Saving weight with USB Power Bank serendipity

As stated in my previous post, I’ve been looking for torches. I have my eye on the Zebralight H600Fd Mk IV but I’ve been thinking, hmm, 84.6 grams with a battery, plus a charger–that’s quite heavy.

Then I started thinking, what if I had a USB power bank which allowed me to use my own 18650 lithium batteries? Would it be lighter? Would there be any problems with it? The Zebralight H600Fd Mk IV would therefore be only a 39 gram weight in my backpack while not in use because I could use the 18650 lithium battery for something else.

If you buy something like a 2 cell powerbank, it obviously has way less plastic than a 6 cell powerbank. If you’re -very- lucky, said powerbank will have high quality cells in it, but it’s a bit of a lottery in some cases.

When you google a disassembly of the powerbank, you’ll often notice they’re the same batteries you’d normally buy, only they’re soldered together.

So I thought, what if I buy a 2 cell powerbank case which allows me to use my own batteries and then I’ll buy a bunch of batteries, thereby saving the weight of the plastic. Interestingly, the Tomo M2 External Power Bank Battery Charger Box weighs just 55 grams. Combine that with 4 x 18650 lithium batteries at 48 grams each (and that’s if they’re the heavier 18650 panasonic batteries) and you’re left with 192 + 55 i.e. 247 grams for 13600 mAh compared to the RAVPower 12,000 mAh at 331 grams.

This simply raised more questions…

How would I charge all the batteries without rotating them? What if the powerbank case broke? Why does it have micro USB? I hate micro USB. Will the charge input and output be enough? To answer the last question, there seems to be numerous reports that it will reboot when supplying 2 amps. This isn’t really acceptable. Whereas a lot of the RAVPower and Anker devices are known to accept really high loads.

At the moment, I’m still thinking about how I’ll solve this problem. I might buy a 4 cell lithium 18650 holder that would barely weigh anything. Modify a pre-made USB power bank, strip it of all its casing and then put it inside a small and extremely thin plastic container. Alternatively, I could buy a boost module and a cell balance module and make the whole thing myself but I’m not sure if I will run into the aforementioned problem regarding amperage.

My last question, and perhaps someone can help me here, if you remove one cell of a typical Anker or RAVpower USB power bank, will it still function as normal? If they’re wired in a way which this is a problem, that might be an issue. I’d like to add a near depleted battery to the mix and it not be an issue.