Inverters / generators

[Tigercubrider]

Any ideas welcome.

Someone's asked me about using a video projector in a field.
So I am thinking either inverter or (quiet) generator.

I am guessing 500W for a projector.

I know that some generators can be very quiet, but most are noisy. How electrically "dirty" are they? I know from musician friends that some basic generators don't work well with audio gear.

Inverters seem to be used by caravan people but maybe for low power stuff. They might need a ton of batteries for a 30 min video at 500W?

thanks

 

[HERTS P&D]

You would need a Honda generator.

https://www.justgenerators.co.uk/honda-generators/honda-eu10i-generator.html

Andy

 

[SUNRAY]

Plus one from me, quiet and perfectly controlled sinusoidal output.

 

[flameport]

They might need a ton of batteries for a 30 min video at 500W?

Not really.
A standard 80Ah lead acid leisure battery would be more than adequate.

500W for 30 minutes is 250 watt hours.
An 80Ah 12V battery is 960 watt hours.

 

[Jackrae]

Not really.
A standard 80Ah lead acid leisure battery would be more than adequate.

500W for 30 minutes is 250 watt hours.
An 80Ah 12V battery is 960 watt hours.

Only when discharged at the rate specified by the manufacturer on a full charge at 100% battery efficiency. 'standard' rate is usually specified at C20 (20hour rate) Hence an 80Ah battery will be rated at 4 amps for 20 hours.
A 500watt discharge rate equates to over 40 amps which is C2. On a good day you might get 40Ah out of a 12volt 80Ah battery at that rate which gives a run time of 1hour at best. But that means discharging to 100% depth-of-discharge which is the most effective way of killing a lead-acid battery.

For your application you should use a deep-discharge type of battery (not the run-of-the-mill 'starter' type battery) which don't come cheap.

If you want to go down the battery route I'd recommend you go for a 24volt inverter which will reduce the current demand and hence depth of discharge.

By the time you've bought an inverter and a pair of 80Ah deep discharge batteries you'll be at least 80% of the way to paying for a 'silent' Honda generator.

If you intend doing more than a single projection show then a generator would be my recommendation.

 

[SUNRAY]

I've been here a time or two. John is quite right, we did the calculations for lights on a float, 48V 10W bulbs every foot along both sides of a 30ft trailer = 600W = 12A we had 4x 65AH fairly new batteries which an Act Gold Analyser never displayed less than 57AH and we predicted between 3 to 4 hours use. 3 hours was about the limit, but by about 8 carnivals we were down to 1 hour, I'd completely destroyed 4 reasonable batteries in a season even though they still tested OK with the Analyser. Admittedly these were 'car batteries' and not any form of leisure or other deep discharge batteries but I didn't expect just how quickly they failed. I had a second similar set fitted in a caravan for public address work, charged with exactly the same charger in use for about 15 years, by the end their performance was well down but would happily run a village fete, or possibly two, without falter.

These days I use 80 or 115AH leisure batteries at up to twice the price as I now use 24V or 12V kit but longer use 48V, meaning the discharge current is much higher.

I don't run without mains power very often these days but if I did I'd have purchased a Honda inverter generator as linked before. One of the hardly known features of them is the ability to link them together to increase capacity or to be able to refill the petrol without interuption.