Why these USB lithium-ion battery chargers are must-haves for my tool bag

Rechargeable batteries are just amazing.

Not only do they reduce how much waste goes into landfill (or, if it’s being handled properly, what goes into the recycling plant), but they’re also a lot more convenient. Rather than make a trip to the store to get a pack of batteries, just pop the dead battery on the charger, and in a few hours, it’s ready to go again.

Look after rechargeable lithium-ion batteries well, and they’ll last literally years (assuming you buy decent ones — it really is false economy to cheap out on them. For AA and AAA batteries, I always buy Eneloop batteries).

But everything comes to a sudden halt if the battery dies. And that becomes a bigger problem if you don’t have a charger.

Which is why I like to carry a charger (or two) in my toolkit.

I don’t mean those big bulky chargers. While I have those at home and the office, they’re cumbersome to transport. But I’ve found some alternatives. These are battery chargers that work off USB power and that are small enough to slip into a pocket.

I’ve tested both options below extensively and trust them to be safe in use.

First up is the TrustFire UC10. 

TrustFire UC10 tech specs

• Voltage range: 3.6V to 4.2V
• Output to battery; 4.2V/1A (Max 1.2A)
• Compatibility: 32650/26700/26650/26500/25500/22700/22650/22500/21700/20700/18700/18650/18500/18490/18350/17700/17670/17650/17500/16650/RCR123/16340/17350/16500/14650/14500/14430/14350 and more
• Protections: Reverse link protection, overcharge protection, and short circuit protection
• LED indicator: Yes
• USB output: 5V/1A

Cheap and cheerful, the UC10 is basic but capable and safe.

Hook up the charger to a USB port and then attach the magnetic ends to the appropriate terminal on the battery you want to charge (don’t worry if you get it wrong, nothing is going to blow up or burst into flames) and away you go.

A cool feature of the TrustFire UC10 is that if you have a charged-up lithium-ion battery, you can use it like a power bank to charge up other USB devices, up to 1A output. That’s not all that fast by today’s standards, but better than nothing.

Next up, I have a Flex Charger that’s a bit more expensive but has some different features. These are available with a lot of different branding — mine is from Olight, but there are alternatives.

Flex Charger tech specs

• Compatibility: Will charge most cylindrical Li-ION and NiMH rechargeable batteries. NI-MH NiMH batteries (1.2V): AA, AAA
• Lithium-ion batteries 3.7V: 10440/14500/16340 (RCR123A)/16650/17670/18650/26650 and more
• Input: DC 5V, 800mA 4W
• Max output: 4.2V, 750mA
• LED indicator: Yes
• Protections: Overcharge protection and short circuit protection

One of the great things about this charger is that it doesn’t matter which way you connect it to a battery — polarity doesn’t matter, and the charger will figure it out for you.

I’ve found that this charger is good at charging batteries that have been run down so low that other chargers can’t recharge them, so it can revive batteries that might otherwise be junked.

On the downside, this charger can’t function as a power bank.

My Flex Charger has certainly paid for itself in revived batteries.