I might just do that. Redundancy is my friend...
I'm still stuck on the general problem of wanting the smart battery charger to be able to charge the batteries from time to time but it seems like any battery I put the generator's alternator on is always going to see the 14.5V and won't get any benefit from the smart charger.
I was more worried about the alternator immediately bringing the electrolyte up to 14.5V and tricking the "smart" charger into thinking all is well and going into standby mode.
We need to stop being paranoid with all the myths and lore that surround charging & "confusion" of charge sources...
Generally all charge sources go to the house bank. All sources are voltage regulated and thus if one charge source can maintain 14.5V then you clearly don't need the others. There is no "confusion" as I have seen it referred to in the past there is only voltage superiority. If one charge source has the slightly higher regulation point the others will simply drop off the system. If they were needed the high volt source will not be able to maintain it and the others will simply kick back on..
If a battery immediately comes up to 14.5V it is either:
A) Sulfated
B) Not as deeply discharged as you thought.
Another related question is, would there be any benefit to putting both alternators on the house bank? If they're both on at the same time would there be additive effects from them?
MedSailor
Yes the benefit would be additive, in bulk charging, which is where you want it to be additive. Once into absorption the alternator with the lowest voltage would simply drop out of the charge loop and the other alternator would continue to charge. If that alt could not maintain voltage the other alt would simply cut back in until one source could maintain it.
Even if it did have it's own starting battery, it would still be confusing the smart charger I would think... I want the smart charger to have a chance to do it's magic of float charging etc.
If you are cruising, and your charger has gone to float, off the genset, you are simply wasting fuel and lightly loading the genset..... If anything you want
extended absorption charging after multiple cycles of partial state of charge to help shed some sulfation.
Float is really for dock side use, solar or a loooooooong motor run but you would need an external regulator to accomplish this.
For a boat with a genset there are 80 ways from Sunday to wire it. I never complain about keeping or adding a genset battery. You don't need anything more than a group 24, 27 or 31 deep cycle. Feed its alt directly to that battery. Use a cross connect switch so the rest of the boat could be fed from this bank in an emergency or the main engine could be started from it..
I would use a Blue Sea ML ACR for this, the one with the yellow manual override switch and remote control switch.
Feed all other charge sources, including the shore charger, directly to the house bank bus and allow another ACR or an Echo Charger to feed the main engine start battery.
In any system with multiple banks we want
Redundancy - Each bank on-board should be able to serve all purposes if the need should arise
Isolation - Each bank on-board should be able to be 100% isolated in the event of a failure.
For general running leave the genset ML-ACR to OFF. If you need the extra boost from that alt into the rest of the system, on top of the engine and charger then simply activate the ML-ACR... Otherwise the genset alt will always keep its own battery charged.
You can also use a single bank for
starting both the main engine and the genset but for the added weight of a dedicated genset battery, on a Nauticat, it is probably worth it......
The ultra simple system would be two banks...