Bottom balancing?

[morph999]

I didn't say Jack was right about all his conclusions. And GGoodrum is not right about everything either. There is nothing wrong with charging to 4.2v per cell. Even Thundersky says so. They make the batteries. Well....I'm going to leave this forum because I can see everyone has their nose so far up this GGoodrum's guys ass. My word is just dogshit. Have fun spending $250 on A BMS THAT YOU DON'T EVEN NEED. LMAO.

 

[liveforphysics]

I didn't say Jack was right about all his conclusions. And GGoodrum is not right about everything either. There is nothing wrong with charging to 4.2v per cell. Even Thundersky says so. They make the batteries. Well....I'm going to leave this forum because I can see everyone has their nose so far up this GGoodrum's guys ass. My word is just dogshit. Have fun spending $250 on A BMS THAT YOU DON'T EVEN NEED. LMAO.

You and Jack can share in the continued and frequent cell failures together. If your goal is to damage the cells as fast as possible, why stop at 4.2v? Bring it up to 5-6v. The cell doesn't explode, so it must be a good idea. I could write it up on a spec sheet for you so you feel safe about it.

PS: I've never bought a thing from Gary, and I've never used a BMS in any of my packs. The cells stay in perfect balance because I have well matched cells, and because I run 3.2-4.12v voltage range on cells that COULD function between 2.5-4.35v, but this would mean plauges of cell imbalance, and doing damage to the cells everytime I charged, just like Jack does everytime he brings thouse TS cells to 4v. LiFePO4 is done at 3.7v. Its over. The brand name on the battery doesn't make a bit of difference, its charged. You CAN bring them up to 5-6v/cell if you want, they just sit there and take it, but you're causing permanate damage when you do it.

 

[amberwolf]

I didn't say Jack was right about all his conclusions. And GGoodrum is not right about everything either. There is nothing wrong with charging to 4.2v per cell. Even Thundersky says so. They make the batteries. Well....I'm going to leave this forum because I can see everyone has their nose so far up this GGoodrum's guys ass. My word is just dogshit. Have fun spending $250 on A BMS THAT YOU DON'T EVEN NEED. LMAO.

The spec that TS prints is almost certainly not correct (and is probably the result of poor translation of technical documents from Chinese to English, not an uncommon occurence), as has been determined by experiences of multiple owners of TS battery packs in various EVs. If you charge them to that voltage repeatedly, you're going to cook them, and their life will be very short.

Take a gander around on various EV forums, such as over at DIY Electric Car, and you'll be able to read experiences of what happens to packs that get charged that way.

It's your pack, so charge it however you like. Just don't cry too hard when it dies an early death.

 

[AndyH]

Guys - there's nothing wrong with Thunder Sky's spec sheets. They quote nearly the full voltage range of LiFePO4 cells, that's all. They are only saying that to get more than 2000 cycles from their cells, keep voltage between 2.5 and 4.25.

Compare TS's data with this from A123-Systems (page 30 of attached report):

View attachment A123_Voltage.jpg

I like Jack's work - but while he's en engineer and has some expensive 'stuff', he appears to be fairly new to LiFePO4, EVs, and data logging/analysis. He's learning though. :wink:

Andy

 

[Doctorbass]

I agree with Andy, Gary, LFP here.

I watched every of his video by curiousity to better understand why he is claiming thingh like that. He clearely said that he is new with LiFePo4 cells ( 2 years or less).. but what it is strange is that he claim he tested them so many time that it's nearly impossible to believe.. eventhough hi have more time since he is retired... I like the way he explain things and the time he spend on doing quality video, but i dont agree with some of his theory.. like bottom balancing or anti-BMSism...

I play with LiFepo4 cells since 2007 and is one of the first here who played with A123 cells and posted so many test that today, i can say i know them and get the results i want from them by following my rules that are nearly identical to the manufacture recommendations... as well as i agree 100% with Gary on the way he explain these great cells.


What we should pay attention is that the cell voltage recommendations on the A123 is depending on temperature!!.. On the spec sheet of the M1 cells, they indicate that they can be charged at 4.2V max in low temp conditions...

