To charge a 12V LiFePO4 from an outboard alternator charging coil, what product is suitable to regulate the charging?
Outboard: Manual start, Honda BF6, 12V 6A charging coil
Battery: Lithium (LiFePO4), 12Ah, max charging rate 0.8C (9.6A)
Watched the Victron Q&A Webinar 1 - Using an Alternator to charge Lithium video, and understand that since the battery has a larger C rating than the alternator, alternator current must be restricted using a Smart Orion or similar.
Victron Options Found
Using the VictronConnect app to check the interfaces via the demo mode. Nothing appears suitable:
- Phoenix Smart Charger IP43 12|30 has "maximum charge current" settings of 7.5A, 15A and 30A, the minimum is too high for the alternator.
- Orion Smart 12V|14V-18A Isolated has a LiFePO4 battery preset but no current limit settings (just voltage), and it isn't clear if it's ok with the variable output from an outboard.
- Blue Smart Charger 12|5 can limit charging to 2A or 7A, but is mains powered, and the 2A lower limit loses 4A of potential charging, while the 7A upper limit is too high for the alternator.
- SmartSolar Charger 100|15 can limit charging on a variable scale in 1A increments, but it's inputs are designed for panels only (MPPT controller won't turn on until incoming voltage exceeds Vbat + 5V. Thereafter the minimum PV voltage is Vbat + 1V), it's also unclear what the MPPT varying the exposed load will do to the outboard coil.
Non-Victron Options Found
- Sky RC B6 Charger + Sterling Alternator Protection Device this combination is promising. The B6 charger can tolerate a range of input from 11-18V, and 6A maximum output. SkyRC were unclear under what circumstances the battery would be disconnected, and so there is a danger of damaging the alternator by having the battery disconnected during engine running.
This danger can be minimised using a Sterling device that provides an emergency route for current in the case of disconnection or failure. Sterling device is waterproof.
The battery pack accepted in the spec of the B6V2 is 100-50000mAh (unclear what happens if the battery is over-spec). Also Victron members mention it being difficult to configure. It is not waterproof and so extra weather protection must be added.
Which Victron product will allow the charge to be limited to a safe current for the alternator?
I am in a 3m open-top inflatable boat so the system needs to be compact, light, and simple.
Update May 2022: added promising (unfortunately non-Victron) option
With the existence of the alternator protector, any charging product that can accept variable and lumpy voltage inputs of ~5V-18V while limiting output to 6A and disconnecting if overloaded seems like the perfect solution.