very small/light petrol/LPG generator?

Has anyone come across a source of very small petrol ( or LPG) gemerators, around the 200-500w mark?

240,110,24 or 48V output would be useable. There are plenty of ~1KVA inverter types around, but can't find much below that. I need a lightweight power source for an unusual application, and a small gen may have better power/weight than a battery for the power level we need.

A petrol strimmer or larger RC aircraft engine with a dynamo might be an option but really don't want to get into building the mechanics unless essential...!

Wondering if LPG from a blowlamp refill or camping canister could be an option for fuel - we need 1 hour runtime at 250w load (which is about 1MJ)

Reply to
Mike Harrison
Loading thread data ...

That's achievable with a UPS, unless weight or recharging time is an issue.

Reply to
Andy Burns

OK, so a lead-filled UPS may not be the best answer then ;-)

Reply to
Andy Burns

Energy densities according to WIkipedia : Li.Ion 0.7MJ/kg Lead Acid 0.1MJ/kg Petrol & LPG 49MJ/kg

Reply to
Mike Harrison

How about a thermal battery?

formatting link
has lots of info. Perhaps you can make your own?

John

Reply to
jrwalliker

My APC SmartUPS 700 wouldn't quite make that, maybe 45 mins. Its small 6 x

6 x 15" deep and lump but not desperately so. Contains 2 x 12v 7Ah batteries and a big lump of iron. Nothing to stop you conecting higher capacity batteries to one or a suitably rated cheapie UPS.

Maybe one of the 300W car invertors jobbies? They are small and light apart from the lead acid power source. But medium car battery will have ample capacity for 1hr@250W (20A/Hr ish). A 40 or 50AHr battery won't be fully discharged, car batteries don't take particulary kindly to deep discharge.

It does depends a bit on what you want to power and how fussy it is about the waveform. The cheap stuff can have an "odd" waveform.

Plus point a UPS/Invertor doesn't produce any nasty exhaust fumes.

Reply to
Dave Liquorice

but the latter requires very heavy conversion equipment. Its a classic case of an OP that doesnt include the necessary info

NT

Reply to
meow2222

around the 200-500w mark?

may have better

option but really don't

Well I know a lot about the above, and yes, its ceratiunly dable that way..abck to back asomething like a 3-10cc RC engine with a 300-500W brushless motor and a 3 phase bridge, and you would get something in the low tens of volts at suitable power..

for fuel - we need 1

An hour of fuel for say a .40 cu in 4 stroke would be about 300mls I'd say. Best to get a petrol engine tho. model fuel is horrendously pricey. Small strimmer type thing.

Reply to
The Natural Philosopher

Thats a thought. A lithium battery for 250watt hours would probably weigh less than a motor and generator.

two of these would work

formatting link
about £400 quid.

1.7kg the pair. so what? 4lb?
Reply to
The Natural Philosopher

Have you looked at the power to weight ratio of rechargeable batteries? A D cell weighs at 66g and can have 6WHr, ie 1.2V and 5Ah. If you have 50 in series - parallel with diode protection between banks, the solution would only weigh 3.5Kg or so. Am I going wrong somewhere?

Lead acid equivalent would be 3 or so times the weight.

Reply to
Fred

And lithium polymer about half the weight.

With A123 cells in between.

Reply to
The Natural Philosopher

option but really don't

A motorcycle alternator might be a suitable electrical end.

for fuel - we need 1

How lightweight? Can you park up a vehicle nearby (which if you are using the vehicle to get there is 'free' weight)?

How much can a fit man on a bicycle generate?

Owain

Reply to
Owain

I discounted lithium on cost - but not sure what the cost would be. Rechargeable D cells if bought in bulk would be relatively cheap - few £ each.

Reply to
Fred

about 50w.

Reply to
The Natural Philosopher

I'd heard about 80W, but I don't know if that's meant to be continuously (e.g. a horsepower is an approx measure of what a horse can maintain for most of a day). I can generate a horsepower belting up the stairs, but I can't do it all day long.

I tried out a measuring bike someone had in their living room, and even though I was dressed up in suit, tie, and jacket (seeing a customer), I could generate 250W quite easily, but certainly couldn't keep that up for too long (especially in the suit and without any cooling breeze).

I would love to have a meter on my (real) bike which told me how many watts I was generating. I think I saw one once, but it was very expensive (IIRC, it used the chain speed and used some way to estimate the force on the chain, to work it out). Must admit I haven't looked for a few years now.

Reply to
Andrew Gabriel

formatting link

Reply to
Richard Head

the average "in-shape" cyclist can produce about 3 watts/kg for more than an hour (e.g., around 200 watts for a 70 kg rider), with top amateurs producing 5 watts/kg and elite athletes achieving 6 watts/kg for similar lengths of time. Elite track sprint cyclists are able to attain an instantaneous maximum output of around 2,000 watts, or in excess of 25 watts/kg; elite road cyclists may produce 1,600 to 1,700 watts as an instantaneous maximum in their burst to the finish line at the end of a five-hour long road race.

quote from Wikipedia

Reply to
Kevin

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.