To me.. that mean that since we know that cell RI increase as temp decrease, ee must rise the charging voltage to carry the same current into the cell That mean... the cell will not take more time to charge if it is at low temp cause we could compensate by increasing the charging voltage. that's what i understand of WHY A123 indicate that we can charge at 4.2V... its to compensate for the RI at low temp.That is my t heory from now. .. I believe that when they say SOLUTE rating that mean in the extreme conditions... and extreme condition can mean temperature... and RI variation...

Jack is claiming that we can not use the RI to decide the way we evaluate or charge the cell...he claim that it is too variable with temperature .... that's true.. but he did not push his research far enough... and that's what he is missing!! But since he mentionned that "he can be wromg".. yes... you've reed that! he said "I CAN BE WRONG".... so if he would use that and keep his ego away for few days and test cell RI with temperature.. he would discover important things about LiFePO4 that certainly could change his mind...


There is something that it<s still strange to me:
He did a video about TS cells where he charged a TS cell at 1C and had let the voltage to rise up to 5.2V for the CV phase until he noticed that when the current began to drop.. then he droped the voltage to 3.7v and noticed that the current was very close to C/20, indicating the normal end of discharge.

He claimed that its not the voltage level that kill or dammage a cell.. but its the overcharge in capacity ( ex: let a cell reach C/20 at 5.2V)

Instead of C/20 at 3.7V in normal condition or 4.2 at low temp i believe...

If he only could open his mind and test what WE TESTED and understand, his presence in the EV community and the time he spend to share knowledge would be alot appreciable!

Doc

 

[MitchJi]

Hi,

I've never used a BMS in any of my packs. The cells stay in perfect balance because I have well matched cells, and because I run 3.2-4.12v voltage range on cells that COULD function between 2.5-4.35v

But you do balance them to 4.12 when charging? How do you insure that no cell goes below 3.2?

I like Jack's work - but while he's en engineer and has some expensive 'stuff', he appears to be fairly new to LiFePO4, EVs, and data logging/analysis. He's learning though. :wink:

Like his work? Killing cells by not having the sense to use LVC is good work?

I didn't say Jack was right about all his conclusions. And GGoodrum is not right about everything either. There is nothing wrong with charging to 4.2v per cell. Even Thundersky says so. They make the batteries. Well....I'm going to leave this forum because I can see everyone has their nose so far up this GGoodrum's guys ass. My word is just dogshit. Have fun spending $250 on A BMS THAT YOU DON'T EVEN NEED. LMAO.

You started a thread extolling someone's advice who doesn't even know enough to use LVC protection and the result is predictable, dead cells. He can't even manually balance and use cells without damage!

Several very knowledgeable people have generously taken the time to try to help you avoid the same mistakes and this is your response? An excellent next step would be an apology.

 

[AndyH]

I like Jack's work - but while he's en engineer and has some expensive 'stuff', he appears to be fairly new to LiFePO4, EVs, and data logging/analysis. He's learning though. :wink:

Like his work? Killing cells by not having the sense to use LVC is good work?

Let those that have never killed a cell cast the first cell interconnect strap.

He didn't start killing cells until he fell under the 'shunt' spell that's so strong in many forums. He's learning about LVC - I expect to see a video from a reformed cell abuser any time now. :wink:

 

[recumbent]

...Let those that have never killed a cell cast the first cell interconnect strap.

Thanks "AndyH" for keeping us grounded.

Okay, I'll keep charging my lifepo4 to 3.6, and never let my pack go lower than about 2.9 as always. Anything lower just drops like a brick anyways.

The "Cellog8" is my new best monitor.

 

[liveforphysics]

Hi,

I've never used a BMS in any of my packs. The cells stay in perfect balance because I have well matched cells, and because I run 3.2-4.12v voltage range on cells that COULD function between 2.5-4.35v

But you do balance them to 4.12 when charging? How do you insure that no cell goes below 3.2?

The pack has JST balance taps, which have cell monitors plugged into them set to alarm at 3.2v. When I see a voltage difference between the cell groups (generally like 0.03v at most), then I plug in the JST balance taps to my Chargery 1010B, and set it to balance charge the pack. I have to break it into sections to do this, so 95% of the time it simply gets charged off a CC/CV power supply.

 

[dequinox]

The pack has JST balance taps, which have cell monitors plugged into them set to alarm at 3.2v. When I see a voltage difference between the cell groups (generally like 0.03v at most), then I plug in the JST balance taps to my Chargery 1010B, and set it to balance charge the pack. I have to break it into sections to do this, so 95% of the time it simply gets charged off a CC/CV power supply.

