We are getting more and more reports that customers are having problems charging their lithium-ion (Li-Ion) batteries, and even some cases where their (expensive!) Li-Ions had to be replaced!

This article is my attempt to explain what's happening, and how to avoid problems.


When you want to charge the battery in your torch, make sure the torch is not "locked out" and that the beam is turned off before connecting the charging lead to a USB port – more on this below.

Don't connect your torch to any kind of "smart" charger, such as the USB port on a computer or a charger for an upmarket phone, tablet etc. 

Instead, connect your torch to a "dumb" port which is designed only to provide power – for example the USB port on a multi-connector like the one below, a power bank, inverter or on a car dashboard.

If this doesn't work reliably, try swapping your USB charging cable for another one. I know it sounds crazy, but these cables can develop problems after a while. You need a standard USB-C charging cable (see below) – you get them from any gadget store.


USB ("universal serial bus") connections will be with us for the foreseeable future, so it's really worth learning how they work. You will encounter three plugs and their matching ports – the USB-A on the left below, USB-C in the middle and Micro-USB on the right.

The asymmetrical Micro-USB is now rare, but still used on some chargers and other devices. It's the smallest, but only plugs into its port one way around. The symmetrical USB-C has replaced Micro-USB, and plugs into its port either way around. USB-A is the big rectangular plug and only goes into its port one way around. 

Note that these are just connectors – what flows through the cable is the same, depending on what it's plugged into at each end. USB cables can serve two functions – to transfer data, and to transfer power – and that's where things get complicated. 

When you connect your iPhone to its charger, the cable between them transfers both data and power. First the phone tells the charger (data) what voltage and current it needs, and then the charger delivers it (power). 


However, when you connect the same charger to a torch, things go pear-shaped because they can't talk to each other. When a smart charger finds it can't communicate with your torch it dials down its output to a trickle, for safety reasons.

Unfortunately you won't know! The charging light on your torch comes on, but it never shows the battery is fully charged. When you decide it must surely be charged by now, and use the torch, you're actually running down your battery even further! 

When the batteries in torches are really low, some flash their beams, others step down or cut out altogether. So naturally you think your torch is faulty – after all, you just charged it, didn't you? 

Well no, you didn't, and worse still, if you put torches away in this state there's a good chance you'll destroy their batteries altogether!


Lithium Ion (Li-Ion) batteries operate in a band between 3 volts and 4.2 volts – anything outside this range will damage them. In particular, any lower than 2.6v and they are toast! Sometimes they will charge afterwards, but they'll run down almost immediately when you use them.

You do get "protected" batteries that have an electronic circuit-breaker that trips out before they run down too far, but they are twice the price and not always available. Shockingly, some claim to be protected when they're not – there's a lot of massaging of the truth when it comes to Li-Ions!

However a good quality "unprotected" battery will last just as long as a good "protected" cell if you charge it in a decent charger, and make sure you never discharge it too far. 

But there's a catch. When you turn most torches off, they actually go to "standby" rather than turning off completely, so they continue to use a tiny trickle of power. This trickle of power is so small that, if your Li-Ion is fully charged, it will take months to reach 2.6v. However, if your battery is already depleted when you put your torch away, it will happen much sooner.


The fix is pretty easy. Either remove your battery from the torch – Li-Ions have a negligible rate of self-discharge so they last for years if there's no drain on them – or use a "mechanical lockout" to stop the gradual drain by your torch.

This "mechanical lockout" varies between different models of torch, and should not be confused with an "electronic lockout" or "automatic lockout", both of which prevent the torch from being turned on accidentally but don't stop the gradual drain.

The most common "mechanical lockout" is to loosen the thread between the battery tube and the head or tail of the torch, but please take a moment (or check with me) to make sure you know how to lock out your torch – it does vary between models.

And please remember you can't charge the battery while your torch is mechanically locked out. It may look like it's charging, but it isn't. Turn the beam on and off before charging to be sure it's not locked out.


If you can't be bothered with any of this, buy good quality "protected" batteries for your torch and don't worry. They come with a warranty and they are very hard to damage, but they do cost twice as much as an "unprotected" battery of similar quality.

Almost all my torches take industry-standard Li-Ions, so you don't have to buy batteries from me, but be aware there are lots of poor quality and counterfeit batteries out there. 

You're probably thinking it was easier in the good old days, when you just bought batteries at your local supermarket – but was it really? Good quality Li-Ions hold more energy for their size, don't leak, don't self-discharge and, with a little care, last for many years and cost less in the long run.

But you do need to know how to look after them (for more on this, see here).

And please don't hesitate to email me (mark@torchguy.com) or WhatsApp me at 084 537 4818 if I can provide any additional information – I much prefer written communications, but if you really need to talk then by all means call.