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.
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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.
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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.
Charging Times
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.
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herp derpson
If needed they could also go to something like a 32600 cell size or even 3 sets of 18650s in parallel for superfatpacks.
Andrew
Sony VTC4’s are rated for 30AMP continuous but have a burst limit of over 100Amps for a few seconds. VTC5’s would be even better. These batteries go for around $6 a piece though, so I doubt it would be cost effective. I’ve actually replaced my old crappy 10A Samsung cells out of my Dewalt 12V Max driver and the performance is incredible. It went from 1.3AH to over 4.0AH without adding a single cell.
Brian
I can go to hobbyking and buy a 5cell 8000mAH battery right now, itll cost me 90 bucks plus shipping.
The form factor isnt too appealing being about 2″x2″x9″ and weighing almost 2lbs. but I could wire it up to power a drill with no modification to the tool or battery other than making a connection and some ducttape to hold it onto the tool.
But there is really no cap in aH other than size/weight. And as derpson said, ultimately theres always the option for cells in parallel if you went too far from the beaten path and could not find a manufacturer.
Drew M
That hobbyking LiPoly pack isn’t nearly as forgiving when it comes to misuse and abuse though. From my years of r/c experience, I wouldn’t even consider buying a tool that ran on a LiPoly pack.
Andrew
LithiumPolymer batteries don’t do very well in power tools. lithium Ion batteries will usually last much much longer, and can take a lot more abuse. Plus you don’t have to wire a balance connector on or dramatically changed the design form.
Justin Guerrera
i have a friend that works for black and decker / dewalt. he told me a year and half ago to be ready for 6 and 7 amp hour packs. the hold up is trying to figure out which way to configure the tools and batteries. For better run time or more power or something in between
Garrick
I would usually vote for more power over runtime. It doesn’t take much time to change, or charge a battery.
Weight, and maybe more important, the size of the tool, is what I consider most, especially if it will be carried and/or used for a significant period of time.
I almost always use a smaller battery pack if available, and accept that I need to check the charge remaining before going far from the charger.
Andrew
The technology has been around for a couple years now, it’s just a matter of being cost effective and design. Either you use good quality (expensive) batteries like Samsung 25R5’s or LG HE4/HE2, Sony VTC4&5, etc to get your 5.0-7.0AH or you add more cheap cells in paralell (which is what 99.9% of companies currently do)
Jimmie
I can envision a setup consisting of belt-mounted battery packs.
Advantages:
– you could fit a day’s worth of battery power on a belt
– the individual tools become lighter in your hand since there’s no battery pack
Disadvantages:
– you’re back to using a cord even if it’s tethered to your belt
– ergonomics might become an issue for some tools since there’s no battery pack to act as a counterweight
Nathan
they have that – it’s called the rambo pack and you need a hobby battery charger to use it.
thought about doing that with my old cordless milwaukee 14.4 volt
Jerry
Theoretically, the limit is probably more about how big/heavy of a battery pack one is willing to tolerate. Realistically, there are other barriers to think about, primarily heat. I am reminded of back when I was in school, someone shoehorned a 400 small block, where a 6 banger used to sit. He had all the power he ever needed, for a few minutes, until it started to overheat due to the small radiator. Ever larger batteries with ever more capacity will require ever bigger heat sinks, which will keep adding size and weight, for recharging as well as use.
I have to think at what point is it better to swap out smaller, lighter batteries more often, rather than lug around a heavy tool. I personally think a faster charge/discharge rate might be better than maximum capacity. I know I get far less fatigued at the end of the day using a high performance 12 volt tool, and making a half dozen battery swaps, compared to lugging a heavy 18v tool, and making only 3 battery swaps. from what I have seen, the 12 volt Fuel models from Milwaukee are becoming more popular than the full size 18 volt units except in places where maximum performance is truly needed.
Nathan
Great write up and good question
weight will be an issue but you know as you get so much power in a confined space – fires and catastrophic failures increase in likelihood.
think 787 battery fire. I suspect other than moving up in voltage I doubt it will go much over 6amp as you start to get too much energy in a small spot.
so much energy in a small space if there is a current overload – or a cell runaway (internally shorts, or over currents) – once it gets hot enough to breakdown between cells – look out. and often you can’t put that fire out with water.
but I have to also ask – how big do they really need to be? I mean why have a 9Ah pack if you use it 2 days without charging it – but it takes 4 hours to charge, and they cost $600. if you can do the project day with a 4Ah pack?
I’ve not run out of juice yet with a 4Ah pack and that was building a deck – but I’m sure someone that’s a contractor might have by now.
BikerDad
Methinks Jerry is on to something. Higher capacity battery packs are fine and dandy as long as the other characteristics don’t change. Once you start adding weight/charge time, they become less attractive for EXISTING tools. What they will do is enable more tools to go cordless. Imagine a practical 1″ SDS Rotary Hammer, brushless and with an 18v 6ah battery.
On the other hand, for a guy doing cabinet installs or such, a 12v brushless or 18v brushless compact is going to be plenty powerful. The times that he would actually need a 18v full size pack for installs is going to be few and far between.
