Power Cuts/Generators yet again

[usenet]

I would suggest that's "different sort of abuse" rather than "more abuse". If you tried starting your car from a 'leisure' battery it wouldn't last long I don't think.

[Andy Hall]

Well yes, I did mean it in the context of being able to be deep discharged......

.andy

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[tony sayer]

In article , Set Square writes

And you can always run a lead in from your car to top it up::::

[Andrew Heggie]

I think the issue is more to do with matching power to load, a synchronous genset will be running at either 1500rpm or 3000rpm depending on the poles of the alternator, it is only optimally matched to the load at 75%ish of its max power. The inverter set can vary speed to match the load better. If this gains more in thermodynamic efficiency than the ~10% electrical losses of rectifier and inverter then fuel cost will be lower, also the engine life will be extended. From my experience of selecting a genset to match peak loads I found the average load was 1/5 of peak.

I suppose you could build much the same with an ex military battery charging genset, 24volt battery and a couple of inverters (1 near sine wave for sensitive equipment , 1 cheaper modified square wave for less fussy stuff) in parallel. The battery could be automotive as it would only handle peak loads or until the genset came up to speed. Float charge the battery and have the genset start using the same inputs either Dave P or yourself suggested. The Honda i series is neat though.

AJH

[Set Square]

Or go for a ride in the car with the heater on to keep warm. May be more efficient!

[Dave Liquorice]

Change the car battery for a "leisure" type battery. Generally car batteries do not take kindly to deep discharges, a few cycles and they are dead or have a dead cell.

[Dave Liquorice]

Erm, exhaust fumes?

I'd look at the plate on the back of your uWave. It maight be a 600W or 800W on thefront but that is the RF power inside the box. Our 800W (category E) actually takes 1240W...

[Dave Liquorice]

You can, I've done it with mine (SmartUPS 700i). However APC don't recomend this cold start for some reason.

[Nick Smith]

which is about what he said isn't it ?

i.e. he'd need a bigger model

Nick

[Set Square]

Well, I'd do it with the widow - or even door - open. More likely, I'd put the generator outside - but I'd then need to keep the electrics dry if it rained.

My microwave is rated at 650watts cooking power - but when I measured the actual consumption with my plug-in meter it was just over 1200 watts. That's why I said I would need the 1600 watt generator rather than the 900 watt version.

[Andy Hall]

Perhaps it's a matter of the application. According to their configurator, if you run this one at 300W (420VA), it will go for 10 minutes. In terms of a PC, this is probably not long enough to do much work if you've started from cold.

One of the common philosophies of UPSes is to give time to perform an orderly shutdown when the power fails. APC provide software to do all this across multiple machines for example.

Perhaps this is more of a customer expectation setting exercise on APC's part. .andy

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[Dave Liquorice]

Yes but probably not big enough. If 900W serves the demand without the uWave you only have 700W "surplus" with the bigger genny. As uWaves are only about 60% effcient from their RF rating even a 600W jobbie will draw 1000W...

More of a heads up than anything else, but an easy mistake to make. Not sure what sort of load a uWave presents either, I suspect very inductive.

[Dave Liquorice]

Under an upturned wheel barrow with the handles supported on a couple of garden chairs? Have the barrow facing into the prevailing wind direction to minimise rain blowing under.

Also I suspect the smell might penetrate rather deeply into any soft furnishings. Are these little Hondas 2 or 4 strokes?

But your probable other load is 250 x 2 for the freezers and 150 for the CH = 650W. You only have 400W "spare" on the 1600W when it's driving the uWave. I guess you could switch the freezers off use the uWave and then (hopefully!) remember to switch them back on again...

Not to mention that all those loads are probably pretty inductive, that always brings in some derating of a genny.

[Dave Plowman]

If I add a 'permanent' charger then effectively I've got an UPS. With a capacity of approx 0.5 kwh. I don't know what you'd expect to pay for one ready made, but my costs are *well* under 50 quid so far, given that most of the bits are either secondhand or new via Ebay.

[Dave Plowman]

It's basically a Vellerman kit from the likes of Maplin with a few mods. It produces a near perfect 50 Hz sine wave when feeding my CH. It would be an expensive solution (perhaps) if bought direct from Maplin as I estimate the parts cost at about 70 quid if bought retail - high for a 160 watt (or

320 from 24 volt) invertor. However, I bought all the bits from Ebay - although it took several months to gather them all together. I intend it for other use than just a CH back up, though.

[Steve Firth]

The last time I saw these at Screwfix, they were priced at £299. If you want I'll sell you the same model (850W) for £200. I'll pocket the £150 profit if you don't mind.

[Steve Firth]

Batteries on a UPS are not up to the job. they give about 4 minutes operation at 150W on a 625VA UPS. They also die rahter quickly if they get run flat. An inverter with a traction battery is much more robust. I have an 800W inverter that runs a normal domestic lighting and CH load for over 10 hours from a traction battery.

[Dave Plowman]

The battery I'm using is a spare for my old Rover bought secondhand from a scrapped car for pennies. I can also adjust the 'drop out' voltage of the invertor to anything I choose, so could set it at a safe(er) amount for a car type battery - reducing the time it would run for, of course. A good make 50 Ahr car battery can be bought new for about 50 quid and has a three year warranty.

[Dave Plowman]

Since I've already got a near new battery for pennies, replacing it with a leisure one wouldn't be cost effective. If I discover it's not reliable enough for my purposes, then of course I'd consider the correct thing.

[Steve Firth]

That Vellerman inverter is suspect though. I've never liked their kits.

I use Nikkai quasi-sine inverters with the drop-out set to 10.5V. This allows me to get good running time without worrying about being unable to charge the battery. The charger itself becomes very important if you want to alternate between rapid charging and maintenance. You can use the cheap Halfords iron-sensed units. But they are hopeless at rapid charging and I wouldn't be happy with leaving one on 24/7.

I use a Sterling switch-mode charger which can deliver 60A maximum but has microprocessor control of output in four stages, dropping off to a maintenance charge. I'm happy leaving that on 24/7 but it's a far more expensive solution (£260) than you are thinking of.

A s/h car battery isn't going to last long under load, but a lot depends on what you are using it for and how frequently. I'm using battery backup as a replacement for mains with 400Ah of battery storage and I'm vaguely thinking of adding another 600Ah and a 1kW wind turbine. At present it is set up to let me make efficient use of a 2600 VA generator. When I run the generator I charge the battery bank. That lets me use silent power at night for lighting.