Tell me about it. A year ago I bought the very same batteries for what I thought was a good price, now they are half that. Early adopters of any technology always pay through the nose.
Hello!
I have a Yamaha 30 with the same YSM12 vberth engine. I run a lead acid starter battery on the starboard side, a group 31 AGM as #1 house on the port side, and a second Group 31 #2 AGM house at the very stern of the port stern quarter berth in the area under the cockpit. That second house battery fits perfectly once you remove the wood panel and then put it back in place. I ran a pair of #4 AWG wires under the starboard side of the floor boards. It’s not obvious but you can do it. I used an old stay wire from some replaced standing rigging and it help lead it perfectly back under the floor boards with a bit of fishing to make the path work. That guage I believe works for the small Hitachi alternator but do your own calculations.
As well, like you I have solar. It's a simple tower at the stern of the cockpit that holds two groups of solar panels (140 + 200) for a total of 340watts via two Victron MPPT controllers. The nice thing is your solar is in the stern at the cockpit and it's close to your original switch panel at the nav table and the #2 AGM under the cockpit. Because you're drawing all your power for accessories like navigation during the day from the original panel I run solar into that panel versus the whole length of the boat to the #1 AGM in the v-berth. So no daytime line loss on solar from #1 AGM to the panel. AGM House #2 is dedicated to the freezer at the stern so I don't screw it up and run it low... but you can group them together as you wish. I can go away for two weeks with my ICECO 42 litre freezer set to -20c (0 F) and it handles it no problem. You can eat for two like a king. That’s in the summer with warms temps in the Pacific North West.
AGM and Lithium have the advantage of quick recharging when the sun shines so both will take max advantage of sunlight and get that done. If I did it again I’d likely go Lithium because the price is improving and you're carrying more capacity via depth of charge. there's some likely extra costs with an upgraded alternator so it might be more than i think. But AGM is all you need.
Note well that the Hitachi alternator on the YSM12 is only 35amps. Not much.. It has some decent overheating protection by quickly self limiting that takes it down to 22 amps . Apparently its quite conservative on temp. Still, it would be a good idea to up your alternator defence with Lithium to avoid some risk of burning it out. And that is the risk with Lithium that will take anything a alternator can deliver up to 80-90% capacity of charge, and run the alternator too hard.
There’s a new product by Victron that is a 50amp variable Dc to DC charger that might fit the bill dialing in and modulating a more modest demand from your alternator to charge to your lithium. It's expensive but I think it might be ideal for a lithium setup. (I don't have or need one with my AGM setup). You only have 10hp continuous so you can’t put a huge alternator on there. I have also read to get enough tension to hold the physical demand on the belt of a very large alternator is hard on the main crank bearing at the pulley. Not sure if that's true but worth looking in to. So a decent solar array is good bet and additional solar is inexpensive compared to all this battery stuff.
My setup is a 200watt solar array feeds the house #2 and is dedicated to the freezer. The 140 watt array is dedicated to everything else on AGM #1. I use a Victron Fet three output battery isolator to charge all three batteries (one lead acid and two AGM's) at a traditional Lead Acid setting if solar isn't enough. And the solar panels are set for AGM setting - that tops up the AGMs later to the AGM spec charge. It works well. If you went lithium you may have to change the alternator etc.
I hope that helps. It's my own experience so confirm any of this with your own research and a pro. Look for Jeff Cote at Pacific Yacht Systems... he has about 400 videos on his channel to talk about yacht electronics and electrical setups.
see you out on the waters of the Pacific North West.
All the best!
Cheers,
Peter
www.altestore.com
