IT is correct with what he has posted.
The reason why ALTS over 85A require twin belts is for two reasons. Firstly, belts have a natural efficiency where slippage vs wear comes into the equation. The unit being driven by a belt may seem to be spinning OK, but if the load is too great, excessive wear of belt and pulley is taking place.
I get what the poster is saying re budgets etc, but one needs also to factor in the time of charging which equates to engine run time, resulting in engine wear, fuel use, noise and so on.
Then there is the charge into the battery bank. It is always best to try charging close to the charge limit of the battery type. It is not critical charging a bank with a low current, but getting a good hit stirs up the electrolyte and means you do not have to do an equalisation charge so often. Over charging is death to batteries. So do not use too large an ALT to do the work. ttt
All well and good when you have either no control over the alternators output (internally regulated) or your external regulator puts the alternator into full output. Belt wear will take place, slippage etc. Being able to soft start and build voltage/current means the output comes up over time, a little longer than full grunt but we are still able to get up to maximum current output within 5 minutes of starting and alternator has no slippage with a temp of less than 50deg which makes a system that will work if you know what you are doing. FLA does require a boot now and again but usually a 16v desulphating cycle. Leaving batteries uncharged for long periods and running them down below their recommended state of charge also builds sulphate on the lead.
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