Replace lead house battery with lithium on boat with 2 engines and 2 alternators and bow thruster

DIY
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1

Hi,

I reviewed many of the example schematics on the victron homepage, but didn’t really find something that is close enough to my situation, which I thought is pretty much standard. But let me explain what I am trying to achieve and what the situation looks like.

What I want to do is simple - replacing the Lead Acid house batteries (2x140 Ah) with a victron lithium 300Ah.

What I have on the boat is:

  • 2 engines with an alternator each - one is at the moment charging the house batteries the other is charging the starter batteries (all 12V)
  • in addition I have a bow thruster with an extra 140Ah lead battery in the bow. This is charged with one of the alternators, not sure yet which one it is
  • I have a MultiPlus 12/1600/70 that is currently charging the house batteries and with the trickle output the statret battery. I want to keep it, but of course when lithium need to change the charging profile
  • I have a solar panel that is currently with a victron MPP charger charging the house batteries
  • I also have a BMV.712 battery monitor

Now my problems/challenges

  • I need a BMS, this is clear, but when I use the 300Ah NG, in the manual is is once written it must be a Lynx, but then it is also written it could be also a VE.Bus BMS NG. I didn’t really understand teh difference, but the Lynx is 3-4x higher price - Any suggestions ?
  • I need a DC-DC charger for charging the lithium by teh alternator, but I also understand that this DC-DC charger needs a lead acid battery as a buffer and here comes my problem: - In most examples I found, it uses the starter battery, but as in my case teh starter battery is connected to a different alternator, I would keep this that way and would like to use the other alternator for charging house. As I have also a bow thruster battery, my thoughts were then to use the bow thruster instead. However, the downside would be to have much longer cables from DC-DC charger to bowthruster and back - the boat is a 37ft onw and I guess it is around 10m (which is the 20m as you need to count both directions) - I am sure I am not the only one with a very similar setup, yn recommendations and thoughts ?
  • and then a more simpler one - whcih DC-DC charger to be used - the older models Orion TR - or teh Orion XS, and isolated versus non isolated

regards,

Peter

2

I would modify or replace the alternator by creating an external field connection.Then add a regulator such as wakespeed.

Then use the lynx bms add a cerbogx for system control and monitoring and use the dvcc for the wakespeed and mppt controllers.

3

thanks for your response. Maybe I missed to say, that I want to make it also with optimized budget. Changing the alternator and using a wakespeed is already quite a high cost as far as I know. The Victron DC-.DC charger are much cheaper than the wakespeed. But maybe I am wrong here with the price point, do you have and idea about the prices of your suggested solution?

But yes, it would solve my second problem what lead battery to inlcude in the dc-dc-charger circuit.