LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[rgleason]

After reading Electrical Design For a Marine Lithium Battery Bank which explains 3 system typologies: Dual Bus, Lead-Lithium Hybrid and Split Charging, I found that he says Alternator Regulator battery temperature sensing and compensation should not be used, and the LFP should be at or very near ambient temperatures and not in the engine compartment! Of course temperature sensing for the Alternator is necessary. Of course the BMS would have battery temperature sensing.


Another Alternator Regulator with current sensing is Nordkyn VRC-200
https://nordkyndesign.com/product/no...ce-controller/

[rgleason]

Originally Posted by jordanbigel

They already exist - look at "Lithionics".

I did not buy these due to the high cost, but they have CANBUS and work with the Wakespeed, etc., etc. They also have a Bluetooth enable mobile app allowing visibility to the BMS data. Crazy $$$.

I bought BestGo (Elec Car Parts Company) which do not have CANBUS but do have signal relay warnings which indicate low/high voltage, low/high current and low/high temp which I've wired to a relay connected to my Balmar regulator's ignition wire to shut down alternator when batteries raise a warning condition (which happens before the BMS actually shuts down), and also to my Victron MP2 and to a relay which cuts off solar panels as well.

ElectricCarParts Bestco battery package 12V 200Ah Lithium Battery 5yr Warranty 12.2"L * 10.2"W * 9.0"H - 53 Lbs The "Pro" version has a 12-pin connector to notify the user with an alert signal to prevent the battery from working outside its limits. This can be used to disconnect the Alternator Field wire. See “Paralleling Instructions for BMS and Meter"

[fxykty]

Originally Posted by rgleason

SmartSolar MPPT 75/15

https://www.victronenergy.com/upload...-20_48V-EN.pdf


Still unclear if absorption and float can be "turned off".
I believe I would need that to avoid overcharging the LFP.

Use a BMS-driven relay to cut the power between panel and controller, as these smaller controllers don’t have remote on/off. If your controller does have remote on/off then use that.

Alternatively, put in minimal voltage values for absorption and float, so it doesn’t matter if the controller goes into those modes.

[mitiempo]

Originally Posted by rgleason

SmartSolar MPPT 75/15

https://www.victronenergy.com/upload...-20_48V-EN.pdf


Still unclear if absorption and float can be "turned off".
I believe I would need that to avoid overcharging the LFP.

You do not need to turn float off - just turn it down to a lower setting where the lithium does not accept current. Absorption can be minimized or turned off with all Victron chargers - MPPT, DC - DC, and IP22 chargers for example.

The bank I set up recently I used 13.8 volts for all charge sources. Float for the MPPT is set at 13.35 volts with restart of bulk at 13.25 volts.

The BMS (Overkill Solar by JBD) is set to shut all charging at 14 volts for the bank.

I do not believe the BMS should be the everyday control to shut charging off - it should be a last resort. All charge sources should be set at voltages that will not harm the battery bank if the BMS were not there. With the charge voltages .2 volts below the BMS high voltage cutoff it should not activate unless one cell becomes very out of balance. The charge sources are all safe at bank voltages and the BMS controls by cell voltages.

[mitiempo]

Originally Posted by goboatingnow

If you have small loads why have Li at all.

Yes I have small loads

I do not have electric cooking.
I do not have multiple fridges or freezers.
I do not have air conditioning.

I do have efficient refrigeration (Engel), plotter, AIS, radar, depth, tillerpilot and a very efficient watermaker.

LiFePo4 allows not worrying about needing a full charge often, very efficient charging, no voltage sag to speak of, smaller size and weight (400 AH and under 100 lbs) as well as long life.

Oh, the other reason is that my 400 AH of Calb cells cost about the same as the equivalent usable capacity of flooded golf cart batteries.

[hjohnson]

Originally Posted by mitiempo

But remember that we a re talking about sailboats. Do you really want to run the engine just to charge the battery bank?

The inexpensive solution is a Fla start battery - group 24 and either sealed or Agm. A DC to DC charger - Victron the best choice - between the start battery and the LiFePo4 bank properly programmed. Simple, not expensive, and whichever alt you have it will not suffer.

Main charging solar.

The dirty little secret about sailing, at least here in the Salish Sea, it’s that if you’re moving about, you’re probably motoring 4 to 5 hours a day anyhow. If you’re going to be doing that, you want to be able to shove as much power into your battery as possible while the engine is running, and have enough capacity to go a few days on the hook without running it.

I’ve got my poor little 1GM10 outfitted with an 85A alternator, controlled by a Wakespeed. I can reliably pull 75A off of it into my LiFePO4 bank. I usually do limit it to 35A to put less strain on my motor. I do have an 18A Orion DCC which maintains a little group 24 starting battery, but it rarely actually does much.

Also, as a 27’ I just don’t have that much room to mount solar panels. I’ve got 120W on my dodger, which definitely helps, but it’sa range extender.

Anyhow, having the full running fully integrated is glorious. The BMS talks to my Wakespeed talks to my Victron Cerbo, which in turn also manages the solar and monitors the starting battery. I couldn’t ask for much more.

[rgleason]

Originally Posted by hjohnson

The dirty little secret about sailing, at least here in the Salish Sea, it’s that if you’re moving about, you’re probably motoring 4 to 5 hours a day anyhow. If you’re going to be doing that, you want to be able to shove as much power into your battery as possible while the engine is running, and have enough capacity to go a few days on the hook without running it.