What is a JST balance tap? Do you have a link to a thread about the general balancing and LVC concepts? I intend to buy 2 of those 20ah 12v TS packs from elite and would like to monitor and balance only when needed.

I am now looking into a charger too. Elite sells them, but it appears as though someone said they were "crap." Is there any truth to that? Is it possible to open up these chargers and adjust the charging cutoff voltage? I want to buy one and try to configure it for battery pack longevity. To me LVC is the way to go, and it's cheaper to boot.

 

[Doctorbass]

For those who are curious about Jack and BMS relations:

Friday, January 15, 2010
EVTV News Show


January 15, 2010. First show of the Year.

This week a short 24 minute description of discharge tests of Sky Energy cells and Thundersky Cells. We discharge these cells at a 1C current load and chart the voltage by percentage of discharge to show you WHY 80% DOD is indeed the magic number.
We also discuss the CellLog 8S - a $29 device that will log the voltage of eight cells to memory and comes with software to graph the results on your PC. PLUS, it features an open collector alarm circuit you can use to build a very low cost "BMS" that will notify you whenever any cell is DIFFERENT from the rest of your cells
by a preset voltage amount.

http://EVTV.me


Doc

 

[dogman dan]

So he is monitoring something at the cell level. I got the impression he was just using a pack voltage lvc.

Much depends on the size of the cells too, in my opinion. With a bike, the pack is not so big, and cells can die pretty quick. With a car size pack, I would think there would be other things that may work if the cells don't go over the cliff as fast as smaller ones do. A bms for a bike pack is cheap, but for a car size battery it does get costly. But I still think you want to mointor cell level lvc.

 

[Toorbough ULL-Zeveigh]

sounds like he might be monitoring ES.
if he really is an engineer then he must be a mech.
in which case we all need to be a little more forgiving & tolerant with them.
speaking more slowly & not using big words would help too.

 

[liveforphysics]

sounds like he might be monitoring ES.

A wise man would. The automotive EV forums are so lead-acid based that there battery knowledge seems about 3-4 years behind ES, as lithium has been a cost viable option for E-bikes for a much longer time.

 

[jrickard]

There is something that it<s still strange to me:
He did a video about TS cells where he charged a TS cell at 1C and had let the voltage to rise up to 5.2V for the CV phase until he noticed that when the current began to drop.. then he droped the voltage to 3.7v and noticed that the current was very close to C/20, indicating the normal end of discharge.

He claimed that its not the voltage level that kill or dammage a cell.. but its the overcharge in capacity ( ex: let a cell reach C/20 at 5.2V)

Instead of C/20 at 3.7V in normal condition or 4.2 at low temp i believe...

If he only could open his mind and test what WE TESTED and understand, his presence in the EV community and the time he spend to share knowledge would be alot appreciable!

Doc

If you would open your mind, it would not be so strange to you. You take little scraps of information, and repeat it to each other long enough, it becomes fact - but only in your mind. You clearly do NOT understand what the maximum "voltage" is on the spec sheet in front of you. I was trying to explain it in the video.
The cell is fully charged at 3.4 vdc. It always was. There is no other "real" voltage. They do not like to be overcharged. The manufacturer gives you a "charge voltage" based on a standard charge current. This is a very brief description of a CC/CV curve. They can describe it essentially in one term - max voltage. IF you charge at ANY current until you reach a maximum voltage of 4.2 v, and then hold that voltage in CV phase until current decreases to 0.05C, you will have fully charged the cell. And if you let it rest a few minutes and measure the static voltage, it will indeed measure something like 3.38 or 3.40 volts. That is the ONLY voltage that actually ever mattered. The 4.2v is a short hand for A, as in 1, as in 1 of MANY, as in fact in 1 of an almost INFINITE, number of charge curves that would also get you to fully charged - 3.4 vdc static.

There never was any magic in it. If you look elsewhere on the spec sheet, you will also see that you can charge at current levels up to 3C. And in fact I have done so. And it works just fine. And nothing gets fried. And its all good. But of course the voltage at the terminals is WAY beyond 4.2 v. As it always would be at 3C.

