# no apparent BMS standard approach?



## dtbaker (Jan 5, 2008)

I am considering LiFePO4 for my next build, but still uncomfortable because I don't see any general agreement about how to configure/monitor/charge at reasonable cost without a lot of manual babysitting of the cells.

q: do cells like Thundersky or Blue Sky arrive far enough out of balance that I would need a lab type variable voltage power supply to do some cell-by-cell balancing before putting everything in series?

q: will a good quality but inexpensive charger with programmable curves (like the ElCon PFC-1500 for $550) execute good enough balancing to maximize cycle life? I do not anticipate needing flexibility of changing pack voltage after the fact, or needing to quick-charge at high amps off 220AC, so really don't need the more expensive chargers.

q: will a 'reasonable' active BMS with high/low cutoffs like the Hardy (for about $1000) provide me with enough functionality so that I don't have to periodically check and balance cells manually?


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## _GonZo_ (Mar 23, 2009)

Our BMS does what you ask for, and will be on your price range.
More info here: http://www.diyelectriccar.com/forums/showthread.php/new-bms-technology-39249.html


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## dtbaker (Jan 5, 2008)

_GonZo_ said:


> Our BMS does what you ask for, and will be on your price range.
> More info here: http://www.diyelectriccar.com/forums/showthread.php/new-bms-technology-39249.html



I am not seeing any detailed information on the specs or price for a unit capable of handling 40 x 100aH Thunderskys for instance. I also would be unlikely to buy the first generation of a piece of electronics, especially from overseas, without a couple positive references. I just am not willing to be the first down an expensive new path......

but I would encourage you to post production details of what your product can do, cost, and the basic principle that makes it 'better' than a shunt system.


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## Voltswagen (Nov 13, 2008)

DT
I will buy a Mastech Power Supply to do the initial individual charging once my TS Batts arrive. It has variable current & voltage and for $139.00 it's cheap insurance.
http://www.mastechpowersupply.com/v...-dc-power-supply-30v-10a-hy3010e/prod_14.html

I'm also considering this battery testing system if I really want to get anal and print out the discharge curve on each cell:
http://www.westmountainradio.com/CBA.htm


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## _GonZo_ (Mar 23, 2009)

dtbaker said:


> I am not seeing any detailed information on the specs or price for a unit capable of handling 40 x 100aH Thunderskys for instance. I also would be unlikely to buy the first generation of a piece of electronics, especially from overseas, without a couple positive references. I just am not willing to be the first down an expensive new path......
> 
> but I would encourage you to post production details of what your product can do, cost, and the basic principle that makes it 'better' than a shunt system.


I understand your point of wiew.
Any way you can see specs here: http://www.diyelectriccar.com/forums/attachment.php?attachmentid=5267&d=1261354887

Price will be available soon.


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## Voltswagen (Nov 13, 2008)

BTW
I can't take the credit for finding those ridiculously inexpensive lab
machines.
My Electrical Parole Officer in Gilroy, CA found them. 
Roy


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## dtbaker (Jan 5, 2008)

Voltswagen said:


> DT
> I will buy a Mastech Power Supply to do the initial individual charging once my TS Batts arrive.


you're not serious considering charging cells individually watching and manually adjusting voltage and amps, are you? Or are you planning on buying this thing just to use for the first time you charge cells prior to hooking'em up? seems like serious (unwanted) babysitting.....


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## dtbaker (Jan 5, 2008)

_GonZo_ said:


> I understand your point of wiew.
> Any way you can see specs here: http://www.diyelectriccar.com/forums/attachment.php?attachmentid=5267&d=1261354887
> 
> Price will be available soon.


well... I see design goals... do you have a product that actually DOES that?

The holy grail obviously would be some kind of combined charger/bms shuttle charge rotating thru cells and checking each status and cell voltage before shooting a burst of charge at some volts/amps for *some* length of time... is that what you are proposing? I look forward to cost and beta test results...


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## Voltswagen (Nov 13, 2008)

DT
Just for the initial charge.
It will also give me an indication of my weakest and strongest cells.
Those are the ones I want to monitor and set HVC and LVC on.


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## dimitri (May 16, 2008)

Voltswagen said:


> It will also give me an indication of my weakest and strongest cells.
> Those are the ones I want to monitor and set HVC and LVC on.


Do you mind sharing how the bench supply will reveal weakest and strongest cells?


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## Voltswagen (Nov 13, 2008)

Dimitri
Not the power supply but rather the battery test system would show the weakest and strongest cells.
I suspect that the power supply could also if careful track were kept of the charging time at a constant current and voltage. Yes? No?


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## dimitri (May 16, 2008)

Which battery test system?

Honestly, if I had no BMS on my cells for the past year, I would have no clue which cells are weakest or strongest, since those properties are only revealed under 2C-3C loads. Resting voltage and even 1C load don't show any differences, but 3C load especially at low temps shows dramatic differences across the pack. Maybe I am unlucky and got some cells from the batch made on Monday morning, but I have 3-4 cells in my pack which are seriously behind others and I would not know this unless I had BMS modules on them and PakTrakr display.



_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## Voltswagen (Nov 13, 2008)

I love your disclaimer .

This battery test system:
http://www.westmountainradio.com/CBA.htm
I had referenced it earlier in the post.

This however is just for the initial setup...........my jury is still out on the whole BMS issue.


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## gss99 (Dec 31, 2009)

Voltswagen, I sent you a PM but not sure if the PMs work on here.


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## gss99 (Dec 31, 2009)

dimitri said:


> Which battery test system?
> 
> Honestly, if I had no BMS on my cells for the past year, I would have no clue which cells are weakest or strongest, since those properties are only revealed under 2C-3C loads. Resting voltage and even 1C load don't show any differences, but 3C load especially at low temps shows dramatic differences across the pack. Maybe I am unlucky and got some cells from the batch made on Monday morning, but I have 3-4 cells in my pack which are seriously behind others and I would not know this unless I had BMS modules on them and PakTrakr display.
> 
> ...


1C loads don't show any difference? I'm putting TS on an electric bike. So a 1C load on a 36v20ah battery pack would be 20 amps. Right? I'll be using 35 amps so just over 1C. 

