Join Date: Jul 2008
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Re: Alternator for Volvo MD2030
Most FET-based isolators have a circuit that puts a low-current battery voltage on the alternator input so that the alternator can see a voltage to start with. If you are buying one, make sure it has this feature and wire the circuit to your house bank.
Cool, I also see that some have the ability to detect the switch, so this can be optional. I'm looking at the Argo 180-3AC.
Curious as to why you are going with an isolator instead of a combiner. I have been assuming you are charging a main house bank and a small start battery.
This is right. The house bank is LFP and the start is AGM.
With a combiner, you would not be holding the start battery at a high voltage for a long time waiting for the house bank to fully charge.
Using a diode based isolator will allow me to run the alternator with a charge reference controller (I'm planning a VRC-200). I'll take the sense from the house LFP bank to the VRC-200. Then the VRC-200 will cause the alternator to give me voltage appropriate for the LFP bank. The AGM will usually remain mostly charged so the current it draws should be low and the diode will then drive its voltage a little higher.
A combiner or DC-DC charger has limited current passing ability and someday I expect I'll want to upgrade the alternator so I can charge the LFP bank more quickly. This design should still be valid with a higher current (like 150A) alternator.