Bosch has just announced their new 18V 6.0Ah Li-ion battery pack, which they say is the industry’s first of its kind. They announced the battery earlier in Europe, along with a rapid charger.
Andy saw news about the new 6.0Ah battery, and wrote in asking about how much higher the battery packs can go before reaching some sort of theoretical limit.
I noticed that Bosch came out with a 18v 6.0 amp battery, and I thought to myself, “what is the Theoretical AMP limit for 18v lithium batteries?” Let’s just say for argument’s sake it’s 9.0 amp, when the 8.0 amp batteries come out might as well stock up on them because it will be a loooonnngg time before the 9.0 battery comes out. It would also be fun to know because that limit what other types of tools could be available as cordless options in the future.
Andy’s question is a good one, although there’s some confusion between amp and amp-hours. It’s a common confusion, which is why I posted a brief primer on amp-hour ratings.
Right now, the highest performing Li-ion battery cells I can find online are rated at 3.6V 2.5Ah. That’s for the current 18650 form factor that most brands use in their 18V (and 20V Max) Li-ion battery packs. Don’t let the numbers throw you off, 18650 describes the battery size in the same way that AA refers to 1.5V batteries of a certain size.
It’s tough to determine which battery cell Bosch will be using, but new Samsung INR18650-30Q cells seem to fit the bill. They’re rated at 3.0Ah each, and can withstand continuous current loads of 15A. Other brands have used 2.5Ah and lower capacity batteries with discharge rates of 20A to 25A, but 15A would work well in a higher capacity battery pack because you can achieve up to 30A in theory with coupled battery pairs.
What this means is that we probably won’t see compact battery packs built with the same cells as Bosch’s new 6.0Ah extended capacity battery pack. The higher discharge rating of the current selection of 2.5Ah battery cells is better than for the new 3.0Ah cells.
From here, if battery brands can improve the discharge rate, we might see future compact 3.0Ah battery packs that are powerful enough to work with heavier duty tools, such as saws that you normally pair with higher capacity battery packs.
There’s no theoretical ceiling that I can see, on the application side of things, where you top out on the energy density that can be crammed into a power tool battery pack. Battery R&D brands seem to have hit a discharge rate limit, for now, where 3.0Ah cells cannot be discharged at the higher rates as the best 2.5Ah cells they can manufacture.
In the power tool battery pack side of things, I do see at least one practicality limit.
Higher capacity battery packs require longer charging times, if you’re using current-standard chargers. A 6.0Ah will in theory take twice as long to charge as a 3.0Ah battery pack, which means a 2-hour wait. Bosch is coming out with a fast charger in Europe that can drop 6.0Ah charging time to 50 minutes, but Bosch USA hasn’t mentioned anything about releasing the faster charger here.
If battery manufacturers can deliver 3.6V 5.0Ah cells that can offer at least 20A of continuous discharge current, and they can sell them to power tool brands at a decent price, you can bet that we’ll see 5.0Ah compact battery packs and 10Ah high capacity battery packs. There’s no reason I can think of why this wouldn’t work, assuming other specs, such as thermal heating and charging rate, are comparable to those of current battery cells.
Milwaukee has sought to address this, with their 6-port M18 and M18 rapid charging station. If 6.0Ah high capacity batteries become the norm, single bay rapid chargers will be greatly appreciated by users who aren’t looking forward to 2-hour charging times.
What Comes Next?
It’s very difficult to look ahead and guess what the next trend will be. Although there is always room for improvement, things are looking pretty good with the latest Li-ion battery packs, and the current push is for tools to catch up to what the latest batteries can offer.
There’s a limit as to how fast the battery industry can cram greater energy density into 18650-sized battery cells used in power tool battery packs, and so the jump to higher capacity packs will continue to slow down. Brands won’t continue to one-up each other, as higher capacity battery cells just aren’t available.
Bosch is looking towards the future, with their new wireless battery charging system, but it remains to be seen whether this will catch on as a trend.