Back in October, I attended Pacificon, the local ham radio convention. While I was there I picked up a couple of wacky things that were super cheap on the vendor’s tables, and among them was a super inexpensive battery charger along with an 18650 3.7V Li-Ion battery.

If you’re like me, you are probably used to the common AA and AAA type batteries for most of your portable electronic needs. If you seek rechargeable batteries, these are often the NiMh or nickel metal hydride type. Typical ratings for such batteries is 1.2V and 2400 mAh, or about 2.88 watt hours of power per AA cell.

Recently though, lithium ion batteries in the 18650 format (18mm diameter, 65mm long) have become available and popular. They are a bit better than a AA (which are 14mm in diameter and 50mm long) but are pretty lightweight, and common types have a voltage of about 3.7V and capacity of maybe 2600 mAh for a total power of about 9.6 watt hours, or a little more than three times the power of a good high capacity AA.

Anyway, decided they might be interesting to play with, and the price was (suspiciously) cheap at the show, so I thought I’d give them a go. The combination was an “Ultrafire BRC18650”, along with a super cheap looking charger with the product identifier of “HZM888MA”. It’s hard to overstate how uninspiring the charger actually is. I admit that I buy a fair amount of dodgy Chinese electronics, but this seemed dodgier than most, and because of the energy density and the rumors of batteries bursting into flames has me paying rather more attention to it

My recollection is that when I bought the charger I did test it by charging up the battery and that it did its usual “red while charging, turn green when done” with its indicator LED. But when I found the charger and battery in my storage case, I decided to try it again. Now, my dodgy charger just blinks the red LED, which in the international language of devices should indicate that something bad has happened. Nothing appears to have caught fire though, the battery doesn’t get hot, so I am not sure what is going on. I decided to get a higher quality Tenergy model to test it, and the same thing happens: blinking red LED.

I have decided that ordering a higher quality charger is probably a good idea, especially one that can handle different battery types, so when that arrives I’ll give them both a try.

In the meantime I looked up the UltraFire BRC 18650, and found this article on YouTube, showing that their rated capacities are nowhere near realistic, and they often have less than one third of the total listed on the packaging.

I guess you get what you pay for.

Anyway, these might find their way into an IOT device that I’m working on, and it will be interesting to see how they perform. I may also tinker together a constant current load to test their capacity myself.

In the mean time, buyer beware.