Upgraded to a lithium battery

I'm curious if anyone in the forum has upgraded to a lithium battery. In my Hanse 325 from 2011, there is a Cyrix-i battery combiner that prevents the starting battery from charging the house battery when the voltage is below a certain level. I am considering replacing this with a Victron DCDC charger. However, I'm unsure whether to choose an isolated or non-isolated version. The electrical drawings indicate that the house battery and starting battery are connected to the negative busbar (MET0016) (see picture below), suggesting that a non-isolated Victron DCDC charger may be sufficient. The poorly labeled cables on my boat make it challenging to confirm this. I have not been able to locate the negative busbar, so if someone could explain its location, I would greatly appreciate it. I am interested to hear if anyone in the forum has undertaken this task and can offer tips on connecting a lithium battery on their boat.

Thank you for your response, many good points here. To answer your questions:

1. I have a 150 AH AGM battery that has worked fine, but I have been somewhat conservative in terms of the equipment I use. I use the refrigerator minimally, have limited use of the autopilot, etc. So, I was thinking of installing a 150 AH lithium battery to enable me to spend a few more nights in remote anchorages.

2. I use the engine as little as possible, only for going in and out of the harbor.

3. I have a fixed 50 W solar panel and a portable one that I believe is 100 W. But I rarely get 150 W out of them.

Some questions:

1. Where did you mount your DC/DC charger? I am considering installing my under the seat along with the battery. Is your also a Victron 12/12V 30A? How is the heat generation compared to the shore power charger?

2. Did you connect your the DC/DC charger as shown in the drawing below?

The dc/dc controller on my boat is installed under the nav table. I made a vent hole in the fiberglass and covered it with pretty vent cover. This upgrade improved performance by a lot. before, i had it in a closed location where it was getting very hot and reduce output.

This modification is very important for the performance of the DC/DC controller.

I notice a challenge in my setup that seems to be resolved in yours by moving the 120V to 12V chargers for shore power to the side where you have the starter battery. Is that correct? - Yes correct. DC/DC senses high voltage and turns on charge mode. Also, in Victron has ON/OFF jumper which I connected to external switch. Sometimes I dont need/want to charge the house battery. this switch allows me to turn it off completely.

When you did the modification did you reroute the positive from the shore power to the starter battery side? - My boat came with 3 battery bank charger (10amp i think). All i did is I disconnected everything but the starter battery charge. Shore power charger doesnt know anything about DC/DC and the same visa versa.

The pink square that you have connected everything to is that a distribution panel? -No. This is the two battery on/off switch. Mine is made by BlueSea but there are many of them.

Did you set up the DC/DC charger in a specific way to ensure that the starter battery is fully charged before the house battery is charged? - No, not really. DC/DC does not know much about my starter battery. it only know what voltage to look for when begin charging. When alternator or the shore power is working, the voltage on starter is at >13.1

That i also use for starting the engine (30hp)

I have kept it simple and it works fine 

Solarpanels are rated 270w in total 110w each side alonge the ligeline and 50w on doghouse 

I have the fridge on all summer and when sailing I use the autopilot and a 12” plotter 

Upp until today charging PC and cellular 

Still batteries are topped by solar each day 

Regardless bad weather in last autumn tend not to totally keep up running every thing on only solar’s but still keep the fridge working 

The cutoff circuit is set for a slightly higher voltage so starting engine is not a problem only a push button to bypass 

Never a issue