Float of LFP

[CaptainRivet]

Originally Posted by patja

OK it is not literally year round. I do use the boat 30 - 40 days per year, and during that time the charge level is up and down as you would expect. But other than that it is at its slip plugged into shore power.

Why do you own a boat for 30-40days a year??
Charter and let care someone else about the hassle.
Below 90 days a year its not even worth to start about thinking owning one.

[sailorboy1]

The published study is from idiots. Listen to me I an an intenet expert. All the other internet experts agree.

You guys are amazing

You don't even try to support your stuff with a study and facts. Just repeated statements.

[s/v Jedi]

Originally Posted by patja

OK it is not literally year round. I do use the boat 30 - 40 days per year, and during that time the charge level is up and down as you would expect. But other than that it is at its slip plugged into shore power.

It would be much better to set the float voltage to something lower, like 3.2V per cell, which makes 12.8V and see what the battery monitor reports as state of charge when you return to the boat.

Of course this means your battery won’t be fully charged when you return to the boat, but you could do that before departure if needed.

The thing with LFP is that just lowering voltage like you already did isn’t enough because the battery will still get fully charged, it just takes longer.

Even when living aboard, where we can fully charge with solar every day, I set the float voltage of my MPPT controllers lower so that the battery discharges to about 95% before solar takes over the load until sundown. This discharge reliefs the pressure of the fully charge on the cell.

[s/v Jedi]

Originally Posted by sailorboy1

The published study is from idiots. Listen to me I an an intenet expert. All the other internet experts agree.

You guys are amazing

You don't even try to support your stuff with a study and facts. Just repeated statements.

Yeah you left out all the supporting bits from my comment SB so it’s just arguing that you want.

[CrispyCringle]

Originally Posted by sailorboy1

The published study is from idiots. Listen to me I an an intenet expert. All the other internet experts agree.

You guys are amazing

You don't even try to support your stuff with a study and facts. Just repeated statements.

I find it strange when these type of discussions come around to "show me the studies, reports, etc". When someone asks a question on a internet forum all I expect is if they have experience with the topic enough to share what they think, they'll do that. After that why would anyone give a rats bass if anyone else takes the answer as fact, helpful, or whatever. People are not getting paid for posts. They are taking their time to do it. Im certainly not going to spend my time doing someone else's homework by providing published studies.

I think of forums more as people standing around the dock sharing knowledge and shooting the breeze. Are people wrong sometimes? Sure. Who cares? Make your own decisions what to do with the comments. But ask to provide you with a link to a study, or what ever. I dont know why it would deserve anything more than crickets. Who cares? Im not sure why anyone would expect otherwise. Its like diverting the conversation by criticising for grammar or spelling. Cripes.

[CaptainRivet]

Originally Posted by s/v Jedi

Yeah you left out all the supporting bits from my comment SB so it’s just arguing that you want.

Agree plus what makes no sense there is no study.
We don't copy internet, we tell from own experience and well that come to the same results, so there must be some truth in it. You have your first LFP on a boat and are the expert...

Store cells at 100% float and you will have a runaway cell and low cell, do it long enough and your drop in is ruined.thats facts. Don't believe it do the study yourself and use your own dropin store it at 100% float to proof us internet copy cats wrong...

[patja]

Originally Posted by CaptainRivet

Why do you own a boat for 30-40days a year??
Charter and let care someone else about the hassle.
Below 90 days a year its not even worth to start about thinking owning one.

I did my first charter this year, in French Polynesia. It was great, but boy was I missing all the things I've done to make my boat livable and performant. Just one example: the "inverter" was a single 150 watt cigarette lighter device. Oh here's another: only visibility to what was going on with the DC electrical system was voltage. No visibility to amps.

[patja]

Originally Posted by s/v Jedi

It would be much better to set the float voltage to something lower, like 3.2V per cell, which makes 12.8V and see what the battery monitor reports as state of charge when you return to the boat.

If I did this, I don't think I would hit the required monthly full charge and rebalance that Victron requires.

[krid2000]

Originally Posted by wholybee

Moreover, if you continue to charge an LFP after it is 100% charged, you will damage it, and that is well documented.

Originally Posted by sailorboy1

Is it? That is the question, post a link to a testing study

A quick google search surfaced the following study. They investigate 10% overcharge conditions.

https://www.researchgate.net/publica...rge_Conditions

HTH
Dirk

[barcoMeCasa]

Originally Posted by patja

If I did this, I don't think I would hit the required monthly full charge and rebalance that Victron requires.

Not a problem is it? Unused cells won't drift much if at all in a few months.

[HeinSdL]

Learning as I go, looking to install LFP batteries shortly. My understanding is that balancing can only occur during charge or discharge of the battery. Current flows through the various in-series cells and as a higher or lower voltage is detected by the BMS it activates/deactivates resistors in parallel with the cells to slightly change the charge/discharge currents flowing through the cells, thereby balancing them.

In this light it would appear healthier for the battery to be cycled, continuously. Charge, discharge, etc, and not be kept at some voltage/fixed SOC as a goal. When maintaining SOC near 100% with little charging or discharging occurring, balancing would not be very effective and a cell might creep up beyond its 3.65 'safe' voltage without it being noticed by the charger (battery at eg 14V) or the BMS (which does notice it) being able to do anything about it (apart from shutting down).

That would be my theoretical reasoning for not maintaining an LFP battery near 100% SOC.

[sailorboy1]

Originally Posted by krid2000

A quick google search surfaced the following study. They investigate 10% overcharge conditions.

https://www.researchgate.net/publica...rge_Conditions

HTH
Dirk

Yes that was for over charge. Not really the subject.

[krid2000]

Originally Posted by sailorboy1

Yes that was for over charge. Not really the subject.

In that case I think you should restate your question as it's not clear to me what you're asking. Are you looking for studies regarding damaging LFP when:

• keep charging an LFP after reaching 100% SOC (obviously not, as you just stated above, but this is often referred to as floating),
• constantly keeping the battery at the voltage that you associate 100% SOC with,
• storing a battery at 100% SOC for a long time,
• ???

Thanks
Dirk

[CaptainRivet]

Originally Posted by sailorboy1

You read it all time that it is bad to float a LFP battery.

Anyone have an actural link to paper on an actural test to support this? Not just a statement from "X" (even if a supplier), but an actural test.

I couldn't.

Thats his original question coming from lead thinking to keep the batterie at or close to 100% SOC all the time.
Again lead thinking as he doesn't understand the Lifepo4 chemistry and how it works, if he would understand he wouldn't ask.
He wants studies instead reading well made articles that made to understand how Lifepo4 chemistry works.

A 17year old bank never floated or absorbed is still 94% of original capacity and thats the age degradation.
A lifepo4 doesn't need float at all so why doing it?
How the float of eg MPPTs need to be hacked to work with Lifepo4 Jedi described above. That it need to be hacked to work properly with Lifepo4 says all about it.

You won't find studies as this is nonsense as already the manufacturer states to not store it at 100%SOC but 40 till 60%SOC and they themselves do it and also deliver the batteries like that.

[Chotu]

These threads make me nervous. Lol. It’s OK to go up and down right? Up to 98% around lunch? Float for a few hours in the afternoon, then down for the night 120AH? Then repeat daily?