Dimitri, how seriously behind were the other cells? Can you give an example? Thanks.


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## dimitri (May 16, 2008)

Sorry, I missed the previous reference to the test system.

So you are willing to spend several hundred dollars on bench test equipment, but not on basic cell level BMS 

Please don't take it the wrong way, I love having bunch of cool tools myself, but I don't see how this helps someone who just wants to drive the car and not spend most of their life in the garage 

Also, any test equipment drawing less than 1C is not going to give you accurate real life information since these cells only start to show their real face around 2C-3C loads.


_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## Voltswagen (Nov 13, 2008)

Dimitri
Who loves ya babe! Me! 

If that is true then I'll have very little problems with my pack as I dont drive or accelerate at 2 - 3C loads. I try to keep my acceleration below 150 - 175 amps.
My approach is to manually balance top and bottom getting the cells as close as possible before the first test drive. From there I'll manually monitor cell by cell for variations.
Should the cells drift widely.....I'd then consider a BMS system.

And, yes, I do enjoy playing with toys.
If this wasn't fun Dimitri............I wouldn't be here.


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## dimitri (May 16, 2008)

gss99 said:


> 1C loads don't show any difference? I'm putting TS on an electric bike. So a 1C load on a 36v20ah battery pack would be 20 amps. Right? I'll be using 35 amps so just over 1C.
> 
> Dimitri, how seriously behind were the other cells? Can you give an example? Thanks.


I only go by what I see in my own 40 cells TS 160AH pack, so its possible I have some weak cells. I have been running my pack for almost a year now on a daily basis. Last few days have been unusually cold in Tampa, getting close to freezing temps and I have no insulation on my cells. In the morning my cells are about 35F-40F temp. Up to 1C loads everything looks fine, normal voltage drop for this temp, about 3.15V on fully charged cells at 1C out of the garage. However, at 2C-3C loads during acceleration, most cells drop to 2.9V, but 3-4 cells drop to 2.5V-2.6V. These 3-4 cells were sagging deeper than others even at normal temps, but low temps make it really obvious.

Also, during charge at low temps, those 3-4 cells are always ahead of others to reach HVC.

Clearly these cells have significantly higher internal resistance, which is even more visible at lower temps. But I don't think I could see any of these issues with a basic bench equipment unless I had cell level BMS.

Perhaps I will get few more months out of these weak cells and then I will swap them for new cells of the same size.

This also confirms many rumors I read about 10% failure rate for TS cells, but again, maybe I am just unlucky.


_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## Voltswagen (Nov 13, 2008)

Dimitri
I had also read that about TS cells....approx 10% failure.
This is why I took Jack's suggestion and ordered 4 extra cells.
Add 10% manufacturing defects to the bad things I can do to cells all by myself  and I'll be glad to have some spares.


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## MN Driver (Sep 29, 2009)

dimitri said:


> I only go by what I see in my own 40 cells TS 160AH pack, so its possible I have some weak cells. I have been running my pack for almost a year now on a daily basis. Last few days have been unusually cold in Tampa, getting close to freezing temps and I have no insulation on my cells. In the morning my cells are about 35F-40F temp. Up to 1C loads everything looks fine, normal voltage drop for this temp, about 3.15V on fully charged cells at 1C out of the garage. However, at 2C-3C loads during acceleration, most cells drop to 2.9V, but 3-4 cells drop to 2.5V-2.6V. These 3-4 cells were sagging deeper than others even at normal temps, but low temps make it really obvious.
> 
> Also, during charge at low temps, those 3-4 cells are always ahead of others to reach HVC.
> 
> ...



Sorry to hear about your cells, I agree that you wouldn't have seen those issues without the cell level monitoring, you would find out when they collapse after sagging too far down in voltage and they get damage from the abuse from low voltage, then after one or more cells is stuck at zero volts, the charger would charge the battery to its standard voltage, but it would effectively be as if you were charging at an even total higher voltage since the one cell(or more) at zero will cause the pack to appear 3.65 volts, or whatever VPC is being charged, too high, so a 45 cell pack would then be at 3.73 per cell, lose 2 and you would be at 3.81 per cell. If you lost all 4 and you are at 3.97 volts per cell but you wouldn't know it because your charging voltage looks fine and dandy for the pack. ...now for those who charge at higher voltages with their Thunder Sky cells such as 3.8 volts per cell will have damage with fewer cell failures.

...but what would tell you that you have dead cells? Likely nothing, and pumping energy into/through(assuming it is shorted) a 0 volt cell doesn't chime in as a good idea to me. It would probably crop up one day when the car has lost enough cells to either affect acceleration performance or range which could also be the same time that overcharging has killed off capacity, or killed in general cells that were otherwise good in the pack.

To me a single voltmeter on the pack doesn't cut it, I'd rather know if a cell has an issue and if I can catch it before it fails, I'd be even more happy, which is why I prefer to have a BMS that can cut with high and low voltage extremes.

-On a different note: I wonder how the voltage profile under load will compare with the Yttrium and other advances that have been coming through with these TS cells lately, I'm curious to see how they compare when placed in series.


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## Voltswagen (Nov 13, 2008)

Splain this to me. 

1. You have a BMS system which monitors and protects every cell.
The system indicates that you have a cell going bad. BMS can't repair any individual cell....so you have to pull that cell and replace it.

2. You have no BMS system. But you might have an E- Meter. 
A cell begins to go bad. The effect is loss of acceleration or range or Ah reading on your E-Meter or all of the above. 
You read individual voltage after an extended run, find the offensive cell ............so you have to pull that cell and replace it.
Same outcome.

I'm still trying to convince myself that a BMS is worthwhile.
Convince me.


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## JRP3 (Mar 7, 2008)

You might not feel anything with a single low cell, and you may not see enough voltage drop depending on your pack size and you may end up killing a cell. That said, I'm planning on going without a BMS. I will not discharge more than 80% of my weakest cell and I'll find that cell with one of these data loggers:
http://hobbycity.com/hobbycity/stor..._Name=Cell-Log_Cell_Voltage_Monitor_2-8S_Lipo
I'll also monitor the pack in two sections and compare the two voltages for differences. If one half drops significantly more than the other the imbalance will show the problem.


