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Need to buy a generator

 
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clv101
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Joined: 24 Nov 2005
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PostPosted: Sat Oct 08, 2016 7:31 pm    Post subject: Need to buy a generator Reply with quote

I have a barn which is soon to become a workshop but it's off-grid. It needs electricity for lighting (~50W LED few hours a day, not every day) for which I'll set up a 12V battery system. It also needs ~2kW for power tools with a low duty cycle.

Initially I was thinking of a 100% solar system - for the lights that's no problem, but a battery store and inverter capable to running the power tools is a much more serious undertaking. So I'm now looking for a generator for the power tools and to keep the battery topped up for the lights.

Can anyone recommend a decent, affordable generator? My very limited research to date points me toward the Kipor IG2600. I like the pure sine AC, the 12V DC output for battery charging and the relatively low noise. However, I'm not so keen on the 600 price tag!

This one has similar power output, battery charging, also claims 65dB noise and it's only 160: SGS SPG2200.

Why are the 'suitcase' generators so much more expensive than frame generators. How important is pure sign for power tools?
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woodburner



Joined: 06 Apr 2009
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PostPosted: Sat Oct 08, 2016 8:53 pm    Post subject: Reply with quote

Look here http://www.petepower.co.uk/choosing-generators.html good honest advice. Also consider gas conversion. This will give reliability for intermittent when petrol will have gummed up the carb.

160 will not buy longevity and reliability which is what most people would want from a backup supply.
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adam2
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PostPosted: Sat Oct 08, 2016 10:33 pm    Post subject: Reply with quote

The "suitcase" generators are often inverter types and these tend to be significantly more expensive than the simple alternator direct driven from a small petrol engine.

Inverter generators have better voltage stability on fluctuating loads, and also have a longer life and lower fuel consumption when run at low load.

If the duty cycle of the power tools is low, I would reconsider the battery and inverter option.

A generator does of course give the option of prolonged full load operation provided that you have fuel on hand.
A modest sized generator is a lot more portable than a battery bank and inverter, and in INFREQUENT use might outlast the battery bank also.

A cheap generator should be fine for power tools, provided that you don't skimp on the rating.
Cheap generators may be rated in Chinese watts.

Petrol has the merit that the same fuel may be used for a car, and rotated by use in the vehicle to avoid it spoiling.
LPG is potentially more reliable, and keeps forever. IMHO, LPG is not worth the hassle of keeping a supply of the fuel UNLESS LPG is already used for some other purpose.
Small petrol or LPG engines are easily started by hand.
Diesel is safer and cheaper, but again not worth the hassle factor unless you already use diesel fuel for some other purpose.
Diesel engines are more challenging to start especially when cold and electric starting is therefore advisable which adds cost and complexity.

ANY portable generator is very attractive to thieves and proper precautions should be taken.
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Little John



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PostPosted: Sun Oct 09, 2016 1:27 am    Post subject: Reply with quote

I bought a 1.8kwh ex-showroom petrol "shop-soiled" genny off ebay four years back. Cost me 150. have used it regularly (at least a couple of times per month for at least two or three hours for around 4 years. Only had to service it once at a cost of 30 quid. If I had serviced myself, I reckon the cost would have been less than a tenner. Never heard of the make or model. So guessing it is of Chinese origin
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johnhemming2



Joined: 30 Jun 2015
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PostPosted: Sun Oct 09, 2016 8:20 am    Post subject: Reply with quote

>Cheap generators may be rated in Chinese watts.
I can understand that the Chinese mains voltage is 220V, but I don't understand what effect that has on the definition of Watts and hence the rating.

I have three petrol generators, but have not had cause to use them although I did lend them to a friend of mine who was running an outdoor market and they worked quite well. This thread has reminded me that I intend to set them up to be easily used.
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adam2
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PostPosted: Sun Oct 09, 2016 9:00 am    Post subject: Reply with quote

"Chinese watts" is a term widely used in the electrical industry to refer to ratings and specifications that are misleading but not actual lies.

For example, a reputable brand of UK manufactured generator sold as 2000 watts can hopefully produce 2000 watts continually under normal working conditions.

An imported alternative sold as "2000 watts" will probably have a number of caveats, get outs, and clauses in small print that mean the actual output is less.

2000 watts

for 30 minutes maximum, continual output is 1,800 watts
at 60 cycles, derate by 17% for 50 cycle operation.
at ambient temperature of 15 degrees, reduce at higher temperatures.

