[Woodsmith]

Just thinking out loud (dangerous I know) and was wondering about the problems of switching and controlling dc high voltage and current particularly for heaters.

I have a small 600/800W 240v inverter in the back of my work car and I have been thinking of up grading it to maybe 2-3kW as it is so useful for running bits of mains powered tooling and equipment.

Is there an 'off the shelf' inverter that will convert typical pack voltages to ac 120v or 240v at 50/60hz? I was thinking of UPS inverters etc.
Though it would be an expense it would make switching and controlling the high power heater much easier and also provide an ac supply for running 'other equipment' as required.

I can find plenty that will convert 12v or 24v to anything up to 8kW at 240v but nothing working at, say, 96v-144v dc supply.

Just thinking how useful that might be to someone who needs it or who may be looking at off grid living.

[gdirwin]

Interesting idea - switch back from DC to 120V AC and use the numerous AC devices out there... I will check into this.

Also consider using SSR (solid state relays) - they get up to 500 kV and 10 kA (5kW) but need heat sinks.

The ones below are expensive, but there are lower cost alternatives (about $25-30 each for 200VDC and 40A):
http://www.crydom.com/en/Products/Ca...VDC&SBCatPage=


I am just battling with my heater now - I just posted my tentative plan that uses many SSRs for variable heat control with ceramic heaters: http://www.diyelectriccar.com/forums...3&postcount=59

[Woodsmith]

Hi, yes, I have been watching your thread with interest. Your's and others have lead me to think about the alternatives when using high power ac heaters on dc.
If we have to do a lot of wiring and use special relays and suffer the cost and losses around that then why not make it easer and have a secondary usefulness out of it.

When I am away on my studies I have a colour laser printer in my car and also charge my laptop there. For work I am charging batteries while driving and running power tools and other work equipment to save running long leads to site or powering generators.

[dtbaker]

I went looking one time and found some big wattage invertors going from 48vDC to 120vAC, but didn't find any from 96vDC or 120vDC. I'd guess you could put a bunch of the smaller ones in parallel? But I dunno if you would have to balance them....

I was considering this basically just to energize my HOUSE from the car if I lost grid power. During the day I need only a little wattage to energize my solar panal invertor so it sees line voltage. During the night though I would need an invertor that could handle full house load..... probably pretty expensive.

[Woodsmith]

Same here, I found this 8000w 12vdc to 230vac inverter on Ebay.

Would it be less difficult to make a 144v to 120v/240v inverter then it is to make a 12v to 120v/240v inverter?