Would this work as sine wave power line conditioner ?

[studer58]

Aside from the impracticality of lugging a sealed lead acid car battery to recording locations (which may or may not be a deal breaker, depending on circumstances) would one of these devices be a reliable substitute for a Furman type of line conditioner, or for a line interactive UPS which reconstructs the AC sine wave ? I realize you wouldn't get the UPS benefit from it, but in most cases it would be the power filtering aspect that I'm chasing anyway...for example when running a simple laptop, A>D converter and preamps. How much running time could you expect from a car battery powering these devices at a concert anyway ?
The items in question: Dick Smith 300W Power Inverter | Dick Smith Online Shopping and: Dick Smith 150W Power Inverter | Dick Smith Online Shopping

I guess in the case of a line interactive UPS you're getting from 8-20 or so minutes of safe shutdown time if the power dies suddenly, and the benefit of line conditioning as well, whereas with these boxes you get a longer (though finite) running time regardless of possible mains dropout, together with a line conditioning effect ? Or perhaps their reconstruction of the AC is less accurate than is required for audio work ? Does anybody have experience or further background on such devices ?

[MichaelPatrick]

My concern with devices of this sort, and UPS circuits too, is the switching circuits they often use.

Look at disadvantages in this article: Switched-mode power supply - Wikipedia, the free encyclopedia

[chris319]

My knowledge of these things is admittedly minuscule, but unlike the units you linked to which have a modified sine-wave output, I understand you want one with a pure sine wave output:

Pure Sine Wave Inverters and Power Inverters for your Car – The Inverter Store

[studer58]

Originally Posted by MichaelPatrick

My concern with devices of this sort, and UPS circuits too, is the switching circuits they often use.

Look at disadvantages in this article: Switched-mode power supply - Wikipedia, the free encyclopedia

Yes, those switching circuits generate lots of EMI, for example laptop power supplies and mobile phone chargers. Who'd want to introduce one of these noisemakers directly into the power line of a location recording chain !!

[studer58]

Originally Posted by chris319

My knowledge of these things is admittedly minuscule, but unlike the units you linked to which have a modified sine-wave output, I understand you want one with a pure sine wave output:

Pure Sine Wave Inverters and Power Inverters for your Car – The Inverter Store

Yes these look more like what's required, but then the prices are approaching those of on-line UPS devices... which should give the same benefits with the battery enclosed in the unit as well ! It would be interesting to line up some of these candidates and do some real-world noise tests and AC line stability checks on them...?

[chris319]

Can you post a link to an on-line UPS at a comparable price?

[Richard Black]

If you want to go all the way, get a power electronics engineer to make up a DC-DC converter for you that can supply suitable DC direct to the internal power lines of your kit (you'll need to mod the kit itself, of course, if only to bring out connections to the outside world) and also to the DC input of the laptop. Why go to the trouble of converting to AC, then transforming down, converting back to DC - your overall conversion efficiency will be rubbish at best! If you get decent efficiency, you'll need about 20W for the laptop (very rough figure depending on model, what software you're running, yadda yadda) and probably 5-10W each for the preamp and A-D, so you should get plenty of running time for an evening's work out of a 12V 20Ah sealed lead acid battery.