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## dimitri (May 16, 2008)

Voltswagen said:


> Splain this to me.
> 
> 1. You have a BMS system which monitors and protects every cell.
> The system indicates that you have a cell going bad. BMS can't repair any individual cell....so you have to pull that cell and replace it.
> ...


The way I see it is that BMS helps me identify weak cell and significantly prolong its useful life. Yes, eventually I will want to replace weak cells, but I will do it on my terms when I am ready, while my EV is still operational every day, even if its less range or less acceleration. 
Without BMS, those weak cells will become dead cells very quickly, at the worst possible time, likely render EV useless for weeks while waiting for replacements. Common argument against BMS is that it doesn't save bad cells, true, but it helps to prolong the life of weak cells so they don't go bad as fast.

As for E-Meter, it costs more than some BMS's and by just comparing half pack voltages its not guaranteed to identify weak cells, and it can't even take action to prevent overdischarge.



_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## Voltswagen (Nov 13, 2008)

Dimitri
I appreciate a lot of your points.

Here's where we get into semantics and intervention.
Define "Weakest Cell".....one that reaches HVC before all others?
Or one that sags the most under load?
And then....define "Strongest Cell"........

Be kind...Roy still loves ya!


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## Voltswagen (Nov 13, 2008)

JRP
I have also considered that cell logger.......looks inexpensive for what it can do........if it can do it.


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## JRP3 (Mar 7, 2008)

Check out Tomofreno's SwiftE build thread, near the end, he has graphs from the cell logger.


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## dimitri (May 16, 2008)

Voltswagen said:


> Dimitri
> I appreciate a lot of your points.
> 
> Here's where we get into semantics and intervention.
> ...


In my opinion, both early HVC and early LVC define weak cells, which may or may not be the same cell. However, early LVC ( i.e. deep sag under load ) is deadlier since you can kill the cell within minutes if you let it go to zero volts which will make other cells reverse this cell instantly and forever.

Early HVC is not as deadly, but it means you get less energy in your pack since you have to stop charging sooner because of the weak cell, which will essentially determine your pack capacity and range. You can live with shorter range for a while, but it will be getting worse over time as this cell's capacity continues to decline.

So, both conditions require some kind of attention, whether manual or automated, I prefer automated.



_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## dimitri (May 16, 2008)

JRP3 said:


> That said, I'm planning on going without a BMS. I will not discharge more than 80% of my weakest cell and I'll find that cell with one of these data loggers:
> http://hobbycity.com/hobbycity/stor..._Name=Cell-Log_Cell_Voltage_Monitor_2-8S_Lipo


JRP3, those cell loggers can be considered as a form of BMS, so if you plan to use them, don't say you will go without BMS


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## Voltswagen (Nov 13, 2008)

Dimitri
I like your definition.
Do you believe that a bad cell can sabotage the other cells in the pack?


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## dimitri (May 16, 2008)

Voltswagen said:


> Dimitri
> I like your definition.
> Do you believe that a bad cell can sabotage the other cells in the pack?


Since I have not actually experienced a dead cell yet, I can only guess and repeat what others are saying. If cell is dead and shorted, it will conduct current from other cells and you can still drive, but I suspect there will be nasty thermal issues and possibly spewing of liquid or physical disformation. Someone here described what happened to TS cells in his bike and it wasn't pretty 

If cell dies and won't conduct current, then you can't drive until you bypass this cell, which means less voltage and more strain on the rest of the pack, which means next weakest cell is in line for early grave. Plus, if your charger voltage is not configurable, then you have issues charging your smaller pack until you replace dead cell.


_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## Voltswagen (Nov 13, 2008)

Did you read the problems Brian was having with his TS cells in the Honda?
If I recall correctly he had 4 cells which were nearly dead but he only had his VoltBlockers installed on each cell not really a full BMS system.


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## dimitri (May 16, 2008)

Voltswagen said:


> Did you read the problems Brian was having with his TS cells in the Honda?
> If I recall correctly he had 4 cells which were nearly dead but he only had his VoltBlockers installed on each cell not really a full BMS system.


Yes, Brian's problems also started when temps dipped, which makes weak cells even weaker, plus his pack is likely undersized for the hills he has to climb every day. Original VBs were designed only to top balance, not for HVC and LVC. Later versions had optional HVC and LVC, but lack of head end solution prevented many people from taking actions on HVC and LVC events. This is what prompted me to design MiniBMS as a complete and affordable solution, including head end control board and documentation on how to tie it to the charger and motor controller.

In my EV, I had HVC and LVC for a long time. At first HVC was not very useful since it was warm and cells weren't that much apart. LVC had already saved my cells couple times when I got reckless with Soliton1 power  , so perhaps this is why I still have weak, but not dead cells.

Now that my garage is almost freezing, I also observe HVC tripping on weak cells since their voltage is rising faster at low temps. Honestly, I am surprised how poorly these cells behave at low temps, this was not clear from TS datasheets, but we all knew not to trust those Chinese specs 

I still believe that LFP cells are superior to LEad Acid and still worth the price in the long run, just need to adjust your expectations and realize there are no miracles.


_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## Voltswagen (Nov 13, 2008)

dimitri said:


> I still believe that LFP cells are superior to LEad Acid and still worth the price in the long run, just need to adjust your expectations and realize there are no miracles.


From what I have read, I agree. 
I have no real world experience with these cells and you're probably right it would be less expensive for me to purchase a BMS system rather than
purchasing extra cells and the 2 bench machines. 
Theres just something inside me that wants to know more about these cells and like you I don't fully trust the Chinese Specs. 
I'm one of the fortunates who work from home and don't depend on my EV for everyday commuting so I have the luxury of experimenting with it.
Thanks for the input guys!


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## Tesseract (Sep 27, 2008)

Voltswagen said:


> Splain this to me.
> 
> 1. You have a BMS system which monitors and protects every cell.
> The system indicates that you have a cell going bad. BMS can't repair any individual cell....so you have to pull that cell and replace it.
> ...


