Ken wrote in asking for some advice on how to choose between Dewalt’s 20V Max and 40V Max cordless outdoor power tools.
This is a rather loaded question, and having not had extensive experience with cordless lawn & garden tools, I’m left relying on generalities. If you’ve tried a bunch of cordless outdoor power tools, which is difficult to do since many such tools only came out in very recent years, please chime in with your experiences!
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Ken wrote:
I was researching some articles you guys have regarding Dewalt and the new 40V Max Litium Ion Batteries and I thought I saw that you mentioned they will be coming out with a 20V Max version of the 6Ah battery that will power the outdoor tools like the trimmer and blower.
My first question is this, before I buy one of these tools how would it benefit me to wait for this 20V battery versus the current 40V they are including with the tool?
Next question that might be a little too techy for me to understand but I will give it a shot is in regards to the output and runtime. So basically what is the difference between a 20V battery and a 40V battery both running at 6Ah? I guess both questions are trying to achieve the same answer so any help would be appreciated so I can make an informed decision.
First, Dewalt hasn’t announced any 20V Max 6.0Ah Li-ion battery pack yet, at least not to my knowledge or active memory.
The highest capacity batteries in 20V Max and 40V Max platforms are 5.0Ah and 6.0Ah, respectively.
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40V Max vs. 20V Max
Generally, the higher the voltage, the greater the power. And the greater the power, the beefier the cordless tool motor. This is with a lot of things being equal, such as considering tools of the same brand. A pro-grade 12V Max tool will often out-brute a consumer or homeowner-grade 18V or 20V Max tool.
Often, there’s a balance of greater power and runtime.
Power, in wattage, is dependent on supply voltage and current. Current draw (amps, A), not charge capacity (amp-hours, Ah), which is the spec you often see tied to cordless power tool battery packs.
Comparing the 20V Max and 40V Max blowers, note that the smaller voltage one can push air with a max speed of 90 mph, while the higher voltage one can achieve speeds of up to 120 mph. Both can push the same volume of air, which means the 40V Max blower is doing more work.
20V Max vs. 40V Max
Generally, with lower voltage tools you’ll see less power, lower costs, lower weight, smaller size, and sometimes less runtime. Often, lower voltage tools will be optimally designed for the matched battery system.
Circular saws are a great example of this. The smaller the supply voltage, the smaller the blade size, although this doesn’t necessarily hold very true anymore, thanks to the power boost made possible by brushless motors.
Which to Buy?
For larger tools, such as lawn mowers, 40V Max and even higher voltage systems are definitely the way to go. Mowers such as the Ego mower we reviewed are well-recommended with few compromises. You need that extra power in order to achieve good performance, and it’s easier to design for a higher operating voltage than to top-out the current draw of lower voltage battery packs, if even that would be enough.
For smaller tools, there’s a compromise to be made either way. Do you want a smaller and lower powered tool, or a bigger and higher powered one? The answer should depend on how you intend to use the tools.
John Blair
I purchased the 20V max one because I have five 3 AH battery packs and three chargers. Here is my overview. The 20V string trimmer works very well for a non professional. I had let my backyard go in anticipation of testing.
The unit has two speed settings low and high. Low feels fine when cutting around edges and weeds but is now powerful enough for tough plants. High feels much more powerful but cuts battery life. Neither are as powerful as the gas trimmers they use outside my work (which swing solid blades for edging) but it is around the same as my electric model. The string length isn’t that long (the bump head is larger than my electric) and the guard leaves something to be desired (wear eye protection).
Battery life on high for me under continual usage was 22 minutes with the include 5 AH battery. On low under the same scenario I got 22 minutes with the 3 AH batteries I already had. So basically assuming normal math, low has 67% longer run time. Normally I wouldn’t be cutting tall grass, weeds and plants with the motor running 95% of the time. Doing the front yard took a single 3 AH battery and was a mix of high and low. Interestingly enough, regardless of selected speed, the unit ran at your desired speed until it stopped, then it just stopped. A couple of times it still showed 1 bar but wouldn’t run anymore.
For me the benefits of more power of 40V units weren’t worth it. I already have plenty of 20V Max batteries and this way I can use the included 5 AH battery in tools I use more often and don’t have another charger to keep track of. As a home owner, it makes trimming much less unpleasant. I don’t regret waiting for the 20V unit.
John Blair
If it was not clear, I am talking about the Dewalt 20V Max string trimmer. PS now = not in the above comment.
