Alternator amp rating.
If its real low, yes it will try to max out the alternators output. I don't know the the limit on charge demand, maybe it won't take 100 or 200 amps but nor will the fusible link... ha!
My observations have been that after extended cranking the battery might draw 10 to as much as 25 amps at the beginning of recharge. In a few minutes it will be down to 5 amps or less.
When a battery is really run down from something like leaving the parking lights on all day, then the battery will try to draw 30 or more amps. That's when its best to let it idle and keep the speeds down when driving. Because yes, as soon as the rpms come up even stock type alternator can deliver 35, 40 amps or more - and if nothing else is on - then everything but what is needed for ignition is going through the ammeter to the battery. When I've had to do it, I've turned the headlights on and shifted in N at every opportunity. The other bad thing about so much current to the battery is the battery gets hot - worse the AGM types. Hot battery doesn't charge as well and can also boil off battery acid. So 15 -20 minutes of even that much is really the limit, some would say too much. Let it cool down and it will charge a heck of a lot better the next round.
With a battery charger, there's generally a lot more control. Get it going and see the current draw, if its too high, cut it back a bit so it doesn't get hot. I took some pictures last time I was using an old charger. This one originally had a thermostatic probe to stick in one the cells. Lets see if I can load up the sequence.
OK. Here we go.
Turned the dial up 'til my voltmeter showed 14.2 Volts across the battery's terminals - typical system voltage for most vehicles. Then notice the current draw.
So after a minute, I cut it back to 13.3 Volt and its 10 amps. OK, that seems reasonable.
If its real low, yes it will try to max out the alternators output. I don't know the the limit on charge demand, maybe it won't take 100 or 200 amps but nor will the fusible link... ha!
My observations have been that after extended cranking the battery might draw 10 to as much as 25 amps at the beginning of recharge. In a few minutes it will be down to 5 amps or less.
When a battery is really run down from something like leaving the parking lights on all day, then the battery will try to draw 30 or more amps. That's when its best to let it idle and keep the speeds down when driving. Because yes, as soon as the rpms come up even stock type alternator can deliver 35, 40 amps or more - and if nothing else is on - then everything but what is needed for ignition is going through the ammeter to the battery. When I've had to do it, I've turned the headlights on and shifted in N at every opportunity. The other bad thing about so much current to the battery is the battery gets hot - worse the AGM types. Hot battery doesn't charge as well and can also boil off battery acid. So 15 -20 minutes of even that much is really the limit, some would say too much. Let it cool down and it will charge a heck of a lot better the next round.
With a battery charger, there's generally a lot more control. Get it going and see the current draw, if its too high, cut it back a bit so it doesn't get hot. I took some pictures last time I was using an old charger. This one originally had a thermostatic probe to stick in one the cells. Lets see if I can load up the sequence.
OK. Here we go.
Turned the dial up 'til my voltmeter showed 14.2 Volts across the battery's terminals - typical system voltage for most vehicles. Then notice the current draw.
So after a minute, I cut it back to 13.3 Volt and its 10 amps. OK, that seems reasonable.
