In all of the Orion TR Smart mixed battery technology installation examples on the Victron website it is the lead acid starter battery that is connected to the alternator rather than the lithium bank. I am trying to understand the logic behind this to make sure that I am not missing some key point.
I am installing an Li /lead acid split system in a sailboat (12V). I have decided to have two banks; the LiFePO for the house/service systems and AGM for the high current occasional requirements (starter motor, windlass, thrusters, etc).
My charge priority is the Li bank as it is keeping the beer cold and running the navigation electronics, communications, autopilot, plus the inverter (coffee machine, microwave, washing machine….) My solar, wind and eventually hydro-generator will be connected to the Lithium bank via mppt controllers set to the Li charging profile.
My plan is to charge the AGM bank via a 360W Orion TR Smart DC-DC charger. I can set this to only connect when the engine is running, perhaps with an override should I ever leave the boat for long periods without running the engine and disconnected from shore power.
(NB I have two outputs my shore power charger with independent charging profiles so no problem with the Li/AGM mix)
My rational is that as the Li bank is the priority and will accept high currents in all states of discharge, then the alternator (engine revs. permitting) will always give its max. (approx. 100A) until the house bank is fully charged. This seems much better than prioritising the AGM bank which will take very little current as it is rarely less than 5% from maximum capacity.
If the AGM bank was connected as in the installation examples, the charging current to the Li bank would be limited by the Orion TR (30A in my case with a single unit).
Other than when starting, power is only drawn from AGM bank when the engine is running. The alternator has an intelligent controller that will be set to the lithium charging profile. This controller will derate and eventually switch off the alternator in the case of high alternator temperatures.
I add that as much as I would love to move the whole system to LiFePO to simplify charging and cabling, I am seeing sustained 700A+ thruster currents sometimes during 5s or more. As much as this current might be somewhat lower with Lithiums (as the voltage would stay up) I would still need to have additional Li batteries so that the BMS´s don’t shut down. The cost of the AGMs, Orion TR and some extra cabling seems small compared with one or two additional 100Ah Li batteries just to cope with the occasional peak current.
Does anyone see anything dubious here?
Thanks
