Power Problems Please Look

kmfdmk · 02-15-2004, 07:33 PM

Currently I'm having some finnicky problems with the power supply system. The power transfer goes like this.

12vdc from Alternator/Battery -> 330W(rms) Inverter (which outputs) -> 120vac -> 320W PSU -> Computer.

This method though it sucks, is the cheapest way to go, and also lets me re-use any one of the power supply components if I were to un-install the carPC. DC->DC power supplies are available, but are extremely expensive ($160+). Therefore I chose to go the easy way (or so it seemed @ the time)

I DO have an 450W / 700VA APC UPS (SU700-NET) that has a pure sine-wave output & under/over-voltage correction. Problem is even with it fully charged up, it will NOT turn on when plugged into the inverter, even though the computer pulls less Wattage than what would be the max RMS power rating for the inverter. I do know that the model I have does have a "Site Wiring Fault" inidicator, and that might be stopping the UPS from powering up but I'm not sure. I need to look into this. If anyone has had similar problems please get ahold of me. However running the carPC w/o the UPS to filter the AC electricity doesn't seem to have any adverse effects on the computer.

I think it has something to do with the "Site Wiring Fault" protection that it has built into it. The "Site Wiring Fault" light comes on, so I think I need to make sure that:
All Cases Commonly Grounded (DC->AC Inverter), UPS, & carPC
Negative Prong on 120vac is Connected to Common Ground (Car Frame)

My problem, I believe, is low voltage. Upon backing out of a parking spot, stopping @ night, or in slow traffic when the engine RPM's are low (less than 900) the low voltage alarm on the Inverter sounds and sometimes the inverter will turn off, thus in effect Hard-Turn-Off of the computer every hour or so. It's worse @ night when the running & headlights are on.
(mind you all that extra stuff in my sig, (the CB, 2-Way Radio Radios, Stereo, etc) are all OFF only thing running is the Car, & the carPC.)

I'm *NOT* having a problem with the car not starting after a long day of war-driving. My problem is the power shutdowns. It's probably going to kill my hardware. I believe I need a large Capacitor. Possibly 1/2 farad or 1 farad similar to the types used in the hard-core car-stereo competitions.

I do have a 63Amp alternator that's not yet been installed. This was intended to power the computer system while the car was running, and the UPS was intended to allow me to run the computer for short periods of time. (basically shutdown after Ignition key in Off position, Power Chute system).

Any thought or input would be greatly appreciated.

Later for now. I'll keep you guys updated.

frodobaggins · 02-15-2004, 07:37 PM

As far as the UPS part goes, you will not be able to run it off the inverter, at all.
Cheap inverters (ie the ones we can afford) put out a modified sine wave which the
inverter sees as dirty power. The UPS will never work on that.

Frodo

frodobaggins · 02-15-2004, 07:39 PM

For your second problem, I don't think your alternator is putting out enough to keep it running at low rpms.

kmfdmk · 02-15-2004, 07:51 PM

Quote: Originally Posted by frodobaggins

For your second problem, I don't think your alternator is putting out enough to keep it running at low rpms.

You don't think it's putting out enough Voltage? I think the amperage is covered epecially once I add the 2nd alternator (for a total combined of 118amps, 63 just for the computer)

I was thinking of adding an overdrive pulley (a pulley smaller in diameter) to the carPC alternator to keep it running faster @ the lower RPM's. Though it might eventually burn the alternator up, it DOES have a lifetime warranty, so that's not an issue.

BTW I did get the PC to power up off of the UPS + Inverter today, though I think you're correct that the UPS will not power the PC off of the inverter. From the indicator lights on the front it was telling me it was running off the battery.

none · 02-15-2004, 07:59 PM

Wait - you are going to install TWO alternators? One alternator just for the PC? No PC needs that much juice. A DC-DC PSU is not THAT expensive.

I think your problem is a bad battery or alternator. Alternator REPLACEMENT, not augmentation, is called for if that is the cause.

kmfdmk · 02-15-2004, 08:38 PM

Quote: Originally Posted by none

Wait - you are going to install TWO alternators? One alternator just for the PC? No PC needs that much juice. A DC-DC PSU is not THAT expensive.

I think your problem is a bad battery or alternator. Alternator REPLACEMENT, not augmentation, is called for if that is the cause.

Well I can't really justify 190 dollars for a 150W Opus. I've already got 3 pci cards in the system (Video, Audio, & 802.11b). And yeah I'm planning on installing the 2nd alternator.

Personally I think it's a decent way to go since I've already got a lot of other peripherals that can run on the existing car Alternator. (Scanner, 180watt head unit, 200watt amp, CB, 2 way radios, and a couple of neons)

Keep in mind when I am running the PC *NONE* of these are on just the Car & the PC.

