Mainship 400 going with Lithium I think?

[jefndeb]

Hello all,

I am planning to replace our 2 House 8D AGM 200ah batteries with 2 new Epoch DP12300H 300ah Lithium Dual Purpose batteries. Partially because our DC bow and stern thrusters are supplied from the house bank, (via the factory) which is really odd and I know it is killing these deep cycle batteries when blast them with a 525 amp draw multiple times on a windy day of trying to dock. Could you guys do me a favor and offer suggestions as to "where in the diagram" I would make the changes when I replace these 2 house AGM batteries to Lithium?...

I hand traced the wiring in the boat one weekend in order to develop a better understanding of the DC system and I created this Visio diagram for reference.

When I say changes, I say this because I plan to keep the one AGM 8D engine starting battery so think I have to modify the charging system somehow so the AGM battery is "isolated" so it is is charged with the correct AGM charging voltage and not the new Lithium charging voltage setting. Am I saying that right?

I know I can reconfigure the Alternators Balmar AH-5 External Regulator for Lithium and the Victron MultiPlus as well but understand that the AGM 8D shouldnt be charged with these new values..

I guess I am asking this...how does one reconfigure this system (add devices? DC to DC charger?) in order to charge both the new Lithium house bank and the AGM starting battery from the alternator with the correct charging profile...

your suggestions are appreciated...

 

[Clark]

I'm not seeing many replies to your post. It seems like there are a number of problems and questions with the schematic diagram. First, to get it out of the way, the fusing to protect wires seems to be missing is some cases. For example, the path from the house to the breaker panel has no fusing. Similarly, there's no fusing on the top bow thrusted to the first battery and on the bottom start battery to the alternator.

Second side point, I don't know if there is a normal position for the switches. Are the house batteries normally switched paralleled? Is the bow thruster switch normally open or normally closed, effectively paralleling the thruster battery with the house bank. Where does the negative from the bow thruster battery go, to the house battery negative so the shunt reads correctly when the switch is closed or to the negative bus so that the shunt read correctly when the switch is open. Granted, thruster doesn't use many AH, but it should be wired correctly depending on whether the thruster battery is part of the house or not part of the house.

Third, you have 4 charging sources here. Two battery chargers, a solar charger and finally the alternator. It is important to figure out what sources charge what batteries. Is the solar charger able to be set to charger the LiFePO4 batteries? If it is set for Li battereis then they will not be set for lead acid. ACRs from the Li to the lead batteries may not be good with the different charging profiles so maybe DC-DC 3 stage chargers, as from Victron and others, are needed. But then, they can also charge when inverter/chargers or solar chargers are running. Also, are all of the ampacities of these wires suitable for Li and do all the fuses have the sufficient AIC for a Li bank.

I seems to me that you would want to look at a redesign of the whole system based on what you want to accomplish. It is likely not going to be a simple cut and connect a wire here or there. What sources do you want to charge each battery? I recommend a GOOD marine electrician to design a system for you. Ignoring fusing, wire ampacity or the AIC rating can cause a fire, especially with Li.

A last small point, the stern thruster will cause a voltage drop when it is operated and it may cause sensitive electronics to drop out because of the transient, but it may not be damaging your house battery. I have 3 8D house batteries with a 650 amp steady state stern thruster and I have no concerns about battery damage. I would look at the battery CCA or MCA specifications and the thruster specifications to determine if they are out of align.

Clark

 

[SteveK]

This is just my opinion. Assumption single engine, one ALT.
1) I would not go dual purpose batteries, also with LFP I would not go 2 banks. Reason, with LFP house you can discharge to near zero when needed. The old system of two banks gave you a second chance if over discharged. If you have enough for needs, no worries.
2) keep the AGM start. I would add thrusters to it directly or switched and away from the house. I see you have a bow thruster bat, will that stay due to distance and line loss? Again with a switch in place I would move to the start battery as backup.
3) I would charge the new house bank from all sources directly and then charge the start battery from the house via DC2DC.
4) Not sure why you need an isolator for batteries OR how the ALT & Balmar regulator is wired to the battery. It should go direct to the house bank.

 

[DavidM]

David