Nathan
I see them making more 40V tools and still aimed at more pro grade.
I’ve not used either though – I imagine for the suburbanite home dweller the 20V stuff is plenty good enough but get you a 4 or 5 Ah battery back. if it doesn’t come with one.
otherwise my dollars I’m leaning more toward the 40V stuff if I were to buy any – it’s not going to have to work as hard – and in theory would last longer.
Charles McDaniel
Amperage causes heat not voltage. Theoretically the higher voltage tools should run cooler and last longer. The power difference between the 2 systems is not as vast as one might expect. However run times are.
Nathan
well Power is Volts times Current in DC electrical system. Higher Voltages usually offset higher currents. but then, hydraulicly – power is Pressure times Flowrate – similar principle.
guess what – flowrate like current can be a bad thing. carrying around 5 amps to run a motor means thicker wires, more IR noise potential and get then – higher risk of defibulating your heart.
but things being equal.
36 volts at 2.5 amps pull would be similar to 18 volts at 5 amps pull. however – 5 amps is proabably all the current rate those batteries can muster.
so the 36 volts system – when demanded could provide more power.
likewise though motor for motor – the 36 volt motor won’t have 5 amps going though it at the same demand load. and without getting into motor design and magnetic flux as it related to load voltage – it’s more efficient too.
so the 36 volt system doesn’t have to work as hard, and can be more efficient, while having reserves for harder tasks.
is that better?
Nathan
I wish I could edit. I really can’t type for crap these days.
Brett
I wish more companies would use 2x 20 V batteries in series for a part that needs 40 V. The thought of buying into a battery system just for lawn care makes me cringe.
Jimmie
Speculation here: one reason why you might not see many power tools that operate with dual batteries is that li-ion batteries when connected in series can be dangerous if there’s a significant charge imbalance between the cells. With a single battery pack, it’s reasonable to assume that the cells within the pack are at roughly the same spot on the charge curve (excepting cell failure). But a configuration with multiple removable batteries connected in series can’t make that assumption.
Brett
Charge imbalance in a series connection isn’t a problem per se, but over discharge could be if you connect a pair of packs with a significant difference in charge level. I should think this would already be addressed by whatever protection circuit is built into the battery pack but I’m no expert there.
BikerDad
What Brett said. I came across a good deal on the DeWalt blower last week, was all ready to succumb to an impulse purchase, and them BOOM, I realized it was 40v, achieved with a SINGLE battery. Had it been 2x20v packs, I’d have taken it home. I’m not going to go into a different battery platform for a not inexpensive rarely used tool of convenience.
firefly
I used to do my own lawn and I have own almost every single brand out there at some point. I just love to test them out 🙂
My thought is don’t pay attention to the voltage, but rather the weight and the feel of the machine for lawn equipment. Trust me, after holding a trimmer for more than half an hour or so, the ergonomic will factor in real quick.
The second thing is the power. When I said power it’s not the voltage, though there is likely a correlation there, but rather how well does it perform. In case of a trimmer, for example, factor such as torque, RPM, and the weight of the line that it can handle play a major role of how well it will perform out in the field.
Pete
Go to homedepot and they have a ryobi 20v and ryobi 40v blower powered up and available for in store testing. I found the 20v to be too small in length and too little power. It seemed like the 40v had almost twice the blowing power and a long enough tube to actually reach the ground.
I love the idea of running only of a 18/20v line but i love power more lol
Chad
I bought the 20v blower mainly for cleaning my woodshop. The main reason for this type and voltage was because I have a dozen other 20v tools. As a shop cleaning blower it works great!. No more starting the gas blower and waiting a minute for it to warm up before running at load (or) dealing with the fumes inside my garage and shop.
My gas trimmer has always been problematic. Will I add the 20v trimmer? I’m on the fence. I hate the thought of a 40v battery system but for one tool I might consider it. It would be nice to not have a running trimmer while walking between the trees or trim areas on my acreage.
rob
I have owned the Black and Decker 20v blower/trimmer combo for the last few years and overall been happy with them. The blower is great for quick cleanups of a deck or sidewalk, when it’s fall and I have leaves all over the place then I have to break out the higher powered electric or gas blower. It’s basically the same with the string trimmer, when I need to do a quick trim of the lawn after mowing it works fine, but once a month or so I find I have to break out the gas trimmer to really clean up the edges.
