The yacht has two 12V lead-acid batteries with different chemical and electrical characteristics: one starter battery with can provide a high curren but has a low capacity and a service/"house" battery with high capacity which allows deep cycles. The system are completely independent. The starter battery is only connected to the engine and exclusively charged by the alternator. The alternator is an old-fashion, regular alternator which constantly provides 14V. The service battery powers the cabin and navigation lights as well as the radio. A PV panel with 54V system voltage and an old PWM solar charger. Currently, there is no option to charge any of the batteries from on-shore power.
The setup shall be upgraded. Both batteries shall be charged by the PV panel but kept separate otherwise as they are different in chemistry and purpose. An option for on-share charging shall be added. The PWM charger shall be replaced by a MPPT charger.
If possible, I would like to keep the batteries and the PV panel in a first step and maybe replace the batteries in the future after they are will be worn down.
I have several questions:
- In order to charge both batteries, I need a DC-DC charger such as the Orion-Tr Smart DC-DC Charger. The manual suggests that the charging direction should be from the starter battery to the service battery. Why? Intuitively, I assumed that it would be more efficient to connect all chargers (on-shore AC charger, MPPT solar charger) to the service battery and the charge the starter battery from there. Most DC loadS which constantly draw power are connected to the service battery, while power is drawn from the starter battery only during engine startup. Hence, I guessed that it was beneficial to have power input on the service side, too.
- In theory, I could also connect the alternator to the service battery. Recommended?
- The alternator does not consider the SoC of the battery, but constantly provides 14V. Is it advisable to put another DC-DC charger between the alternator and the battery such that the battery is charged more "gently"? Or is the superfluous luxury?
- I found the Smart BMS which in theory seem to provide which I intend to achieve with the extra DC-DC charger. However, the manual explicitly states that the Smart BMS are designed for the VE LiPo batteries. Are the Smart BMS also compatible with lead-acid batteries as house batteries?
- How do several, different chargers interfere with each other, when they are connected to the same battery and all intend to charge the battery at once, i.e. the MPPT solar charger, the AC on-shore charger and the alternator (possibly decoupled via a DC-DC charger)? Are the "intellegent" enough to avoid any negative side effects?