Inverter low power alarm

**vadik29** · 03-07-2005, 11:30 AM

Hi guys,

I have a newbie question, hope someone can help.

I have a simple power scheme for my carpooter: 175W inverter + ATX power supply. The computer itself is an old P-3, minimal configuration. The screen is Sony PS 5" (7W power)

The problem is that after some while (15-20min) when I'm stuck in traffic, or going in a city on low speed the inverter starts beeping "low battery" alarm. I mean, it is saying it has not enough power, even with the engine running. When I go to highway, over 40-50miles/hour everything is fine.
The car is mitsubishi galant, the battery is pretty old, but that should not be the issue if the engine is running, right?
And the power usage is not really that high, the inverter is 175W so I don't think it is taking more than that.
The computer itself is working good, no shutdowns, no audio noise, I'm just afraid to drain the battery.

Is there anything I can do, other that changing the whole computer to low-power model? Can it be a problem with alternator?

Would appreciate any help.

**WebDog** · 03-07-2005, 11:44 AM

my old inverter works in my moms car pluged into the cig socket and when i plug it into my car even wired direct to the battery it does the same thing, i dont know what causes it but i went DC-DC route this install so i never figured it out,.

**n8scstm** · 03-07-2005, 11:49 AM

What gauge wire are you using? Does it plug into the cig ligghter? Its a good chance your alternator cant keep up but it such a small inverter that the alt. shouldnt be a prob. unless its broken. You can pull it out and take it to any auto parts store and they can test it for you to make sure its putting out properly. Sounds to me like your wire is too small though.

**vadik29** · 03-07-2005, 12:27 PM

The wire is the original inverter wire plugged into cigarette sock. So, it should not be a problem... Maybe I should try another inverter. But it works fine when the speed is high, so the problem seems to be with the alternator. Is there a way to check alternator without taking it out?

**KyferEz** · 03-07-2005, 01:50 PM

One moderatly easy thing to do is get a new, smaller diameter pully for the altenator. What this does is force the altenator to constantly spin at a higher speed, even at idle.

KyferEz

**jcdillin** · 03-07-2005, 02:05 PM

hardwire it to the battery, the cigarette lighter is probably the source of your troubles

**falconey** · 03-07-2005, 02:12 PM

Originally Posted by vadik29

The wire is the original inverter wire plugged into cigarette sock. So, it should not be a problem... Maybe I should try another inverter. But it works fine when the speed is high, so the problem seems to be with the alternator. Is there a way to check alternator without taking it out?

I agree with JC. I'm sure this is the reason for your problems. That cig lighter outlet was not meant to allow the amount of current you need to be constantly running to your car pc. Go buy you some cabling to wire the inverter positive directly to the positive terminal on your car battery.

**vadik29** · 03-07-2005, 02:20 PM

Guys, thanks a lot for your help.

But what makes you think the cig lighter socket is the problem? Inverter is beeping only when the car moves slowly, if it runs on a higher speed everything is fine. If the problem is with socket it would be beeping all the time, right? Or I just dont understand something.

**falconey** · 03-07-2005, 02:27 PM

Originally Posted by vadik29

Guys, thanks a lot for your help.

But what makes you think the cig lighter socket is the problem? Inverter is beeping only when the car moves slowly, if it runs on a higher speed everything is fine. If the problem is with socket it would be beeping all the time, right? Or I just dont understand something.

When you are slowing down your rpm's reduce. The lower your rpms the lesser the voltage produced and sent out by the alternator. At that point all the accesories you have running and your engine start fighting over power. Since the cig lighter socket was created to produce small amounts of power for short periods of time there really isn't anything in the design(i.e. wiring, fuse rating, etc) that would make it one of the priorities for the current to flow. If you have a small car that has an altenator that doesn't produce a lot of power this will probably be the case. Buy you some 8/10 guage wire and run it from the positive on the battery terminal to the positive on the inverter. This should solve your problem.

**pirate_king00** · 03-07-2005, 02:29 PM

Vadik,

The cigarette lighter wasn't meant to supply power to a computer. What I did was run 3 guage wire to a distribution block (from there it goes to amps, inverter). I do not have the problem, and it survices me cranking the engine. Its like this.....YOu have a large pipe, you split the end into a Y one end being bigger diameter than the other. Now the question is Which end do you think you will go more volume of water?

Now use the above logic for your situation, and I think you will be good to go.