I am struggling with the math, help me on this one!

[jerseyjeff]

I have a pair of gas saws a redmax 4500 with a 16 inch bar with a bored out muffler that is fantastic, and a dolkita 6400 with a big bore piston kit running a 24 inch sugihara bar it is a really great saw for power to weight. I also have an echo PAS 10 inch pole pruner, so I may have lied about just 2 saws. I would like a battery powered chainsaw because neither of my current saws are subtle, and sometimes it would be nice to have something a little more quiet. I have Makita 18v tools and EGO 56v mower, and blower, so that narrows saws down to the Makita 18/36 v or the EGO. Ego is making some claims that I can not get the math to work on.

https://egopowerplus.com/16-inch-chain-saw-40cc/

They claim there 16inch power plus is equivalent to a 40 cc saw. OK great, so Sub 10 lbs, 2-2.4 hp, 13000 rpm, Good stuff, but then the math goes to crap. I know it has a brushless motor so, way more torque, right away, but still. EGO claims with a 3/8 .043 gauge 52 link chain, 40 cc equivalent with a 2.5 amp battery, 20 m/s chain speed.

Now the numbers.

Volts x Amps = Watts

all EGO batteries are 56 Volts, the 2.5 delivers 140 watts. the 5 amp 280, and the 12 amp, 672.
Turns out there is 746 watts per hp.
My 45 cc saw makes 2.5 hp or 1865 watts.

140 does not equal 1865. I know there are torque differences, but it is a watt difference of 93 percent.

Help! I don't get it!

 

[nedsim]

I have a pair of gas saws a redmax 4500 with a 16 inch bar with a bored out muffler that is fantastic, and a dolkita 6400 with a big bore piston kit running a 24 inch sugihara bar it is a really great saw for power to weight. I also have an echo PAS 10 inch pole pruner, so I may have lied about just 2 saws. I would like a battery powered chainsaw because neither of my current saws are subtle, and sometimes it would be nice to have something a little more quiet. I have Makita 18v tools and EGO 56v mower, and blower, so that narrows saws down to the Makita 18/36 v or the EGO. Ego is making some claims that I can not get the math to work on.

https://egopowerplus.com/16-inch-chain-saw-40cc/

They claim there 16inch power plus is equivalent to a 40 cc saw. OK great, so Sub 10 lbs, 2-2.4 hp, 13000 rpm, Good stuff, but then the math goes to crap. I know it has a brushless motor so, way more torque, right away, but still. EGO claims with a 3/8 .043 gauge 52 link chain, 40 cc equivalent with a 2.5 amp battery, 20 m/s chain speed.

Now the numbers.

Volts x Amps = Watts

all EGO batteries are 56 Volts, the 2.5 delivers 140 watts. the 5 amp 280, and the 12 amp, 672.
Turns out there is 746 watts per hp.
My 45 cc saw makes 2.5 hp or 1865 watts.

140 does not equal 1865. I know there are torque differences, but it is a watt difference of 93 percent.

Help! I don't get it!

Those 2.5/5/12 amp figures are amp*hours (Ah on the web page you pointed to), a measure of the battery's capacity, not the instantaneous current it can deliver.

56 V * 2.5 Ah = 140 watt*hr
140 watt*hr / 1865 watt = .075 hours = 4.5 minutes
746 W / 56 V = 13.3 A

So, neglecting losses, the 2.5Ah battery is capable of producing 2.5 HP for 4-1/2 minutes, and delivers 13.3 A while doing so.

 

[WI_Hedgehog]

Your units are inconsistent.
The 2.5Ah battery has a stated capacity of 140Wh, or 140 watts for a period of 1 hour.

2.5Ah * 56V = 140Wh

EGO doesn't state what the power rating of the motor is, so we don't actually know it can produce 2.5 HP for 4.5 minutes, it could be 1.25HP for 9 minutes or 0.75HP for 18 minutes.

The Poulan Pro PR4016, 16 in. 40cc 2-Cycle Gas Chainsaw makes 2.0 claimed HP, which is probably accurate and more in line of what EGO is considering 40cc, but the kW output is more like 1.5 (see the STIHL chart for the MS 180), not the 1865kW used in your calculations. That seems to be about right in my opinion, EGO is a respected name in battery powered saws and was tested by ProjectFarm with good results if I recall correctly.

---
Sources:
https://egopowerplus.com/battery-2-5amp-fuel-gauge/https://www.amazon.com/Poulan-Pro-967084601-Handheld-Chainsaw/dp/B0738DPDKF?th=1https://cdnassets.stihlusa.com/1670862913-2023-chainsaw-comparison.pdf

 

[jerseyjeff]

Those 2.5/5/12 amp figures are amp*hours (Ah on the web page you pointed to), a measure of the battery's capacity, not the instantaneous current it can deliver.

