Electric chain saw for custom pole or boom attachment

[BillCroasmun]

Not wanting to hijack Bobs Boom thread I figured I'd reply to one of his messages here as a start to this one...

Since it looks like a tank, Clint Blake will have to have one.

I was thinking about the chain saw also. That will be one pretty good size inverter and the load on the PT battery would be very high. You could bring along a dedicated battery. The battery current into the inverter is 10 or 12 times what the saw current would be. The starting current on the saw would be probably at least 3 times the running current. At least a 2 or 3 KW inverter (continuous rating) would probably be needed. Check with the inverter supplier to make sure.

I don't know about the angle irons. If it was not strong enough, you could add the cable above it.

I've looked at some small electric saws like this 12" Remington. This one is 1.5 HP. 1 HP equals 746 Watts so it would be about 1200 Watts. I have to check but I think my inverter is 1700 peak. I didn't stop to think about the amperage draw on the PT though. I bet it may be too much for the PT180.

I'll round up the actual numbers and see how they line up. If they don't work out there is always more than one way to skin a cat!

 

[BobRip]

Not wanting to hijack Bobs Boom thread I figured I'd reply to one of his messages here as a start to this one...


I've looked at some small electric saws like this 12" Remington. This one is 1.5 HP. 1 HP equals 746 Watts so it would be about 1200 Watts. I have to check but I think my inverter is 1700 peak. I didn't stop to think about the amperage draw on the PT though. I bet it may be too much for the PT180.

I'll round up the actual numbers and see how they line up. If they don't work out there is always more than one way to skin a cat!

Yes, one horse power is 746 watts. However, no motor is 100% efficient. If you assume (just a guess on my part) 85% efficiency then the wattage is about 1300, this could be continuous depending on the load (how hard you are pushing against the wood). Startup power and current will probably be higher. A 1700 watt continuous inverter might be able to handle it, but as you said this is your peak rating. Inverter ratings (in my very limited experience) are not really a good indication of how well they will handle a surging load like a chain saw. If possible, can you take your inverter to a store or friend and try actually cutting a branch with the saw.

I have a 1000 watt, 3000 surge inverter that was unable to start my large refrigerator, which runs at less than 3 amps. The starting current on a refrigator last too long. I was using two six volt golf cart batteries (220 ampere hours) in series. I have a larger battery now (4 golf cart battery in a series parallel arrangement) and will try that some day.

Let's hear from others who have tried something like this.

 

[J_J]

Yes, one horse power is 746 watts. However, no motor is 100% efficient. If you assume (just a guess on my part) 85% efficiency then the wattage is about 1300, this could be continuous depending on the load (how hard you are pushing against the wood). Startup power and current will probably be higher. A 1700 watt continuous inverter might be able to handle it, but as you said this is your peak rating. Inverter ratings (in my very limited experience) are not really a good indication of how well they will handle a surging load like a chain saw. If possible, can you take your inverter to a store or friend and try actually cutting a branch with the saw.

I have a 1000 watt, 3000 surge inverter that was unable to start my large refrigerator, which runs at less than 3 amps. The starting current on a refrigator last too long. I was using two six volt golf cart batteries (220 ampere hours) in series. I have a larger battery now (4 golf cart battery in a series parallel arrangement) and will try that some day.

Let's hear from others who have tried something like this.

Way back when I used to be an electronics technician in the Navy, we learned about Peak Power , Average Power, rms, etc. If I remember right, most of the manufactures like to advertise their products as Peak Power. What you want to know is the Average Power. Taking Peak Power and multiplying that by .707 will give you Average Power. I believe this is correct. So if you take a 1000 watt inverter, times .707, you get 707 watts.
If your chainsaw takes 6 amps at 110v, that is 660 watts, then you will be close to the limits of the inverter, and the surge at start up may go above 6 amps, and possible smoke the inverter. A smaller chainsaw or a larger inverter is called for.

The other option is to take that 2000 watt Honda generator into the woods using the PT and power up that chainsaw and and give it a workout. Just my humble opinion.

 

[BobRip]

J_J, I think the generator idea is a good one. Generators are more forgiving that inverters in my experience.