The voltage at the terminals during charge never did matter. It was a target. The only voltage that matters is the voltage of the cell itself, which you do NOT want to go over 3.4 vdc static. The problem is how do you "get there." Here's a real slow way. Charge at whatever voltage and current you like for a couple of minutes. Now wait five minutes for the cell to return to a static level and measure it. Now repeat. It will take you about 3 days to charge the cell. But it will work.

The CC/CV to 4.2 is a charge curve methodology that will allow you to get there actually at a variety of current levels you would be likely to have available. If you pick 4.1 v and do the same thing, you will undercharge a smidge, but not much. And that will likely increase the life of your cells.

In practice, we charge serial strings of TS cells to 3.65 vdc. And the little bit of additional charge we fail to put in, is very minor. And it prolongs the life of the cells.

The point made, that you missed because your mind is closed and you already know everything from having typed so very very much, is that currents up to 3C can be accommodated, and the voltage you are so busily monitoring with your BMS and guarding against, isn't what you thought it was. It is a CC/CV description. Nothing more.

I find it beyond belief that you silly people have actually denigrated my reporting real test data BECAUSE I'VE DAMAGED CELLS????? What idiots, and from what planet? I don't lose ANY cells on my car. And I rather view it as my job here to damage cells otherwise. THAT'S HOW YOU LEARN. Your mission is to preserve your cells and I all too well understand why and sympathize with completely. They are expensive. They are ALSO expensive FOR ME. But there's not much to learn about a cell that works fine, and after using it, also works fine. THis is precisely how all this online typing/mythology gets so carried away. You learn NOTHING, and then make up some wild shit to explain it, and then repeat it to each other. THEN YOU ALL VOTE ON IT. Yep. That's what's right. More of us believe it than don't believe it AND SO IT BECOMES SO.

You're not going to learn anything about LiFePo4 cells without hurting them. That's pretty much what I do these days, torture and murder LiFePo4 cells. And the whole point is so that you don't have to. And I've kind of taken that as a little bit of a mission for you. Then you claim I don't know anything about them because I've killed them? A fine thanks that is.

On this specific point you can quite handily charge at current levels up to 3C, though it is noted that there is some loss of capacity in doing so. And your voltage can be quite beyond 4.2 vdc when you are doing so. The problem is then detecting when to terminate the charge so they are not overcharged. And the voltage you read at the terminals while charging has no bearing at all on it, which is why your BMS strategies are simply nonsense. By making them ever more convoluted and ever more complicated, you never seem to get there, because what you're doing doesn't need to be done in the first place.

NOW all the rage is LV cell detection. I can absolutely and definitively demonstrate cell voltage levels QUITE below 2.0 v on FULLY charged, fully functional perfectly operational cells that are in fact doing precisely what they should be doing. I'm not philisophically opposed to the concept of LV monitoring, I don't even understand what you are trying to do or why you are trying to do it. And that's because YOU don't understand how they work - after playing with them since 2007. They can quite commonly read below what you're monitoring for without having any cell problems at all, just a high current demand for a brief period. The same cell, showing an even HIGHER voltage under a lesser load, could be badly badly damaged and about to go far far away at any moment and your monitor won't even peep. Ergo my question, entered with a quite open mind, you are monitoring FOR WHAT, and you are going to do WHAT with the information??????

And I do know how it all happens. You take measurements under static conditions or at very low current levels, and extrapolate them endlessly by typing on your keyboard about it a lot. I want you ALL to go get these Cell Log 8S devices. That will allow you to record actual cell voltages under actual driving conditions in differing temperatures and then review it on a computer screen. I think you'll get a lot smarter that way then by typing a lot, and my job will be a lot easier. What you will see is that the "voltage" of the cell varies a lot more than you think, depending first on current loads, and then varying from THAT depending on what part of the discharge curve you are on, and then varying from THAT depending on ambient temperature, over such a wide range that the entire concept of LV cell monitoring becomes ridiculous.

How would actually monitor anything useful? Well that pretty much requires some "comparative" analysis. We can assume a couple of things here. The current through one cell will be pretty much identical to the current through all the other cells. The ambient temperature may vary slightly but should be broadly the same for all the cells. And so the voltage of any particular cell, should be pretty close to the voltage of any other cell, under the same conditions.