56 V * 2.5 Ah = 140 watt*hr
140 watt*hr / 1865 watt = .075 hours = 4.5 minutes
746 W / 56 V = 13.3 A

So, neglecting losses, the 2.5Ah battery is capable of producing 2.5 HP for 4-1/2 minutes, and delivers 13.3 A while doing so.

 

[jerseyjeff]

That helps a bunch, I blanked on going from hours to minutes. I saw the project farm, and the ego is kind of tempting, but the company is a bunch of jackasses. I called and after a bit of work, the chap said, it is a 40 cc equivalent. I asked how they got there, and he said, the website, and they have people. I asked well what did the people do? and he said tests. Finally they said I can write a letter. An electric saw would be handy but if it runs for a whopping 4.5 minutes, that is really not a great replacement for either of my gas burners! It is also really hard to go from Gas to electric too. The torque curves are very different too. Yeesh.

 

[nedsim]

Your units are inconsistent.
The 2.5Ah battery has a stated capacity of 140Wh, or 140 watts for a period of 1 hour.

2.5Ah * 56V = 140Wh

EGO doesn't state what the power rating of the motor is, so we don't actually know it can produce 2.5 HP for 4.5 minutes, it could be 1.25HP for 9 minutes or 0.75HP for 18 minutes.

The Poulan Pro PR4016, 16 in. 40cc 2-Cycle Gas Chainsaw makes 2.0 claimed HP, which is probably accurate and more in line of what EGO is considering 40cc, but the kW output is more like 1.5 (see the STIHL chart for the MS 180), not the 1865kW used in your calculations. That seems to be about right in my opinion, EGO is a respected name in battery powered saws and was tested by ProjectFarm with good results if I recall correctly.

---
Sources:
https://egopowerplus.com/battery-2-5amp-fuel-gauge/https://www.amazon.com/Poulan-Pro-967084601-Handheld-Chainsaw/dp/B0738DPDKF?th=1https://cdnassets.stihlusa.com/1670862913-2023-chainsaw-comparison.pdf

How so? Is not 56V * 2.5Ah = 140 watt*hr (my equation) exactly the same as 2.5Ah * 56V = 140Wh (your version)?

I said the battery could theoretically output 2.5HP for 4.5 minutes. I have no idea what the motor is capable of, but brushless motors capable of producing 2.5HP for short periods of time that weigh considerably less than the bare saw's 9 pounds are not uncommon. But, yeah, 2.5HP continuously for 4-1/2 minutes is not gonna happen.

 

[northmanlogging]

my bass player, swears by his EGO stuff, has the riding mower and a couple of chain saws (sold his husky 272 and kept the EGO) as well as the 3000w inverter we use to put on a 12 hour concert every year (Full PA, lots of power hungry tube amps, and lights, well ok 2 3000w inverters and about 20 of the big ego batteries)

 

[WI_Hedgehog]

That helps a bunch, I blanked on going from hours to minutes. I saw the project farm, and the ego is kind of tempting, but the company is a bunch of jackasses. I called and after a bit of work, the chap said, it is a 40 cc equivalent. I asked how they got there, and he said, the website, and they have people. I asked well what did the people do? and he said tests. Finally they said I can write a letter. An electric saw would be handy but if it runs for a whopping 4.5 minutes, that is really not a great replacement for either of my gas burners! It is also really hard to go from Gas to electric too. The torque curves are very different too. Yeesh.

It's not that hard to change from gas to electric, I did it this weekend. With "cheap" saws don't be aggressive or the motor will let out the magic smoke and it'll be dead (Ryobi).

The saws actually ran quite a while on batteries while brush cutting (1.5" trees and smaller), no earpro and light was quite nice. The ones I was able to try are slower than gassers, but ProjectFarm pretty much showed that also (in my opinion). I just "fed them flat" (no rocking back and forth) and let them do the job, they all did fine. The owner had 3 batteries per saw so each saw ran for about 1 hour of aggressive brush cutting/stacking, which admittedly is subjective. Trying to be helpful, I'd say if you plan on cutting 10-25% of your time, electric is great. 50% of your time...it's okay. If you're repeatedly cutting anything sizeable you'll probably want a gasser, like when I'm bucking logs I'd want a gasser.

I'm a guy who really humps it when I'm on a job, so electric is great for small brush in my opinion because it's not much slower than gas given the over-all handling time, anything bigger and I'm running gas. The set-down/pick-up time of a light tool is pretty quick compared to a 40cc chainsaw, so they almost even-out in my usage.

