien which can viewed after a break

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