The Misadventures of Quinxy truths, lies, and everything in between!


Moments of Clever – The Joy of Overcoming Minor Crises

There are too few moments when I feel like I get to apply anything like cleverness. With programming you certainly can, but it is always 1% extreme cleverness and 99% tedious plodding. This past Monday I got to be a little clever in the real world... It wasn't the extreme type, just a bit of very minor but satisfying cleverness. I was driving back from New England. About six hours from home the battery light comes on, indicating under-voltage. It was instantly clear the alternator was almost certainly the problem (or the rectifier/regulator within the alternator). The battery was losing charge. A car runs fine without an alternator, since the battery alone can power the spark plugs, fuel pump, lights, A/C, etc. while it still has charge. The car would run until the battery fell below 8-10v (at which point the spark plugs or fuel pump would stop working). So it was a race to see if I could make it home before the battery voltage dropped too low. Sadly by the time I saw the voltage problem it was already well below normal.

Now my car has a rather unusual device that I installed when I thought I was going to get into off roading more than I ultimately did. It has two full sized batteries rather than one, and they are controlled by a switch next to the steering wheel. I can run off one battery, the other battery, or both batteries. It was in the both position when the problem occurred, which meant that both batteries had been depleted before I knew there was a problem. But it still meant I had twice the watt-hours compared to a single battery. First thing I did was switch to the main battery only. That way I could keep going towards home and when that battery died I would know it and be able to switch to the other which would have enough to get me off the road and to a hotel or service station. A few miles later I realized I needed to conserve electricity to extend my range, so I pulled over and pulled all the most draining and unnecessary relays/fuses under the hood.  I killed my daytime running lights (which would be the biggest avoidable draw of current), killed my interior (door triggered) lights, killed the heating/ac, etc. Sadly I did a stupid thing and shut off the engine not knowing how long I was going to stop and forgetting that cranking the engine would use more energy than just idling for a few minutes. So when I go to restart I find the main battery doesn't have enough juice to start it up. I switch to the second battery, start the car, then back to the main battery to run until it dies (since the main could still power things once it was running).

About an hour later the battery needle has dropped well below 50% and the dash warning lights all illuminate, the battery is effectively dead. I quickly switch to the second and keep going. I realize I'm probably not going to make it but now I've only got about 3.5 hours left. I then come up with another solution to extend my range, I keep myself under-shifted, so that the engine is always revving ~30% higher than normal. I keep it in 4th gear doing 80 to keep the RPM up (but still far below redline), and keep in 3rd or 2nd when the speed drops for construction/traffic. Usually a failing alternator is still putting out something, albeit way too little, but keeping higher RPMs will help it put out more and slow though not reverse the battery drain. And on I went. The battery drain was non-linear, so I was doing fantastically well until I got within about an hour from home and then the voltage started to plummet. But, somehow I managed to make it home. I don't think I would have made it even five or ten more miles. The voltage was right where the voltage had been when the other battery stopped being able to keep the car going. The windows would barely roll up after I shut off the engine.

I love non-life threatening crises, they sharpen the mind wonderfully.  Whether it's car trouble, being locked out of your home, or what have you.

^ Q