We use a totally idiotic circuit that measures the bottom half of the pack voltage and compares it to the top. It displays a centered bar on a bar graph. If either half varies from the other by more than a few tenths, the bar moves a digit right or left. At rest, it is more or less centered. Under acceleration, all cells are carrying identical current, and while there is some small variation in internal resistance and voltage, they are pretty close. And so it stays centered at rest, at 10 amps, at 100 amps, at 300 amps, and at 540 amps. It also stays centered at the top of charge, at 50% DOD, and at 80%DOD. And it stays centered at 100F, at 75F, at 45F, and at 10F. If it goes off center by more than a few bars, you should check your individual cells. And I'm particularly looking for variation under significant load, because that tends to indicate an increasing internal resistance, a sign of a failing cell that either needs attention or replacement BEFORE it fails completely.

The Cell Log 8S actually will do this kinda/sorta in a more needlessly complicated way, and still satisfy your insatiable desire to dick around with these batteries constantly. You can set the alarm to work on a difference voltage, such that if any cell varies from the other 7 by a set amount, it will trip the alarm. It is more complicated, more expensive, and no more effective, but it will give you something to do, and it IS kind of of value to then go look at the logs and see the bad cell sagging dramatically more than the others on the graph from actual drive data. So it is a learning experience that involves almost no typing or repeating of common wisdom endlessly.

Truly truly, it is NOT my mission to upset all these apple carts and dethrone the little tin forum Gods that have gained such a following by typing a lot. But if you had been doing primary research instead of spending so much time in the forums, there would be no need. I know, I know. You've been doing it all for a hundred years, you're the biggest stick in the EV universe, and how dare anyone challenge your pronouncements from on high. Well, if you had been doing your little tin God job and actually learning about them, which yes, does involve mostly cell DESTRUCTION not preservation, does indeed involve some time, and is of course expensive both in cells and equipment, then I would neither be making such a splash or need to. I've actually been drawn off into this topic much farther than I foresaw or wanted to. We are literally beseiged with requests for MORE of this info, because there are a LOT of people out there quietly LOSING cells following your misinformation, spending THOUSANDS of dollars on BMS systems that don't do shit and in many cases are damaging both batteries and cars. I am stunned that they do NOT want to talk about it in your forums because they are EMBARASSED that they have lost cells, and it must be something THEY are doing wrong. I am getting literally HUNDREDS of these e-mails from people in this situation, whom you have gravely damaged in a very dollar denominated sense, with your nonsense.

I don't mind embarrassment at all. And for a very simple reason. I only learn by failure. Every time I've ever done anything right, or that worked out successfully, I've always wondered what parts I could have left out and it still worked? Every time I've failed at something, I can pretty much come up with EXACTLY what caused the failure. And after a sufficient serial number of years both succeeding and failing, I've learned that the only value anything has is in the failure mode. Once it works, I'm completely disinterested.

So I don't CARE how long your cells have lasted. If it is working for you and you are having a good time, do it till the sun don't shine. You can weigh down your car with $120,000 worth of instrumentation to detect every coulomb passing in the night. But then assuring anyone that will listen that they need to do the same or they will surely lose cells is just nonsense. If you have some real data, generated by actually hurting or killing a cell, that can be duplicated with test equipment, I would be very interested in reading about it. And sure, some of your magic dust and mystical incantations are entertaining, as long as they don't hurt anybody.

Finally, my presence in the EV community is not subject to your approval or appreciation Doc. I am first uncertain that I am in your community, and secondly not too concerned about it either way. I'm not really a "community" kind of guy. We have found a fascinating world of electric cars and batteries and components, and we're having a ball with it. I'm going to publish videos to share what we learn. And if it doesn't match what "you tested" and understand, I don't know what to tell you. I'd like to say I'm sorry but I'm actually not. I don't have any emotion about it at all. Retest. Reunderstand. Do something. I am very pleased with the very surprising response we've had to the videos, apparently they are meeting some need that the forums have not met, and there's a bit of information in that for you I would think. I thought they would be very esoteric and of course very long winded videos of interest to a very narrow group of people who were either intensely interested in the topic or just REALLY hurting for some video to watch. Since our first published video in May 2009, we've just gone over 150,000 COMPLETED video views - that is watched to the end. I don't even know what to make of it. There isn't 2500 LiFePo4 cars on the planet yet.

And yes, I'm here because three of your forum guys tattled on you. I can't type as much as you guys, but as you can see from this message, I can type a LOT when I have to. I don't actually get any smarter when I do it. But I can do it.

