Newer battery powered saws

[Cantdog]

It probably took 10 battery charges but the saw cut the rounds. 14" .043 chain.

Looking at the saw marks on the end of rounds I ain't buying it......the bar is barely long enough to reach even half way through those sticks and it looks to me like there are rounds with cuts completely across the diameter.......stihl ain't buying it......sorry......

 

[toadman]

Recently sat through a webinar with a Husqvarna rep who was very convincing that this is not the case. There are a lot of factors, including run time, torque, chain speed, battery discharge rates, etc., etc., etc. Any of these can be misleading when taken by themselves. Best to go by the overall performance of the finished tool.

I used to say '36 Volts or above', but a lot of people like the 18 V Milwaukee chainsaw.

Watt-hours are important: You can quickly see the battery capacity, and get an idea of how much work it can do.
5 Amp-hours @ 18 Volts = 90 Watt-hours (Makita)
2 Amp-hours @ 120 Volts = 240 Watt-hours (Redback)
6 Amp-hours @ 40 Volts = 240 Watt-hours (Oregon)

Philbert

As posted earlier, I don't have much experience with the chainsaw... but in other power tools milwaukee m18 tools do more work per battery watt hour, than my hilti 36V and bosch 36V. The milwaukee doesn't overheat as fast as the higher voltage packs, or at all.
IIrc in an electrical engineering class I took, and rebuilding my own batteries, the 36v has all that voltage from cells in series... the last one in series is in a constant state of over charge with the tool pulling power from the pack, & becomes a bottle neck as the overall voltage goes up in relation to the individual cells base voltage. This becomes less of a problem, as the required amps go down as total volts get higher on the same task.
I am not an engineer, that class was just a required certification for a job, but that's what was being taught... Feel free to correct me If I'm wrong in this, and somebody else knows better.
In most case milwaukee 18v's are faster per task as well vs. 36v.

 

[alabama xl]

As posted earlier, I don't have much experience with the chainsaw... but in other power tools milwaukee m18 tools do more work per battery watt hour, than my hilti 36V and bosch 36V. The milwaukee doesn't overheat as fast as the higher voltage packs, or at all.
IIrc in an electrical engineering class I took, and rebuilding my own batteries, the 36v has all that voltage from cells in series... the last one in series is in a constant state of over charge with the tool pulling power from the pack, & becomes a bottle neck as the overall voltage goes up in relation to the individual cells base voltage. This becomes less of a problem, as the required amps go down as total volts get higher on the same task.
I am not an engineer, that class was just a required certification for a job, but that's what was being taught... Feel free to correct me If I'm wrong in this, and somebody else knows better.
In most case milwaukee 18v's are faster per task as well vs. 36v.

more batteries in series is definitely more difficult to charge evenly. it's quite possible that more in series is less balanced when discharging too.

 

[alabama xl]

Watt hours really needs to be computed using nominal voltage. Doing otherwise is misleading advertising. Nominal voltage for the common type of lithium ion cell is about 3.6 volts, the max voltage is about 4.0. To act like there are max voltage times amp hours yeilds watt hours is deceptive. In the above example the Makita is using nominal voltage. We have been through this with Oregon before and their exploded view of the battery.

Another thing to note is on the recharge end of things an amp at a lower voltage puts less energy into a battery than an amp at a higher voltage. For electric vehicles this becomes relevant to how long it takes to get fully recharged as I understand most dc fast chargers only put out a maximum of amps and often one pays by time.

Lithium batteries have certain charge-discharge ranges and rates that keep them happy. Makita doesn't put a full charge on theirs, and makes the tool stop before it gets discharged too low, also. this is part of how they manage to charge so quickly, and also why the batteries last for a very long time. I've had an 18V drill/driver set for ages, and still using the original batteries, much longer than I would have expected too. I'm looking at getting the little brushless top handle saw for myself, since I can use the batteries with other tools.

 

[Philbert]

That battery stuff is beyond me. Same thing with the brushless motors, control circuits, etc.