 

[Franny K]

I said the battery could theoretically output 2.5HP for 4.5 minutes. I have no idea what the motor is capable of, but brushless motors capable of producing 2.5HP for short periods of time that weigh considerably less than the bare saw's 9 pounds are not uncommon. But, yeah, 2.5HP continuously for 4-1/2 minutes is not gonna happen.

The best cells at this time, it is my understanding can discharge at 10c max and charge at 4c max. so a total discharge in 1/10th of an hour or six minutes. Modify the 4.5 minutes to six min or multiply your 2.5 hp times 0.75 to get the theoretical max hp from that battery at 10c discharge ratio. 1.9hp.

You are on the right track fully discharge it non stop and note the time, recharge it and note the watt hours and then see what hp one gets. I think I read my double battery lxt is 1.1hp not sure but the compares to xxcc gasoline is wildly optimistic most of the time.

Use the watt hours on the battery not max voltage times amp hours. Nominal voltage times amp hours is the energy that should be available. 18 volts nominal is the same as 20 volts max.

 

[HumBurner]

Non-stop cutting, bucking rounds, especially nearly or fully buried (16", razor sharp chain), the Husqy BLi300 gives 15-20 minutes run time. Never overheated and had the saw shut itself down, even on a hot summer day.


I can get 2-4hr run time doing brushwork, or 2-3hrs mixed falling/limbing/bucking/brushing. One battery is 2 years old and has probably 300-400 charge cycles on it, often fully discharged to where it won't spin the chain again, but not always. Have barely seen any time loss on it compared to the 1 year old battery with ~100 or less charge cycles on it.

My two cents.

 

[Philbert]

Forget the math. You may calculate yourself into the wrong decision.

Clear your head and go try, or at least handle the saws.

Good call on the batteries, for general use. STIHL and Husqvarna have some nice, ‘PRO’ battery saws, but $1,000+

Ego has a good reputation for their batteries, but based on your other saws, I think you will find it clunky. Good for homeowner use.

Makita saws will feel more nimble. And, now that they are out of the gas saw business, are working on more battery saws (not all may be compatible with your batteries).

Some Home Depot locations rent Makita battery saws, so you may be able to try at least one model.

Philbert

 

[Franny K]

Non-stop cutting, bucking rounds, especially nearly or fully buried (16", razor sharp chain), the Husqy BLi300 gives 15-20 minutes run time. Never overheated and had the saw shut itself down, even on a hot summer day.

A 64 dl loop in .325 was a 15 inch bar in Husqvarna until this new mini .325. 16 inch for the heavier chassis .325 16" is 66 in Husqvarna. It (.325 54dl) is the same length essentially as a 56dl loop of 3/8lp.

The model saw you have blows air through the battery while on both the saw and the charger. The Makita lxt 18-volt batteries only have cooling air on the charger, not sure about the Ego. Just a note to the readers here. It does make a difference in the summer for run time and how hot the batteries get in general. Heat is supposed to relate to faster degradation. Your saw will get max performance from a BLI200x battery so the Bli300 battery likely isn't pushed to the edge of its capabilities like other battery/saw combinations.

 

[HumBurner]

A 64 dl loop in .325 was a 15 inch bar in Husqvarna until this new mini .325. 16 inch for the heavier chassis .325 16" is 66 in Husqvarna. It (.325 54dl) is the same length essentially as a 56dl loop of 3/8lp.

The model saw you have blows air through the battery while on both the saw and the charger. The Makita lxt 18-volt batteries only have cooling air on the charger, not sure about the Ego. Just a note to the readers here. It does make a difference in the summer for run time and how hot the batteries get in general. Heat is supposed to relate to faster degradation. Your saw will get max performance from a BLI200x battery so the Bli300 battery likely isn't pushed to the edge of its capabilities like other battery/saw combinations.

Good info, thanks for the post!


Other notables:

For the first 18 months, I didn't run the 540i with the dust guard on. The internals had a light caking of dust/pitch. I've split the case twice (trying to deal with a brake-sensor) and blown it out both times. This buildup would have trapped heat and reduced air-flow.

I'm soon going to split the case again and see how much buildup there is after operating with the dust guard in use.


Without the dust guard, initial air-flow was *ALMOST CERTAINLY* higher initially, but it's unknown when that ratio changes negatively.

 

[jerseyjeff]

To date I have kept my ego stuff outside and the makita stuff in side with the exception of the blower that I use to inflate whitewater rafts and inflatable kayaks, I tried an earlyy 36v makita at a tool show and was non plussed, I definitely wanted a bit more saw, the egos look to have a bit more, but also look far less pleasant to strap to a backpack and hike in to to trail maintenance. I think I need to find an ego in the store and feel the balance.

 

[Philbert]

e. I think I need to find an ego in the store and feel the balance.

Make sure the battery is in it!

Philbert