Regards;

Jack Rickard
http://EVTV.me

 

[vanilla ice]

Hey Jack, I appreciate you destruction testing your stuff, just like I appreciate these guys here that do the same. Whats that they say.. "If two agree on everything, one is unnecessary."

 

[pm_dawn]

@Jack: You sure know how to piss on quite a crowd.

A number of guys/(girls?) here at the ES are these RC helicopter guys that you are referring to. That actually has really nifty Chargers/dischargers
A number of guys/(girls?) here at the ES are testing cells to the limits both on the bench with there WestMountain stuff and Celloggers, but also in the real life doing over 30C discharges on there bikes. They post discharging grafs. I would pretty much say that they are testing there cells a bit more brutal than getting credit for by you. I think you should check the A123 20ah pouch testing thread, if you haven't done that yet.

I kind of agree a bit with you about the LVC deal. There is really not that much of a voltage to look for, as there is a difference to look for.
I have a 40s TS LFP 160ah pack that I drive daily in my Renault. And boy does the sag differ between different temps, and SOC. Up to now I have only been using the ver 2.5 of the BMS from Goodrum/Fechter but I put 2,7v LVC detectors on it instead of 2,1v which was in the original design.

Today I was driving and was pretty low on charge about 30- 40% SOC and the temprature was below -20 centigrade. I was tripping that LVC at as little as 0.3C discharge. The pack was sagging about 35V @ 0.7C from its 133v resting. I know that if I have a high SOC like 80-95% I can pull atleast about 0.8C at the same temperature without tripping the LVC. So I agre that IR is really all over the place depending on numerous things.
But this has also been discussed here at ES.

I have bought me a couple celloggers, and I plan to use them pretty much as you have your Porsche setup, checking for difference in cell voltages.
But the problem with the celloggers is that you dont see the whole pack difference. I sure hope that they will produce a Cellogg45s as being proposed here in an ES thread. That way it would be possible to see the difference on the whole pack and pinpoint any bad cell at once.

How far have you come with that Arduino project. What current sensor are you using ?
Anyway I like your shows, I get info from them and I try to make some use of it.

Best Regards
/Per Eklund
Snowy Sweden

 

[heathyoung]

LVC is still a great way to avoid killing - mismatched - cells. In a perfect world, every cell from the same batch would have the same ESR and capacity - but they dont. Dropping cells too far or reverse charging them will kill them.

A lot of people here are buying from the low end of the market - eg. drill cell rejects from god knows what batches, with no capacity matching, prysmatic and cylindrical cells of dubious origin blah blah. If you have mismatched cells, you need to derate the pack to suit the point where the lowest capacity cell drops to LVC. I built a 'runt pack' of konion cells, some that were OK, and some that were reformed from as low as 0.2V (yes, this chemistry will support this).

I made up a 6S6P pack, which was balanced charged, and then had the snot beaten out of it (600W load for 15 minutes) until 18V LVC total. Measuring the cells, the good ones were at about 3.1 - 3.2V, but the really bad set (reformed) were sitting at 1.9V or so. Ouch. It was then stuck on a 25V 6A current limited supply, charged till C/20, and tortured again. This time it fared worse - 15 minutes at 600W, but the low cells measured barely 1V. Hmmm... Charge again, discharge again, 0.65V. This would have killed a LiFePo4 cell in a very short order.

Charged again, balanced this time, discharged 600W for 15 minutes, measure bad cell pack, 1.9V. Better.
Running this crap pack without a cell based LVC would have meant probably 50 cycles tops, but with the illusion of a higher capacity pack.
Running without balancing AND a cell based LVC, probably 20 cycles if you were lucky. Low cell only got charged to 3.5V, then 3.0V, with the other cells getting charged progressivly higher.
Running with both balancing and cell based LVC, considerably longer, but with an ever-decreasing capacity before total LVC.

On an ebike with a high discharge rate, and lower capacity mismatched cells, cell based LVC and balancing is a must. If you have wildly mismatched cells, they will die much quicker without protection. If you try this with more volitile chemistry, and on a larger scale, you are risking your life (not just your wallet).