But tool design involves a lot of trade-offs. Torque, speed, run time, etc.

My recommendation is to not select primarily by the voltage, as much as by trying out the actual tool if you can, or by recommendations you trust, if you can’t try it personally.

Also, look at the range of tools supported by that battery platform, company reputation, etc.

If a company offers both a 40 Volt and 80 Volt line, see which one they consider their‘ PRO’ line. It might have some hard to see features as well.

Philbert

 

[alabama xl]

The main thing that's bugging me trying to compare some of these saws for myself, is the peak watt draw from the battery is a limiting factor, and the wattage of the motors is not specified on pretty much any of them. I don't often wish for new regulations, but I do wish that amps and watts at full load of the motor were specified on all tools like this. When I see a saw for sale that comes with a 2AH battery, I can be pretty sure that the saw is not pulling more than 1000W max, as the individual cells are usually spec'd at 20A max current per cell. so a 2P (2 sets of cells in parallel) can deliver 40A x the number of cells in series, 3P 60A. Some batteries are rated for even higher discharge rates, but there starts to be a balancing act between max discharge rate and total number of watt hours you get from the battery.

Anyway, I hate the lack of information, because there's no way to compare like you can with a gas saw with HP/torque specs.

 

[Philbert]

Have to compare them by how they cut wood!

Philbert

 

[alabama xl]

The ego 14" saw comes with a 2 or 2.5 AH battery. their 16 and 18" saws come with 5Ah batteries. So I'm trying to figure out with them if they've actually got two different powerheads, or if they're just changing prices with battery size + bar length.

greenworks commercial has this beast:

https://greenworkscommercial.com/global/en-us/products/chainsaws-gs-181-0
and they actually have a KW figure (2.5) which is significantly more than their previous model of 82V commercial saw which was only 1.5KW. I know power figures aren't all there is to it, but it would be so much nicer if these were published for all the tools, rather than just some of the commercial ones.

 

[alabama xl]

It's hard to compare how they cut wood without having them all side by side, which involves more money and commitment than I'm willing to invest!

 

[Philbert]

Oregon’s ‘40 Volt’ battery packs started out at 1.25 Ahr, then 2.4 Ahr, then 4.0 Ahr, and now 6.0 Ahr. Same physical size, and approximately the same weight.

There’s something else going on there. Maybe better ‘ions’?

Philbert

 

[alabama xl]

Oregon’s ‘40 Volt’ battery packs started out at 1.25 Ahr, then 2.4 Ahr, then 4.0 Ahr, and now 6.0 Ahr. Same physical size, and approximately the same weight.

There’s something else going on there. Maybe better ‘ions’?

Philbert

there have been advances in batteries. started out that the 18650 cells were good for about 2Ah each, now they're using 2.5 - 3Ah cells. no way that the 2Ah and the 6aH have the same number of cells in them, though. They may have left their battery packs relatively empty with the lower Amp hour batteries, if they're physically the same size.

 

[alabama xl]

By the way, Philbert, you can expect about a 25% increase in efficincy using brushless motors. meaning more power, or longer runtime, or a mix of both, compared to "regular" DC motors. This is why all the handheld tools are going to them over the past 5 years or so. I was just looking at a comparison of some battery saws, and the makita brushed DC saw compared to the brushless stihl, showed about that increase in speed of cut. Coupled with more efficient chain, you get more usable power. I am guessing that the current makita brushless saws using 5Ah batteries are probably on par with that stihl in terms of overall performance.

https://www.protoolreviews.com/tool.../review-36v-cordless-chain-saw-shootout/5979/

 

[Philbert]

there have been advances in batteries. started out that the 18650 cells were good for about 2Ah each, now they're using 2.5 - 3Ah cells. no way that the 2Ah and the 6aH have the same number of cells in them, though. They may have left their battery packs relatively empty with the lower Amp hour batteries, if they're physically the same size.

