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Old 27-11-2021, 07:16   #1
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Adding a LFP4 to house bank with Victron DC-DC charger

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 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
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Old 27-11-2021, 07:40   #2
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Quote:
Originally Posted by luisglezi View Post
(Dufour, 38ft, 2014). I would like to hear opinions about the setup I am considering


- 1 MPPT (100V/20A), connected to House batteries




- add a new Victron MPPT (100/20A), connected to the new LFP4, since I intend to install additional solar panels
Please explain adding more solar panel, where you mount this panel. this is almost max solar panel size for 38 ft boat.
2x150W on arch,you cud putt little bigger solar panel but this is ugly
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Old 27-11-2021, 08:51   #3
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Today I have 2 flexible solar panels (2x160w) on top of my bimini

I am considering to install an arch with 1 additional rigid panels (150W)
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Old 27-11-2021, 10:27   #4
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Quote:
Originally Posted by luisglezi View Post
Today I have 2 flexible solar panels (2x160w) on top of my bimini

I am considering to install an arch with 1 additional rigid panels (150W)
For this flexible you need victron 10-15 A max
watch this
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Old 29-11-2021, 04:14   #5
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Quote:
Originally Posted by more View Post
For this flexible you need victron 10-15 A max
watch this
Agree. I guess I could save a bit by purchasing a MPPT 75/15 or 100/15 instead of a 100/20. The boat is relatively small so I don't think I will be able to place more than 3x160W in production anyway.

This is a topic for another thread i guess, but I am not happy with the flexible solar panels either. I have been running flexible for a few years on top of my bimini (just hesitant to spend big bucks on an arch and rigid panels). Results were not catastrophic but it is true that degradation is very noticeable after one or two seasons.

The initial reason for investing in a 100/20 would be to have enough capacity to perhaps go in the future for a simpler configuration of just 1 MPPT (Victron) servicing 2 rigid panels. At that point I might get rid of the non-victron MPPT
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Old 29-11-2021, 04:38   #6
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Why not put both FLA house batteries and the new LFP in parallel and use the best attributes of both chemistries to your advantage.

So during normal use the LFP4 charges and supplies power easily. Only when you are down to say 12.5v do the FLA take over and provide power. Remember the LFP4 will charge far more quickly than FLA which is super for when solar is a major source of power.

What will it look like? well both MPPTs directly to the bus bars for both LFP4 and FLA. DC>DC Orion from engine start battery to the house bus bars. Extra switch to remove LFP4 from circuit occasionally to give the FLA and really good charge and stir up the electrolyte. The DC>DC Orion charger gets really hot so must be mounted in a well ventilated area. I have recorded 59'c and that is with a hole behind the cooling fins. The MPPTs can go anywhere but closer to the batteries is good as the cable from the MPPT to the batteries might be a different size from the cable connected to the solar panels.


We have been doing this all summer and it works really well. The -72A draw is the kettle being run at night time. During the day its low 60s as the solar contributes some power.

Pete
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Old 29-11-2021, 12:12   #7
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Thanks, a very interesting suggestion. I will take a look to try to understand the implications (although in my case a main constraint is that I want to avoid as much as possible changes to the initial wiring)

I am also concerned about the heat dissipation of the DC-DC charger. Many reports from dissatisfied customers in the Victron forums. I am placing all new components of my system (DC-DC charger, MPPT regulator, LFP4 battery) as well as the old ones that I am moving to a new place (Inverter and the other MPPT regulator) on a panel in one of the aft cabins, to maximize ventilation, but I am not happy to have equipment at 60+C on display
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Old 29-11-2021, 12:27   #8
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

There was a recall for earlier DC>DC chargers, need to check mine.

I moved our house bank as part of the installation with a new fuse box for the supply and use connections. This was quite an eye opener as the wiring from the original alternator was tiny so replaced that. Then found with all the additions over the years, the supply to the original distribution panel also needed upgrading, so worth doing.

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Old 29-11-2021, 13:23   #9
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Have a look at this, he explains it better than me:

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Old 29-11-2021, 14:08   #10
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Awesome video. Specially because this approach seems to have been tested

Still I think that keeping a DC-DC charger between LFP and FLA sounds even more safe than having just a big resistor to balance voltages, but I am happy to see that a hybrid approach is possible rather than a "dump FLA to keep things easy"

Actually what this tells me is that I could move all my mppts and my inverter to the "LFP side" of my design, keeping the FLAs as "night chargers" to the LFP

Thanks a lot for your input, Pete. Really helps
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Old 29-11-2021, 14:24   #11
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Re: Adding a LFP4 to house bank with Victron DC-DC charger

Quote:
Originally Posted by luisglezi View Post
Agree. I guess I could save a bit by purchasing a MPPT 75/15 or 100/15 instead of a 100/20. The boat is relatively small so I don't think I will be able to place more than 3x160W in production anyway.

This is a topic for another thread i guess, but I am not happy with the flexible solar panels either. I have been running flexible for a few years on top of my bimini (just hesitant to spend big bucks on an arch and rigid panels). Results were not catastrophic but it is true that degradation is very noticeable after one or two seasons.

The initial reason for investing in a 100/20 would be to have enough capacity to perhaps go in the future for a simpler configuration of just 1 MPPT (Victron) servicing 2 rigid panels. At that point I might get rid of the non-victron MPPT
when you put real solar on your boat buy SHINGLED PERC Mono solar if price be 100% more expensive buy this. On boat every watt is important because space is very limited.
this is max what can stay on Bavaria 36-40 ft https://solarv.de/product/enjoysolar...ping-180w-12v/
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