Not to get too theoretical, but here I go. I think the peak power you are talking about is not the same as what the inverters are using.
They are basically saying that the electronics will handle RMS power that exceeds the continuous rating of the inverter for some time period. Unfortunately, I have not found how long that time is. For a chain saw that is heavily loaded this could be many seconds. For an inverter it is probably a very few seconds (1 to 5?). This difference in time frames, makes the inverter ratings almost useless for motor driven loads. Testing seems to be the best solution at this time. The inverter that I have protects itself, but it does shutdown. I suspect with a chain saw, you could start it up with no load, let it get to speed and then learn how much force you can apply before the inverter quits.
Sorry for the long explanation without a lot of help.

 

[SPYDERLK]

Not wanting to hijack Bobs Boom thread I figured I'd reply to one of his messages here as a start to this one...


I've looked at some small electric saws like this 12" Remington. This one is 1.5 HP. 1 HP equals 746 Watts so it would be about 1200 Watts. I have to check but I think my inverter is 1700 peak. I didn't stop to think about the amperage draw on the PT though. I bet it may be too much for the PT180.

I'll round up the actual numbers and see how they line up. If they don't work out there is always more than one way to skin a cat!

Bill, I have direct experience with running Remingtons 14" Limb and Trim on both Xantrex and Vector 1000W inverters. This has turned out to be a long term compatible combination. The saw is rated at 8.0A, 120VAC, which means it requires around 960W at load. The Xantrex has been mounted on our BX1500 hood for years and the Vector is on the Kub 2550 also long term. The invertors pull about 100A to run the saw so DC wiring must be good. This is more than the tractors alternators put out but with the engine running even on the little one you can do several continuous minutes of heavy cutting or 20-30min limbing before the inverter cuts out due to low supply voltage. I have had trouble with other inverters in these useage conditions. These are mechanically and electrically robust. Ive had no problem with the startup surge except when I had a poor DC connection. You can spot check those by running a 500W shoplite or other substantial load and measuring across each DC connection with a digital Voltmeter. This will allow you to compare the quality of each individual connection. You want very low voltage readings like 0.1V or less at this 60A load. If not, the higher loads inherent in startup will cause the inverter to kick out because it isnt getting high enuf supply voltage.
I love these things - lets my wife use a chainsaw. She can pull enuf to start a gas.
Larry

 

[BobRip]

Bill, I have direct experience with running Remingtons 14" Limb and Trim on both Xantrex and Vector 1000W inverters. This has turned out to be a long term compatible combination. The saw is rated at 8.0A, 120VAC, which means it requires around 960W at load. The Xantrex has been mounted on our BX1500 hood for years and the Vector is on the Kub 2550 also long term. The invertors pull about 100A to run the saw so DC wiring must be good. This is more than the tractors alternators put out but with the engine running even on the little one you can do several continuous minutes of heavy cutting or 20-30min limbing before the inverter cuts out due to low supply voltage. I have had trouble with other inverters in these useage conditions. These are mechanically and electrically robust. Ive had no problem with the startup surge except when I had a poor DC connection. You can spot check those by running a 500W shoplite or other substantial load and measuring across each DC connection with a digital Voltmeter. This will allow you to compare the quality of each individual connection. You want very low voltage readings like 0.1V or less at this 60A load. If not, the higher loads inherent in startup will cause the inverter to kick out because it isnt getting high enuf supply voltage.
I love these things - lets my wife use a chainsaw. She can pull enuf to start a gas.
Larry

Great - Actual real world experience. Thanks for the comments.

 

[BillCroasmun]

SPYDERLK, Thanks for the input! I thought my inverter was about 1700 peak but it turns out it's 2000 peak and 1000W continuous and it's a Vector. Probably the same model as yours!

So now I know for sure it can handle the 14" limb and trim if my PT can give it the juice it needs... still more research to do. About 15 years ago I used to do a lot of 4-wheeling and installed two battery systems in my CJ-7 and in a friends Blazer to help handle all of our accessories. I wonder how a system like that could benefit a PT? This project alone wouldn't justify it but maybe if other electrical hungry applications come up it may be worth while.

 

[Gravy]

Bill,

I'd be concerned about burning out the PT charging system trying to keep up with the electrical demand of the inverter and saw. You might do better to use a deep cycle battery that gets recharged with a regular battery charger.

Gravy

 

[MrJimi]

between the cost of an inverter and the wiring etc. how about a cordless chainsaw?
Jim