Okay... in the scenarios above a "weak cell" is a defective cell. But what if by "weak cell" one is simply talking about it being slightly lower in capacity? E.g. - 161Ah; 163Ah; 165Ah. The 161Ah cell is the "weak" one. It's going to reach HVC first when charging, and LVC first when discharging. EVERY battery pack, no matter the chemistry, is going to have a "weak cell". The key thing here, and where a BMS (at least LVC and HVC, anyway) comes in handy, is that it prevents you from turning a "weak cell" into a "dead cell" from repeated cycles of overcharging and overdischarging.

THAT is the merit to a BMS. (as I see it, anyway).


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## dimitri (May 16, 2008)

Tesseract said:


> Okay... in the scenarios above a "weak cell" is a defective cell.


I'm not sure how to qualify "weak" vs. "defective" cell. Manufacturers and resellers do not define how much difference in internal resistance should qualify a warranty replacement. They especially don't qualify how IR changes with temperature. Its a grey area.

The cell may be "weak" by its IR and even weaker at cold, but it still works. With BMS it will continue to work for a while, without BMS its likely to be killed sooner than later.

If there was only a few AH difference in capacity , but not in IR, I could care less, once balanced the pack would get same amount of charge and discharge as long as you avoid extreme ends of the curve. But when IR swings on some cells and not others it becomes difficult to avoid those ends of the curve on individual cells unless youu have cell level BMS.

I have been saying this for a while, but have been ridiculed. Maybe I am still wrong, but what I have seen recently with low temps tells me I was right, at least with my own cells. If anything is learned, is that 3C discharge as listed on TS datasheets is something I would avoid at all costs. Oversize your pack as much as you can. Get a couple of spares if you can afford it. As for BMS, see the disclaimer below ....

_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## Qer (May 7, 2008)

Dimitri, please define "low temps"? Hearing about batteries behaving bad at low temps is a bit worrying to me considering it was -24C (-11F) when I drove home from work yesterday...


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## Tesseract (Sep 27, 2008)

dimitri said:


> I'm not sure how to qualify "weak" vs. "defective" cell. Manufacturers and resellers do not define how much difference in internal resistance should qualify a warranty replacement. They especially don't qualify how IR changes with temperature. Its a grey area.


Well, I don't know *specifically* where to draw the line between a weak vs. a defective cell, either, but I wasn't trying to.

Voltswagen's point was that if a cell is defective then BMS or not you have to yank it. My counterargument was that in the case of a cell just having a slightly lower capacity - a couple Ah, maybe - that a BMS will ensure it is not repeatedly overdischarged and overcharged, thereby converting it from a "weak" cell TO a "defective" cell.

I suspect both abuses manifest themselves as higher internal resistance, which, if it gets or is much higher in one cell than the rest then that's a pretty good sign - to me - that the cell is "defective", not simply weak.

Not playing with semantics here, just trying to point out a situation were a BMS comes in handy.


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## dimitri (May 16, 2008)

Tesseract said:


> My counterargument was that in the case of a cell just having a slightly lower capacity - a couple Ah, maybe - that a BMS will ensure it is not repeatedly overdischarged and overcharged, thereby converting it from a "weak" cell TO a "defective" cell.
> 
> I suspect both abuses manifest themselves as higher internal resistance, which, if it gets or is much higher in one cell than the rest then that's a pretty good sign - to me - that the cell is "defective", not simply weak.
> 
> Not playing with semantics here, just trying to point out a situation were a BMS comes in handy.


That is a good point, and may explain issues some people observe, but it doesn't explain my case. I have been taking good care of my pack, I can't explain why 10% of my cells are "weak", other than manufacturing differences. Perhaps there are multiple issues involved, but in any case BMS helps to address those to some degree. These past few days are the first "cold" days for my EV, since I got in on the road after last year's cold days. So it hard to tell if these cells would also be weak on day one and how much weaker they get over time.


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## dimitri (May 16, 2008)

Qer said:


> Dimitri, please define "low temps"? Hearing about batteries behaving bad at low temps is a bit worrying to me considering it was -24C (-11F) when I drove home from work yesterday...


I don't have empirical data, just observation of my cells which have no insulation. As temps dip to 10C-15C and lower I observe reduced performance at loads over 2C. It gets pretty bad at freezing temps.

I would recommend to insulate your cells and keep them above freezing, preferrably close to 20C if you can manage it.

Hope this helps


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## JRP3 (Mar 7, 2008)

dimitri said:


> JRP3, those cell loggers can be considered as a form of BMS, so if you plan to use them, don't say you will go without BMS


Well they don't actively do anything, they don't do anything other than monitor voltage and log that information, a voltmeter with a memory if you will. I consider it test equipment as it won't monitor the whole pack and will only be used occasionally to check the cells. That's my story and I'm sticking to it


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## JRP3 (Mar 7, 2008)

Seems to me that a better investment than a BMS for low temperatures is actively heating your cells, and good insulation. If trouble develops below a certain temperature it would make more sense to keep things above that temperature, not try to manage things with a BMS.


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## _GonZo_ (Mar 23, 2009)

dtbaker said:


> well... I see design goals... do you have a product that actually DOES that?
> 
> The holy grail obviously would be some kind of combined charger/bms shuttle charge rotating thru cells and checking each status and cell voltage before shooting a burst of charge at some volts/amps for *some* length of time... is that what you are proposing? I look forward to cost and beta test results...


Yes our BMS is working now as stated.
Will post video tomorrow.



> I'm not sure how to qualify "weak" vs. "defective" cell. Manufacturers and resellers do not define how much difference in internal resistance should qualify a warranty replacement. They especially don't qualify how IR changes with temperature. Its a grey area.


Well on the cells specification sheet there should be deficned a maximun IR for the cells. (this is stated at determined frecuency and temperature)
As well a minimun capacity. (as well defined at a certain discharge draw and temperature)
Any cell that do not meet that when new can be considered defective.

A IR curve vs. temperature is not provided usually but you can ask for it to the cells provider. (usually what you will get is a discharge comparation chart at different temperatures)
I am sure that TS will have them available.


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## _GonZo_ (Mar 23, 2009)

I do not understand the discrepancy about using or not using BMS.

Your small battery on your mobile phone has a BMS, your laptop, your ipod etc...
And now you talk about packs that costs thousands of Euros and able to destroy a building if something goes wrong and you want to use them with out any monitoring. 

