# Houston, we have a problem



## GerhardRP (Nov 17, 2009)

Bummer,
Were the low ones TS or CALB? 
Also, do you have any history of measurements or other data?
Gerhard



spdas said:


> Today, I did a 75 mile journey. And now I have a problem. As I mentioned on another thread I went over a hill/pass and was able to maintain 50mph and 150-200amps. On the way home at about 60 mile mark cruising at 60mph and 100amps, I noticed my pack voltage around 130v (sluggish) and just a moment before it was 143v or so at cruising speed. I thought I was just getting near the end of the charge and the zilla was warning me out. So I jumped off the freeway and limped home another 15 miles @ under 50 amps and about 135v.
> When I got home I found 5 cells in mid pack in a row at .3 to .5 Volts (yes 1/3 to 1/2Volt) and they were warm! The rest of the pack was at 3.301 - 3.306v for the 180 calbs and 3.22 - 3.27v for the used TS 160's. And yes, all cell bolts are snug
> 
> I have a light charge @ 8amps and the 5 cells are at around 1.7v now. Tomorrow I will isolate these 5 and charge them separately.
> ...


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## spdas (Nov 28, 2009)

This was the second charge for the NEW calbs and it was these 5 that totally discharged. The used TS 160's are fine and all cells were top balanced and charged only to 3.478 max pack voltage of 80v/23 cells. As expected the TS that are 160ah ran down more but there were still a good charge in both the other Calbs and TS cells.
Just trying to find out whatever mistake I could have made or was it defective cells?

Francis


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## tomofreno (Mar 3, 2009)

If the pack was top balanced the CALB cells obviously should not have discharged before the TS cells unless they were lower capacity than the 180Ah spec or defective in some other way. Do you have cell voltage data to show these cells were indeed charged to 3.47V8V?
They will likely recharge ok, but I would then hook up a cell log8 or similar to log voltage on these cells. They may show significantly more voltage sag than the other cells. I'm guessing you will need to replace them.


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## GerhardRP (Nov 17, 2009)

Do you have a picture of the battery boxes?
Are the failed ones successive serial numbers?
You say the failed ones were in the middle and warm. Does anyone think this is a cooling issue?
Were these in the same strapping group? Maybe not enough compression.
Gerhard


spdas said:


> This was the second charge for the NEW calbs and it was these 5 that totally discharged. The used TS 160's are fine and all cells were top balanced and charged only to 3.478 max pack voltage of 80v/23 cells. As expected the TS that are 160ah ran down more but there were still a good charge in both the other Calbs and TS cells.
> Just trying to find out whatever mistake I could have made or was it defective cells?
> 
> Francis


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## dtbaker (Jan 5, 2008)

There are so many possible reasons with mixed manufactures having different IR, mixed capacity, and mixed age of your cells combined with your split-pack charging which probably introduces significant unbalance between your 'strings' of cells... bound to hammer on some cells much harder than others.


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## spdas (Nov 28, 2009)

dtbaker said:


> There are so many possible reasons with mixed manufactures having different IR, mixed capacity, and mixed age of your cells combined with your split-pack charging which probably introduces significant unbalance between your 'strings' of cells... bound to hammer on some cells much harder than others.


Yeah all the above has been going through my mind. The TS are in the front of the car and all 160 and used and charged together. All the new Calbs are in the trunk and no TS are mixed in, and are charged as one unit. When I took them off the charger both packs after 2 hours rest were at 3.445 and 3.444. Looking at my voltage for each cell after my ordeal all were pretty much even (except the TS that were of course lower voltage). I expected the TS to risk damage as the Calbs would push them on to 0 volts. 
They seem to be taking a charge now though. I will top balance them and do a 20amp load test with my West Mountain to see if any capacity is lost, but who knows if the cycle numbers are affected?

Are the failed ones successive serial numbers?

will check

You say the failed ones were in the middle and warm. 

middle of the array, but on the outside of the pack. 

Were these in the same strapping group? Maybe not enough compression.

There is a lot of compression and none of the cells have any room at all to swell.

