Nearly all of my torches are designed to work with 3.7v lithium ion (Li-Ion) rechargeable batteries which are found in almost every cellphone, laptop and digital camera today because they are much more powerful and durable than the batteries sold in supermarkets.
Li-Ions can be recharged hundreds of times, hold their charge for months, are resistant to high and low temperatures, weigh less, are more friendly to the environment, and have no "memory effect". To learn more about the difference between lithium ion (Li-Ion) batteries and other chemistries, please go to my FAQ and scroll down to the section on batteries.
I sell top-quality Li-Ions branded with names like Keeppower and Sofirn, who don't make batteries themselves but take pride in selling the best cells at good prices. I don't sell "cheap" batteries because they almost never live up to their specifications and can be downright dangerous. You can compare many of the Li-Ions on the market for yourself here.
These days I keep a variety of different sizes and capacities of Li-Ion, some of which are designed for regular powered torches (up to 1,000 lumens per battery) and others for high-powered lights, which are increasingly common. My own preference is to have two sets of batteries and rotate them, giving longer run-times and allowing you to recharge one set while using the other.
Note that some of my batteries are "protected", which means they turn themselves off if they are over-charged, over-discharged, overloaded or short-circuited. When you put them in a charger they are re-set and carry on as if nothing happened. This means you can't run the battery "flat" – which would trash it – it will turn itself off before it reaches that point.
I also sell "unprotected" Li-Ions which cost much less and actually supply higher currents, so they suit high-powered lights. In theory you CAN run these flat but if you discharge them below about 2.6v they will be irreparably damaged. In practice this is unlikely because all my torches warn you when their batteries are getting low, but if you ignore these warnings, or leave a torch on standby when the battery is depleted, you may drain it past the point of no return.
It's important to understand the quality of unprotected Li-Ions is not necessarily worse than protected cells – with just a little care they will last just as long as those with a protection circuit board and save you a bundle of cash. For the full story, please see here.
Lithium ion batteries have a longer shelf-life if they are stored with a partial "storage charge", which is how they come from the factory, so when you get a new battery you will need to charge it before use.
Note that I don't pre-charge Li-Ions partly because I don't have the time but mostly because, in your shoes, I'd wonder whether a fully charged cell is actually new, and how long it's been stored with a full charge?
I know it can be tantalising to get a new torch and then wait half a day for the batteries to charge, but isn't it nice to know your cells are in the best possible condition when you get them? (If you want me to pre-charge yours, please let me know when you order your torch).
Note, too, that it can take a few charge/discharge cycles before your batteries settle down into a predictable runtime, so don't be too quick to take out your stopwatch.
I'm VERY aware that lithium ion batteries are expensive – they can cost as much as the torch itself! The upside is that all my torches use industry-standard Li-Ions that are easy to replace (unlike the bespoke battery packs in some brands) – if you use a torch regularly, you will definitely save money using Li-Ions.
That said, at R250 or more, it's important to know how to squeeze the most life out of each Li-Ion. You'll find the detailed answer to this question here at the Battery University. However, there's a difference between theory and practice. For example, if you keep a Li-Ion in a fridge with a 40% charge for maximum shelf life it's going to take a day to get it ready for use, which isn't very helpful in an emergency. While storing a battery this way may extend its life a bit, it will last almost as long – and be much more useful – if you follow these tips:
Li-Ions degrade over time, so it makes more sense to buy new Li-Ions after four or five years than to attempt to store them for that long. In real terms they are likely to come down in price during that time.
Having two sets of batteries is great – if you forget to charge your cells after an outing, you can simply swap the depleted batteries for the freshly charged set, and charge the depleted cells while you're using the fully charged set. And if you need maximum run-time (like a neighbourhood watch patrol, a night at the game reserve's waterhole or an overnight bike race) you can carry charged spare batteries with you.
Oddly enough, the biggest problem for old timers (like me) is that we don't use our torches very often, and Li-Ions don't like to be left for long periods (i.e. many weeks) with a full charge.
We still think of torches as expensive to run, not very durable, and only useful for a few things. However youngsters have no such hang-ups – I have young customers who use their torches as bedside lamps and who walk around their home at night with headlights on – even when there's no load-shedding (truly!)
Li-Ions like to roar – so use your torches (and batteries) all the time... and don't worry!
You need to be aware that the energy contained in all lithium ion batteries (even those in your cellphone or laptop) can be destructive – in theory they can burn fiercely, although in more than ten years of selling torches and Li-Ions I've not seen or heard of a single case, but it is still important that you:
I provide a one-year warranty on Keeppower protected batteries. If your battery gives trouble within 12 months of purchase, send it back to me and I will repair or replace it – as long as you haven't abused it. Signs of abuse from rough handling, modification or overheating are pretty clear. This doesn't apply to unprotected batteries (e.g. Sofirn) since they can't defend themselves against mistreatment and abuse is not detectable.