A Lixx pack needs control and monitoring PERIOD. 

Minimun requirements of control and monitoring:
LHV (per cell and per pack)
HCV (per cell and per pack)
Maximun current charge limiting
Maximun current discharge limiting
Shortcut protection.

Anything you can add to that is obviously welcome.

This functions can be taken by the charger, controler, etc. but they have to be there.

And another point: no battery manufacturer (including us) will cover any garatie of its cells or packs if the pack is not protected with a proper BMS.


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## dimitri (May 16, 2008)

JRP3 said:


> Seems to me that a better investment than a BMS for low temperatures is actively heating your cells, and good insulation. If trouble develops below a certain temperature it would make more sense to keep things above that temperature, not try to manage things with a BMS.


Who said that BMS does anything related to cell temp? I was simply relating my experience trying to show that low temps have drastic impact on these cells and there may be cases when BMS would prevent cell damage if for example heater fails or temps get unusually cold. I never planned to insulate my cells, there are only a few days a year here with such temps, so I expected lower performance, but not this much lower, so my beef is mostly with TS specs and their 10% failure rate, but even that was somewhat expected, so I am not complaining, just relaying information, hoping it will help someone in planning stages of their conversion. If you are in freezing climate, insulate your cells and keep them warm, and avoid 3C discharge if you can.

_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## JRP3 (Mar 7, 2008)

_GonZo_ said:


> I do not understand the discrepancy about using or not using BMS.
> 
> Your small battery on your mobile phone has a BMS, your laptop, your ipod etc...


They don't use large format LiFePO4 cells, not the same thing.


> And now you talk about packs that costs thousands of Euros and able to destroy a building if something goes wrong and you want to use them with out any monitoring.


LiFePO4 cells don't explode or self ignite. Many people have over discharged and over charged their cells with not explosions or fires.


> A Lixx pack needs control and monitoring PERIOD.


Except for those people who aren't actively controlling their packs and not having problems.


> And another point: no battery manufacturer (including us) will cover any garatie of its cells or packs if the pack is not protected with a proper BMS.


EVcomponents offers a one year warranty with no BMS. Faulty BMS's damaging cells have resulted in more cell returns as far as I'm aware.


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## EV-propulsion.com (Jun 1, 2009)

Dimitri,
As far as cold temps effects, can you pinpoint how much sooner LVC warning comes on? i.e. how it is affecting range? Are you getting warnings at 30 miles instead of say 50 (or when ever you had normally gotten them at "warm" temps) or have you not driven it far enough these last few days?
Also, can you say how quick the pack has warmed up while driving? Possibly using the paktraker temp sensor....
Up north here we have to worry about these things! Thanks!
Mike
www.EV-propulsion.com


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## _GonZo_ (Mar 23, 2009)

JRP3 said:


> They don't use large format LiFePO4 cells, not the same thing.LiFePO4 cells don't explode or self ignite. Many people have over discharged and over charged their cells with not explosions or fires.
> Except for those people who aren't actively controlling their packs and not having problems.EVcomponents offers a one year warranty with no BMS. Faulty BMS's damaging cells have resulted in more cell returns as far as I'm aware.


I am not talking only about security issues, but obviously it is one of the most important points.

You pretend to tell me that the people who aparently are not controling the battery are:
- Not controling the LVC with the controler
- Not controling the HVC with the charger
- Not controling the charging current with the charger
- Not controling the maximun current draw with the controler
- And not havin a fuse installed

This what is all about a Batery Monitoring System (BMS)

And as I sayd all of this point are mandatory.

They are only missing point in this case that is more less aceptable in this case is the LVC and HVC per cell control, that if you do not want to destroy prematurely some cells is a must as well (on other Lixx chemstrys not LiFe are a must due security reasons)

Sorry if I am a bit agresive it is not my intention to create any polemic.


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## JRP3 (Mar 7, 2008)

_GonZo_ said:


> You pretend to tell me that the people who aparently are not controling the battery are:
> - Not controling the LVC with the controler
> - Not controling the HVC with the charger
> - Not controling the charging current with the charger
> ...


I don't consider a charger that controls current and voltage part of a BMS, that's part of the charge system and is of course part of any EV. Also all controllers that I'm aware of have built in limits on how much current can be drawn, again this is not part of what I'd consider a BMS, nor is a pack level fuse or circuit breaker. When talking about a BMS, I, and I think most of us, are talking about cell level active management through HVC and LVC signaling and control, and possible shunting and or shuttling.


> They are only missing point in this case that is more less aceptable in this case is the LVC and HVC per cell control, that if you do not want to destroy prematurely some cells is a must as well


This is where the disagreement exists. A few of us feel that as long as you limit your charge and discharge across the entire pack such that your smallest capacity cell is never over or under charged you should not prematurely damage any cells. Your range will always be dependent on the capacity of your smallest cell no matter what you do.


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## dimitri (May 16, 2008)

_GonZo_ said:


> Sorry if I am a bit agresive it is not my intention to create any polemic.


You are not going to win any arguments with this tone and attitude. This subject has been discussed a million times, some people have different views and opinions. Hell, even I had opposite views a year ago 

I suggest you stick to specific data and logical arguments, no need for emotions. DIY is a tough crowd, get used to it 

When it gets too frustrating, unplug for a few days, enjoy offline life for a change 

Some people learn from mistakes of others, some only learn from their own, its just the way it is.


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## dimitri (May 16, 2008)

EV-propulsion.com said:


> Dimitri,
> As far as cold temps effects, can you pinpoint how much sooner LVC warning comes on? i.e. how it is affecting range? Are you getting warnings at 30 miles instead of say 50 (or when ever you had normally gotten them at "warm" temps) or have you not driven it far enough these last few days?
> Also, can you say how quick the pack has warmed up while driving? Possibly using the paktraker temp sensor....
> Up north here we have to worry about these things! Thanks!
> ...