 

[AndyH]

For those who are curious about Jack and BMS relations:
<snip>
Doc

Hi Doc,

Jack's been active on DIY Electric Car and the Thunder Sky Yahoo group, at least. It makes sense, I guess, since he's coming from the eCar world. I think it's unfortunate that he found those places first, rather than E-S. I found this place after spending time on other forums - the level of sophistication and IQ points here is unmatched in forum land as far as I can tell. Some time spent here could have helped speed his progress - folks like you, Gaston, Gary, Richard, et al have already 'been there' with much of what he's discovering.

Andy

 

[AndyH]

@Jack: You sure know how to piss on quite a crowd.
<snip>
Best Regards
/Per Eklund
Snowy Sweden

Brilliantly said, Per

 

[bigmoose]

I always try to approach new ideas with an open mind because of my background in technology. I too like Jack, retired from a first career ... but from his surroundings, I am definitely not in his financial/social class...

I took an hour or two to page through his site and get a feel for what he is trying to do. He "feels" like a retired manager/business owner with a EE background. He has decent taste in "tools" However I think I have an extra digit on my voltmeter. << (that's a joke, just in case no one got it.)

That said, I think his desire for a simple battery "oversight" system is well intentioned, but will not be fruitful. My suggestion to him is that he take some time to read Gary's threads on the new Battery Management system here, especially absorbing Low Voltage Cutoff (LVC) limits and how to implement them.

So Jack, I welcome you to the Endless Sphere. You have your reading cut out for you for like the next month! Kick back, get to know the folks on here. There are some great people and ideas kicking around the sphere... I have only been here a short time and am still reading 90% of the time.

 

[Doctorbass]

Jack,

I think you missunderstand me on many points.

I dont have any approaval to give to anyone here. Everybody is free to contribute in a great way or not contribute on this forum. and i will encourage every person here to help, share contrinution in knowledge or experiments.

I did my own experiment and reed alot about battery using my electronic and physic background from a while and i am still very open to any new positive contribution or different theory. I will not enumerate every past test and graph, experiemnts or new great product i shared with the E-S crowd now, since everybody that appreciated that already know about.

You may be surprized if i say you i recommanded your video to alot of persons since i discovered them to help them to better understand EV. For sure.. like i said in this thread and other thread talking about you i dont agree 100% with you on everything as you would.

If i see something that is strange to me and that may conterdict or offer a different way to understand something when you explain your theory, i will offer my version, just like many other could do.

As many here know me, they also know that English is my second language.. and i still learn it. That is difficult to me to explain perfectly my point of view on things since my vocabulary is not as evoluate as i would in this language, but from now i do my best. Sometime, you could see Ypedal or some others members correcting my on some explaination because they perfectly know what i meant but that i wasn't able to perfectly write it here.
Language is not a barrier but it may create divergeance of oppinion just becaose it is missing the right words.

Jack, like I said, I like what you do and already said that before here eventhough i not agree 100% on everything you say. We need people like you to share time and experiments to help better understanding this great passion we have.

If only you could have reed every test and infos we shared on ev forums, you could probably have better idea of what we already know, have tested, and understand about battery.

But please stop saying our shunt based BMS will kill cells.. the hard work Gary(aka ggoodrum and Fechter) did already have proven to work and save more cell than it could kill them. We are lot of person that bought it can debate on that.

Internal resistance of lithium cells ia a very crytical parameter we must pay attention on.. it connect on every other parameters. I still like one of my credo i still use as a master reference and that you should read when you'll have time.. that i think you have now. It's the Battery Univercity website. They make very precise instrument for cell test and conditining under the brand caddex. Every informations on the chapter you find on their website correlate are some of the best i've ever reed.

I want to respect you and your work Jack eventhough you are a community guy or not, have 50 000views for your videos or not....or that i dont agree 100% with your claims.

To me our E-S forum is probably the best place where EV people can get infos and share infos. We have great tallented and knowledgeable persons and also curious. That is why this forum have grow as fast as that and i'm proud of it. Also you can find every important new discover about battery HERE.. this website is up to date.. and you will always fid someone talking about the lastest battery technology.. ex: like the 4Ah 18650 cells...

Our mind is open Jack I think you should just scrolled enough the pages of our great forum.
I would be surprized you could be the only one who can't appreciate it.

Oh I would like to add: (like Bigmoose wrote)
I am well intentionned to you too as well !and would like to say welcome on the E-S Jack. I just hope this false start could be arranged over the time as you could better understand us.

