Recently, we've been receiving quite a few complaints from unhappy customers about the unreliability of their brand name lithium-ion battery packs. Truth is, all brand name manufacturers are about equal when it comes to the reliability of their lithium cells as there's only a handful of big name manufacturers that supply the 18650s that powers most modern cordless lithium-ion tools - where they differ is in the electronics to guard against over-discharge or over-charged situations or how each manufacturer implement ways to keep the lithium cells cool.

While we understand that few professional have the luxury of paying attention to the state of charge (SoC) of their cordless tool's battery during use, many however don't know proper battery care - after all, it's not even stated in the user manual. With care, you can typically get significantly more mileage out of your battery packs.

As we've highlighted in our previous post, lithium-ion batteries do not like to be stored fully-charged (100%) nor left fully discharged below 40%, but that's just one of the many reason that affects the useful life of your lithium-ion pack.

Only 300 to 500 recharge/discharge cycles?

According to batteryuniversity.com, a site sponsored by Vancouver-based Cadex Electronics Inc to help consumers gain a better understanding of rechargeable batteries, a lithium-ion battery typically has an estimated 300 to 500 charge/discharge cycles - with one recharge/discharge cycle defined as completely draining a 100%-charged battery to 0% and recharging it back to 100%. A half recharge cycle is draining a 100%-charged battery to 50% and recharging it back to 100%.

So let's assume a contractor fully-drains a fully-charged lithium-ion pack in a day and he or she works 6 days a week. In a month, that's 24 recharge/discharge cycles and in a year, that battery pack would've gone through 288 total cycles.

Based on Batteryuniversity.com's estimated 300 to 500 recharge/discharge cycles, that's only 12 to 212 cycles left. This however does not take into account other variables such as temperature extremes, high charging current (which is less of a problem thanks to smart chargers), any lithium cell manufacturing defect, etc.

Don't take off all your clothes.. well, not just yet!

To make things worst, lithium-ion cells are equally affected by temperature - too cold, and they refuse to work and they start to age faster when temperatures are higher (typically above 50°C). In sunny Malaysia, we typically see temperatures hovering around the mid-30°C to the lower 40°C.

In a typical job-site scenario, a lithium battery has to put up with not only high drain but also high discharge/charge cycles as well as the high ambient temperature (batteries typically run hotter during hard use or while charging).

Best practices?

Ideally, you would only charge and discharge your lithium-ion battery pack from 80% to 40% and back again, but it's not always practical and unless you have a multimeter and know the exact voltage values, it's can be quite tricky to determine the state of charge (SoC) of a particularly battery - more so if your charger only indicated charging and fully-charged.

Here's a few tips as well as a summary on lithium-ion battery care;

1.) avoid running your lithium-ion battery totally flat, use two or more batteries, and recharge them before they drop below 40% charge and if possible, remove from the charger before 90% charge.
2.) if you do end up running a battery totally flat, immediately charge it as soon as possible.
3.) if you're not going to be using it for a while, store it at 50% capacity and constantly monitor the charge every month.
4.) allow battery to cool down prior to charging - if you can't spare the time, direct cool air towards the battery pack during charging.
5.) store your batteries in a cool, dry place.