Mike, I wish I had more empirical data, but its only been a couple of cold days and I don't drive that much lately. The key observation I made is that some cells are weaker at low temps than others, so when talking LVC we need to consider a strong cell and weak cell. Strong cells behave just like expected and do not trip LVC prematurely. Weak cells trip LVC under 3C load if you push it long enough. I have my LVC delay at 5 seconds and its good enough to accelerate and then reduce current, so I am driving OK for now. However, I can trip LVC at will on weak cells if I floor the pedal for more than 5 seconds. This is good thing, since BMS works as designed and prevents me from killing the weak cells. 

Without any insulation and heating in my EV and making short trips there is not enough time for cells to heat themselves up.

All I can say is keep them as warm as you can, as close to normal temp as you can reasonably get.

Oh, and try not to buy any weak cells if you can help it 

Hope this helps.

_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## _GonZo_ (Mar 23, 2009)

> I don't consider a charger that controls current and voltage part of a BMS, that's part of the charge system and is of course part of any EV. Also all controllers that I'm aware of have built in limits on how much current can be drawn, again this is not part of what I'd consider a BMS, nor is a pack level fuse or circuit breaker. When talking about a BMS, I, and I think most of us, are talking about cell level active management through HVC and LVC signaling and control, and possible shunting and or shuttling.


Well I think all that controls in any certain manner the battery parameters is part of the BMS, sorry for the missunderstud.



> This is where the disagreement exists. A few of us feel that as long as you limit your charge and discharge across the entire pack such that your smallest capacity cell is never over or under charged you should not prematurely damage any cells. Your range will always be dependent on the capacity of your smallest cell no matter what you do.


I agree with you, that is correct for shunting balancing but at least it is partially palliate with shuttling balancing.



> You are not going to win any arguments with this tone and attitude. This subject has been discussed a million times, some people have different views and opinions. Hell, even I had opposite views a year ago
> 
> I suggest you stick to specific data and logical arguments, no need for emotions. DIY is a tough crowd, get used to it
> 
> ...


Thank you very much for the advice, I have a problem and it is that english is not my mother tong, so manny times I do not find the proper words to say ideas in a shoft manner. 
I always try to stick to data and logical arguments but you know that sometimes it is not allways posible as there is differnet ways to get similar/same results and all of us "fight" in order to try to make others understand that own way is the best...


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## Voltswagen (Nov 13, 2008)

Dimitri
If I had your EV, I'd park it in my living room.
I heard the deep south is in for some snow before spring.
You might want to cover that pack with an electric blanket. 

To say it has been cold here in New Jersey is like saying the Atlantic Ocean is damp. Thank God I don't have to drive my EV right now.
And I'll bet John has had twice the snow we have had here.

Gonna go pour myself a JD and put some more logs on the fire.

Roy


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## honn1002 (Nov 26, 2008)

JRP3 said:


> You might not feel anything with a single low cell, and you may not see enough voltage drop depending on your pack size and you may end up killing a cell. That said, I'm planning on going without a BMS. I will not discharge more than 80% of my weakest cell and I'll find that cell with one of these data loggers:
> http://hobbycity.com/hobbycity/stor..._Name=Cell-Log_Cell_Voltage_Monitor_2-8S_Lipo
> I'll also monitor the pack in two sections and compare the two voltages for differences. If one half drops significantly more than the other the imbalance will show the problem.





Why not just build an affordable device like a cellLog8 to monitor and control low voltage cut-off (LVC) per cell per pack and high voltage cut-off (HVC) per cell per pack. Connect the alarm output to a DPDT relay to cut off the charger when over voltage and cut off the controller's KSI when under voltage.


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## Voltswagen (Nov 13, 2008)

Honn
This is what I had in mind for a simple monitoring system. The only thing I was missing was the relay. Thanks for that. 

But using your diagram, is there a way to monitor 36 cells with only one cell logger? Or would I only connect it to my 8 weakest cells?

Also, assuming deep voltage sag such as Dimitri experienced in cold weather, will the KSI automatically reset itself once voltage has bounced back or am I stranded?


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## JRP3 (Mar 7, 2008)

I don't think you want to kill the power to the vehicle when you might be in traffic. Use an alarm or a throttle reduction but don't strand yourself in a potentially bad situation. You'd need more than one cell logger since it only does 8 cells, unless you know your 8 weakest cells and hooked it up to them, which could probably work. If you want all cells controlled Dimitri's solution looks to be the most cost effective.


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## Tesseract (Sep 27, 2008)

Voltswagen said:


> But using your diagram, is there a way to monitor 36 cells with only one cell logger? Or would I only connect it to my 8 weakest cells?


No, or, at least, not yet. And the cute little $29 cell logger mentioned here absolutely expects to monitor a series-connected string, not just any random selection of 8 cells in a larger pack! That is to say, it expects to see maybe 36V maximum between its most negative and most positive terminals! The logger would need to have isolated (floating) voltage monitoring inputs to be able to connect to any 8 cells out of, say, a 40 cell pack. Is this possible? Sure. But the parts cost for a fully isolated 8 cell logger would exceed that of a totem-pole 40 cell logger (a la the way it is done in the PakTrakR).





JRP3 said:


> I don't think you want to kill the power to the vehicle when you might be in traffic....


I totally agree, which is why we are adding a "cell level LVC" input to the Soliton1 which will basically regulate the allowed battery current whenever activated, just like the existing pack-level "LVC" works. Ie - if a single cell triggers LVC in, for example, Dimitri's MiniBMS the Soliton1 will reduce allowed battery current until the LVC signal goes away.

We may modify this behavior depending on how it behaves in real-life with dimitri's MiniBMS - as it could lead to some motion-sickness inducing oscillations - but that's the basic plan as of now.


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## Voltswagen (Nov 13, 2008)

John

Yeah, maybe just an alarm would be sufficient. Hopefully it would only trigger under acceleration letting you know that a bad situation is beginning to develope and you should then give it some attention.
This seems to be what is happening in Dimitri's case.

BTW.......how much snow did you guys get?

Roy


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## JRP3 (Mar 7, 2008)

Not much, about 8 inches. The big stuff went north of us, I think 55 inches in Fulton


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## Voltswagen (Nov 13, 2008)

Tesseract
BTW...thanks for responding to my 2 scenarios. You made some good points about preventing a "weak cell" from becoming a Dead cell.

