Lithium battery pack for house & electronics

The old (2017) battery bank in WF gave up the ghost two weeks ago.  It was made up of two 6V batteries that each weighed around 60 pounds.   Since I have an electric motor (48V) I wanted to replace the 12v house battery bank with a 48V battery.    That way I have a backup power source for the motor.

The new bank weighs a lot less.  Maybe 100 pounds less.  When I took out the old batteries it definitely left the boat sitting higher in the water.  It may be my imagination but the boat feels a little lighter.  Has a little better acceleration.   100 pounds is a lot on an 1800 pound boat.

The 48v to 12v converter outputs a steady 11.8v to power the chartplotters, lights, autopilot.   My autopilot uses around 1 to 2A on average so it is well within the 30A max.

It powers the outboard (epropulsion spirit evo 1.0) full range of throttle.  On average I cruise at around 350W.  With just this 20Ah battery that will give me around 3 hours additional time.   I’ll probably add another 20Ah pack now that I have some confidence in it.   This will give me a backup and additional hours for ocean day sailing, just in case.   

The battery monitor I bought (listed below) detects the watts of the motor pretty accurately.  I doesn’t do a good job on smaller draw items such as chartplotters.   I ran for around 3 hours and the volt level on the battery barely budged.   Started off around 53.2 and ended up around the same value.  Just chartplotters, wind sensor, speed/depth sensor.   20Ah / 48v may be all that I need for this day sail racing boat.

My notes on the battery pack build: