Lithium Battery Charging Question(s)

[SoonerSailor]

Melbourne Park - the Battery University voltage data you provide references Lithium Ion chemistry, NOT Lithium Iron Phosphate chemistry, which is what is being used for house banks.

[Melbourne Park]

Originally Posted by newhaul

One thing I do know is on my cell phone there is an option to extend battery life at the expense of the top 20% it is in the firmware of the Bms ( yes they have them) it stops charging at 80% but reports as full. Does the same at the bottom .
My point is that the manufacturer says not charging the last few % is beneficial to the longevity of the bank .
On EVs the battery is fully charged and immediately starts discharging so battery never spends much time at full. As to storage they recomend 50% charged for a reason. It is not stored at full, ( which is proven to cause damage)but still sufficient power to survive an extended period of inactivity without self discharge taking it below the BMS safety disconnect.value. now consider that several on here ( on the forum) that lost their batteries to self discharge . ( due to the covid lock downs) even after the BMS disconnects on Lvd the battery will continue to self discharge . Eventually actually reaching 0% and suffering non repairable damage. A battery that starts storage at 50% can survive several years of self discharge in storage.

Yes. My point is that no one here has provided scientific data which shows the effects on longevity of Lithium Iron batteries. While manufacturers talk about storage, that is an entirely different issue. Insurance being just one issue - as batteries are transported from the maker to the user.

I just want some proper data - and without it, I'll consider all the issues that a maker, then distributor, then retailer, and all the issues surrounding those businesses, will also have to consider. As just one example - how much extra would it cost the maker of batteries, to send them out fully charged, compared to a limited charge? What about insurance issues relating to fully charged batteries, coming all the way from China? Given me the science, and at least then, I can make a logical decision.

And while I found data on some forms of Lithium, I haven't found it on Lithium Iron. Why not? An example of one thing I have read, is this one. But I would like a paper studying Lithium Iron Phosphate batteries, or LiFePO4.

Here is such a paper which I browsed through ... https://core.ac.uk/download/pdf/323272674.pdf

I cannot discuss this further at the moment, as I am going away. But assistance would be most appreciated!!

[Melbourne Park]

I could list a number of things that degrade Lithium life cycles, and also, some reasons why. But a common issue is high current. So, as someone here has said they do, one boils water etc. to drain the lithium batteries down, doing so is a high current event. And high current usage damages lithium battery life cycles. And then if one charges them up quickly, the same issue applies. Damaging high current usage.

So, is it wise to drain lithium batteries down, and re-charge them, in order to avoid leaving them at a high rate of charge?

Tactically, it seems the best thing to do, but what exact benefit is being achieved? What one might need, is to drains the batteries very gently down, and then stop the power drain at a certain capacity. And then, slowly bring them up to capacity for usage, whenever that is.

While that sounds reasonable, is it practical? It's not how I intend to use my batteries. And there are more circumstances and conditions that can damage lithium battery life. One thing I read, said that currently (a very recent paper too) that there a no formulae to come up with predictive age. The science is still immature.

[newhaul]

Originally Posted by Melbourne Park

I could list a number of things that degrade Lithium life cycles, and also, some reasons why. But a common issue is high current. So, as someone here has said they do, one boils water etc. to drain the lithium batteries down, doing so is a high current event. And high current usage damages lithium battery life cycles. And then if one charges them up quickly, the same issue applies. Damaging high current usage.

So, is it wise to drain lithium batteries down, and re-charge them, in order to avoid leaving them at a high rate of charge?

Tactically, it seems the best thing to do, but what exact benefit is being achieved? What one might need, is to drains the batteries very gently down, and then stop the power drain at a certain capacity. And then, slowly bring them up to capacity for usage, whenever that is.

While that sounds reasonable, is it practical? It's not how I intend to use my batteries. And there are more circumstances and conditions that can damage lithium battery life. One thing I read, said that currently (a very recent paper too) that there a no formulae to come up with predictive age. The science is still immature.

Boiling water is not even a high current draw on my little bank . ( im only 250ah ) When I do boil water it still never draw above a ..25C and that is not a high power draw. Now you go to one of the guys here with a 1000 ah bank and even a 2,000 watt inverter draw is nothing . As to rapid charging the best I can do is a .5C and that is nothing . On boats we don't do high draw ( unless electric propulsion and that has issues all its own. )
As to charging and discharging well most of us that live aboard that is just a normal day. ( you will get used to that ) well as to predictive aging there is plenty of data to read and put together tomcome up with a good idea as to what will affect cycle life. Most of them are listed on this forum somewhere. Do a search and be prepared to do the reading we all have already done.

Please post a link to the recient paper you read that there is no formula . The science is not immature. It has been around for plenty of time

[newhaul]

Originally Posted by Melbourne Park

Yes. My point is that no one here has provided scientific data which shows the effects on longevity of Lithium Iron batteries. While manufacturers talk about storage, that is an entirely different issue. Insurance being just one issue - as batteries are transported from the maker to the user.