That's stuff that I have been trying to understand. People will quote the 3.6 Volts per cell for Li-Ion, but not the Ah. Most just start talking about serial and parallel and their unique controller cards / circuitry. I assume that, like flashlight batteries coming in 'AA', 'AAA', 'C', D', sizes, etc., these cells come in different sizes, especially for applications like Teslas, Boeing 787s, etc. If Oregon left extra space in their battery packs for future expansion, that is smart product design. But the weight did not increase significantly either.

By the way, Philbert, you can expect about a 25% increase in efficincy using brushless motors.

Battery capacity limitations have driven a lot of research into motor efficiency, IMO. I always think of the scenes in the movie "Apollo 13" where Gary Sinise keeps trying to squeeze out every Amp in the simulator by reordering the re-entry sequence.

Philbert

 

[OM617YOTA]

Oregon may have been limiting their depth of discharge significantly before too. To squeeze a few more AH out of the same exact batteries, they might be allowing a deeper discharge and accept a shorter battery life.

My Kobalt 80v batteries are 2AH. There are now 6AH batteries available, but they're roughly 2x the physical size, which is still pretty good for being 3x the capacity. For handheld applications and having been completely fine with the 2AH runtime and performance, I'll probably stick with the lighter 2AH batteries when it comes time for replacement.

 

[alabama xl]

That's stuff that I have been trying to understand. People will quote the 3.6 Volts per cell for Li-Ion, but not the Ah. Most just start talking about serial and parallel and their unique controller cards / circuitry. I assume that, like flashlight batteries coming in 'AA', 'AAA', 'C', D', sizes, etc., these cells come in different sizes, especially for applications like Teslas, Boeing 787s, etc. If Oregon left extra space in their battery packs for future expansion, that is smart product design. But the weight did not increase significantly either.


Battery capacity limitations have driven a lot of research into motor efficiency, IMO. I always think of the scenes in the movie "Apollo 13" where Gary Sinise keeps trying to squeeze out every Amp in the simulator by reordering the re-entry sequence.

Philbert

Lithium batteries come in different physical sizes, but for the most part the greatest power density per unit of size/weight is the 18650 cell. 65mm long, 18 in diameter. Newer Production methods have allowed roughly allowed a doubling of useful capacity From 1.5Ah per cell (or series string of cells at a higher voltage) to nearly 3Ah per cell, and some even higher. So old tech at 3Ah is now replaced with cells that can deliver closer to 6Ah depending on the load they’re given. High load, high heat can affect the total amount of power delivered in a given charge/discharge cycle.

 

[OM617YOTA]

High load, high heat can affect the total amount of power delivered in a given charge/discharge cycle.

That's a really good point. I wonder how much of the new capacities are marketing wanketeering. A battery that can produce 2AH when discharged at 8amps for 15 minutes may produce 3+AH when discharged at half an amp for 4 hours, even though no power tool is going to be used like that.

Lots of ways to fudge the numbers, if a company is so inclined.

 

[frank_]

the batteries i use on my grinders can draw 300 peak amps,and fast charge too the cells are multi-layered like a sandwich not spirally wound like the 18650,s

https://www.ebay.co.uk/itm/12V-8000...rand=Unbranded&_trksid=p2047675.c100005.m1851

 

[toadman]

I rebuilt one of my 36v bosch batteries a few years ago & the cells from the factory where 1200mah Panasonic. I replaced them with 3000mah LG cells that had the same full load amp potential, but higher capacity.
The pack weighs the same (within an ounce), but went from a factory 2.3 ah rating, to a measured 6.1 ah on my resistance discharge test before cutting out.
I get roughly 2.5 times the tapcon holes vs. the same battery when it was factory condition & new.
So a lot of the higher capacity we see now could very well be in the cells.
One of my slim MIlwaukee m12 batterys has 4200mah cells as an experiment, & while I can't use it in the most power hungry 12v tools due to the max allowable current draw on each cell, I do get 2/3 more drywall screws per charge with my impact vs a new 2.0 ah factory pack.