DIY alternator generator build, one-wire alternator, Predator 212 alternator, 12V battery charger, off-grid power setup, alternator pulley ratio

Here's how to build a high-amp 12V battery charger from a junkyard alternator and a small engine. A GM Delco 10SI or 12SI with a $10 self-exciting regulator becomes a one-wire alternator, so it needs only one cable to the battery. Car alternators are only about 50% efficient, so 100 amps at 14 volts takes about 3.75 horsepower. A 6.5 HP, 212cc engine like the Harbor Freight Predator handles that easily. A 2:1 pulley ratio spins the alternator near 6,000 RPM. Parts list: a 60 to 100 amp alternator, a 5 to 7 HP engine, pulleys, an adjustable V-belt, a steel base plate, heavy-gauge cable, a fuse near the battery, and a volt/amp meter. Run it outdoors, and always use a belt guard.

00:00 Why buy a generator?
01:00 From dynamo to alternator: Chrysler's 1960 breakthrough
02:20 How a car alternator works
03:15 What a junkyard alternator costs
03:36 The $10 one-wire regulator trick
04:28 How much engine you really need
05:10 Pulley ratio and alternator RPM
05:52 The generator spec most people never read
06:45 Alternator vs generator charging efficiency
07:15 Downsides of a DIY alternator charger
07:52 The lithium battery mistake to avoid
08:32 Parts list and build tips
09:25 Best use: solar backup charging

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