Hi All
Anyone have any experience with running small power tools off of a automotive power generator? Is it possible? What are the issues?
HC
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Start-up current is probably the main issue. Any sort of motor device draws a lot of start-up current, and many converters are not designed to handle this surge. (Surge-handling capacity adds a lot to the cost of the converter.) Also, of course, one needs a converter capable of handling a full-load situation, which can be quite a few amps. Finally, the converter should at least be able to protect itself in the face of a "locked rotor" load, and ideally should do so, at least briefly, without throwing a breaker, so you don't have to climb down from a ladder to reset it when your saw blade jams.
The ideal setup would probably be a converter and a rotary storage unit. This rotary storage unit is essentially a large AC/DC motor with a flywheel. It absorbs energy when tools are idle and then returns it when a sudden load occurs. I've in the past used a drill press motor to serve this purpose when using a cheap electric nailer on a long extension cord -- the drill press motor stored enough energy to power the nailer, even though the extension cord couldn't deliver the needed power surge.
That last bit confused me Dan... (sorry to butt in). I assume your flywheel arrangement is coupled to a generator? Or am I missing something entirely?
Paul
An AC motor can also act as a generator.
That is what was happening in his example of using a drill press at the end of a long line.
That said I am not sure that Dan is correct in his conclusion. Power electronic devices have come down in price and there are lots of industrial electronic power systems in use. For example VFD (variable frenguency/speed drives) and people are buying them to use just as single phase to 3 phase converters.
But a Radio Shack $79.99 inverter ins't going to do anything.
I have not tried shopping, but I suspect that in the few hundred dollar range that you could get something that would run a circular saw, sawzall, or drill.
But it still not be able to start a loaded compressor. You would need to upsize a bit for that.
I have a little one that does 1200 Watts continuous and 2000 surge. Works fine for VERY small tools like a drill or a couple chargers or a little 5-amp trim saw. It won't run a full-size circular saw and certainly not a compressor. I'm not sure that they are available or practical much bigger than this. Mine sucks 100 amps DC and needs to be hooked direct to the battery. Much bigger and my alternator won't be able to handle it.
I have seen combination generator/alternators before. Replace your alternator with one of those and it will put out more like 5,000 watts. Some even have built-in welders. I looked at buying one a couple years ago. There are some issues about speed control and the resulting AC frequency. I'm not sure that any of them actually could do speed control.
One of the reasons to have the "momentum energy storage" device is that it reduces the peak draw on the DC source. Without some storage the battery or whatever has to instantaneously supply the current necessary to ride out a surge. This may be beyond the capacity of the battery, even if it's within the capabilities of the converter.
Yes, when you are working off 12 volts you have a large current draw even for the steady state loads.
I sure have been enjoying your company in these posts lately.
Ive see a lot lately with all the different people working I inspect . I dont have time to be friendly , but Ive seen some stuff Ive wondered about.
Big electrical crew had a big work truck with a diesiel engine. They were installing multiple meter loops . 45 or so on one street.
They worked all their drills off a plug in off the front grill. Motor idling. They had a 5000 watt generator that was heavy and awkward also.
Any way what I was wondering was why I dont see more 1500 or 2000 watt generators to run one tool as was mentioned. Ive seen a bunch of crews sporting a 5000 watt, which really seams over kill. I would rather have two small ones that one man could carry and split up. But ,,...... I havent seen one yet. Of course I own a 4000 Onan that I cant lift now after my surgery of a year ago and Im never going to be able to lift it .
Tim Mooney
On our older ambulances I installed 2000 watt inverters to run a sawsall.
Worked fine and never had problems.
Jeff
On our older ambulances I installed 2000 watt inverters to run a sawsall.
Jeff,
Same here. Bought a 2000watt inverter (vs. a generator) to have in the event of a power failure. Seems to run all my 120V tools just fine.
WSJ
Note that for 2000 watts you need about 200 amps from the battery/alternator. An ambulance is likely equipped with a heavy-duty alternator that can provide this much, but the normal vehicle isn't.
Dan
You are correct.
Our Ambulances are equipped with 250 amp alternators and triple batteries.
Jeff
"On our older ambulances I installed 2000 watt inverters to run a sawsall"
What do you need a Sawsall in an ambulance for?!
You doing amputations on the road?
Or is it as a mini-, low-cost jaws-of-life?David Thomas Overlooking Cook Inlet in Kenai, Alaska
David
In our area, the Ambulance corp does all the rescue and exrication.
