Finalish Sailboat Build/Design choices/build.


Solar Enthusiast
Apr 8, 2020
After lots lessons learned, I figured I'd talk about my latest build changes in my 46 foot sailboat.

#1: 24V Inverter/solar battery pack.
The solar pack is a ~600Ah 24v lifepo4 pack. Its managed by a REC Q BMS, which talks canbus to my victron Cerbo.
The REC has a pre-charge controller with a optimizer contactor for pack disconnect.
The inverter is a Victron Quattro 5000/24. All of my 120 passes through it today, but I do have a couple of pre-inverter breakers that I could utilize if I wanted some different inputs. I have yet to add a dedicated generator line to it, but it's tempting to put a hook up on the bow so I could stick a generator up front if I really need it. (Shore is in the cockpit)
The pack is built from 305ah and 280ah eve cells. This is a bit of a cludge for now, but mixing tested cells gave me a 600ah pack instead of 300ah so I'll take it.

#2 Solar controllers:
I run three 540w solar panels. Each has a dedicated Victron 100|20 MPPT controller. All three are connected via VE.Direct cables to the cerbo.
These receive DVCC charge control commands from the Cerbo.

#3 WS500/24v Alternator
I use a Wakespeed 500 controller with a Balmer 94 24v/120a alternator. This charges the inverter pack.
It also talks canbus to the Cerbo GX so the BMS can command the charge rates.

#4 Dedicated AGM Start/Windlass/Winch batteries
I use a pair of Duracell AGM cells for diesel start, 12v windlass ops, and even 12v winch motors.
These are maintained by a dedicated 24/12 victron DC-DC charger. I'll probably add a second at some point as these have a 1+2 battery switch that allows for isolation.
I may add shunt based monitoring to these but with AGM, voltage is pretty sufficient and the #5 system has an aux monitor input for voltage.

#5 12v house lifepo4 pack
For house 12v - fans, lights, nav, etc I have a 300ah 12v Lifepo4 pack, managed by an overkill solar fet based BMS.
This pack is simplicity and works great. If voltage of the inverter pack drops enough, this pack kicks in. It provides a buffer for things like the bilge pump loads. It also allows me to drain the inverter pack to near empty while knowing I have enough 12v house power for a few days.
A BMV-712 provides appropriate alarming (the BMS monitors too but doesn't support alarms)
Charging is once again a 24/12 DC-DC charger. The charger can run the house by itself but adding the Lifepo4 after it adds some voltage stability and redundancy.

5: Loading - Optimize the AC unit.
I bought a 16k btu Vaiair air conditioner. It wasn't cheap but it has some amazing feature. It does have an app, which is total crap so far. Ignoring that, it has variable speed brushless motors and a variable expansion valve. That means that it can scale from 5k btu up to 16k btu. In testing (sans water pump) I saw it go as low as 140 watts! This should allow me to keep the interior of the boat somewhat comfortable during the day and over night. On weak solar days I'll probably need to kick the engine over or run a generator to boost the charge a bit.

Fun notes:
The cerbo gx is on my ethernet network and I can view status and control some items from my chart plotters. (Allowing me to check charge status while running the engine from the cockpit for example.
The bluetooth app on the JBD/overkill BMS allows for charge/discharge on/off controls. I like these enough that I'd be very tempted to add more 12v packs for redundancy.

I also have a dive compressor that'll run of my inverter. Math says a fill should take about 1KwH, which means I can be a supremely environmentally conscious diver!