Hi Steve, my thought is the alt will keep charging to the start battery at 14.2 volts or 30 to 40 amps while feeding the DC to DC charger until the Lifepo4 is full. There won't be a float charge for the start battery until that point. So am I boiling out my start battery on a 2hr run? We need a big brain ( Steve D. maybe ) to chime in.
Do you now have regulated charging on your start bank? In other words, does it now get a bulk/absorption/float charge with specific voltages? (I have an outboard motor, so I don't have a way to do that and hence am not up to date with eg Wakespeed, etc.)
On my previous set up, the house bank (FLA) would be charged thru an ACR after the start was charged
The way I understand it, an ACR doesn't charge the start battery "first" until it is full, and and
then charge the house bank. Rather, the ACR is basically a gate between the start and house banks. It can either be open or closed. The ACR looks for a specific voltage and when it sees that it opens (something like 13.6 volts). Basically, this signals the ACR that there is now charging being applied to the start bank (without charging a lead acid start bank would not be at 13.6 volts), so it's ok to open the gate.
Once the "gate" opens, both the start and house bank are being charged. The ACR can't charge the house bank without going through the start bank (at least in any setup I've had). So unless I'm mistaken, the start bank is also "seeing" charge voltage the whole time (though it is likely full and not taking any more). The ACR "gate" closes again when the start bank voltage goes down to something like 12.6 for X minutes. In other words, when there is no longer any charge being applied to the start battery, so the gate needs to close (so the start battery can't be depleted at anchor).
Unless you have some fancy charge settings between the alternator and the start bank? (Maybe you do; as mentioned above my charge source is not able to be regulated -- though of course it is now before it gets to the house bank after the Orion XS).
Caveat: I now have a boat with an outboard motor, so I am not able to use any fancy alternator regulators or etc. (eg Wakespeed).
I wonder if, once the start bank is full, it's acting more like a powerpost (or nearly so). I do know you have to have a battery on both ends of the Orion. In other words, it can't have an alternator hooked up to it directly on the engine end; but has to be hooked to both a source and destination battery.
Frosty
PS: Of course with an outboard motor, the start battery is always being charged, and always with motor output voltage, which is well upwards of 14 volts. In practice this doesn't seem to kill them noticeably prematurely, I don't think.
Be interested to hear what others have to say.