Charging Lithium With an Alternator

Question:

Hello, I am working on a racing sailboat. The boat is being optimized for double-handed and single-handed offshore racing (Pacific crossing). The boat is equipped with solar panels and a fuel cell, we want to stay away from charging the batteries with the engine as much as possible. We do not want to use AGM and in order to optimize weight and performance, lithium batteries are being used (most likely 2 x 100amp Victron). the engine is a 20 year old Yanmar 1GM10 and the alternator is 35amp. Is it possible to use the alternator to charge the lithium batteries (as a backup if neither the solar panels or the fuel cell were able to do so)? Thanks a lot for your input!!  - Jerome

Answer:

Hi Jerome, in short, yes. With the use of external regulator connected to an alternator, you can charge a Lithium battery. Once a Lithium battery gets full you’ll need to instantly stop the charging, hence the external regulator. Also, your alternator will most likely need to be changed for a more robust continuous-duty alternator. Otherwise your alternator will wear out prematurely.  - Jeff