The increasing capacity gives the manufacturers two opportunities. First, to bring the fringe cordless tools and those that haven’t even been considered for cordless into the fold, presenting decent run times and power levels.
Drew M
Recently, I read a mind-numbing thread on a ‘pro’ forum where no one there seemed to understand the relationship between charging current, pack capacity and charging times. They kept going on and on about ‘1hr chargers’ and ’30 minute’ chargers and how their ’30minute’ charger actually took over an hour to charge a 4 or 5AH pack.
In the end, what the industry needs are smart batteries and smart chargers. They recognize the pack and charge it accordingly. When a 6AH pack is plugged in, it charges at ~9A to achieve a ~45min charge cycle. When a 2.5AH pack is plugged in, it charges at ~4A to still achieve the same ~45min cycle.
I have some serious high power ‘hobby’ chargers that make most power tool battery chargers look like they’re driven by water wheels. Sure, each one cost ~$250 but they can each push 1300w.
Andrew
While that would be conveinent and fast, it isn’t advisable to charge batteries at 9A, they could vent or even catch fire. Reccomended Max charging rates for Li-Ion is 2A. Anything over that like Makitas Rapid charger that I happen to own actually does damage to the cells over time as its well above 2A. I only use the black charger for this reason.
BikerDad
Second, introduce premium 12v and compact 18v tools. Make the compact tool the flagship, rather than the full size tool.
Paul
I don’t know what the theoretical maximum of the current technology is but in the distant foreseeable future, I can envision that 12V max will become the new 18/20V max for many of the tools that we currently associate with cordless technology. That’s just the evolution of things becoming smaller and more powerful. Eventually, and it may already be happening, the power output of a particular tool is good enough to get the job done well and the battery run time is more than sufficient for the job. The next logical step is to miniaturize the platform while delivering the same performance. Think back a few years and you may notice how most of what was once only available on the 36V platforms are now available on 18V. (Example: A friend of mine has an old DeWalt 36V hammer drill that is big and built like a tank. My 20V XR compact hammer drill can now pack more of a punch than it in a 1/3 less mass) Now, only the most supper power-hungry tools are 36V. As the 12 volt platforms overtake the the 18/20’s, the 18/20’s will replace what is left of the 36 volt platform (with the exception of the super power hungry like small engine replacement categories, out door equipment, lawn mowers and weed-whackers and phasers [ok, that one is just me dreaming] which are an entirely new segment. Cordless full-sized routers on anyone’s wish list?
Please note that there is one other factor diving this miniaturization force – cost! As the bill of materials decreases, so does the gross cost for raw materials. Manufacturers can demand a higher percent profit/tool while giving a better product at the same or lower cost to consumers. Marketing departments around the world are standing by salivating. Just look to the electronics industry. This is concept is not a mater of if; it’s a mater of when.
And now for something completely different. Everyone (myself included) is excited on what just might go cordless next but many of us are still tied to a cord – er hose – that cannot be cut. Clean up is the biggest pain in the [body part] of any project. Or that just me? There are lots of dust collections systems integrated with power tools – more in Europe but Festool comes to mind as a company whose brand trades on their superior dust collection systems integration. Having dust bags or a hose connected to shopvac for cordless tools makes no sense to me especially if you are on a ladder or ripping plywood where the weight of the hose (and currently the power cord) pull you down especially if they get caught somewhere. Running a shop-vac behind later is no fun to maneuver either with never long enough hoses or power cables. Why doesn’t a tool manufacturer develop a small vacuum that could be warn as a backpack or tool belt? It wouldn’t have to be big like the yard blowers but it could be small like a Dustbuster or something along those lines. Make an auto retractable hose or switch on the end to turn it on and off and boom – no shop vac cord or hose to get tangled! Yes, I know there would be tradeoffs between size and weight and how often (or how mechanically so you don’t have to take off the pack) you have to empty it, but the trade off may be worth it.
Bringing this full circle back to the battery conversation, vacuum technology is getting smaller and more powerful. Just looks at some of the Dyson vacuums with HEPA filters. This type of vacuum could be one of the new tools that would be able to take advantage of this latest generation of 5 and 6 Ah batteries. I have a feeling that no on really knows what are the limits or what is really practical with the future of cordless technology. Until then, we can dream and we will have to wait and see what the future holds. But I think we have some really cool stuff ahead of us.
rx9
3 – 4 ah in a 20C discharge capable battery is probably where conventional lithium ion will top out in the next few years.
On the horizon are new technologies including: silicon nanowire lithium ion, lithium sulfur, aluminium-air batteries and supercapacitors.
Nathan
some hobby batteries are 6+ Ah at 30, 40 and even 50C discharge rates. and I’m not sure what most power tool batteries are – but I could see where the 5Ah pack and say the potential 36 Volt packs for the bigger tools – start to move toward the higher end of the C scale. IE something that can take a 40-50 C discharge rate
(for those curious – the C rating is the fraction of the depletion time of the battery – IE if it’s 10 C and the battery capacity is 2Ah – then 10 C indicates it depletes in 1/10 of an hour – or it’s through put was 20A. ) The individual cells are tested on capacity, then voltage stability, and max throughput at safe temp – this created the C rating for each cell. there is much more beyond that.
anywho – I highly doubt cordless power tools pull as much as 20 Amps though, maybe inrush but not constant. but when you get toward a 6Ah battery, if 20 amps is still plenty then you can go down a bit on the required C rating for the constituent cells in the pack – like say a 5 C rating yields 30Amps of potential throughput current.
heat in the pack will always be a major concern – in use and during charging.
