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 1.2v NiMh rechargeable 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, go to my FAQ, here, and scroll down to the relevant section.
I sell top-quality Li-Ions made by Samsung, Panasonic, Sanyo and LG, made in Japan or Korea, most of which are assembled in China by KeepPower, which is one of the biggest and most reputable OEM companies in the battery industry. I don't sell "cheap" batteries, which 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.
My standard battery is the 2,600mAh cell which gives the most runtime for your rands. I also keep 3,200mAh and 3,400mAh high-capacity cells which offer more run-time but cost quite a bit more. My own preference is to have two sets of 2,600mAh batteries, which will not only give you longer run-time overall but allow you to charge one set while using the other.
Note that my standard batteries are all "protected", which means they turn themselves off if they are over-charged, over-discharged, overloaded or short-circuited. When you put them in the charger they are re-set and carry on as if nothing happened. This means you can't run the battery "flat" - it will turn itself off long before it reaches that point.
I also sell high-drain batteries (only needed by a few ultra-high performance torches), some of which are "unprotected". In theory you can run these flat, but if you discharge them below about 2.5v they will be irreparably damaged. In practice this is unlikely to happen because all my torches will warn you (by flashing their beams) when the battery is getting low - but if you ignore the flashing or leave the torch on standby mode you may drain the batteries past the point of no return over a period of days (so, to be on the safe side, take unprotected batteries out of your torch after the beam has flashed).
However, if your torch is flashing its beam and you turn it off and leave it for a while, it may work again for a bit without flashing. This is because lithium ion batteries "recover" some of their voltage after the load is removed. This recovery is more noticeable if you've been using your torch on maximum power - if you were using it on moonlight mode there won't be much recovery.
If the protection circuit (PC) on a protected battery has tripped, it won't work at all until it's been put back in the charger. It takes just a few seconds in a charger to re-set the PC but it will take a few hours to charge the battery if it's fully discharged. Li-Ions don't like to be rapid-charged, so it can take up to 12 hours to re-charge them. Topping up batteries - which I'll discuss shortly - is much quicker.
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 first get your battery you need to charge it before use.
Note that I don't pre-charge batteries, 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 acutely aware that lithium ion batteries are expensive - together with a charger, they can cost more than the torch itself. The upside is that nearly all my torches use industry-standard batteries which are easy to replace (unlike the bespoke battery packs in some brands) and most use the same chargers, so you don't need a new charger with each torch. If you use a torch regularly, you will definitely save money using Li-Ions.
That said, at R200 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 half a day to get it ready for use - which isn't very useful 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. If anything, they are likely to come down in price during that time.
Having two sets of batteries is great - it means that if you forget to charge your cells after an outing, you can simply swap the depleted batteries for the freshly charged set. Better still, you can charge your depleted batteries while you're using the fully charged set. Best of all, if you need maximum run-time (like a neighbourhood watch patrol, a prolonged power outage or an overnight race) you can carry 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 lithium ion batteries don't like to be left for long periods (e.g. 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, so it is important that you:
You can use lithium primary (i.e. disposable) batteries in place of Li-Ion secondary (rechargeable) batteries in some torches (check the specifications). One CR123A primary can usually replace a 16340 secondary (as long as the torch uses only one), and two CR123A may be compatible with torches that normally use a single 18650 Li-Ion (not always – be careful!)
CR123A batteries are available from discount pharmacies (Clicks and Dischem), have an exceptionally long shelf-life (typically ten years) and have roughly twice the energy of a rechargeable battery of similar size, so keeping a few handy for emergencies is a great idea. Unfortunately they are too expensive to be practical for everyday use.
I provide a one-year warranty on my 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. Note that this doesn't apply to unprotected batteries, since they can't defend themselves against mistreatment, and the effects are not detectable.