Here's a goofy way to look at it.....
It's really no different than a kid's money.
The size of your alternator is like the allowance.
The capacity of your batteries is similar to the size of your piggy bank. The piggy bank has a maximum amount of change it can hold. The batteries have a maximum amount of amp/hours it can store.
Your electrical accessories are your spending habits.
Some spending is large, but infrequent. Like winching, stereo bass hits, etc.
Some spending is consistent like lighting.
If the kid is spending money non-stop, then the piggy bank will eventually run out because the allowance can't keep up.
If the kids has a reasonable allowance and a big piggy bank, occasionally he can safely splurge on some big items.
My point is, that most electrical loads are intermittent. The alternator doesn't have to keep up with them real-time. The batteries have the capacity to supply 400 amps to the winch for a few minutes, and then has an hour to charge back up. The stereo may be hitting bass, but it's only a few notes.
Basically, if the sum continuous amp load of the accessories is higher than the alternator's max output, then sure, at some point your batteries will be discharged. A bigger alternator fixes that. But loads like that are really uncommon.
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