LiFePO4 and absorption charging

[newhaul]

Originally Posted by sailorboy1

doesn't matter what I think, I am just a forum member trying to live in a practical world

I had a thread once about charging FP batteries to 100% charged all the time and that is pretty much the same as this thread. I searched and read tech papers for days and the closest to this I could find was about leaving them fully charged at storage. In that it looked that the capacity loss was 3-5%. That in a practical boat world is meaningless plus we weren't really talking about leaving them there. I got crucified by the "experts" who "knew" the right answer.

In all these threads it seems people have lost sight that we are talking about boat battery use. Batteries are there to serve us, we aren't there to serve them. We lived in past with acid batteries and now we are concerned about a few % of LFP capacity, which is still WAY better than the acid batteries were. And the LFP batteries are now cheap in the big picture. My cheap drop in LFP batteries cost what my current house electrical cost is for 7 months and have been operating for 2 years. What a GREAT deal!

Firstly the comment was in general
As to battery management I agree I just hate the micro management that some on here think is the only way to do it. Works for them myself I prefer to enjoy the scenery.
Mine have been going strong for 5 years with barely even looking at the monitoring meter. Just annual capacity test.

[CaptainRivet]

Originally Posted by newhaul

I build my banks unless customer specifically asks for ' drop ins" and I use dumb BMS units .top balance 1 time on the bench then verify balance once a year with a fluke meter to .001v
Never have had any out of balance more than .005v in a 5 year time-frame. So don't see the need to micro manage the bank like you seem to feel should he done .
Just run the bank from 20% to 90% and stay off the knees .
Do you have technical reports from manufacturers to support your opinions?
I do.

Yes you have a reference because you put it together and made sure they have a top balance. You know the BMS ans the cells. Buyers often not, they assume it's perfectly top balanced but they are not.
So A lot buy, drop it in and adjust to 13.8V and let the system run, nothing happens for x month and then one day surprise battery cut off at 13.7V. Because it had no top balance and balancer couldn't handle due to only 13.8V quite short time to balance.
That's the classic scenario...
Saw a lot happening on that Chinese surprise boxes in different quality levels and I am the one that fixes the issues then after they happen.
Sure if for 4 times a year you see nothing happening at your top balance then just check once a year. No problem with that.

I and all i helped have no issue all 3 month just setting before lunch one MPPT via victron connect app to 14.7V and then look at my BMV712 or the bat monitor they have what was the voltage after it cut off. No effort, don't even get your hands dirty. The bank is one of the top 3 on a boat and you also regularly check the oil level of your engine...and here you regularly check the health of your bank. Sure if all is rock solid once a year is ok too. but a lot aren't, especially in the beginning till all is correctly adjusted with dropins that have no communications.

[CaptainRivet]

Originally Posted by Chotu

this is interesting. Really liking where the thread has gone. I’m going to try the top cutout test out a bit later.

is it harmful to the solar charge controllers to have the load just pulled away like that while they are in the middle of charging? Is that abusive to them at all?

my BMS cuts out only for a second, literally, and then is back on, then cuts out for a second, then back on and repeats. This is the default cut out for over voltage.

Overcurrent is a 20 min cutout, returning if the short is fixed. it behaves differently for different situations


Was thinking of doing this on the generator with AC->DC charger that i care less about and never use

No issue for your MPPT at all, it's actually the best for that test.
Your in the upper knee and current is minimal as the LFP only pulls what is needed.
That's a special BMS and actually not very save as the cut off only happens when something is wrong and you don't want it to shut on after a second.
In eg elelectrodacus I have overvoltage cutoff at 3.63V but can adjust the voltage it's re-engages (have it at 3.45v) and a delay for the time the voltage must be under that so it engages.
Then I have an overvoltage Lock at 3.7V means if that's reached the BMS will permanently lock any charge until I reset manually.

