Trailer yacht charging

Hi,

I have got a 25Ah Lithium Lifepo4 battery on my trailer yacht, used for a chartplotter/depth sounder. I might install some basics like nav lights and VHF eventually too.

I have a question on charging. I have a choice of alternator charging (12V 5A) and/or a small solar panel (~40W).

What would I use to connect these power sources up to the battery? Is there a device that will handle both? It will need to be able to charge the battery while the plotter (and other loads) are switched on.

Keen to use Victron and preferably something with Bluetooth - I love the AC charger and Android app that I’ve got.

Hopefully a not too complicated question but I’ve got confused about solar controllers and dc chargers etc having done some reading.

Many thanks.
Chris

The solar is easy, use a Victron SmartSolar MPPT 75/10, good for up to about 150W of solar.

The alternator is more difficult. For alternator to lithium charging you need the alternator connected to a lead acid battery, say 10Ah in your case then you have a DC to DC charger between the two batteries. The smallest of these is the Victron Orion-Tr Smart DC-DC Charger Isolated 12/12-18 good for 18A, you may be able to reduce the max current.

Thanks, so there’s no way of doing it without a lead acid battery?

The manual for the outboard/alternator says the minimum battery is “12V
40Ah/20HR, 330 Cold Cranking Amps (CCA).”

I was hoping there would be a way of using the Lithium battery without the lead acid, to save weight.

Glad I asked now as that could radically change my approach.

If you connected the alternator directly to the lithium and the lithium battery got fully charged and the BMS disconnected the sudden loss of load can over voltage the alternator and damage it. There are non Victron devices for
a. Direct alternator to battery charging DC to DC that do not need an intermediate lead acid battery.
b. Alternator protection from load dump.
c. Lithium batteries designed for engine start service, perhaps these are capable of direct supply from an alternator.

Thanks pwfarnell, in that case I think it’s going to be easier to use a solar charger. Good to know before I buy the engine.