Inverter powered UPS for CarPC?

AWDNUT · 09-03-2005, 10:54 PM

I have a 600w inverter with a digital switch on it running a small 500VA UPS and the CarPC is plugged into that UPS for power and it has a USB cable running to the UPS for status info.

When the UPS switches to battery mode it sends the CarPC a warning to shutdown/hibernate in 12 minutes (the CarPC can run for ~25-30 minutes on the UPS), and if power comes back it cancels the shutdown. This works perfect for gas stops or short visits where I don't want the GPS or the PC to be rebooted. Because the inverter has a smart switch it can autmatically turn off due to low car voltage and so even if I forget to switch it off, it won't nuke my battery.

I have a row of switch blanks in my dash so re-routing the inverter switch and status LED is just child's play that I could of done even without the assistance of drugs or alcohol..

So what I want to know is what's the downside to this? The UPS battery will get worked, and the car battery needs to be good too.. But other than that and the lost efficiency, it's a plug-n-play solution?

I have an Optima Red Top that is fine with the drain of the inverter, and other than some alternator woes (I need a decent alt) it seems reliable?

PURDooM · 09-03-2005, 11:43 PM

Good luck using an inverter to consistantly get that battery charged. If I understand right you plan on draining the UPS every time you power off your car, and in that case your never going to be able to get it very charged before you power it off again.

TimmyM · 09-04-2005, 12:14 AM

couldn't you just use a battery isolator to charge the batteries in the UPS and eliminate the inverter all together?

DarquePervert · 09-04-2005, 06:43 AM

Quote: Originally Posted by TimmyM

couldn't you just use a battery isolator to charge the batteries in the UPS and eliminate the inverter all together?

No.
There's more to the UPS than ust a batter. There's circuitry to communicate w/ the PC as well. It's designed for 110v (or 220v in some countries) AC input, so the 12v DC input fromt he vehicle battery ain't gonna cut it.

Sc0rian · 09-04-2005, 11:32 AM

use a 555 timer...? so it cuts out after 5mins and doesnt drain the battery...just uses 30% or so...

lez · 09-04-2005, 01:21 PM

Quote: Originally Posted by DarquePervert

No.
There's more to the UPS than ust a batter. There's circuitry to communicate w/ the PC as well. It's designed for 110v (or 220v in some countries) AC input, so the 12v DC input fromt he vehicle battery ain't gonna cut it.

The batteys in most ups units are small and crap, but the inverters are usually good, remove crap batteries and use a car battery in place of them, a 80aHr would be nice....

Dont ever bother to connect 110/220 to it, just use some 30 amp relays to connect your alternator to the new inverter batteries when the engine is running, a split power charger relay from a camping supplier is ok for this.

once used to run a webserver with an old ups wired to a bank of 6 car batteries, could go for at least 12 hours without mains, never did find out just how long it would go.

lez · 09-04-2005, 01:46 PM

Quote: Originally Posted by DarquePervert

No.
There's more to the UPS than ust a batter. There's circuitry to communicate w/ the PC as well. It's designed for 110v (or 220v in some countries) AC input, so the 12v DC input fromt he vehicle battery ain't gonna cut it.

The batteys in most ups units are small and crap, but the inverters are usually good, remove crap batteries and use a car battery in place of them, a 80aHr would be nice....

Dont ever bother to connect 110/220 to it, just use some 30 amp relays to connect your alternator to the new inverter batteries when the engine is running, a split power charger relay from a camping supplier is ok for this.

once used to run a webserver with an old ups wired to a bank of 6 car batteries, could go for at least 12 hours without mains, never did find out just how long it would go.

TimmyM · 09-04-2005, 06:01 PM

Thats what I've been thinking of doing. I have a rack mount APC 1250 UPS with bad batteries. There are two of them about the size of motorcycle batteries. I thought I'd replace them with new and use the UPS to power my computer among other things. I orginally was going to use an inverter running off a second car battery with an isolator but then got to thinking of the old UPS and thought "why not cut out the middle man (second car battery and inverter)". Then I would wire a shutdown controller from the key power on to the computers serial port and let the inverter stay on all the time.

AWDNUT · 09-09-2005, 12:44 AM

Well it takes a long time for the internal inverter to drain the UPS when there is no load. The PC triggers an auto shutdown in 12 minutes when the UPS signals it has lost power. So if I don't shutdown the PC the drain on the UPS is only there for 12 minutes and then its very minimal after that.

I love the idea of skipping the inverter all together and supplying power to the battery of the UPS from the car. The fact is that the UPS has a complex circuit that charges and monitors the battery, so I really doubt it would be happy with the extra input.

Right now I am cheating.. I have to plug my car in every night anyways so the UPS gets constant DC power overnight. I don't live in the cold or anything, I just have a 2nd battery in the back for the stereo (I refuse to be stuck without power) awaiting connection to a nice phat 140amp isolator running off the car's power. Until then it has to be charged manually.

The whole thing is comical in how I needed so many parts and how I keep getting one thing at a time. Right now it's a HO alternator.. I bought a used STi 90amp and it's sucking bigtime..

Y'know I could just use the 2nd battery plus the isolator (it has a low voltage cutout too) to run the carpc and I'd just need a simple controller to handle a smart shutdown of the carpc when the acc power has dropped.

AWDNUT · 09-13-2005, 10:53 PM

Okay this is a really easy 'idiot' proof method of getting a CarPC into your car but it's an idiotic way to do it.. Efficiency aside, as the UPS battery dies the UPS seems to really kill the inverter causing power fluctuations that go right to the PC and crash it..

So either I need alot better UPS/inverter or it shouldn't be done at all, just use DC-to-DC.. I'm leaning to the latter.

mushin · 09-13-2005, 11:30 PM

I'm glad you decided it was a stupid way of going about it

Not everyone can come out and denounce their own idea either, so props to you for that.

I encourage you to go the DC-DC route. And get/make a time-delayed shutdown controller to handle the short stops scenario.