[newhaul]

Originally Posted by CaptainRivet

Yes you have a reference because you put it together and made sure they have a top balance. You know the BMS ans the cells. Buyers often not, they assume it's perfectly top balanced but they are not.
So A lot buy, drop it in and adjust to 13.8V and let the system run, nothing happens for x month and then one day surprise battery cut off at 13.7V. Because it had no top balance and balancer couldn't handle due to only 13.8V quite short time to balance.
That's the classic scenario...
Saw a lot happening on that Chinese surprise boxes in different quality levels and I am the one that fixes the issues then after they happen.
Sure if for 4 times a year you see nothing happening at your top balance then just check once a year. No problem with that.

I and all i helped have no issue all 3 month just setting before lunch one MPPT via victron connect app to 14.7V and then look at my BMV712 or the bat monitor they have what was the voltage after it cut off. No effort, don't even get your hands dirty. The bank is one of the top 3 on a boat and you also regularly check the oil level of your engine...and here you regularly check the health of your bank. Sure if all is rock solid once a year is ok too. but a lot aren't, especially in the beginning till all is correctly adjusted with dropins that have no communications.

Yes I check my engine oil weekly if I have run the engine that week also check transmission fluid every 100 hours change oil annually or 100 hrs whichever comes first. Also new impeller with oil. Check puke tank at same time as checking the oil.
Have several customers on the same schedule so it's easy to keep a good maintance log .
On mine and theirs . Except oil changes only happen every 500 hours on 2 of them as they put that on in a month .

[CaptainRivet]

Originally Posted by newhaul

Yes I check my engine oil weekly if I have run the engine that week also check transmission fluid every 100 hours change oil annually or 100 hrs whichever comes first. Also new impeller with oil. Check puke tank at same time as checking the oil.
Have several customers on the same schedule so it's easy to keep a good maintance log .
On mine and theirs . Except oil changes only happen every 500 hours on 2 of them as they put that on in a month .

Exactly, you still check the engine oil even it didn't use any oil for the last 50h.
so why don't get the house bank consisting of no communication dropins ,thats minimum as important as the engine, a health check every 3 month because you have no monitoring of cell voltages to do that visually, especially if it's that easy. Better safe then sorry.

[HeinSdL]

Just to reply to some of the posts regarding micro management, hatred even for being obsessed by a ... battery ... Well I like to learn about these things. Here. At the screen. Not when entering a harbour at night in tricky conditions and all of a sudden you have no clue why no more 12V. And there are people here with ideas and know-how which I like to hear out/learn from. That's why this is a ... forum! It does not mean I spend my sailing hours gazing into a Victron app but it does mean I am less likely to join the rather large brigade of people out there on the water who, frankly, have no clue about very much really. In any case not about their own boat/boat's systems.

Spending a few minutes here reading up on a topic ≠ spending hours on the boat doing the same

[newhaul]

Originally Posted by CaptainRivet

Exactly, you still check the engine oil even it didn't use any oil for the last 50h.
so why don't get the house bank consisting of no communication dropins ,thats minimum as important as the engine, a health check every 3 month because you have no monitoring of cell voltages to do that visually, especially if it's that easy. Better safe then sorry.

If I get 50 hours on my engine in a year I'm not sailing enough. I like to sail on and off the anchor especially off of it slipping away with the morning fog.

[CaptainRivet]

Originally Posted by HeinSdL

Just to reply to some of the posts regarding micro management, hatred even for being obsessed by a ... battery ... Well I like to learn about these things. Here. At the screen. Not when entering a harbour at night in tricky conditions and all of a sudden you have no clue why no more 12V. And there are people here with ideas and know-how which I like to hear out/learn from. That's why this is a ... forum! It does not mean I spend my sailing hours gazing into a Victron app but it does mean I am less likely to join the rather large brigade of people out there on the water who, frankly, have no clue about very much really. In any case not about their own boat/boat's systems.

Spending a few minutes here reading up on a topic ≠ spending hours on the boat doing the same

That's exactly the point. If you understand your system and know what to do to limit failures and what to do if they are happening you can help yourself and make everything safer.
You micromanage in the beginning to get to know the system and how it reacts to different adjustments, important is you do just one at a time so you see what effects each adjustment have.
Nobody spends hours staring at a victron app that know his/her system, that's stable and the main desaster use cases are tested, why...you have trust in your system and if something happens know what to do.
The ones that have no idea are doing that as they don't know how it reacts after an incident happened and mostly they continue because you did f.. up in the beginning and don't know thats the root cause and just fix the symptoms instead the root cause.

