I have a remote workshop/storage area with no pole power run to it. I have a need to use electrical power tools, such as a table saw, circular saw, pancake air compressor and such.

Any recommendations on an inverter that I can use. The 300td I believe has a stock alternator. The circular saw pulls around 14 amps. I tried a small inverter, maybe a 750 or 1000 and it barely turned the saw blades. It will run a corded drill

Is there a formula to work this out. I have a couple generators but the noise level does not lend well to the work environment. I would also like the inverter to have during hurricane season and for bugging out if the shtf from other reasons. I can carry an inverter in my wagon but a generator is a bit much.

Would a 3000 watt inverter kill my battery and alternator? Using the power tools would not be a constant thing. Like cut a board, measure, nail or glue something then cut some more, drill a little, then whatever and then cut some more. So it won't be a constant draw. Now for hurricane or other emergency use I can see a need to power fans, fridge and etc in continuous use.

Inverters are rated in watts, appliances in amps. An inexact but fairly close estimate to wattage can be calculated by multiplying amps by volts. So your 14 amp saw multiplied by 120 volts gives 1680 watts. This isn't exact for AC circuits, but close enough for this use.

Your saw will only use full wattage under full load. When starting, motors draw between twice and ten times their rated current for a few brief moments. Deep well water pumps are notorious for this - they have to get hundreds of pounds of water moving from a dead stand still.

Most inverters are rated to handle a starting surge roughly twice their rated continuous output for this exact reason. A resistance load, like a heating circuit(incandescent light bulb, heater, etc) will look like just about a dead short when the elements are cold, and as they heat the resistance goes up and the current consumed drops down to the rated level.

Your alternator, if stock, is around 55 amps at 12v nominal, for 660 watts. Your alternator will not put this out at idle, nor will it put this out continuously without overheating and failing.

Now, the good news. Your use, sawing through a 2x4 or driving a few screws here and there, with time for the battery to recharge in between uses, will probably be just fine. For continuous use powering fans and stuff during an outage, you can bump up the idle a bit, run fans and some lights just fine. Powering the fridge continuously will will be asking a bit of your alternator, you could try it while monitoring voltage and temperature.

So for the circular saw scenario what inverter size should I be looking at?

BELT DRIVEN GENERATOR | POWER MITE | UNDER HOOD GENERATOR | FABCO POWER

cool product but pricey...would make the 300td a killer bug out vehicle!!!!

2KW should do you just fine on the circular saw.

That Fabco looks neat. Wonder what it costs compared to a high-output DC system and an off the shelf inverter.

Not exactly addressing this situation - but I also had a problem with using power tools near my car and not having line-power handy.
This was initially solved with an 18-volt Ryobi cordless drill & 5" circ-saw combo, found on sale at Home Depot. But the ni-cad batteries supplied have a short life and take too long to charge. Upgrading to lithium-ion batteries is very expensve and requires a different charger.
So I gutted a dud Ryobi battery and rigged a cord and alligator-clips to connect directly to my 12V car-battery. With the engine running, the 14 volts is adequate for my uses. Certainly more reliable than the ni-cads.

Since then, I found a similar Craftsman 14V saw & drill set, with tired batteies, at a thrift-store for $12, and rigged it up the same as my Ryobi.

I've seen other used 14 or 18-volt cordless tools at yard-sales, flea-markets, etc... that simply aren't worth investing in new batteries, but can be rigged to run off a car battery.

Happy Motoring, Mark

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DrDKW

More Batteries?

You would be better situated by using a bank of batteries, such as a couple of golf cart batteries, and using the alternator to charge them. Even a standard car battery can put out ~3000 watts for a short period of time. Think of them as a very large capacitor. Then you can use numerous methods to charge them, whether it be your alternator, generator or even alternative methods such as solar or wind (which are expensive and likely for long term considerations).

As mentioned before, any inductive load will require significant power to start and even to operate. Consider the fact that larger inductive loads usually have a starting capacitor to get things moving. Audiophiles use large capacitors when they have numerous speakers (inductive) connected in a car system.

Then you will need an inverter that will handle the large power load. Most are nominally rated, which means about 60% of peak. Any time you are converting from DC to AC, and vice versa, you will see significant losses.

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Sam

84 300SD 350K+ miles ( Blue Belle )

I would upgrade the alternator on the car to as big as possible, then just use a heavy duty inverter (3-5,000 watt), should run things fine so long as you don't use high continuous loads. Modern fridges use a lot less than people think. My 3 year old fridge uses about 200 watts at the most.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I also have the Ryobi 18v setup and would be very interested in hearing more about your battery modification to run off the car battery. That would provide a good temporary solution for some tools. I would still need to run a table saw.

I used this inverter from RoadPro to keep my full size non-automatic defrost freezer going during 5 days of outage during Hurricane Sandy. Had the inverter connected to an Optima Deep Discharge battery, which was in turn hooked up using jumper cables to my 2009 Versa sedan. With the engine at idle, I had no problem keeping the freezer cold. I would run the car for about 4 hours a day, and that was enough to keep all the food frozen. Two years ago, I purchased the inverter off Amazon for about $100.00. I believe it was a closeout and the unit would normally sell for about $250.

ROADPRO 2000/5000 Watt DC to AC Power Inverter - Direct to Battery Hook-Up 2000 Watts Continuous Power

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96 E300d

My 2K Harbor Freight inverter ($139) handles my table saw, my vacuum pump, and easily handles my refrigerator and lights and a small (4Kbtuh) window unit for long periods. when I am running long use, I tie in an additional MB battery. I have a 90 amp alternator on the SD for this purpose.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

for extended use in a shop with no power available, I'd get a bank of golf cart batteries, and a set of Solar panels. Northern Tools has 150 watt panels for 299 and craigslist has some sellers offering 250watt panels for around 200.00 each (less in bulk) tie that into a 5KW inverter true sine wave and you've got a nice shop ready for most anything.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

A larger alternator will do a much better job keeping up with an inverter's load with the engine at idle but it looks like we don't know the model (123 or 124) of the 300TD. It's fairly easy to find a large alternator for the 124, less easy for the 123. There are threads here about putting a 143 Amp unit on a 123, I believe it's a fairly tight fit. In a 124 you can go up to 150 Amps and there are no fit problems at all.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Honda 2k generator is a nice tool to have.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

thanks for all the responses. my vehicles are 79 through 85 300d sedans and 300td wagons and sedans, all w123. my optimal situation is to keep it all vehicle based and not involve any stand alone generators at this point. relatively low budget and I want to stay low profile as well. generators in emergency situations become magnetic and attract attention. a parked vehicle is easy to blend in and they have a pretty big fuel reserve as well

long term for the work area may include a generator or solar setup but for now its not in the cards. I don't spend enough time there to justify a big expense and want to keep the setup mobile based as well. I do like the Honda eu2000i generators. Small and efficient but close to $1000 in price.