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2 alts better than 1


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The beauty of two alternators is the redundancy offered, this is a good enough reason on it own. I've had a 120 amp alternator charging house batteries plus original Yanmar alt charging dedicated engine battery for almost 20 years and have never had a problem starting the engine. It's a simple system and 100 % redundancy you won't regret it.

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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

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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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Leaving batteries uncharged for long periods and running them down below their recommended state of charge also builds sulphate on the lead.

Actually, Sulphation starts as soon as the battery drops below full charge. The speed of sulphation increases proportionally to the level of discharge. The time that the battery is left below full charge goes into the hardening of the Sulphates on the plates. Soft Sulphate can be removed during a good hard charge. But once it becomes too hard, nothing will remove it. Nothing. Not even those charging devices that say they rejuvinate the battery.

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