Lithium house bank on long term shore power

[Nightsky]

Hi All. I have a lithium house bank with Victron inverter/charger. I am currently at a dock plugged in to shore power and notice that the battery SOC is always at 100%. This has me concerned in that I read that it is not healthy to Lithium banks to be kept at a constant 100% SOC. Is this so? I intend to leave the boat for several months plugged in to shore power to keep dehumidifiers running to minimize moisture and mold issues so need the shore power. Also, the bilge pumps are powered off the house bank so I don't want to let the house bank get too low if I turn the inverter/charger off. There is no separate battery charger in the system, only what the inverter/charger provides. Do I need to change the charge parameters on the Victron or is this really not an issue at all?
TIA

[lmxr]

Originally Posted by Nightsky

Hi All. I have a lithium house bank with Victron inverter/charger. I am currently at a dock plugged in to shore power and notice that the battery SOC is always at 100%. This has me concerned in that I read that it is not healthy to Lithium banks to be kept at a constant 100% SOC. Is this so?

It depends somewhat on the battery type, temperature and a few other parameters, but a capacity loss of 5 to 10 % per year is not unheard of.

Originally Posted by Nightsky

Do I need to change the charge parameters on the Victron or is this really not an issue at all?
TIA

You can try to adjust the charge parameters. But I'm afraid that it will be difficult to find a setting that reliably keeps the LFP batteries around 50 % SOC because the SOC vs. voltage curve of LFPs is very flat.

Would running the dehumidifiers off a small lead acid (starter battery?) present an option? The Multiplus would be connected to that LA battery such that the LA battery is always kept full (I assume your Multi is more than powerful enough to compensate for the draw of the dehumidifiers and bilge pumps). The LFPs can then be discharged to 70 % SOC or so and disconnected completely.

[Philtao]

I had that situation, but with solar panel.

From memory, I think I set the bulk voltage on the MPPT regulator around 13.45V, absorption time set to minimum and float at 13.2V. The batteries were at 60 - 65% after one month.

Now my BMS takes care of it all. I set min and max SOC. When max is reached, charge is disabled... then re-enabled when SOC reaches min. I can also set it to allow a full charge every XX days.

[s/v Jedi]

Get SOC down to 70% or so, then disconnect the battery and use an AGM battery at float charge, which they love.

[Nightsky]

Originally Posted by Philtao

I had that situation, but with solar panel.

From memory, I think I set the bulk voltage on the MPPT regulator around 13.45V, absorption time set to minimum and float at 13.2V. The batteries were at 60 - 65% after one month.

Now my BMS takes care of it all. I set min and max SOC. When max is reached, charge is disabled... then re-enabled when SOC reaches min. I can also set it to allow a full charge every XX days.

My batteries come with a BMS that has no external control, unfortunately.

[Nightsky]

Originally Posted by lmxr

It depends somewhat on the battery type, temperature and a few other parameters, but a capacity loss of 5 to 10 % per year is not unheard of.


You can try to adjust the charge parameters. But I'm afraid that it will be difficult to find a setting that reliably keeps the LFP batteries around 50 % SOC because the SOC vs. voltage curve of LFPs is very flat.

Would running the dehumidifiers off a small lead acid (starter battery?) present an option? The Multiplus would be connected to that LA battery such that the LA battery is always kept full (I assume your Multi is more than powerful enough to compensate for the draw of the dehumidifiers and bilge pumps). The LFPs can then be discharged to 70 % SOC or so and disconnected completely.

This would require some re-wiring which I am loathe to do.

[basssears]

Originally Posted by Nightsky

Hi All. I have a lithium house bank with Victron inverter/charger. I am currently at a dock plugged in to shore power and notice that the battery SOC is always at 100%. This has me concerned in that I read that it is not healthy to Lithium banks to be kept at a constant 100% SOC. Is this so? I intend to leave the boat for several months plugged in to shore power to keep dehumidifiers running to minimize moisture and mold issues so need the shore power. Also, the bilge pumps are powered off the house bank so I don't want to let the house bank get too low if I turn the inverter/charger off. There is no separate battery charger in the system, only what the inverter/charger provides. Do I need to change the charge parameters on the Victron or is this really not an issue at all?
TIA

Is there wifi where you're on shore power? The Victrons can be internet accessible (IIRC), you could manually turn the charge on and off as needed?

[donradcliffe]

Following. What is harder on the batteries, a series of daily discharges of 5-10% SOC for six months, or being floated at 13.4v for 6 months?

[MartinR]

I second the Victron remote management option. I can control my Victron chargers from wherever I am. Is not a big investment at all.

The alternative is to keep the batteries at the lower “knee”, about 20% of charge . This is better than floating them at 100%. There is no way to set a charge controller to keep the batteries at 50%, as the curve is completely flat there.

[sailjumanji]

Ok, shoot me. But where does it say holding LiFePO4 battery at 13.5 volts, 100% SOC for long period is bad? Am asking because I have a Mastervolt system with their MassCombi, SolarChargemaster, a couple of Mac Plus DC-to-DC chargers, and their MLI Ultra battery. All of these chargers have MLI-specific settings, which include float.

[HBrew]

Originally Posted by sailjumanji

Ok, shoot me. But where does it say holding LiFePO4 battery at 13.5 volts, 100% SOC for long period is bad? Am asking because I have a Mastervolt system with their MassCombi, SolarChargemaster, a couple of Mac Plus DC-to-DC chargers, and their MLI Ultra battery. All of these chargers have MLI-specific settings, which include float.

+1 - I have more or less the same setup and I too have left mine on shore power (100% SOC) for long periods without any apparent issues.

[Dirk01]

Originally Posted by Philtao

I had that situation, but with solar panel.

From memory, I think I set the bulk voltage on the MPPT regulator around 13.45V, absorption time set to minimum and float at 13.2V. The batteries were at 60 - 65% after one month.

Now my BMS takes care of it all. I set min and max SOC. When max is reached, charge is disabled... then re-enabled when SOC reaches min. I can also set it to allow a full charge every XX days.

Would really like to see which BMS brand you use.

Cheers
Dirk

[Philtao]

Originally Posted by Dirk01

Would really like to see which BMS brand you use.

Cheers
Dirk

I use the TAO BMS (www.taobms.com)

[Dirk01]

Originally Posted by Philtao

I use the TAO BMS (www.taobms.com)

Many Thanks! I was on the road to victron or R.E.C, but TAO BMS seems to be the best solution on the market. I'll have a deep dive into it.

Cheers
Dirk

[Nightsky]

Originally Posted by basssears

Is there wifi where you're on shore power? The Victrons can be internet accessible (IIRC), you could manually turn the charge on and off as needed?

No wifi here, private dock.