I’ve got my poor little 1GM10 outfitted with an 85A alternator, controlled by a Wakespeed. I can reliably pull 75A off of it into my LiFePO4 bank. I usually do limit it to 35A to put less strain on my motor. I do have an 18A Orion DCC which maintains a little group 24 starting battery, but it rarely actually does much.

Also, as a 27’ I just don’t have that much room to mount solar panels. I’ve got 120W on my dodger, which definitely helps, but it’sa range extender.

Anyhow, having the full running fully integrated is glorious. The BMS talks to my Wakespeed talks to my Victron Cerbo, which in turn also manages the solar and monitors the starting battery. I couldn’t ask for much more.

This sounds like our use, although the engine hours tend to be 8 hours for no wind days or 1-1.5 hrs.


Can you attach some photos of the installation?

[s/v Jedi]

For an alternator, I think you could set it to 3.4 V per cell as a fixed value. this will not fully charge quickly or ever, but I don’t think it would hurt the cells is done for periods up to a couple of days.

[newhaul]

Originally Posted by hjohnson

The dirty little secret about sailing, at least here in the Salish Sea, it’s that if you’re moving about, you’re probably motoring 4 to 5 hours a day anyhow. If you’re going to be doing that, you want to be able to shove as much power into your battery as possible while the engine is running, and have enough capacity to go a few days on the hook without running it.

I’ve got my poor little 1GM10 outfitted with an 85A alternator, controlled by a Wakespeed. I can reliably pull 75A off of it into my LiFePO4 bank. I usually do limit it to 35A to put less strain on my motor. I do have an 18A Orion DCC which maintains a little group 24 starting battery, but it rarely actually does much.

Also, as a 27’ I just don’t have that much room to mount solar panels. I’ve got 120W on my dodger, which definitely helps, but it’sa range extender.

Anyhow, having the full running fully integrated is glorious. The BMS talks to my Wakespeed talks to my Victron Cerbo, which in turn also manages the solar and monitors the starting battery. I couldn’t ask for much more.

We need to speak direct about your solar I will be at cap Santee on the 10th for a week pm me then
Rob SV Stephen Ulysses.
Will be on the MV Sukai .

[hjohnson]

Originally Posted by rgleason

This sounds like our use, although the engine hours tend to be 8 hours for no wind days or 1-1.5 hrs.


Can you attach some photos of the installation?

I put together a thread on my setup a few months back: https://www.cruisersforum.com/forums...cs-262718.html

Thus far the system has been working great, other than a few minor connector issues with our LTE router (need to drop by the marina again to plug the USB-C power cable back in). Thus far, over the past month, the solar has kept the batteries topped up and I haven’t bothered even running the shore power cable.

[kmacdonald]

Don't worry too much about a BMS. It will never do anything if you use half way decent prismatic cells and dont try and run AC. The design of the system including battery capacity and charging is much more important. It's best not to top off the batteries and charge conservatively.

[kmacdonald]

I have a 326 Ah LiFePO4 bank. It runs a 7 cubic foot frig with 3" insulation, a 63 qt portable freezer with only 2" of insulation, 2 chart plotters, VHF, AIS, Linear drive autopilot, and all house loads. More than keeps up during the day with 320 watt solar but need to run the engine every other day for an hour or two when using the autopilot contiuously. Without the freezer I'd be fine.

[Kiwi Dave]

Originally Posted by mitiempo

Yes I have small loads

I do not have electric cooking.
I do not have multiple fridges or freezers.
I do not have air conditioning.

I do have efficient refrigeration (Engel), plotter, AIS, radar, depth, tillerpilot and a very efficient watermaker.

LiFePo4 allows not worrying about needing a full charge often, very efficient charging, no voltage sag to speak of, smaller size and weight (400 AH and under 100 lbs) as well as long life.

Oh, the other reason is that my 400 AH of Calb cells cost about the same as the equivalent usable capacity of flooded golf cart batteries.

Hi - I have the same house bank as yours (400 amphour CALB at 12V) - & similar loads. Rare occasion does solar (140 amphours a day) & normal motoring (120 amps/hour - from the Volvo D1 - 30s with externally regulated 115 amp externally regulated alternators) not keep up. Winter - is spent out of the water doing maintenance & may needs charging occasionally.
I love my LiFePO4 house bank for exactly the same reasons (still have AGM engine batteries charged from the housebank via DC-DC chargers. I think I'm at 5 1/2 years and still going strong.

[goboatingnow]

Originally Posted by hjohnson

The dirty little secret about sailing, at least here in the Salish Sea, it’s that if you’re moving about, you’re probably motoring 4 to 5 hours a day anyhow. If you’re going to be doing that, you want to be able to shove as much power into your battery as possible while the engine is running, and have enough capacity to go a few days on the hook without running it.



I’ve got my poor little 1GM10 outfitted with an 85A alternator, controlled by a Wakespeed. I can reliably pull 75A off of it into my LiFePO4 bank. I usually do limit it to 35A to put less strain on my motor. I do have an 18A Orion DCC which maintains a little group 24 starting battery, but it rarely actually does much.



Also, as a 27’ I just don’t have that much room to mount solar panels. I’ve got 120W on my dodger, which definitely helps, but it’sa range extender.



Anyhow, having the full running fully integrated is glorious. The BMS talks to my Wakespeed talks to my Victron Cerbo, which in turn also manages the solar and monitors the starting battery. I couldn’t ask for much more.

Excellent high efficiency install. Congrats.

[badadim]

I hope this helps