Design Help Wanted: Flashlight to Jumpstart Your Car.

Flashlight Modding and DIY Parts
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In my old Cavalier (RIP), I think I got 12yrs or more just from the come-with AC-Delco battery.

After that, I pretty much just bought boneyard batteries and milked them for 4-5yrs or so, each. Never a problem starting. After running even a short time, a fractional-second “crank” would start it right up. From a cold start, like overnight, about 1-2sec or so max.

That little donk had 9.3:1 compression, too.

Then again, I stuck on the biggest alternator I could. 78A? Only the 105A was bigger, but even then was available only with something like the cold-weather package from the factory. Only aftermarket racing-type alternators (Pro-Master, etc.) would have more oomf. Then again, they’d fit where a standard 12SI would fit, but mine had a slightly different mounting-ear, so couldn’t go that particular route.

It’d always kick out 14.5V except when heavily loaded. An “in-warranty” alternator I got was the smaller 65A alternator, and that’d start out at 14.5V for a few min, then drop down to the customary 13.8V when it’d heat up. Think that was the first time I had battery woes.

Someone mentioned to me that big rigs go through batteries every 2-3yrs or so! Dunno if that’s true, but the “secret” to longevity was to keep them as fully charged as possible. And from my own personal experiences, that seems true.

Someone who “did something” to his rig, tweaked up the alternator voltage or something, installed a second alternator, forgot what it was, claimed that he could then get 5-7yrs instead, doubling his usual battery-life.

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For the record, I had a 0-5V (1mA@5V) analog meter with a scale of 10V-15V. Perfect! 9.6V zener diode in series with a regular 1N4004 dropped an almost perfect 5.0V (drop was only about ~0.5V @ 1mA). Aluminum box, lighter-plug, 24/7 voltmeter! So I could see in realtime down to a tenth-volt what the rails voltage was.

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Yup and it really wasn’t until the last few years that most cars have had the electronics to monitor every circuit for unexpected drains and shut them down. My 2006 Subaru doesn’t and there are many domestics which didn’t until recently. While I have both flashlights and jumper packs in my car, I probably wouldn’t be interested in a hybrid device either, because it’s not likely to do either jobs very well. Knowing the kind of current it takes to start a car and packing that kind of power in a sealed metal tube would give me great concern.

I have used and tested lithium based jumper packs from $40 to $100 dollars and they’ve all worked when needed, even after sitting unmaintained in the back of the car getting hot and cold over the seasons. Sure most of us living in the city can “generally” rely on a cell phone to call for help, but for some the inconvenience of waiting and the cost of even a single rescue is more than enough to justify the small cost of buying one or even two. Another thing about jumper packs is that you can still be a good samaritan and help someone else in need without potentially jeopardizing the electronics in your car by using jumper cables.

KuoH

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@Lightbringer, yea those old cars had huge starters that were overkill. They were dangerous to bench-press from underneath :smiley: Those were the good old days. Now in the new cars the starter fits in one hand and is just-big-enough.

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Well nowadays with better (stronger) magnets, they can make them physically smaller. Same with alternators. As long as they can start the engine in a second or two, they should work. Most starters are just hugely overdriven motors anyway, meant to have an extremely small duty cycle, and not crank for more than a few seconds. Like using an LED as a flashbulb by firing through huge amperage for lots of light but before it cooks itself to death.

My LaCrosse has I think a 130A alternator for all the electronical doodads. Doesn’t look much bigger than an old-timey 12SI.

And whups, misspoke. It was PowerMaster, not Pro-Master. Been a while…

Point being, even the top-of-the-line racing-style alternators of the time couldn’t come near 130A without being physically huge and very thoroughly cooled. Or just suffer premature death. My Regal’s alternator is even smaller than a 10SI, but the case is almost a squirrel-cage and exposes lots of nice shiny copper, so it’s got pretty nice ventilation and cooling potential. And that’s over 100A (but forgot how much).

Anyhoo, as long as the critter cranks easily enough, physical heft shouldn’t matter. Trying to crank a huge diesel in winter will obviously take a way bigger/stronger starter, and need a way beefier battery to do it, than a little road-rat would need.