Adding a LFP4 battery to my house bank with a Victron Orion-TR DC-DC charger

Nov 25, 2021
4
Dufour 382 Cartagena
Hi all

I am adding a LFP4 battery to increase the battery house capacity of my boat (Dufour, 38ft, 2014). I would like to hear opinions about the setup I am considering

Current setup (mostly factory set-up)
- 1 Starter battery (FLA), 90AH
- 2 House batteries (FLA), 95AH
- 1 AC battery charger connected to Starter and House banks (independently) - 25A
- Mitsubishi 125A alternator (Volvo D2-40)
- 1 MPPT (100V/20A), connected to House batteries
- 1 Victron Inverter (500W)

Needs
I would like to add 1 additional LFP4 battery (Victron). Probably 100AH or 150AH
- reducing to the minimum the changes to the existing wiring
- since current house batteries are quite new, if possible I would like to keep using them

Plan
My plan is to maintain the current setup as much as possible, with the following changes:
- add the new LFP4 battery to the existing house bank, connected thru a Victron Orion-TR Smart DC-DC charger
- add a new Victron MPPT (100/20A), connected to the new LFP4, since I intend to install additional solar panels
- move all "services loads" (fridge, navigation, lights, etc) to the LFP4. This implies basically moving a single cable to the new battery (though a new busbar)
- I will keep the existing Victron Inverter and MPPT attached to the FLA bats

This is the simplified schema (no cabling, busbars, etc)
1638014016510.png



This setup is somewhat different to the usual scenario of a Victron Orion-TR, in which the LFP4 battery charges from the Start battery (and LFP4 becomes the single house battery)

I have read extensively all the info about DC-DC chargers in this forum (and others, like Victron community forums) and could not figure out any significant issue, but obviously I am not an expert. Any remark about this configuration?

Any remark about where to place the MPPTs? I am assuming that splitting my solar charging to both environments (FLA and LFP4) makes sense (in order to maximize energy storage), but I am not sure if this would have significant drawbacks. I acknowledge that I will need to find suitable voltage levels when programming the DC-DC charger so that I the charging of the batteries in the different scenarios (day/night sailing, motoring, connected to port, etc)

Thanks in advance and sorry for the long message
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
With all due respect to the very knowledgeable forum members, you would do well to consult with a professional marine electrician who installs LiFePO4 batteries and systems.

If you are going to use Victron equipment, a call to their tech support or pre-sale support folks would be in order to prevent expensive mistakes.
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
I agree with dlochner that calling Victron to check would be a good idea. Off-hand it seems like your plan for the DC-DC charger would be about the same type of situation as its normal use in a start/house bank system, but I don’t know if there are any nuances that Victron might caution you about.

The other thing I would consider is swapping the location of the LFP and FLA in your plan. Doing that would allow the LFP to service the higher amperage load of the inverter, and receive the higher charging amps from the alternator. The FLA could take the lower charging amperage and loads. That setup might better align with the strengths of LFP for higher charge amperage capacity and less peukert losses.
 

Johann

.
Jun 3, 2004
420
Leopard 39 Pensacola
It seems to me in this setup you are keeping the LFP full, which it doesn’t like, and cycling the lead, which they don’t like. I would consider exploiting the advantages of the LFP by putting both MPPTs to it, and reverse the Orion to charge the FLA, keeping all the loads on the lead and cycling the LFP while keeping the lead as full as possible.

Or look up hybrid banks. Basically just connect the LFP to the house FLA, connect the Orion to charge the hybrid house from the start battery when the alternator is charging, and configure all your house chargers for LFP. The LFP will do all the work until it drops to 20% SOC or so, then the FLA will begin helping out. Around 12.2v you’ll need to start recharging… the FLA will be around 50% and the LFP around 10%.
 
Nov 25, 2021
4
Dufour 382 Cartagena
With all due respect to the very knowledgeable forum members, you would do well to consult with a professional marine electrician who installs LiFePO4 batteries and systems.

If you are going to use Victron equipment, a call to their tech support or pre-sale support folks would be in order to prevent expensive mistakes.
Totally agree. I intend to purchase all the equipment to a local distributor so I expect from them some "official guidance", specially in terms of avoiding security mistakes. Thanks for the advice
 
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Bob J.

.
Apr 14, 2009
773
Sabre 28 NH
Why not just get rid of your FLA house bank? It would make life alot simpler...
 
Nov 25, 2021
4
Dufour 382 Cartagena
Why not just get rid of your FLA house bank? It would make life alot simpler...
Good point. That was the alternative. I guess I could just take out the FLA batteries out of the picture, but why should I discard 200AH of available and fully funcional energy storage?
 
Nov 25, 2021
4
Dufour 382 Cartagena
It seems to me in this setup you are keeping the LFP full, which it doesn’t like, and cycling the lead, which they don’t like. I would consider exploiting the advantages of the LFP by putting both MPPTs to it, and reverse the Orion to charge the FLA, keeping all the loads on the lead and cycling the LFP while keeping the lead as full as possible.

Or look up hybrid banks. Basically just connect the LFP to the house FLA, connect the Orion to charge the hybrid house from the start battery when the alternator is charging, and configure all your house chargers for LFP. The LFP will do all the work until it drops to 20% SOC or so, then the FLA will begin helping out. Around 12.2v you’ll need to start recharging… the FLA will be around 50% and the LFP around 10%.
Yes, this is the main issue. The way I am designing the physical layout, I can move the MPPTs from one bank to the other quite easily, just moving a cable from busbar to busbar. So my plan is to decide on the final layout once I see what is the usual benaviour

The alternatives I was considering were
1) both MPPTs connected to the LFP. In theory this would maximize the LFP SOC for each night at anchor. I think I would never consume more than 80Ah on a night, so the FLA would be usually idle
2) both MPPTs connected to the FLA. This would imply a lot of load on the DC-DC charger since all power consumption would have a direct impact on it
3) a split schema. Theoretically I would maintain the FLA at 100% in a sunny day, and in most situations LFP at 100% before sundown. FLA would ony have to provide amps to the LFP if for whatever reason the LFP battery was not 100%
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
The more complicated the system, the more points of failure. The more the system deviates from standard systems, the harder it will be to trace and identify problems.
 
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Bob J.

.
Apr 14, 2009
773
Sabre 28 NH
but why should I discard 200AH of available and fully funcional energy storage?
They are FLA so the reality is you have 100 AH of energy storage.
IMHO, for what you will spend in adding additional equipment to integrate LFP with your existing FLA bank, you'd be better off putting that money towards a larger LFP bank. In the long run this in itself will make life simpler.
 
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