And AFAI Can Tell I think it's a voltage problem, lower RPM's and the voltage drops, that's my guess. So far no one's been able to help me out in that matter. Everyone's just ripped on the DC-AC-DC setup. Why all the negativity, it WORKS, and it's cheaper and I can get MORE power, even IF it's inefficient. I'm not getting alternator or line noise either.

When I can get a 300W Opus for 90 bucks let me know becuase that's what I have in my Inverter & UPS. And actually as of right now I'm not running the UPS, so I've got 50 bucks in it.

The need for alternators aside.

Do you think I can run an AMD 550 Slot A, 30GB hdd, 3 PCI cards and a couple USB devices off of a 150W Opus??

none · 02-15-2004, 08:51 PM

Geez, one sentence out of six was about DC-DC, and only since you mentioned it first. Touchy. Seems you know you have a problem in that regard.

I gave you your solution. Battery or alternator. Cheap invertor isn't helping.

none · 02-15-2004, 08:54 PM

Quote: Originally Posted by none

I gave you your solution.

As did Frodo.

kmfdmk · 02-15-2004, 09:07 PM

Quote: Originally Posted by none

Touchy. Seems you know you have a problem in that regard.

I gave you your solution. Battery or alternator. Cheap invertor isn't helping.

I know the DC-AC-DC system is inefficient. I also know it's not the Battery and not the Alternator. Both of those are brand new as of October last year. And they are practice proven, I drove the car on a 2000 mile road trip after both were installed. And I'm not trying to pick a fight, I just don't like the fact that so many people pass Opus off as the End-All to Beat-All solution master and yet many people on here still use inverters. And for what I can put into a 150Watt Opus I can buy a 300W Pure SineWave Inverter which is what I may do.

The question is in regards to the voltage supplied by the Alternator.

Does anyone know if overdriving a second alternator in conjuction with the primary alternator will create higher voltages overall.

Second part to that question is if a large capacitor (1/2 -> 1 Farad range) would alleviate the momentary voltage drops that I incurr on back up/stops.

The system runs fine when in reverse, when the brakes are applied and the engine is @ low rpms, backup lights are on, and THEN the brake lights come on it's a momentary voltage drop and as soon as it's in a forward gear it's ok. I'll actually measure the voltage drop tonight with my multi-meter.

R3l0ad · 02-15-2004, 09:10 PM

Then can you justify 80 bucks for a PW-120 or PW-70 and an ITPS??? because that is the cheapest DC-DC your going to need.... and I think a second alternator is complete overkill.... you are not going to save yourself any money putting a second alternator in and having all of that bulky equipment in your car. I had a similar solution hooked up for my carpc at one point in time and quite honestly I'll never go back, my PW-120 and ITPS are great... and a justified investment. If you don't want to swing for the OPUS (the better PSU sollution) then check out the PW-120

kmfdmk · 02-15-2004, 09:17 PM

Quote: Originally Posted by r3load

ou are not going to save yourself any money putting a second alternator in and having all of that bulky equipment in your car

I've already got the second alternator, and It's probably going to be needed when I finally do run all the electronics or a majority of them @ once.

I also dont' really consider an alternator, that's replacing a non-functioning AC compressor, and a power inverter all that bulky. Even if I did, space isn't a factoring issue.

My question STILL stands about a ITPS + PW-120 being able to run 3 PCI cards in addition to a Athlon 550 Slot A. (the 3 pci's being Sound, Video, and 802.11b) I could theoretically get rid of Sound & 802.11 but the Video I cannnot, and also removing the W-Lan and Sound to make the system run is ruining the point of putting the system in the car in the first place to be able to have Video/DVD & mp3 on the go as well as 802.11b compatability and the GPS location setup.

none · 02-15-2004, 09:24 PM

Yes, a 150 watt Opus should have no problem running that system. But that is beside the point, you system as it is right now should be working better than it is, and that should be fixable. Let's not get distracted

we know you don't want a DC-DC. I think there probably IS something wrong with the electrical system on your car, but it could also be poor wiring leading into the inverter, or a faulty inverter.

frodobaggins · 02-15-2004, 09:34 PM

Try a smaller alternator pulley.
But I would still check the electrical system first to make sure it's not
something else.

kmfdmk · 02-15-2004, 09:35 PM

Quote: Originally Posted by none

I think there probably IS something wrong with the electrical system on your car, but it could also be poor wiring leading into the inverter, or a faulty inverter.

I think you might be right. As of right now I'm running the inverter via the Cigarette lighter. I'll try the setup later this week with leads running directly from battery & frame to test the theory that it's an ineffective connection between power leads.

I also think I might be able to get the UPS going on the nasty 120v supplied by the Inverter, the UPS I Have (an APC SU700NET Smart-UPS) has the ability to adjust how sensitive the UPS is to jumping in and providing battery power. I hope to get the setup working when I tweak the sensitivity on the UPS.

Thanks for the input, I may go to a 150W Opus @ a later date if I come to the conclusion that all this gear sucks and is too buggy/inefficient. (of course I'll have a lot of stuff to ebay off

)