System Restarts whenever I start my car

Blue Falcon · 04-23-2001, 09:31 AM

Every time I start my car my computer reboots. The car is only a couple of years old. I have a dc-dc supply from keypower. I have also tried it with an inverter and had the same problem. The inverter would always beep indicating low power when I was starting my car. Any Ideas???

hornet · 04-23-2001, 10:02 AM

Either get a bigger battery, or get a second battery exclusivly for the carputer, and some sort of aux battery controler, to make sure that it charges, and doesn't drain when the car is being cranked.

Aaron Cake · 04-23-2001, 12:07 PM

Have your battery load tested. Sounds like it is losing capacity.

Falcon62Travis · 04-23-2001, 03:55 PM

I had my DC-DC psu temporarily plugged into my cig lighter for power. whenever I started the car the computer would reboot. As soon as I found another power source the problem went away.
Some cars turn off all ignition sourced power to start the engine. If you take a look your radio probably cuts off too when you start the engine. I have no idea how old my Batt/Alternator are. All it took for me was getting power from the right place!

cenwesi · 04-25-2001, 07:16 AM

I agree with Falcon62Travis....Most car do just that.

magnetik · 04-25-2001, 07:56 AM

Falcon62Travis/cenwesi have probably hit the nail on the head..... but with most cars it does take a bit of battery juice to kick over an alternator..... but seriously is it really such a bit problem anyway?

Blue Falcon · 04-25-2001, 08:31 AM

I've run the power directly from the battery. I plan on having the battery checked out. It's really no that big of deal, but it would be nice not to have to wait for it to reboot after going into the store for just a few minutes.

accord · 04-25-2001, 11:36 AM

I think it's battery problem, if you go to a shop to check battery , they might tell you the battery is ok.

It's b/c , when the car engin cranks the volt of the battery can go down to 8V (specially in cold weather). If you have a voltmeter check if it does it when it cranks.
and your computer reboots b/c it doesn't get enough power to run. It's not your power supply of the inverter problem.

Your battery might be ok for your car yet but for your computer it's diffferent story.
If you are going to get new battery, I recommend Optima Yellow top Battery. It's little expensive but it's one of the best battery you can get. look around for best price. Try shopping.yahoo.com , I think I saw it for around $135 one time.

If you are useing a lot of power from battery (such as AMP. , computer , & etc) you need good strong battery.

zootjeff · 04-25-2001, 08:12 PM

You guys all have it wrong. I found a simple solution, you don't need to buy a big battery, you don't need to spend 100 bucks on a aux battery, (all though that would work and be effective if you don't mind lugging around another battery!) If your using a DC to DC converter or a DC-AC inverter, chances are it has some threshold voltage at which it shuts down. If you are restarting during your engine start, it is because the voltage drops below that threshold voltage of 8 volts, or 10 or 4 or whatever it happens to be. If you look at it on an oscilliscope during an engine start, you could see what it looks like. The solution I used was to feed my DC-DC converter with a little one way tank circuit low pass filter consisting of a high current Schottky barrier diode and a large filter cap. The schottky barrier diode has a forward operating voltage of .4-.5 volts or so, but it's not a problem. When I start the car the tank capacitor makes up for the loss in voltage. It's pretty easy to make but if you want, I'll make you one for 10 bucks or so.

Before I used this method, MpegBox would restart every time I started my car, even if I just started it as fast as I could with a little jerk of the key.

This will only work as long as your battery doesn't get too drained from powering the mp3 player. I can go and get gas, or run into a mini mart but if I leave the thing sucking 3 amps for more than 10 minutes with the car off, I'm pretty much screwed if I want to start my car. But then again I have a little honda accord battery that has been completly killed a few times.. :-)

Hope this helps.