While we have a fully equipped rescue truck, our smaller ambulances also have extrication equipment.
A sawsall is on each rig for extrication work.
(Of course, I know a few times an amputation of a few heads would have been nice)
Jeff
Yeah, but I imagine that the ambulance crews are discouraged from doing cosmetic surgery.
Look to marine supplier for good info. Like Westmarine. Much better than Radio Shack or Harbor Freight. Great catalog. Their customers might take a year to go around the world and they talk to each other about what works and what doesn't.
But when sailors talk about battery-storage and battery-life, you can go a bit lighter. Because you always have a 12-volt source (your vehicle) that you can easily fire up. It won't keep up with a 100- or 200-amp draw (certainly not on idle), but it will top the battery off again pretty quickly so it doesn't go into a state of deep discharge.
I'm thinking of typical construction work here - where our tools are actually spinning for 5-10% of the time. A/C for roofers or nailing off siding - don't use an invertor. Rent a gas A/C that day.
Try shopping at a truck stop. You can find inverters up to 15amps. that will be big enuogh to run one of anything. seams to me the cost was about $400 for 15 amps of power. If you are just runing tools you can get by with the cheap one (like above) If you go to a marine store you can pay $2500, for for an inverter with power so clean you can run computers without worry.
Cody
Call Home Depot. My store has them up to 3000 watts
A 1000W / 1200W surge inverter can be had from COSTCO for $70. That is sufficient for an 8A tool, which would include most drills, jigsaws, and sanders. One would need a larger unit for a circular saw or sawzall, and they get rapidly more expensive.
The biggest issue is cabling and fusing. That 1200W will require cabling for 100A so you are looking at a pair of 2AWG battery cables, plus a means of connecting a 100A fuse. Marine stores carry most of the knick knacks for doing this as 12V storage batteries and electrics are common on boats.
On an auto, you can buy adapters which provide quick connects to the front grill (tow trucks have them for fast jump starts) from the battery. A car battery will only provide that 1000 watts for a short period of time. Inverters are about 90% efficient, and the amp-hour rating on the battery is for a 20 hr discharge. Anything faster means lower capacity. That 80A truck battery won't give you 960W/hrs at a 960W rate. It may only last 10 minutes. Additional power can be supplied from the alternator, but it would have to be rated at over 100A to both recharge the battery and run the engine.
At a friends suggestion, I built a battery box for emergencies. Basically, it is a wood box with a pair of 85AH deep-cycle marine batteries inside and a Xantek 1000W converter on top. Total cost was around $175. This is for use when the power is out but you don't feel like cranking up the generator. Therefore it is very DW friendly. My batteries are in series but the connectors are 2AWG battery cables fused at 80A. For emergencies is has about 2KW-hr of stored energy if discharged at a 20 hr rate, so it is good for running low power items through your typical blackout. Its really nice at night when you want a light in the bathroom buy don't want the generator running.
If I were using this frequently for job stuff, I'd think about going this route and not having to run the car/truck to generate power via the alternator. You could keep a one or two cell battery box on a slow trickle to keep it topped off. You didn't specify how long or how much power you would need. Longer and heavier uses may require a small generator.
Long ago the service truck had an inverter. 1200w I think but it never worked very well. Earlier technology.
More recently I invested about $80 at Wally World to get a simple 750w model, advertising a surge load capacity of 1500w, that clips directly to the battery on my truck. This little unit has pleased me greatly. I originally intended to just run a small 3/8" drill at about 4.5A or 540w plus starting surge. This it did quite well.
On a lark I tried my hammer drill at 6.8A. Don't know if it would handle it if it was bound up but it drills small holes in concrete and handles the 1" paddle bit, most of what I need, as an electrician. I also ran a couple of small pumps. 1/3 and 1/2HP at the same time. Very cool.
After I lost power because of the hurricane I ran a PC with 17" monitor, a 19" color TV and a 24" fan all at the same time. It will also run my refrigerator but I haven't tried it in combination with anything else. I might spend an afternoon experimenting.
A good place for information and decent deals, a friend inspired by my unit, bought a unit from these folks:
http://www.donrowe.com/index.html
Check out their FAQ section.
Originally I was planning to get a 1200w unit but seeing as that the 750w one seems to handle most everything I really need, not to be confused with everything I could conceivably use, I may stick with what I have. An advantage being is that the 750w one is relatively compact and it fits easily in my cross-bed tool box. The 1200w, or even the 1000w, is substantially larger. An important consideration on a small truck.