So what you are saying is that one would have to first determine the weakest 8 cells and then align them sequentially somewhere in the pack.
That makes sense. 

What did you think of Honn's diagram? Couldn't one wire the relay output to an alarm instead of the KSI? Bear in mind you're talking to an "Old Wrench Guy".


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## dimitri (May 16, 2008)

A positive side of cold weather and having some weak cells is that I have a chance to test LVC behavior in MiniBMS without actually draining the whole pack 

I find that 5 second LVC delay works quite well for me and 50% throttle reduction creates unmistakable , yet still gentle enough alert. There is no motion sickness, just momentary reduction of power, for a split second, then back to normal. Since 5 seconds kicks in every time, you don't get frequent jerks, so it feels just right. I could, if I wanted to, manipulate the value of the resistor clamping the throttle to apply say 30% reduction instead of 50%, to make it even more gentle, but I think 50% works well.

Someone on TV said that we don't know what to do with LVC alerts, well, I'd have to disagree, I think throttle reduction with a small delay works very well. Granted I get LVC alerts too soon because of my weak cells, but that is exactly what BMS is expected to do, save those cells until I have replacements ready.

I would strongly recommend against cutting controller power, this would create dangerous road situation and also put stress on drivetrain and controller's circuits. Delay also seems critical to avoid oscillations.

As for Honn's circuit, I hope it was meant as an example and not to be literally done like that. Relay must be rated to carry charger's current, coil must be rated not to burn off the gate in the cell logger. There is no delay either, so it would be jerky. IMHO, charger control must be latching, otherwise your charger will be dancing on and off every few seconds as cells fall below HVC and then climb back again.

My head end board from MiniBMS can be used with cell loggers, but I don't like that cell logger has NO output instead of NC, this could lead to missed alerts. You could convert NO to NC and then use my head end board, if you convince me to sell them without cell modules 

_DISCLAIMER: I am biased on this subject, since I am offering MiniBMS for sale, so please take all my comments with a grain of salt . I have been accused of misleading forum members because of my bias, so I will put this disclaimer on all BMS related posts _


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## tomofreno (Mar 3, 2009)

> So what you are saying is that one would have to first determine the weakest 8 cells and then align them sequentially somewhere in the pack.
> That makes sense.


 Jack has discussed how set up relays for HVC/LVC for several of these cell log 8's on a pack on the "lithium battery monitor" thread here:
http://www.diyelectriccar.com/forums/showthread.php/lithium-battery-monitor-39708p2.html

I still like the minibms better due to its many safeguards and one wire hookup. If you want the cell log 8's where you can see them you have to run something like an 11 conductor shielded cable for the 9 cell connections and two alarm leads, for each cell log 8. You'll need a relay for each cell log 8, triggered by the alarm output. These are connected in series to trigger another relay for the actual HVC/LVC signal to a charger or controller. This has all been done for you on the minibms. Just one wire connecting cell level boards to the main board, and the relays to interface to the charger and controller are already there on the main board. It is more costly than using say 5 of the cell log 8's as Jack describes, but a lot less trouble to install, and more reliable due to less connections. I also don't know what the circuitry of the cell log 8's looks like, so not sure if it is possible to get a failure like I did on some other "regulators" causing significant leakage current from cells. Dimitri has addressed this on the minibms. The minibms appears to me to be the most "bullet proof" right now. You can pay me later Dimitri.

The little cell log 8's are great for data logging cells while charging or discharging to identify your lower capacity cells cells though. You easily see which ones hit HVC sooner, and what relative voltages they started at. Can also see relative sag under load. You really get to know your cells I thought it would be nice to be able to see the little bar graph of cell voltages while driving, but it is so small I think I might rear-end someone trying to look at them. Also, I don't really want to have to do this all the time. I'd rather have HVC/LVC alarms to just let me know if something is wrong, and otherwise just drive and not be bothered - like ICE vehicles are set up.


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## tomofreno (Mar 3, 2009)

An example of cell log 8 data during charging is at post #250 here:
http://www.diyelectriccar.com/forums/showthread.php/swifte-36621p25.html
Note each cell has a different scale on the ordinate. You can export this data from Logview to an Excel spreadsheet and graph it all with one scale. My pack is limited by cell3 in this graph. It reaches HVC at a bit more than 0.02V before most other cells (that is a lot compared to the typical +/-0.002V difference between most cells). That means the others are down at less than 3.40V if the charger cuts off when this one hits 3.60V (SkyEnergy cells). There are a few others similar to this one - the ones discharged by the regulators. I put insulated alligator clips on the cell log 8 leads and just clip them on the cell straps to take measurements, then remove them.


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## honn1002 (Nov 26, 2008)

Voltswagen said:


> Honn
> This is what I had in mind for a simple monitoring system. The only thing I was missing was the relay. Thanks for that.
> 
> But using your diagram, is there a way to monitor 36 cells with only one cell logger? Or would I only connect it to my 8 weakest cells?
> ...


Voltswagen- It's better to connect the CellLog 8 to the 8 weakest cells. It's more complicated to have more than one CellLog 8 connecting in series because it's not isolated. See the new diagram instead of killing the KSI, you can use a small SPDT relay connected with a 5K resistor to parallel with the throttle pot 5K when the relay is turned on.

After the voltages recover from the deep sag and the voltages increase to more than the minimum cells voltages like 2V for example, the CellLog 8's alarm output will deactivate the relay and you're going back to normal operation, unless the voltages dive below 2V again.


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## AndyH (Jun 15, 2008)

Guys,

There are a number of ways to protect cells from over discharge but unfortunately only pulling the throttle down 1/2 way is not one of them.

Pulling the throttle down 1/2 way still allows pulling power from the pack - and fairly significant power. It's also gentle enough a signal that it can be missed while driving.

If you're going to pull the throttle, pull it all the way off. Once the load is removed from the pack and voltage recovers (or you ease up on the throttle), you'll have power back. It does not leave you stranded on the road, does not make you a hazard, and will absolutely protect the pack.

I've tested a number of LVC cut options on the road - down to and beyond cut-off...to the point of 'Flintstoning' down an access road at 2-3mph until I can get the bike to a plug. A 'hard' LVC will protect a pack. Lights, buzzers, and 1/2 throttle will not.

