2000 Ford Expedition Eddie Bauer - Bi-Fuel Gasoline/CNG
Intel D945GCLF2 w/512MB RAM, CL Audigy w/KxProject, M2-ATX, Lilliput EBY701
That can also happen if you increase current requirements, by adding USB devices or other components, upgrading the PC to something bigger, etc. The current required to boost is higher than the output. For simplicity, say double (plus some) the output amps at half the volts.
Also, the one bad thing about using just a diode with an SLA battery instead of an isolator is that when the battery starts wearing out or shorts a cell, it will drain your main battery. So keep that in check.
Hmmm. I'm trying to work out why it only happens for me sometimes. I figured there was a voltage drop on the 12v+ line the moment I cranked, because the engine needs the juice to start up. But my PC only resets itself sometimes, not every time, and I have not added any extra USB devices. The battery is the one that came with the car when it was bought brand new in May 2007.
The only time I've had trouble starting the car was when I had the car off and car PC on, and I used the car PC for about one hour (playing music, watching movie clips, surfing the web). Then when I cranked, the engine turned a little and the PC instantly switched off and didn't turn on. And then the engine would just make a clicking noise. I jump started it and it's been fine ever since.
So now I probably need to rig up that diode circuit and see how I go.
I agree - weak battery. (Or bad connections/cables etc.)
Usually in that case though if relays drop out, they don't pull back in - ie, 12V relay may pull in at 8V and drop out @ 5V.
But there are inductive spikes etc that can cause the relay to pull in.
You could try a different relay - a new one or one with a lower drop out voltage.
Or ensure good connections.
Or Curiosity's RC network, though ironically that's what we were trying to avoid in the first place.
I try to design for an 8V - 16V operational range automotive stuff.
Many systems won't work below 8V and many vehicles won't start that low either (no CPU, slow starter, no spark) - some not below even 10V. (Mine starts cold at 5.2V but is carby - not EFI.)
It's also a reason some use a 2nd battery for PCs etc.
I don't mind having the RC network but I'm not sure if it will fix my problem.
I'm using 16awg wire on the 12v+ line and this seems adequate because it doesn't heat up at all (perhaps the section that's close to the battery gets warm but that's due to engine heat, not a result of too much current on a thin wire).
I might have a look at the -ve connection because it might be a bit loose - I tied it tightly around a small hole in the chassis just behind the car PC when I installed it.
Assuming your carpc uses say... 4amps? That's 48 farads per second you want to run(iirc). That's ignoring the fact that towards the end if it, your voltage is going to drop to an unusable amount.
"stop with the REINSTALLS, what do you think we got some lame-o installer!!!" - mitchjs