I spoke to the owner of Balmar at a recent show. He didn't think mixing battery chemistries was a problem. He recommended running his high output alternator to the LiFePO4 bank with his controller, and then using a blue sea type combiner that connects the start battery to the system when voltage is high enough. I already have a couple renogy DC to DC chargers that I might reverse such that the house is the source and the engine is the battery that gets charged since I will have the alternators charging the house bank. That way, any time either the victron or the alternators are charging the house, the DC-DC will charge the engine batteries which are just regular starting batteries anyway.- Retaining a lead battery on the boat is good economy, as all old charging sources (solar, alternator, ...) do not need to be changed.
- Battery chemistry must NEVER be mixes/connected. All power generated (cf. above) should passe through a DC-DC device (and there are many other brands than Victron, not least Sterling-Power who have devices which handle 60A).
- A fully charged LiFePo4 battery has an output potential of 13,2V. So, charging can take place at all voltages between 13,2 and 14,6V. The latter is too close to harmful levels, so never go above 14,4V. The difference between charging with the low voltage and the high voltage is the time it takes to reach full charge (you can squeeze the coulombs faster into the battery when you apply a higher force = higher voltage).
Sorry if above repeat some points stated before in this thread.
Someone talked about why you would want to combine technologies? For one LiFePO4s are not to be used as a starting battery as the starter can pull a whole bunch of amps. Or at least my LiFePO4s are not to be so used.