I just want some proper data - and without it, I'll consider all the issues that a maker, then distributor, then retailer, and all the issues surrounding those businesses, will also have to consider. As just one example - how much extra would it cost the maker of batteries, to send them out fully charged, compared to a limited charge? What about insurance issues relating to fully charged batteries, coming all the way from China? Given me the science, and at least then, I can make a logical decision.

And while I found data on some forms of Lithium, I haven't found it on Lithium Iron. Why not? An example of one thing I have read, is this one. But I would like a paper studying Lithium Iron Phosphate batteries, or LiFePO4.

Here is such a paper which I browsed through ... https://core.ac.uk/download/pdf/323272674.pdf

I cannot discuss this further at the moment, as I am going away. But assistance would be most appreciated!!

All of the answers you are looking for are in that paper you posted. Next what size bank do you actually want/ need. To do what you want then you can start figuring out what you can do . And I'm sure you won't be able to have enough charging capability to exceed .5C

[goboatingnow]

Indeed this graph is telling

[goboatingnow]

If you are prepared to read the various research articles I think you will readily accept that higher SOC storage values degrade overall cycle life

Whether that’s important to you is another question entirely

“Figure 5 shows the results of the calendar capacity loss tests. These results indicated that the capacity loss increased under the higher temperature and SOC conditions. It is thought that the main cause of this large capacity loss is that the reactions between the lithium ion and the electrolyte are accelerated under high temperature and SOC conditions. As a result, the absolute amount of lithium ions decreases due to the growth of SEI films.”



Analysis of Degradation Mechanism of Lithium Iron Phosphate Battery

https://mdpi-res.com/d_attachment/we...ion=1526611546

( mostly acedemic researchers at Waseda University )



“Lithium iron phosphate batteries were aged in two ways, by holding at a high potential corresponding to 100% SOC and cycling at 1C/6D at elevated temperature. In both cases, differential thermal voltammetry (DTV) was capable of diagnosing degradation in a similar way to incremental

“capacity analysis (ICA). It was possible to directly correlate peak parameters with capacity fade, resistance increase and inhomogeneous electrode performance suggesting that the technique could be used for SOH estimation in real applications. “


Tracking degradation in lithium iron phosphate batteries using differential thermal voltammetry

https://spiral.imperial.ac.uk/bitstr...oltammetry.pdf

Given that multiple research papers largely say the same thing LFP degrades faster at higher SOC then lower. I think we can safely conclude that storage at medium SOC values consistent with leakage/self discharge/standby current time scales is better then storage at high SOC%

[SoonerSailor]

Melbourne Park - maybe you are over thinking this. We know having LiFePO4 regularly sit for extended periods (day) at near 100% or near 0% will shorten ultimate life. Or charging or discharging at 1C rates may also shorten ultimate life. These are things we can easily control if we wish to achieve the 2000+ cycle life of the chemistry. Realistically, with just a modicum of care, these batteries can last a very long time, and even with mild abuse that can be many years in the average use case. By that time, even better/cheaper solutions will likely have arrived. It’s not worth stressing over the details, even if it is interesting. I can be sucked into the same whirlpool myself, though I try, with irregular success, to avoid it!

[hjohnson]

On my boat, at least, I just tell the victron kit to limit the target voltage to 13.2v, which leaves us at around 55% SoC. The day before we take the boat out for a weekend trip where we're actually going to be using the power system significantly, I remote in and remove the artificial limit, and let the battery go up to 100%.

[fxykty]

Originally Posted by hjohnson

On my boat, at least, I just tell the victron kit to limit the target voltage to 13.2v, which leaves us at around 55% SoC. The day before we take the boat out for a weekend trip where we're actually going to be using the power system significantly, I remote in and remove the artificial limit, and let the battery go up to 100%.

We’re living aboard in a marina for now so connected to 230V shore power all the time except of course when we leave the berth. We’ve set the charge voltage to 13.0V and that holds us at 31% SOC. We’ve tried a variety of voltages: 12.8V = 19% SOC and caused problems when electric cooking, 13.2V = 48% SOC, which we figured was higher than optimal for steady state.

Same as hjohnson we reset the charge voltage half a day before we plan to leave the dock back to 13.8V, where we keep it until we return to the berth. This is a single setting in our BMS’s CanBUS configuration. We don’t touch the Victron settings as all of those components are controlled by our BMS. Of course every charge source and load source is properly set to do the right thing in case CanBUS goes down, and the BMS relays are there to back stop the settings and to protect the battery.

We’ve set our BMS to our basic 35-80% SOC charge profile and it only charges up to 100% SOC once every 30 days to reset the SOC calculation. Otherwise, it stops all charge sources via CanBUS at the upper limit SOC of the charge profile. We use 2.5% C for trailing amps at the charge voltage of 13.8V to calculate the 100% SOC. We’re probably giving up a bit of capacity but really don’t need another 5% capacity or whatever that forcing the battery to a higher voltage would give us.

