12v -> 120v + UPS + Extra Battery

kmfdmk · 02-28-2003, 09:52 PM

I've been reading through most of the threads here in the forum, as well as other forums across the net, and been doing some thinking. After much deliberating I've decided on a power supply setup I think will serve me the best.

The Stuff:

- Aftermarket High Amp Alternator
- Additional battery stored in trunk (this may prove unnecessary)
- 4 or 500W 12v - 120v Inverter
- UPS w/ Brown Out/Surge Protection

The Setup:

1. - Computer Powers up, running off of Trunk Battery + UPS power.
2. - Power Good Signal from PSU activates a Relay that connects a power cable from stock battery to Trunk Battery. This allows the trunk battery to be charged.

*note* there will actually be 2 relays, the Power Good Signal from the PSU will activate one leg of a relay, a "Car is Running/Charging" signal will activate the other leg of the relay. This way the computer will only drain the trunk battery & not the the stock battery.

3. - The Computer continues to operate off the trunk battery utilizing the filtered, and voltage corrected supply provided by the UPS.

4. - Powering down the computer & removes one of the 2 required legs to the charging relay to the circuit in the trunk battery.

*note* An additional 'Power Good Signal' could be routed to the relay so that the Trunk Battery could be charged w/o the computer itself being on.

Pro's of the Setup:

- Ease of setup, aside from the wiring & all.
- UPS + Battery allow system to be operated w/o running car.
- Filtered & Voltage Corrected supply.
- Benefit of having 120v in car to power other peripherals (N64, PSX, VCR etc.)
- Ability to Operate Computer for extended times via extension cord & plugging it into a wall socket.

Con's of the Setup:

- Efficiency, Converting 12vDC -> 120vAC, and then back to 12vDC isn't the most efficient of ways to convert the power.
- Cost, the battery will run near $55, an Inverter around $100, and the UPS around $125, $20 bucks for the 2 relays, and probably close to 20 bucks for the heavy duty power cabling, and probably close to $10 bucks in connectors, & the extra switch.
- More as I think of them.

My estimate is that total cost for this setup is this:

125 - UPS
100 - Power Inverter
55 - Battery
20 - Relays
20 - Power Cabling
10 - Connectors
+________________

Total Cost = $330 bucks

Expensive Yeah, Reliable, I should hope so. You could also cut corners a bit cost wise, don't get as big a UPS, skip the extra battery, use a switch instead of a relay, and maybe save 100 bucks or more on all that.

Shoot this fulla holes, but it's probably what i'm going to be using in my car. It doesnt' require a hugely intimate knowledge of electrical wiring, is component replacable, and I just plain like it.

I'm planning on mounting a igloo cooler, with a fan & vents in it in my trunk, I'll put the battery, Inverter & UPS in that. The only downside is running the cabling back up to the front seat where the computer will be.

Any thoughts, ideas feed back? Suggestions?

Charliey · 02-28-2003, 11:32 PM

One thing that might not be good, and you can search here for more information, but i dont know if a UPS will like being run from an inverter. i know UPSes have been talked about before here, i just dont remember the details.

frodobaggins · 03-01-2003, 02:33 AM

If you can get a UPS to run off the invertor, go ahead. Haven't tested this, but let me say something about UPS.

The cheapo UPSs don't run the board inside all the time, they just route it through to the plugs unless surge,brownout, powercut etc, so you are still getting good old dirty modified sine wave output from the invertor.run straight to your plugs

Some mid-range UPS do run the board inside all the time, but guess what, they produce good old dirty modified sine wave output, so gotcha again

High end UPS run their board all the time, they put out pure sine wave output, nice, but they COST ALOT.

and last, since I doubt you're foing to be running a super EXPENSIVE invertor, it is going to have modified sine wave output, and your UPS might not like that

kmfdmk · 03-01-2003, 03:16 AM

Cheapest I could find them was right around 280 bucks.

Pricewatch for APC SU700NET

Saw one on ebay for 59.00 starting bid.

I'm sure I can find/make something work for MUCH cheaper than that. If it comes down to it, I'll make something. I think I'm going to try the inverter & UPS w/ voltage correction for now. I can always use the UPS on my home pc.