Stuart
Hobby batteries are often built with Lithiun Polymer cells, which aren’t as suitable for power tool use as Li-ion cells, at least from what I’ve read.
Nathan
well there are so many different battery make-ups now but the cells are currently all rated the same that I know of.
be it LI-PO, LI-ion (generic term) Li-FE-MN etc. and so one.
cell volt, cell cap, C rating tend to be common.
But I’m not a battery engineer, so grain of salt and a shot.
George Edge
In terms of amp draw, I have measured some of my cordless tools while using an amp meter and my Ridgid18V 7 1/4″ brushless circular saw will draw a consistent 23A cutting through a 4X4 lengthwise, moving up to about 28A where it tends to shut itself off around this point due to my not maintaining a straight enough line. I was purposely stalling out the blade to measure maximum amp draw. The battery pack apparently limits the amp draw allowed. My worm drive draws about 86A if its 120V is converted to 18V to produce around the same wattage of about 1560 watts. At some point the idea of using batteries becomes self-defeating. Being able to grab the saw and use it for tasks that will only take a few minutes, and for doing trim work on door frames and such, can be the best use of high drain cordless tools like a circular saw. With the cordless hammer drill, then it can be a genuine substitute for a corded drill for most things, but not so much for drilling a dozen or so 3/4″ holes in concrete. For the occasional user of the tool at home I can see the value of a cordless drill, but the cordless circular saw, maybe not. A corded tool can be cheaper, last longer, do whatever job is needed, and never need a stinking battery.
Andrew
Very excited for super capacitors 🙂 and nano technology implemented into Li-Ion and Li-Po batteries. Should be interesting
DownUnder
How can Bosch claim this when AEG already have had a 6ah battery out for their 18v pro tools.
http://www.bunnings.com.au/aeg-18v-6-0ah-lithium-battery_p6230220
Same manufacturing company as Ryobi and Milwaukee tools, so will expect them to be out on those soon.
rx9
One thing I really hope to see is a universal 12v, 20v, and 40v battery pack standard, so I don’t have to commit to one manufacturer’s system.
Andy
Thank you for the quick response to my question. When asking about amp limits I did forget to mention, “theoretical limit, assuming similar weight and size”. Obviously manufacturers could make a pack 8 inches tall if they wanted to. Many great comments to a well written post, this is why Toolguyd is my first stop in the morning before I check the news.
Stuart
You’re welcome, and thanks for the kind words!
For the past few battery pack generations, brand have maintained the size and approximate weight.
You shouldn’t see a balance or ergonomics difference if you have a 3.0Ah battery pack or 6.0Ah pack paired with a tool. The same goes for 1.5Ah, 2.0Ah, and 2.5Ah compact battery packs.
Brands have stuck with the 18650 form factor from the start of their slide-pack Li-ion offerings. The same with 10.8V/12V Max packs, which have 3 cells for the compact batteries and 6 for the high capacity ones.
Right now, batteries keep jumping up in capacity for competitive reasons. I don’t know if they will all go to 6.0Ah, but they probably will. I think that 4.0Ah will be the “standard” high capacity size, as it offers a good balance between size, performance, and cost.
Niklas Karlsson
Hi if I connect this to a device that need X Ampere
How much can X be?
2,5A ? Or 5? Or 20?
Stuart
I’m sorry, but I don’t understand your question.
Gil Vizcarra
Sorry but you guys are all dreaming. There’s one thing that you can count on in life, things always change. That rule has an an ancillary too, the change usually comes from an unexpected place. In this case it’s from the same place twice. Tesla Electric Car Co. last time Texaco (yes the gasco) bought the rights to the nicad battery technology they had planned on so they fist turned to laptop soft cells and in r&d changed to the 18700 the best hard cells they could buy in quantity at the time. And now they have partnered with Samsung one of the worlds best and largest producers of lithium batteries. They have built the largest battery factory in the western world. And it has started production. At first they will use every one that comes thru the doors. But together Tesla & Samsung are a pair of giants and all battery manufacturers will follow suit. They are are already becoming available and so are counterfeits. So buyers beware. I know they ere rated at 4.2v sorry can’t trust my memory on the amps. But I suspect some of the 6amp battery packs are just that not fake but legitimate new format larger cells.
Stuart
This post came out 2-1/2 years ago, before Milwaukee’s 9.0Ah battery, Dewalt’s FlexVolt batteries, other brands’ new 21700 and 20700 6.0Ah and up battery packs.
3.0Ah per cell seems to be the practical or commercial limit for 18650 cells. To go above 6.0Ah battery packs, there are currently 2 options – bump up battery pack sizes to 15-cell configurations, or bump up the cell size from 18650 to one of the larger sizes. Some battery packs do both.