Regards

Doc

 

[dequinox]

I really don't know what to say other than I read just about every thing that I have time to of Doc's, Gary's, Jack's...methods...LFP's and anybody who's ever built an ebike. I've found most things I've read to be useful...whether I agree with them or not. Even if someone comes off as an asshole I will still read through any technical information in their posts. That is what I'm here for, not personal status gains. I'm here to share, read, enjoy the EV revolution, and be a part of it.

The wonderful thing about the sciences to me, the thing that makes their pursuit very human and not just a vocation of chasing data, optimization and solutions to problems...is that moment when we as a mortal and fallible being, take a stab at what that data means and how we should modify our choices in life based on our guess. And as scientists (of all levels...it isn't just a title for those carrying a degree) we must be responsible for our conclusions. The important thing is that if we've made an incorrect conclusion that we are prepared to fess up to it and change it.

That said I think most people are taking a financial risk by going into lithium batteries and starting an EV project. Even all the research on this forum cannot save someone from getting a drop of water on their BMS by accident, wiring a charger backward, or killing a few cells for any number of other unforeseeable reasons. The info here gives people a guide to educate themselves by, and they need to do the leg work and research all of this by reading as much as they can if they want to dig into it. It is not the responsibility of people doing this testing to protect others from accidental system failures...all you guys can do is try to give us as much info as you can so we can avoid as many of the major road blocks as possible.

 

[liveforphysics]

Jack- If your cells drop to 3.4v on there own after charging, you've all ready damaged them. This is the tell-tale sign to know if LiFePO4 cells have been damaged.

The cell should drop only and exactly by charging current x Ri the instant the charger is removed.

As an example, if you're charging a 100Ah TS cell with an Ri of 3mOhm, and you stop the charging at C/20 (5amps), you should see a voltage drop of 0.015V the moment it's removed from the charger.

If you're charging cells so the terminals say 4v, then removing the charge current, and the cell drops down to 3.4v on it's own, this is a clear indicator of cell damage.

Take a fresh A123 cell. Charge it for hundreds of cycles using a CC/CV method to bring it to 3.65v. It will sit at 3.6-3.65v for months. Now over-charge the cell to damage the cathode coating (there are other ways to damage it as well). Charge the cell up again with the same CC/CV method, let it sit, and watch it self-discharge down to 3.4v.

I've now done this with 26650 A123 cells, 15Ah and 20Ah prismatic A123 cells, and headways 10Ah cells (all LiFePO4, this failure mode seems to be both unique and common to LiFePO4 that has been over-voltaged). They all have roughly 2-3 times the Ri they had before being damaged, they all exhibit the same self-discharge to 3.4v, and they all measure roughly the same capacity they had when new, but of course the increased Ri means 2-3 times the heat and voltage drop.

Also, we to loads of cell killing in testing here. But we've learned which things damage cells to the point that we don't intentionally try do them as part of our normal charging process.

Best possible way to charge a LiFePO4 cell? CC/CV to 3.65v.

Best possible way to cahrge a LiFePO4 battery? This has many solutions, but the the goal of all of them should be to try and simulate the CC/CV to 3.65v/cell method, but distributed through the whole series string of batteries.

 

[markcycle]

I've been using TS cells for a year now. My experience is; if you charge a new TS cell to 4 volts disconnect it and let it sit, the voltage will sag back down to 3.4 volts after a day or so, I've done this many times with a single cell charger.
this may be a character of TS cells not seen in others.

Now my take on "How much is left in my tank"

This is what I do and what I have come to understand.
1) Low voltage monitoring or cutout is necessary, I use monitoring as at high peak loads the voltage can go below 2.1 volts momentarily
2 Amp- hours used; It is the combined parameters of LVM and A/H used that determines for my system the amount of energy I have left in the tank. When I get near 30 A/h used (40AH pack) I pay close attention to the cell level voltage at low throttle, low load. I also monitor the A/H the charger puts back in the tank - every time, so I know how much I am putting back into the batteries every time I charge, with experience or a good computer program and this data, a understanding of how much energy one has available for a given ride can reached.

3) Charging, I charge until the weakest cell reaches 3.9 volts and then call the pack full (If it is or not) I tried balancing at the top and it made less than 1 A/H of total pack capacity increase. I have found with TS that charging to 3.4volts gets one to 99% of full.

Mark