Generator only systems - Separate from legacy solar

[mr_rob]

Is anybody just using a generator and lithium solution whilst keeping their old factory installed solar?
E.g. an ex charter boat with a 5kw generator, connected to a 5KWH lithium bank.

Maybe even a 48v LIFEPO4 system with a 48 to 12v conversion to back up the old 12v system.

I'm thinking if one already has a generator, perhaps this is a cheaper solution than investing in solar panels and MPPT/12v charge controllers and all the fat heavy cables associated with that.

Would perhaps a Victron Multiplus 5kva work? Ideally you'd probably want to get all your charging done in an hour at a 0.5-1C charge rate while you're running a water maker etc.

[Dockhead]

In my opinion, solar power (which we had on the previous boat) and lead-acid batteries go together like cookies and cream. Because solar can give the kind of finishing charge which lead batteries love.

Generator and lead batteries -- what I've had for the last 15 years -- is suboptimal. You have a choice of either not fully charging the lead batteries, or running the generator forever. And the inefficient charging of lead batteries means more generator hours. At least a little solar is very desirable with lead batteries.

Lithium? Goes with anything, because unlike lead, lithium is like a gas tank. Put power in, take it out, it doesn't care when you stop charging. And can take a much higher C rate.

This is great for a generator. Get your charge as a side effect of using the generator for some heavier load; store shore power or alternator produced power.

Lithium being much lighter and more compact per kWh of storage, and now much cheaper than lead, means you can have much greater storage capacity. My new system will have fully triple the practical storage capacity of my previous lead system. The more storage you have, the more opportunistic you can be about when to charge.

So in my view, solar, even if it's still great, is much less necessary, if you have lithium.

[GordMay]

Both, mr_rob, and Dockhead, make sense, in my, inexpert, opinion.

[Quadrille in JB]

With with a solar/MPPT setup you are not going to have to add heavy cables. With quality panels you’ll have higher voltage with lower amperage out. The only heavy cables should already be installed connecting your battery bank and the inverter.

[SailingHarmonie]

Despite the endless arguments there is no one system that is best for all boats, or all boat usage patterns, or all pocketbooks.

Many boats can not fit the amount of solar needed to be 100% fuel free. That is certainly the case on my boat. I have sufficient solar (600W which give about 3.25 kW-hrs/day) to supply half my needs, a 3.5 kW DC genset supplies the rest in about 90 minutes run time every other day in sunny topics. The solar is sufficient to fully top off the gel battery bank on days the genset runs.

This system has worked well for a long time. If I had the horizontal acreage, I’d have added sufficient solar but that can’t happen.