Electric chainsaw efficiency vs gas.

[Hermio]

I put away my Stihl MS 500i for the season, but I had a bit of cleanup to do with a treetop, so I used a Kobalt 80 volt saw for that. I cut about 1/2 cord using 6.5 amp-hours at 80 volts. That works out to about 1 kW-h per cord, battery usage. Allowing for about 90% motor efficiency, it would be about a net energy usage of about 0.9 kW-h/cord. It took me about 1 hour to cut it, so that would be about 2 hours per cord. When I cut with my MS500i, I get a cord done in about an hour, so it is at least twice as fast. It uses about 53 ounces of fuel per cord. Energy density of gasoline is about 12 kW-h/kg or about 0.3 kW-h per fluid ounce, so the gross energy consumption is about 15.9 kW-h per cord. The saw itself has a maximum power output of 5 kW, so if it were running at full power the entire time, it would be about 31% efficient. But since it is loafing much of the time and idling some of the time, it is probably delivering at most 3 kW-h per cord. Still, that is much higher net energy used than the electric saw; perhaps triple. This may be because the Stihl uses 3/8" RS chain, and cuts about twice the kerf. I am not saying we should use battery saws. I like to get the job done quickly. And the batteries are way too expensive to keep enough on hand for using several hours at a time. (A 2AH battery has a run time of about 10 minutes on the Kobalt saw.) But I just thought it would be an interesting comparison.

 

[Hermio]

I did not withdraw this post. Not sure why it was marked withdrawn.

 

[Seachaser]

I keep a Milwaukee hatchet in my truck for quick limbing or pruning. But it will never replace the 500i in any shape, form, or fashion. No replacement for displacement.

 

[Colonel428]

Probably withdrawn because your post doesn't belong in the for sale section. Hopefully it can be moved. Interesting topic.

 

[gregozedobe]

I keep a Milwaukee hatchet in my truck for quick limbing or pruning. But it will never replace the 500i in any shape, form, or fashion. No replacement for displacement.

I use whichever saw is best suited to the job at hand. While I would never use my Milwaukee Hatchet for larger cuts it is perfectly suited to (very) small limbing, and does the job better than a much larger, heavier saw with much more power but a less wieldy bar. Having it run quietly as soon as I pull the trigger but sitting quietly with no fumes until I'm ready to cut is also nice.

As another old saying goes: "Horses for courses".

 

[Hermio]

I use whichever saw is best suited to the job at hand. While I would never use my Milwaukee Hatchet for larger cuts it is perfectly suited to (very) small limbing, and does the job better than a much larger, heavier saw with much more power but a less wieldy bar. Having it run quietly as soon as I pull the trigger but sitting quietly with no fumes until I'm ready to cut is also nice.

As another old saying goes: "Horses for courses".

My wife loves her one-hand Kobalt saw, with an 8" bar. She uses it for minor limbing and to kill off wild grapevines, which choke our trees. She occasionally girdles unwanted trees, such as honey locust.

 

[OM617YOTA]

I spent almost two hours using my Kobalt 80v stuff today. I'm surprised at how much work those tools will do on 160wh of energy.

 

[Franny K]

The 80 volts is peak or nominal? If one depletes the battery one uses the nominal voltage times the amp hours. Ball park peak is 4 volts per cell, nominal is 3.6 and before the battery management kicks in and stops things the voltage is likely around 3.2 volts per cell. A kil a watt meter is pretty inexpensive and that measures the ac current used by the charger. The ac used and your electric bill will allow you to figure the cost to compare to gas and mix oil. If you are curious how the capacity is dropping off with time or use if you keep records or remember what it takes.

There is some testing done and some manufacturers list a grams of mix per kwh. I would assume that is at the sprocket. For my Husky 540mk3 the value is 387 grams per kwh. I think I have another saw that needs about 500 grams. The Stihl 500 fuel injected saw might not be among the more efficient models, it is not a stratified charge it does have what I call long transfer tunnels and others call it front fed.

Not exactly your computation but I came up with 80 pounds of battery to equal a gallon of gasoline mix in a open port catalyst type modern chainsaw. I think the electric dirt bike battery at 60 pounds or so is equivalent to 2/3 gallon of gas in a 125 two cycle case reed engine.

 

[Hermio]

The 80 volts is peak or nominal? If one depletes the battery one uses the nominal voltage times the amp hours. Ball park peak is 4 volts per cell, nominal is 3.6 and before the battery management kicks in and stops things the voltage is likely around 3.2 volts per cell. A kil a watt meter is pretty inexpensive and that measures the ac current used by the charger. The ac used and your electric bill will allow you to figure the cost to compare to gas and mix oil. If you are curious how the capacity is dropping off with time or use if you keep records or remember what it takes.

There is some testing done and some manufacturers list a grams of mix per kwh. I would assume that is at the sprocket. For my Husky 540mk3 the value is 387 grams per kwh. I think I have another saw that needs about 500 grams. The Stihl 500 fuel injected saw might not be among the more efficient models, it is not a stratified charge it does have what I call long transfer tunnels and others call it front fed.

Not exactly your computation but I came up with 80 pounds of battery to equal a gallon of gasoline mix in a open port catalyst type modern chainsaw. I think the electric dirt bike battery at 60 pounds or so is equivalent to 2/3 gallon of gas in a 125 two cycle case reed engine.

Your 80 lb number is in the ballpark of some other figures I have seen. The rule of thumb seems to be about 13 times as much energy per unit mass for gasoline as for lithium ion batteries. Differences in battery construction and engine style can make this figure vary a bit. As for the 500i, just using my own experience, it cuts more wood per unit of fuel used then my previous saw, which was an MS441C. It runs about 35 minutes on a fill-up vs 45 minutes for the 441C, but it cuts more wood in that time than the 441 did in 45 minutes.

 

[brgrdr]

Really interesting numbers y’all have come up with, and it makes sense to me.

The use case I have in mind for adding an electric string trimmer and saw to the arsenal is for the wife when she wants to do a little yard work without having to find the mix/bar oil etc. battery power would be easier, less smelly, and less potential for burning up a machine/leading to marital strife… she likes to run the equipment but doesn’t care for the exhaust smell.

 

[Philbert]

They work. If they do the job for you, they can be a good choice.

Philbert

 

[brgrdr]

They work. If they do the job for you, they can be a good choice.

Philbert

Yeah, I’d be surprised if she’d use it more than 10-12 hrs/year. I prefer gas stuff myself, but making it as simple as plugging a battery in might mean I get some help…I don’t care much for yard work lol.

 

[diver64]

I've been running a 4 cycle Ryobi bought factory refurbished from Home Depot for $100 or so. Several years now and it does great. No exhaust smell. You might look that way. Battery is nice if you have a small yard, extra batteries or power at hand.

 

[OM617YOTA]

I have a typical homeowner size yard for this area, slightly over 1/3rd of an acre. You couldn't give me gas powered equipment for a yard this size. For the average homeowner, I really think gas is dead, with certain exceptions.

Someone with acreage, or pro users, is an entirely different matter.