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00X · 07-10-2024, 16:01

Quote:

Originally Posted by sailorboy1

I didn't say "all will be good".

I said you should ask your manufacturer the question instead of unknown forum people. Forums are full of expert parrots and just because you read it on one doesn't make it true no matter how often a parrot repeats it. But hey, go ahead and ask a forum and then chose the "expert" answer you wish.

Well it would have been helpful to everyone if your replies were a little less cryptic twisted tongue and more concise and to the point. Maybe English is not your first language though?

Chotu · 07-10-2024, 16:23

looks like the trolling motor is out of juice ha ha ha

no one is falling for it anymore

sailorboy1 · 07-10-2024, 16:44

Quote:

Originally Posted by Chotu

looks like the trolling motor is out of juice ha ha ha

no one is falling for it anymore

I bet you feel you are witty, but we all know you are 1 drama post from running away because we have seen it.

Chotu · 07-10-2024, 16:55

Quote:

Originally Posted by sailorboy1

I bet you feel you are witty, but we all know you are 1 drama post from running away because we have seen it.

you have a nice evening and good luck with any hurricane stress you may be having. you shouldn’t be much affected up there

**s/v Jedi** · 07-10-2024, 17:51

Quote:

Originally Posted by Chotu

you have a nice evening and good luck with any hurricane stress you may be having. you shouldn’t be much affected up there

Bless his heart… he’s the second one I blocked tonight

sailorboy1 · 07-10-2024, 18:15

Quote:

Originally Posted by s/v Jedi

Bless his heart… he’s the second one I blocked tonight

funny I put you on ignore years ago, but I get weak sometimes

**newhaul** · 07-10-2024, 19:23

Quote:

Originally Posted by s/v Jedi

Bless his heart… he’s the second one I blocked tonight

You must have grown up south of the Mason dixon

HeinSdL · 07-10-2024, 23:14

Sailorboy: get yourself a boat again! ;-)

HeinSdL · 07-10-2024, 23:18

But I do have one question. When does balancing actually occur? I am not sure about that yet. At any time there is current flowing, or always, or only when the battery is almost full, or...? because an imbalance will always be visible to the BMS so correcting the imbalance should be possible regardless of the state of charge as long as there is some current to play with/reroute to favour lower SOC cells?

wholybee · 07-10-2024, 23:32

Quote:

Originally Posted by HeinSdL

But I do have one question. When does balancing actually occur? I am not sure about that yet. At any time there is current flowing, or always, or only when the battery is almost full, or...? because an imbalance will always be visible to the BMS so correcting the imbalance should be possible regardless of the state of charge as long as there is some current to play with/reroute to favour lower SOC cells?

It isn't really consistent and depends on the brand of battery or BMS. However, it can _only_ happen at the top of the charge in the steep part of the curve. Batteries can't be balanced lower than this, because the cells could be at very different charges, but still have the same voltage.

So, somewhere around 3.40-3.45Vpc balancing will start. Some BMSs will only balance while current is flowing into the battery. And some will balance while at rest. But they will all only balance at a high state of charge.

And that is really the only reason to ever charge to 100%, or to have an absorption cycle. The cells are perfectly happy to never be charged to 100%, but over time they will drift out of balance and need brought back.

**newhaul** · 08-10-2024, 05:53

Quote:

Originally Posted by wholybee

.

And that is really the only reason to ever charge to 100%, or to have an absorption cycle. The cells are perfectly happy to never be charged to 100%, but over time they will drift out of balance and need brought back.

Agreed and if the cells are well matched they will stay balanced my bank for instance each cell was charged to 3.65 then built into a battery and top balanced on the bench. Now 5 years later they are still within .002 of each other when topped with my annual capacity test. They have not been balanced since the bench.
My normal is charged to 13.8v and left to rest.

**s/v Jedi** · 08-10-2024, 06:29

Quote:

Originally Posted by newhaul

Agreed and if the cells are well matched they will stay balanced my bank for instance each cell was charged to 3.65 then built into a battery and top balanced on the bench. Now 5 years later they are still within .002 of each other when topped with my annual capacity test. They have not been balanced since the bench.
My normal is charged to 13.8v and left to rest.

Exactly. This is why comments exist on not needing a BMS for top quality lfp cells in series. I see the same.

Passive balancing during charging below the upper knee reduces efficiency while it may not even be needed. This is why balancers only kick in at the knee (where they gain certainty on SOC)

CaptainRivet · 08-10-2024, 17:46

Quote:

Originally Posted by Chotu

Yep. my instruction sheet from 2 years ago says the same.

i used slightly lower 14.2 and 13.6 at the direction of a lot of people online who said even 14.2 and 13.6 were too high.

initially i was at 14.4 for a couple months

my bms seems to very much treat 14.6 as a ceiling. it cuts out when you reach it. (or maybe at 14.7) Doesn’t cut out for a long period of time, just for a fraction of a second to back the charger off. it does that repeatedly if i charge that high

here’s a blog post from the litime site that covers all the general guidel for voltages and explains them too.

https://www.litime.com/blogs/blogs/l...GnlvG84dkfE6iY

So you have no communication means you don‘t have the cell voltages?

Your batteries charge till 14.6 or even 14.7V after 2 years? If yes they are totally fine. If they would be out of balance they would stop earlier.
That means 14.2V with 1h absorption is enough or even to high voltage or too long absorption.
Too check if you go lower and or shorter in absorption you need to do the following procedure:
1) lower absorption voltage to 14,0V and keep 1h. After 1 month charge to 14.7V and see if you still reach 14,6V at cut off. If you don‘t go back to 14.2V and 1h absorption.
2) if you still reached 14.6V then reduce absorption to 13.8V and keep 1h, after 1 month same procedure charge to 14.7V, don‘t reach 14,6V back to 14.0V
3) if reached 14,6V keep 13.8V absorption but reduce to 30min. After 1 month again to 14.7V, not reach 14,6V stay at 13,8V and 1h
4) if reached 14,6V reduce absorption further to 15min and again after 1 month to 14,7V. If 14,6 not reached stay at 30min. If reached your final setting is 13.8V with 15min absorption. Don‘t reduce further then 15min as your balancer just need a bit time to balance tiny imbalances so they don‘t grow and create an issue. 15min at 13,8V doesn‘t harm the cells at all or reduce lifespan compared to 0min absorption but prevent from further problems.
Check after 1 month again if you reach cut off at 14.6V, if not raise absorption back to 30min.

That’s the only way to find your lowest absorption voltage and shortest absorption time possible for your individual installation and usage for LFP batteries that have no external communications independently from what their manufacturer tells you. The lower absorption voltage the better, only then reduce the absorption. That’s for all charge sources you use in daily operations.

Storage or shorepower is different.

CaptainRivet · 08-10-2024, 18:35

Quote:

Originally Posted by s/v Jedi

Exactly. This is why comments exist on not needing a BMS for top quality lfp cells in series. I see the same.

Passive balancing during charging below the upper knee reduces efficiency while it may not even be needed. This is why balancers only kick in at the knee (where they gain certainty on SOC)

That’s correct till 8 cells in series but not for 16S anymore as too many tolerances add up even with the best cells.

But to see that you need the cell voltages at cutoff. If you don‘t have them the only way to find your lowest absorption voltage and time is with the process I described a post before.
Also cells age and that will be also differently, the question is not if but when. So you need to monitor the cells in the upper knee. If you have no external communication you need to charge to cutoff at least all 3month to see if you still reach 14,6V means battery is in balance.