Note that with that charge profile, if charging is off during the afternoon then SOC can fall overnight to 20% by morning, by which time solar charging takes over again, or dino juice if there’s no sun. We’ve gone as low as 11% SOC with voltage still around 12.7V. Not a problem as we’re still well out of the low knee and low voltage cut off.

We follow the charge, then don’t charge until SOC falls to the lower limit of the charge profile, system and don’t bother to mini cycle every day with constant solar charging keeping the SOC up near 70-80% SOC.

This just describes what we do and is not a prescription for anyone else.

[PaulCrawhorn]

It's so nice to see such care practices now better understood and more widely implemented.

Owners of course may not care about longevity, and that's fine, but there used to be so many naysayers that thought it wise to just follow the maxV data sheet as their charging regime and allow the bank to just sit there much of its life.

[Caz]

Hello All,
I have been looking at the Lithionics line of batteries and external BMSs. Unfortunately, my battery box is set up for the 8D batteries. I've tried to figure out how to put a "boat-load" of their batteries in my battery box, which measures:
Battery Box
L: 47 1/4”
W: 22 1/4”
H: 21”

Because they use prismatic battery packs, their batteries are too long for my battery box. They say I need to use their 24 volt batteries and not put 12volts in series/parallel.

I also have very awkward/complicated access. (see pics) And there really isn't any other place to install batteries. Really! So not an option.

So my question: Does anyone know of a manufacture similar to Lithionics that makes a LiFePo4 battery that matches the AGM 8D size? (I tried the BattleBorn 8D, but my system blew up their BMS in a few milliseconds as my house system powers the bow thruster, which has an in-rush current in excess of >>1,500 amps and a steady state of 800 amps.) This lead-acid AGMs have enough internal resistance to limit current. But the low resistance of the LiFePo4 caused the BattleBorn batteries to die.

Thoughts? Suggestions? Other vendors to check out?

[CaptainRivet]

Originally Posted by newhaul

Boiling water is not even a high current draw on my little bank . ( im only 250ah ) When I do boil water it still never draw above a ..25C and that is not a high power draw. Now you go to one of the guys here with a 1000 ah bank and even a 2,000 watt inverter draw is nothing . As to rapid charging the best I can do is a .5C and that is nothing . On boats we don't do high draw ( unless electric propulsion and that has issues all its own. )
As to charging and discharging well most of us that live aboard that is just a normal day. ( you will get used to that ) well as to predictive aging there is plenty of data to read and put together tomcome up with a good idea as to what will affect cycle life. Most of them are listed on this forum somewhere. Do a search and be prepared to do the reading we all have already done.

Please post a link to the recient paper you read that there is no formula . The science is not immature. It has been around for plenty of time

fully agreed, high power draw is above 0.5 C on a cell that can do continuous 1C.
anything below 0.33 is not even considered high current draw and on my 816AH bank that's around 300A Continuous which I draw when operating the 3 burner cooktop on full blast.
but that's not even continuious as the cooktop switches between different power stages.
so unless you have a very small 100 or 200AH bank forget that aging due to high current draw or charging.

[CaptainRivet]

Originally Posted by Caz

Hello All,
I have been looking at the Lithionics line of batteries and external BMSs. Unfortunately, my battery box is set up for the 8D batteries. I've tried to figure out how to put a "boat-load" of their batteries in my battery box, which measures:
Battery Box
L: 47 1/4”
W: 22 1/4”
H: 21”

Because they use prismatic battery packs, their batteries are too long for my battery box. They say I need to use their 24 volt batteries and not put 12volts in series/parallel.

I also have very awkward/complicated access. (see pics) And there really isn't any other place to install batteries. Really! So not an option.

So my question: Does anyone know of a manufacture similar to Lithionics that makes a LiFePo4 battery that matches the AGM 8D size? (I tried the BattleBorn 8D, but my system blew up their BMS in a few milliseconds as my house system powers the bow thruster, which has an in-rush current in excess of >>1,500 amps and a steady state of 800 amps.) This lead-acid AGMs have enough internal resistance to limit current. But the low resistance of the LiFePo4 caused the BattleBorn batteries to die.

Thoughts? Suggestions? Other vendors to check out?

Forget LifePo4 with that power draw. A lifepo4 can do 1C, so you need 800AH minimum which you will never fit into that space.

The only solution for your problem are 40AH LTO cells from Ying long. 6 cells as 1S6P 40AH can do 400A=10C.
for your loads you need 200AH = 30cells making a 5S6P battery that can deliver 2000A.
You can also use 160AH if you can only fit 4S6P.
Had the same problem on my old ketch, bowtrister was in the same range. I had 320AH in a 8S6P config of THE 40AH LTO.
the will survive your boat, cycle live is 30000.

[PaulCrawhorn]

LTO is way less energy dense than LFP.

The higher density chemistries are very fire-risky.

You can find cells in many shapes & sizes, add a BMS and you have your bank.

But for huge currents sustained over minutes rather than seconds, you need the space / volume for a big enough bank to keep the C-rate down.

Physics