Looks like no more Makita Petrol Saws

[Paddy1000111]

9 minutes ago, Dan Maynard said:

The problem is your 20Ah 22.2v battery has about 1.6MJ on those ratings. The 881 power of 6.4kW would need to run 290 amps at 22.2v and the battery would last about 250 seconds.
 

Oh yea, I know it's not right yet. I'm just saying we aren't far away. The spec sheet for the motor was 56V@190A maximum draw. 

[Dan Maynard]

250 seconds cutting time?

Petrol has 34MJ per litre, the battery 1.6MJ. The 881 petrol tank at 1.3litres contains the energy of 27 of those batteries.

Or if you go into forestry, or milling like RoughHewn and carry two 5 litre jerries for the day, that's the equivalent of 212 batteries.

The motor is fine, power density of electric motors has probably always been better than internal combustion engines. The problem is the amount of energy in a battery, and the fact that if you don't change the saw chain then at the end of the day you need the same amount of energy to drive the same chain to do the same job.

Seems far away to me.

[Moose McAlpine]

7 minutes ago, Dan Maynard said:

250 seconds cutting time?

Petrol has 34MJ per litre, the battery 1.6MJ. The 881 petrol tank at 1.3litres contains the energy of 27 of those batteries.

Or if you go into forestry, or milling like RoughHewn and carry two 5 litre jerries for the day, that's the equivalent of 212 batteries.

The motor is fine, power density of electric motors has probably always been better than internal combustion engines. The problem is the amount of energy in a battery, and the fact that if you don't change the saw chain then at the end of the day you need the same amount of energy to drive the same chain to do the same job.

Seems far away to me.

 

Bear in mind energy efficiency between engines and motors. 212 batteries will cut much more than 10L. Electric motors, especially brushless ones, are highly efficient.

[Stere]

I Remember a few yrs ago hydrogen fuel cells were supposedly the future.

 

H2Go Power seeks to power drones with a 'happy gas'

WWW.BBC.CO.UK

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The hydrogen-powered drone which could revolutionise the travel industry.

 

Could be used for chainsaws?

 

Quote

Hydrogen generates three times as much power per kilogram compared to fossil fuels - approximately 39.0 Kilowatt hours per kilogram compared with roughly 13 kWh per kg for kerosene or petrol or just 0.2 kWh for conventional lithium ion batteries.

 

[Dan Maynard]

 
Bear in mind energy efficiency between engines and motors. 212 batteries will cut much more than 10L. Electric motors, especially brushless ones, are highly efficient.

Yeah that's a very good point.

I'm going to pick 25% as a thermal efficiency of a chainsaw engine, think it will be something around that. So we're down to 50 batteries for the day.

I'd still rather carry the petrol.

[Dan Maynard]

I Remember a few yrs ago hydrogen fuel cells were supposedly the future.
 

H2Go Power seeks to power drones with a 'happy gas'

WWW.BBC.CO.UK

---

The hydrogen-powered drone which could revolutionise the travel industry.  
Could be used for chainsaws?
 

Hydrogen generates three times as much power per kilogram compared to fossil fuels - approximately 39.0 Kilowatt hours per kilogram compared with roughly 13 kWh per kg for kerosene or petrol or just 0.2 kWh for conventional lithium ion batteries.

 
It may be, the problem with hydrogen has always been it's dangerous.

I did see a thing about people making a petrol substitute using solar energy, that seems to me to have all the advantages including low CO2, good energy density, existing machines and cars can use it, provides a way to store and transport solar energy, no future lithium wars, no huge holes in the ground.

[Khriss]

48 minutes ago, Dan Maynard said:

250 seconds cutting time?

Petrol has 34MJ per litre, the battery 1.6MJ. The 881 petrol tank at 1.3litres contains the energy of 27 of those batteries.

Or if you go into forestry, or milling like RoughHewn and carry two 5 litre jerries for the day, that's the equivalent of 212 batteries.

The motor is fine, power density of electric motors has probably always been better than internal combustion engines. The problem is the amount of energy in a battery, and the fact that if you don't change the saw chain then at the end of the day you need the same amount of energy to drive the same chain to do the same job.

Seems far away to me.

Big corded electric chainsaw fr milling then. Quieter n cleaner, Stihl used to make one. Not seen one fr years tho. K

[Stere]

logsol do one 8Kw i think

 

Logosol E8000 | LOGOSOL

IE.LOGOSOL.COM

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We at Logosol offers the best woodworking machinery, with a wide range of saw mills, band saws, planers and other...

 

 

 

 

 

 

[Paddy1000111]

Bare in mind that battery was just an example of a random lipo battery. There's loads of different battery chemistry's and sizes to chose from. Also that motor isn't the ideal one. It was only around 7000 rpm max and bla bla bla. It was just an example of what's available. You can't compare the power in fuel to power in batteries. The battery power is rated on usable power and the motors are very, very efficient. If you have a 100ah battery and a motor that pulls 100A it will run for an hour... Petrol motors are massively inefficient turning petrol into heat into longitudinal force into rotary force and then back to longitudinal force in the chain... You would have to work out how much fuel an 881 burns and how much work that saw did which would only be possible by hooking up a Dyno to the saw and giving it a constant load. 

 

The point I was making is not "how hard is it" but more of a point that the technology is there, they have the opportunity. It's just overpriced and not well executed for the money you put into it 

[Rough Hewn]

Logosol make a 5 and 8 kw electric corded saw.
Absolutely ridiculous cutting speeds, insanely fast for a saw.

But if you want to think outside the box...
How about plasma?
Anyone seen the guy who’s made a fully working plasma lightsaber on YouTube?
Imagine a hand held portable plasma cutter lightsaber?
No kick back,
Could shorten or lengthen the flow of plasma to imitate a bar?
[emoji848][emoji106]