PTO Gen, chainsaw, or ...

[SPYDERLK]

Rob-D. Yes, I know about the modified sine/square wave output of these inverters. They do work well with brush motors like you say, and I find induction motors at less than their rated load are ok too - - I have run a sump pump to empty post holes and puddles. I would never attempt to run a welder on what is available from a normal size 12V battery, even if I was using a true sine inverter.
With your apparent knowledge of the subject Im sure you know that you wont deep cycle a normal capacity/size tractor battery with a 1kW load while having the 10.5V cutoff voltage sensed at the load(inverter). At the required 90 to 100A draw for this power, the voltage drop across the batterys internal resistance, combined with the drop in the wires and connections going to the inverter will cause the inverter to "see" 10.5V well before the battery deep discharges. Where you would run into deep discharge problems is with lower amp loads where the inherent battery and conduction losses are not so prevalent. A load that drains the battery slowly will deeply discharge it before the inverter cuts out. You dont want to be running a 100W lightbulb for hours with the engine off. That battery will be pretty dead before the inverter sees 10.5V.
Larry

 

[Soundguy]

Spyder,

As for inverters. The cheap inverters that you buy in Wally Mart or other outlets are called ‘modified sine’ inverters. This is basically a square wave and square waves do not run certain things very efficiently. I could go into the harmonics of the wave and losses incurred but there is a lot of info on this floating around the net.

.

If you are an EE.. be fair.. modified sine wave is not the same as square wave. Similar yes.. square wave.. no way.. the steps do make a difference.

Soundguy

 

[Soundguy]

I would never attempt to run a welder on what is available from a normal size 12V battery, even if I was using a true sine inverter.
With your apparent knowledge of the subject Im sure you know that you wont deep cycle a normal capacity/size tractor battery with a 1kW load while having the 10.5V cutoff voltage sensed
Larry

If welding.. why waste power thru an inverter.. just use 2-3 batteries in series, and weld DC.

As for battery discharge.. 10/5 is way discharged.. heck.. 12v is working on discharged..

Soundguy

 

[patrick_g]

Today I had to remove a fallen oak tree that was across a fence. Luckily the trunk divided into three branches just short of the fence so I didn't have to cut the full sized portion, only the three branches. The smallest of the 3 was about 18-20 inches. My old beat up Husky with 32 inch bar fired right up (38F) and zipped through the oak like a knife through hot butter. I then fired up a Mac 16 inch to trim things a bit. My only complaint regarding the Husky is that it seems to get really heavy really fast but it does a fantastic job. I have two Macs that are OK but are only 16 inch. OF course a good 16 inch is fine on any smaller cuts.

I have friends who have fallen for the lowball price and have Poulans (Wally World quality not any special industrial line) that didn't last and didn't hold a candle to any of my saws even when they were new. Low price can and will bite you.

If you are only pruning and cutting the once in a while windfall and maybe have a buddy with a good larger saw then you can get by with a cheapie, maybe.

The cheapest price is often not the most economical buy.

Pat.

 

[SPYDERLK]

If welding.. why waste power thru an inverter.. just use 2-3 batteries in series, and weld DC.

As for battery discharge.. 10/5 is way discharged.. heck.. 12v is working on discharged..

Soundguy

Yeah, thats how Id weld from batteries.
10.5V under heavy load does not indicate a significantly discharged battery. Check out what your battery terminals quickly drop to when starting on a cold morning - - maybe as low as 9V even tho the battery is fully charged. Voltage at the starter is even lower due wire and connection resistance.
Larry

 

[SPYDERLK]

If you are an EE.. be fair.. modified sine wave is not the same as square wave. Similar yes.. square wave.. no way.. the steps do make a difference.

Soundguy

Modified sine includes square, but does not necessarily mean square. I dont know how many steps the cheap ones use - - maybe just 2.
Larry

 

[Egon]

Have you fot some oak boards in the future Patrick_G ?

In most cases it seems you get what you pay for.

 

[Soundguy]

Yeah, thats how Id weld from batteries.
10.5V under heavy load does not indicate a significantly discharged battery. Check out what your battery terminals quickly drop to when starting on a cold morning - - maybe as low as 9V even tho the battery is fully charged. Voltage at the starter is even lower due wire and connection resistance.
Larry

I was talking static voltage.. not load.

Soundguy

 

[Soundguy]

Modified sine includes square, but does not necessarily mean square. I dont know how many steps the cheap ones use - - maybe just 2.
Larry

I havn't seen a really crude inverter that dropped square or just a couple steps since back in the early 90's / late 80's. Some of the newer ones are dumping some pretty pure looking sine wave on a scope.

I have seen more ring noise with some of the cheaper units.. but you can do a whole lot of clean up an output depending on the componets you stick between the plug and the output.

I've got a couple inverters that are nice large beefy units.. Packed with emi/rfi and then have a 1:1 xformer at the end. Makes utility power look 'dirty' when you compair them.

Ditto with some of the more high dollar ups systems.

Still.. my 3 old trusty inverters that i use around the farm, a 100w, 150w, and 750w run electronics fine.. even stuff with flybacks and colorburst.

i think you'd have to look hard to find a company still selling a square wave inverter or a crude stepped unit. ( unless you built it, or specifically asked for that type of unit from an industrial supply house ).

Soundguy

 

[JKNY]

Here's my 2cents worth. I,m not sure what you mean by oak wilt or how big/tall the oak trees you will cut are - if the they are trees and not saplings or brush I'd go with a gas saw. I have cut wood for heat for close to 30 years and own 3 gas saws and 2 older electric saws. Electric saws have a lot less power than gas saws. Their advantage is no rope to pull and they are handy for a pole saw or light use around the house. You dont get the rpms or torque from an electric saw so I wouldnt want one for felling or any large tree work.I also think it 's a real bad idea to use your tractor or vehicle in the woods near where you're felling trees for safety reasons, so I'm not keen on the inverter or generator idea. Sooner or later you'll have a real expensive day when a tree lands on them. It isnt always the tree youre cutting, it can be limbs or a dead tree that get knocked loose during tree felling that go where you dont want/expect. That being said I have a cheap McCullough I bought 3-4 years ago for $75 right around this time of the year at Home Depot.14" bar-36cc engine. I bring it with me in the woods to limb and do light cutting and its a decent little saw. I also have a larger John Deere saw made by echo and an Echo (both onver 25 years old), and occaisionally use one of my Dad's Stihls so I'm familiar with better saws but if you forsee limited use I wouldnt be afraid of a lower price saw . If you store a gas saw for long periods with no use store it with no gas in it, that will solve alot of problems, or use a gas stabilizer. Lastly as otheers stated , if you dont have experience felling trees get some help from someone who does.If you are cutting very small ,not too tall light stuff in relatively open areas thats a different story and one of the other solutions should be ok as you wouldnt need a couple hundred feet of extension cord to work safely.