In my boat I have a old multiplus(phoenix) set to charge my lithium consumer bank. I also have a Orion smart set to charge the AGM starter bank from the consumer bank, just to keep the AGMs in good shape when the engine is not in use.
Engine alternator is charging both consumer and start bank via a splitter. But when Orion is charging only starter bank receives charge. Could it be that the starter banks high voltage tells alternator regulator not to charge?
Is there some inverse engine shutdown detection?
Some other way I can have the Orion charge only when motor is not running?
Should I just forget about it all and get a newer multiplus with two charging outlets?
@THARAYMAN Boats typically have the alternator charge the house bank using an external alternator regulator. The alternator is directly connected to the house bank. The charge profile is set on the alternator external regulator. The important aspect of this is a temperature sensor to reduce the alternator excitation if the alternator body reaches 100 degrees C. This is required because typically alternators are designed to charge a start battery and not a large bank of lithiums. The alternator can overheat and be damaged if it does not have some temperature sensing.
The start battery can then be charged with an Orion. It doesn’t take much current to top up a start battery so the Orion is perfectly suited to that task. Often the start battery has a different chemistry to the house battery bank and that can be accommodated in the Orion.
The reason charging a house bank and a start battery through a splitter can be troublesome comes about through an interesting problem. Alternator outputs have ripple. The ripple is quite smooth with light load and quite high with high load. If the house bank has a low SOC, the load on the alternator is high. The alternator has high ripple. The empty house bank takes the peaks off the ripple but the very full start battery gets topped up to the very peak of the ripple. In this case during heavy charging the start battery voltage can raise high voltage alerts as it charged to the very peak of the alternator ripple.
A better plan is to simply charge the house bank off the alternator as described above and charge the start battery using an Orion.
Regarding your point about the newer Multiplus having 2 charging outlets, it really does not and it has some potential pitfalls with mixed chemistries.