Cranking : Sign of weak battery?

**masch** · 08-03-2004, 10:53 AM

Hola

I run my power with a morex DC-DC with the Excalibur chip from TI using vvog's mod.

I've run it no problems for the past few months, but just yesterday I noticed after I fuel up at gas stations, when cranking, the PC reboots. Just now I tested it and I learned that it only reboots if I have my headlights on. If I dont have my headlights on then the PC wont reboot at crank.

Now I hardly drive at night so maybe this has been happening before - maybe I just didnt notice.

I checked the battery voltage before cranking with the headlights on and its around 10+V with PC running. With headlights off and PC running its about 11.7V.

Is this a sign that
1) My battery is dying?
2) I need bigger power cables?
3) some wiring went wrong somewhere?

**owenjh** · 08-03-2004, 11:07 AM

all of the above. Take an educated guess. How old is the battery. How much voltage does it put out before the computer is on. Maybe its just that when your headlights are on you have to much draw from the battery so your power doesn't have enough to keep going therefore the computer dies
- im not a power expert mind you.

**falconey** · 08-03-2004, 11:34 AM

Headlights normally will draw a lot of Volts so this seems normal to me. If you haven't had the problem before though I'd think the battery is losing some of its quality.

**masch** · 08-03-2004, 01:00 PM

Thanks.

Are you folks experiencing the problem of computer rebooting if cranking while headlights are on? Or am I seem to be the only person?

**owenjh** · 08-03-2004, 02:05 PM

I havn't tried it but when I do I will let you know... I don't have my multimeter right now anyway so I couldn't tell you all the technical stuff :-P

**Curiosity** · 08-03-2004, 02:20 PM

Uh just curious, why do you need your headlights on while you're cranking?

**falconey** · 08-03-2004, 02:24 PM

I get no reboot under any circumstance. Of course I get a larger voltage drop when accessories are running vs. accessories not running. The two most power intensive accesories that I know of are the lights and the a/c. Your situation isn't anything surprising because of this. What I'd suggest is that you do some research on your power supply and see if other users are having any type of reboot issues. If not then it's your charging system. Still common sense leads me to believe that either your alternator is losing some of it's umph or the battery based on the fact that you said this wasn't happening before.

You need to have someone crank the engine so you can test the voltages at cranking. When you do this check to see what vlotage your power supply needs to stay on. This should start leading you to some answers.

**pip** · 08-03-2004, 03:11 PM

Lot of short trips recently? Maybe it just needs a good charge?

**Gibson99** · 08-22-2004, 01:02 PM

Originally Posted by Curiosity

Uh just curious, why do you need your headlights on while you're cranking?

some cars automatically turn on the headlights and don't give you the choice of turning them off. GM is especially bad about this. some toyotas do it too. i like how VWs turn them off during cranking.

**rockthevolvo** · 08-22-2004, 11:40 PM

Originally Posted by Gibson99

i like how VWs turn them off during cranking.

volvos do it too... some cars go so far as to even ignore the fact that THE CAR IS OFF...and the headlights stay on with doors locked and no keys in the ignition. this happens in my friends toyota.

within the next week im doing my long-awaited (by me) install and im worried about the battery in my car not cutting the mustard for my meager MP3 system.