[We originally published this chapter back in 2016, but I have completely rewritten it to better mesh with recent chapters, so we are republishing it.]
One of the worst myths about lead-acid batteries is that charging them slowly is good for them. Let's deal with that and then dig into how hard we can charge them.
In the first Ohm's Law chapter, we learned that, even with a powerful charging source, we generally won't blow up our batteries as long as we don't exceed the manufacturer's maximum recommended acceptance voltage—typically around 14.4 volts (12-volt system).
Why? Because lead-acid batteries self-limit current (amps) by raising their internal resistance—the harder we push them, the harder they push back.
I'm writing about lead-acid batteries only. Lithium batteries are much less forgiving.
But even more importantly, not only will we not damage a decently-built battery by charging it quickly, testing at LifeLine has shown that charging at higher rates (amps) actually extends the life of their batteries—I suspect most others', too—since it reduces sulphation.
Another battery myth bites the dust.