Re: Converting my Amel 54 to lithium batteries: what I did, what I like and what I don't like (after one year of full time live aboard use)
Scott SV Tengah
Good to hear it's working out for you. Have you tried to run AC all night on battery yet? We draw 25-35% if we run just aft AC overnight.
For your Mastervolt alternator regulator, I had the same problem and solved it with a solid state relay and two Hella relays. See #50689
We charge with 200amps nominal (120a Quattro + 80 a Skylla) and only see high temperatures at the very end of charging (95% SOC +) or if one of the cells is severely imbalanced relative to the rest of the cells in the battery. Note that this imbalance shows up as a voltage difference, but due to the flat charge/discharge curve of lithium, you won't notice it until 90%+ SOC. Can you monitor cell level voltage? With the Victron batteries, you can connect via bluetooth and do just that.
Also I'm surprised you can't change charging current via VictronConnect on your PC. I typically connect to my Quattro using ethernet, but I connect to my solar controller via bluetooth (from my Mac) and can change everything via bluetooth.
Keep in mind that you will need to revise how you think about SOC and longevity. Lithiums do NOT like being kept anywhere near full. I try to cycle mine between 40-85% (ideally no more than 80%) SOC and then charge it up to 100% once a month to balance out the cells, since balancing only occurs on the Victrons when they're nearly full. Independent literature indicates I'll get over 5000 cycles doing this. I know some who take it between 10-100% SOC daily and have been fine for a few years, FYI.
Monthly charging to 100% also resets the BMV-712 battery monitor. Not sure which BM you have, but don't forget to change the settings on it to match lithium. Of course, you MUST set all the chargers to lithium profiles otherwise you will kill the batteries very quickly.
So you've been thinking about charging cutoffs - how do you deal with low voltage cutoff? As mentioned in that post, I opted not to use the BatteryProtect, which would disconnect loads when there's a cell low voltage condition, but rather I'm trying to get the Victron charger/inverter to trigger the generator to start when cell low voltage and/or low SOC is encountered. Sounds like you're an engineer - want to help figure that out? :)
2007 A54 #69