Jeff_

Tony S · 04-26-2001, 02:10 AM

Yeah, Jeff knows what he's talking about. That's exactly why your PC keeps kicking off/on. In fact, the voltage fluctuations could really mess with electronics if your ignition system didn't temporarily cut out when you turn the key. Going straight to the battery negates the ignition cutout. I, too, plan on hooking straight to the battery.

zootjeff · 04-26-2001, 03:02 AM

Quote:

Originally posted by Tony S:
<STRONG>Yeah, Jeff knows what he's talking about. That's exactly why your PC keeps kicking off/on. In fact, the voltage fluctuations could really mess with electronics if your ignition system didn't temporarily cut out when you turn the key. Going straight to the battery negates the ignition cutout. I, too, plan on hooking straight to the battery.</STRONG>

Actually, hooking straight to the battery might not help you that much. I had my box setup so that it was powered from the cig outlet that goes to the back seat. It was not hooked to the ignition, but it was hooked up to the battery through smaller gauge wires. I put a big filter cap right at the MpegBox input. Because the wires that go to the cig outlet in the back seat have more resistance than the ones going directly to the battery, when I started my car, my box would NOT restart. This was because the capacitor stores some charge. When the car starts the voltage at the battery drops a little bit. The capacitor then has to discharge either into the MpegBox or into the starter through the higher resistance lines. It chose MpegBox because current chooses the quickest path to ground, and that was through MpegBox instead of the higher resistance lines to the starter. I then connected my Mp3 player directly to the battery through 12 gauge wire. Then every time I started the car the unit WOULD restart. The low resistance path straight to the battery that didn't have to go through the fuse box (source of more resistance) made it so my filter cap discharged directly into the starter motor instead of keeping MpegBox alive..

The bottom line:
Batteries have what is called "internal resistance" If you battery is new, chances are it has a lower internal resistance. (lower resistances are good) Picture a voltage source that is Exactly 12 volts. Then picture a small "internal resistance" resistor in series with the battery. If that resistance is say, 0.1 ohms if you draw say 50 amps to start you car the voltage AT the battery would be 7 volts. (12 - 50*0.1) You can see if that internal resistance gets very big at all, it won't matter how well you connect to that battery and avoid the ignition. The starter motor is connected to that battery A LOT BETTER than running 5 feet of 14 gauge wire is. If you look at the starter one most cars, you see the positive terminal of the battery going right to the starter solenoid relay. And it is 6 gauge or so wire.

So, yes a new battery might solve the problem because its internal resistance will be low. (That's why you hear "test the battery under load") You are testing the internal resistance of the battery. As batteries get older, their internal resistance gets bigger. Unless you want to buy a new battery all the time, it won't fix your problem. Instead, you can do what I mentioned above, use a diode to block the path back to the starter motor, and use a capacitor to store some of the charge so your Mp3 unit will not be affected but transient power surges. You can do this on your stereo too if you don't like it turning off when you start your car.

I hope this makes sense and I didn't bore anyone to tears with EE jargon..

Jeff_

Tony S · 04-26-2001, 08:54 AM

You're right again. I actually didn't finish my thoughts in my last msg b4 this one. I was @ work so had to cut it short for an issue. Anyway, I plan on hooking right to the battery but using some type of timed relay to start a few seconds after the engine turns over. By then the voltages should steady out enough. That, or the capacitor setup will work, yes.

Falcon62Travis · 04-26-2001, 12:13 PM

So what size Capacitor and diode do I need to get to hook this up? I dont have this problem but I wanted to hook up a capacitor anyway just in case...

Aaron Cake · 04-27-2001, 03:57 PM

Jeff: Sounds like your car is having battery issues. I don't know what type of supply you are using, but you shouldn't need a tank circuit to keep your player from restarting. If you voltage falls below 9V during cranking, you have a problem somewhere.

scoobydoo22 · 04-30-2001, 03:38 PM

I was reading about the installers who developed the install instructions for the Clarion AutoPC and they suggest that a 1/4 farad capacitor should be used to on the Acc line to the PC to prevent exactly this. The "tank" circuit probably does the same thing. By installing it on the Acc line it should prevent the power from feeding back to the starter as the ignition switch already isolates these 2 circuits.

(sorry about not being around for a while, the whole Northpoint DSL fiasco has me without an ISP right now. By the way, I like the new layout of the board.