I have looked at the higher voltage blowers but their current cost is too much I think. I would love the EGO 40v lawnmower but I replaced my mower a few years ago so it doesn’t make sense to do that anytime soon.
caleb
I have the trimmer and it works great for me, especially since it uses the same batteries as my Craftsman Bolt-on. Coupled with my reel mower I do not have to use anything gasoline powered to do lawn care!
Sadly, I missed the combo set back when it was $100 and have been on the fence about the blower. If I could just find it as an open box set like the trimmer I would jump on it.
Brian
The price of the 40v tools is an insult IMO. The price of the batteries is really the problem. $250 for a battery? are you kidding me? I can look up the price of an 8cell 6000mAH battery, its 80 bucks. thats either alot of markup or a very expensive plastic shell.
The tools themselves are 70% battery cost… plus the charger
ignoring that issue, Ill wait to see how the ecosystems shake out. I might toss a “bare tool” into my 20v collection, but Im not going to invest in a $300 battery without knowing if they’ll ever add a worthwhile lawn mower to it.
Luckily all of my gas equipment is working fine, and Ill run it into the ground and hope the landscape has settled (and then probably buy another gas version)
Stuart
I don’t know what you’re pricing out, but if these 36V 40V Max packs are built the same as 18V and 20V Max battery packs, they’ll have 10 cells to bring voltage to 36V nominal, and then another 10 to double the charge capacity.
So that makes it 20 of the very latest high capacity and high current draw Li-ion cells. I would think they’re the same 18650 form factor. The last I checked only 2.5Ah cells were readily available. New 3.0Ah cells seem to have only hit the wholesale market recently.
dave
Even so a manufacturer can get top shelf cells in mass manufacturing volume for under $4 ea so 20 of them would be $80. Add $10 for a charging circuit/display board and a generous $10 for the plastic casing and it’s still coming to only $100.
They deserve to make a profit off of it but IMO, not THAT much of a profit.
dave
Comparing blowers you wrote the 40V at 120MPH was doing more work while the 20V at 90MPH moved the same volume of air.
If they are moving the same volume then the 40V is barely (almost not) doing any more work. All you have to do to any of them to get higher flow rate is just put a tapering nozzle on the end, which wouldn’t be much of a flow restriction if it’s only boosting flow by 30%.
Richie's Mom
Is there a reason why can’t you just change out batteries? Say if one goes dead during your chore, can’t you just switch out to a duplicate (same brand/voltage) battery? In other words, have a spare charged at all times.
Captain Obvious
Takes 20 minutes to deplete the battery.
Takes 7 hours to charge the battery.
You would need 21 batteries…
Tomas
Total confusion to a homeowner buying their first cordless trimmer. For one yard, 60 ft X 100 ft, with lots of trees and shrubs; what should I buy: Voltage? Ah? Weight? Brand (Manufacturer)? One or two batteries? Charging time?
Stuart
Generally, higher voltage tools have more available power.
Ah? You can always upgrade to higher capacity battery packs later, during a promo or when your budget allows for it or needs dictate it.
For Dewalt, I’d look more at their FlexVolt tools, which seem to be very comparable to 40V Max, from what I’ve read, but the FlexVolt system is more convenient for 20V Max users. You could say have a 20V Max blower for light duty needs, and a FlexVolt trimmer.
Richard Murphy
Some quite good answers and some that confused the _____ out of me. To make a long story shorter, I understand the higher Voltage unit would be the better choice, especially for LARGE yards (I mow/trim 1.8 A of my 2.5 A). I have many Ryobi 18 V Shop Tools now and am pleased with them. My Son thinks I should stay with the 18V for Yard Tools also. I am considering the 40V range, though I saw one brand at 62 Volts. Gettin’ too old (79) to fight with the Gas tools. Do you guys have a consensus recommendation? Thank you, Murf
Stuart
Outdoor power tools are very power hungry. For casual or infrequent use, lower voltage can be okay. For regular use, higher voltage can allow for greater power.
36V/40V Max are good, higher voltage can be comparable or sometimes better, depending on the system. Ego’s 56V line is good.
Don
Well what happens when you compare 20v 5.0ah vs a 40v 2ah? Seems like 20v would be the way to go, but I don’t know!
Stuart
I suppose a rough analogy would be comparing an 8-cylinder pickup truck with 40 miles of gas, vs. a 4-cylinder SUV with 50 miles of gas. The difference depends on the tool and work you need to do.