[newhaul]

Originally Posted by HeinSdL

Just to reply to some of the posts regarding micro management, hatred even for being obsessed by a ... battery ... Well I like to learn about these things. Here. At the screen. Not when entering a harbour at night in tricky conditions and all of a sudden you have no clue why no more 12V. And there are people here with ideas and know-how which I like to hear out/learn from. That's why this is a ... forum! It does not mean I spend my sailing hours gazing into a Victron app but it does mean I am less likely to join the rather large brigade of people out there on the water who, frankly, have no clue about very much really. In any case not about their own boat/boat's systems.

Spending a few minutes here reading up on a topic ≠ spending hours on the boat doing the same

With a system setup similar to mine or jedis you won't be hot and dark like that as all the essentials are run off of your lead based start battery .

[CaptainRivet]

Originally Posted by newhaul

With a system setup similar to mine or jedis you won't be hot and dark like that as all the essentials are run off of your lead based start battery .

Mine too (its even certified) but that's not was majority out there have...Chinese surprise box dropins without communication is and will be still the majority out there

[newhaul]

Originally Posted by CaptainRivet

Mine too (its even certified) but that's not was majority out there have...Chinese surprise box dropins without communication is and will be still the majority out there

Ok now you are running a lead based start battery again I see you did finally see the logic in this

[barcoMeCasa]

Originally Posted by HeinSdL

Just to reply to some of the posts regarding micro management, hatred even for being obsessed by a ... battery ... Well I like to learn about these things.

For a high proportion of cruisers batteries have 3 distinct states of health..
brand new
lights came on so won't even think about it.
Dead... and it's someone else's fault


Not even sure how you micromanage a battery.

On this full time cruising boat running on solar there was a few weeks tweaking settings to try to get the smartshunt SOC as accurate as possible then just a quick look each morning to see if anything weird is going on.

And this shows that either I turned something off or upgrading some skinny wires for fat ones yesterday lowered the power draw overnight.

[HeinSdL]

Originally Posted by barcoMeCasa

For a high proportion of cruisers batteries have 3 distinct states of health..
brand new
lights came on so won't even think about it.
Dead... and it's someone else's fault


Not even sure how you micromanage a battery.

On this full time cruising boat running on solar there was a few weeks tweaking settings to try to get the smartshunt SOC as accurate as possible then just a quick look each morning to see if anything weird is going on.

Well that is exactly the way to do it and is what I do. But to be able to "tweak some settings" to get the system functioning as intended I need to learn about it and discussions like this augment my understanding very well. Otherwise there can be no tweaking and you end up with a suboptimal solution.

On the other topic of using lead for critical systems, in particular using the start battery, yes why not but in my case I don't want to go that far with the rewiring. I have a large house bank which does everything since the boat was built and now that is LFP. Charged by Victron's 50A XS directly from the start battery as well as 600W solar. Nothing wrong with that set up, works a dream for me with a boat which doesn't have large energy needs.

But.... I did keep the old AGMs which were still in very good shape and might consider putting them in parallel with the LFP (doing absolutely nothing most of the time) when being particularly reliant on the autopilot on eg a broad reach/run with significant waves and a lot of wind. That is one of the few situations I can imagine when I would not want to entertain an unscheduled shut down. Otherwise a disconnecting LFP I could not care so much about (and is highly unlikely anyway).

[CaptainRivet]

Originally Posted by newhaul

Ok now you are running a lead based start battery again I see you did finally see the logic in this

?? How do you come to that conclusion?

[barcoMeCasa]

Originally Posted by HeinSdL

But.... I did keep the old AGMs

Same here, still have 2 x T105's with a smartguage connected.

Pretty essential really on a cruising boat otherwise any battery work means powering down the whole boat instead of turning a switch to run on the Trojans.

Like a little reminder of how we did it back in the old days with ancient energy storage technology

And this is sort of related, for a quick battery glance what do you want to see?
https://www.cruisersforum.com/forums...ml#post3940549