As a result the advertised 2000 watts tends to be about 1,500 watts in practice under normal working conditions.
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clv101
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PostPosted: Tue Oct 11, 2016 1:06 pm    Post subject: Reply with quote

My most demanding power tool is a plunge saw with a power label saying 1300W, it has some fancy electronics and 'soft start' so I probably don't need to worry too much about high start load. In fact thinking more about that 1300W, if I never run the saw at max speed, or cut the maximum thickness it's spec'd for, surely it's power requirement will be less than the rated 1300W?

I think the generator option will need to be the expensive inverter type, due to the electronics in some of my tools, and the battery chargers for the cordless tools.

The other option is a large lead acid and an inverter. If the max load is 1300W only for a minute or so at a time and I don't want to discharge faster than C5, I'd need 6.5kWh in the battery, so around 550Ah at 12V.

How much does 550Ah of decent 12V batter cost, how much is an inverter... then there's the PV panel and charge controller. A lot more than 600 generator!

It seems pretty much the cheapest inverter generators available are the Impax branded units from Screwfix...
http://www.screwfix.com/c/tools/generators/cat830706
They are likely cheap and nasty but at least I can take it back to the shop if it fails within a year. In fact the 280 1500W version would just about cut it:
http://www.screwfix.com/p/impax-imdy1500lbi-1500w-inverter-generator-230v/15761
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BritDownUnder



Joined: 21 Sep 2011
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Location: Hunter Valley, NSW, Australia

PostPosted: Wed Oct 12, 2016 12:46 am    Post subject: Reply with quote

I would have thought you could get an 12volt DC to 230 VAC inverter to deliver 1300 watts for around the cost of a small generator. You will probably find that your power tool will require some inrush current in excess of what the inverter is rated for but I am sure that you could get an inverter that is rated 10000 watts (even allowing for derating Chinese watts) for a minute and 2500 watts continuously. There are available over here.

Of course you could get a petrol generator and have problems of noise, fuel and unsustainablity. Better get a 12 or 24 Volt solar system and a nice quiet inverter.

In Australia I got 2x 12volt deep cycle 230 Amp hour batteries for AU$200 each, an inverter (3000 watt continuous) for $300 and a solar panel for $200 and charge controller for $100 so around $1000 total. Time has not allowed me to set up the system yet as I have been working away from home too much. These are not the best quality I grant you but I think you would be better thinking long term and not just how long your Jerry can will last you.
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Little John



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PostPosted: Wed Oct 12, 2016 4:42 am    Post subject: Reply with quote

I should correct my earlier post. My genny is 2800 watts. not 1800 watts.
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clv101
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PostPosted: Wed Oct 12, 2016 9:36 am    Post subject: Reply with quote

BritDownUnder wrote:
Better get a 12 or 24 Volt solar system and a nice quiet inverter.


Yes, I think you're right... I'll price up a 12V PV system based around ~500Wp, ~250Ah and a ~2000W inverter.
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adam2
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PostPosted: Wed Oct 12, 2016 5:27 pm    Post subject: Reply with quote

Both the generator and the PV system have good points.
Before making a final decision, here is another option.

Many modern cordless power tools have a performance approaching that of mains powered tools. They find limited favour due to the limited run time and the very high cost of replacement batteries.

It might be worth looking around for any 24 volt cordless power tools that are being sold cheaply due to missing or defective batteries.
These are easily modified to use a suitable power cord that connects to a large external 24 volt lead acid battery.

You will probably need at least 4mm cable, and not too long, but a cheap possibility for use in a workshop.
Current demand at 24 volts will vary but is often in the region of 10 amps average and 40 amps peak.
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kenneal - lagger
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PostPosted: Wed Oct 12, 2016 6:20 pm    Post subject: Reply with quote

Most of the best cordless systems are now at 18V. We have Ryobi +One tools which are not the cheapest but definitely not expensive either and they work for us. My daughter has been building a timber framed extension and the drill, impact driver, SDS drill, skill saw, and jig saw and more recently reciprocating saw have seen quite a bit of work. We have had to replace the drill and we've had some problems with a 16 gauge nailer where the hammer does not retract properly. The nailer was fixed under the two year warranty.

We've also got a very powerful torch, a long reach chainsaw limber (200mm bar) and a small strimmer which work off the same batteries. The batteries have lasted 3 or four years with only one failure so far. They charge in three hours or so off our solar panels in the summer and over night off the genny or our battery system. I'm looking at a brush cutter for rougher garden trimming as I've got fed up with petrol engines which do seem to be troublesome to start/keep running.

I've no interest in Ryobi Tools apart from using them. Makita are a good brand, although more expensive and De Walt are the top of the range and priced accordingly. Depends how much you use your tools.
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