Andy


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## Voltswagen (Nov 13, 2008)

Andy
How do you cut full power in the middle of an intersection without putting the EV in jeapordy?


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## dimitri (May 16, 2008)

AndyH said:


> There are a number of ways to protect cells from over discharge but unfortunately only pulling the throttle down 1/2 way is not one of them.


Andy, with all due respect to your experience, I think its a little too strong of a statement. Perhaps the result depends on other factors like a size of the EV, controller, drivetrain inertia, etc etc.

I found that in my EV 1/2 throttle LVC action is unmistakable, yet gentle enough not to cause nausia or dangerous loss of power. Even with 1/2 throttle clamp, voltage restores immediately above LVC during first alerts. If you ignore them and keep pressing the pedal, alerts become more prolonged and more difficult to ignore.

In a full size EV I would not want full throttle cutoff which immediately jumps back, it would jerk the drivetrain too much.

I guess its something that should be tested and adjusted for each EV, afterall just putting a trimpot in place of clamping resistor would give you full range of options from very gentle to very jerky alert.

When it comes to an empty EV battery in the middle of the road, you have 2 tough choices, do I risk one or two cells or do I risk the safety of entire EV and people inside? BMS is here to alert you, what action you take is up to you.


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## honn1002 (Nov 26, 2008)

AndyH said:


> Guys,
> 
> There are a number of ways to protect cells from over discharge but unfortunately only pulling the throttle down 1/2 way is not one of them.
> 
> ...


 Andy-

For an on road vehicle you don’t want to suddenly cut all the power from the controller, especially when you’re driving on the freeway for safety reasons. By cutting about 50% or less on the controller (depending on the size of the vehicle like Dimitri stated) at least you still have half of the power to drive your ev to a safe location and save your cells at the same time. It’s kind of an alert to let you know that one or more of your cells are at the lvc.


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## AndyH (Jun 15, 2008)

Voltswagen said:


> Andy
> How do you cut full power in the middle of an intersection without putting the EV in jeapordy?


VW, Dimitri, and Honn,

Short answer - you don't. That's not what happens when an LVC trips.

Ultimately it's going to come down to what you want from your systems and vehicles - no doubt.

First - function. Assuming a TC54-based LVC sensor set to trigger a 'low voltage event' at 2.7V. The sensor will trip as voltage drops thru 2.7V. With a bit of wiggle room for parts tolerance and response time, I'm seeing things happening in the 2.68V range. There's a bit of hysteresis built in - the LVC signal is removed as voltage rises thru about 2.8V.

Let's connect the LVC signal to a controller input that causes the controller to stop sending power to the motor. We're not going to cut power to the controller - we're going to leave the controller on-line and tell it to stop sending power to the motor. This means that, as one drives down the road, the LVC signal will result in the exact same effect one has when they completely lift their foot off the accelerator, then pushes on the pedal. Cell voltage recovers fairly quickly once the load is removed. In practice, this results in 'power pulses' about 2-4 per second.

The power cut is very, very temporary (until the pack is completely dead) - there is still power available to move the vehicle. It does NOT leave the vehicle in the middle of an intersection unable to "get out of it's own way".

Let's use a real-world comparison with an ICE vehicle. Fill the tank and drive. Eventually the tank will run dry and the engine will stop. It's probably happened to each of you at least once. If the engine quits at 55mph, the vehicle slows. There's plenty of time to signal, look for a place to pull over, get out of traffic, and get off the road. Yes - the story is different if one is in the middle of 7 lanes in rush hour and the engine quits. Best thing here? If you know you're almost out of fuel - of any type - stay in whatever lane is closest to a shoulder or an off-ramp - leave yourself 'an out'.

Let's 'run out of gas' in our BEV in the middle lane. We push the throttle half way. One cell drops down thru 2.7V and power delivery stutters. Acceleration is reduced, but the car is moving. Easing on the 'gas' pedal reduces the load on the pack, the cells don't drop below LVC, and power delivery is smooth. Our attention swings to signaling and heading for the side of the road. No - you can't pull 450A, but you can pull power to move.

I've had complete power failure in a number of ICE vehicles from causes like electric fuel pump failure and relays dying. I've never had a similar safety concern in an EV with active LVC. (And diesel injection pumps don't self-prime after fuel starvation - one has to open the fuel line near the engine and use a vacuum pump to pull fuel from the tank and thru the pump before driving off after they walk back from the fuel station.)

Bottom line, guys -- I see LVC as the 'Last Signal of Impending Exercise' one should receive after they've either had an unexpected cell failure; or have ignored the dropping volt meter, the clock, or the Amp-hours ticking by. When we get to this point, we've usually already missed the earlier signals and have decided to keep going.

Let's look at how the 'big boys' do it. Ford produced Ranger EVs from 1996 thru 2002, and a number are still on the road. When pack voltage drops below a minimum, the controller throws an error code and shuts down. It latches off to protect the pack. If there's an over volt event during charging - same drill -- error code and shutdown. One has to fix the problem, connect a scan tool to clear the code, then try to drive away.

What's the pack-level LVC for your controller? What does your controller do when pack voltage drops below it's minimum voltage? I'll bet it doesn't simply change a 'smiley face' icon on the dash to a 'frowny face' and keep pulling 450A from the pack.  Mine disconnects power until the pack recovers and then reconnects - resulting in, if I keep the throttle down, power pulses about 2-5 per second. (Sound familiar?!)

For those that choose simply pulling the throttle down 1/2 way. Maybe it'll give a noticeable signal. But it will not protect the pack. If one can continue to pull any power from a pack after cells drop down thru the low voltage point, they are quickly heading to expensive damage. This type of signal - same as a flashing lights or buzzers - will not protect the pack.

Maybe pull the throttle to 1/2 at 2.7V. Flash the 'low fuel' LED on the dash, and activate a buzzer at the same time. But use use a second LVC signal at 2.1V to shut the controller down. This is the final notice that you've run out of gas.

This is what happens on factory electric cars, this is what happens in gasoline or diesel cars, and this is what happens on your cell phone and mp3 player.

Best in your conversions,
Andy


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