Francis


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## coryrc (Aug 5, 2008)

spdas said:


> Today, I did a 75 mile journey. And now I have a problem.
> ...
> When I got home I found 5 cells in mid pack in a row at .3 to .5 Volts (yes 1/3 to 1/2Volt) and they were warm.


What did your BMS log? How come it didn't cut off the throttle to keep the battery voltages from going too low?


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## spdas (Nov 28, 2009)

coryrc said:


> What did your BMS log? How come it didn't cut off the throttle to keep the battery voltages from going too low?


Oh Oh, I guess I will fall into the "to BMS or not to BMS debate. 

Not using a hardwired BMS, I should have seen a problem when I saw the voltage drop from 144 pack to 132 or so Pack instantly, but due to lack of experience, I ignored it and thought the whole pack hit was hitting the bottom knee and the Zilla throttled down and i got off the freeway to the surface streets. Just moments before I was calculating that I probably had 40 more miles available as the voltage when the throttle was backed off was still 3.22v. Will know better next time. The above DOES not convince me to BMS, just to monitor and wire up my Celllogs and wait for the order from Keegan for my final 180 calbs to replace the used TS160's that should be arriving soon. Will use the 160's for my motorcycle trike that I may finally finish

Francis


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## MN Driver (Sep 29, 2009)

What balancing method did you use to join the new CALB cells with the others?


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## T1 Terry (Jan 29, 2011)

Are the effected cells only the new ones you have added to the pack? Were all these cells pre condition charged? I've just been through the process of condition charging a pack of 16 x 90ah Winston cells and the requirement was to charge to 4v per cell and maintain that voltage till the current dropped to 1% of the 0.5C rating, in my case 360ah x 0.5c = 180amps X 1% =1.8amps (4 cells inparallel X 4 sets to make a 12v battery pack). It took a long time because my charge rate was low but a further 120ah went in between 3.4v and 4v, 28ah from 3.8v to 4v. After they settled for 24hr I recharged them to 4v per cell and only an additional 1ah went in but the terminal voltage has remained at ranging from 3.720v to 3.700v after a further 24hrs. I'm thinking you haven't fully charged those cells, let's hope you haven't damaged them.

T1 Terry


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## spdas (Nov 28, 2009)

MN Driver said:


> What balancing method did you use to join the new CALB cells with the others?


Top balanced. lowest after one day rest was 3.387v highest was 3.389.

francis


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## dtbaker (Jan 5, 2008)

spdas said:


> Top balanced. lowest after one day rest was 3.387v highest was 3.389.
> 
> francis


after a day rest it is hard to tell whats going on.... all cells will slip down to a fairly flat voltage. They may look balanced, and be 'pretty close', but not as close as balanced at some voltage up the knee. If they are off by a couple ahr, and you discharge deeply, they might well hit bottom first.

When you say you top-balanced... how exactly did you do that? did you put them ALL (new and old) in parallel and set to some fixed voltage a little ways up the knee at least and leave them till there was no amps from a power supply?


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## spdas (Nov 28, 2009)

I set voltage to 3.478 (80/23) and let the amps go to near 0. I did this for 2 cycles. ie let them rest and then 80volts then rest again and 80v. The last cycle less than 0.2kwh went into the pack.

There seems to be a very large gap in voltage between the 5 batteries that went south compared to the rest of the pack. I am guessing the pack was about 40% SOC when the 5 went bad.
The entire pack was at 3.13v (141volt) or so including Sag @ 60mph, when the 5 cells dropped off. 
Francis


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## dtbaker (Jan 5, 2008)

spdas said:


> I set voltage to 3.478 (80/23) and let the amps go to near 0. I did this for 2 cycles. ie let them rest and then 80volts then rest again and 80v. The last cycle less than 0.2kwh went into the pack.
> 
> There seems to be a very large gap in voltage between the 5 batteries that went south compared to the rest of the pack. I am guessing the pack was about 40% SOC when the 5 went bad.
> The entire pack was at 3.13v (141volt) or so including Sag @ 60mph, when the 5 cells dropped off.
> Francis


hhhmmm, if I am reading what you did correctly, you never really 'top balance' the whole string at all, and may well have put quite a strain on the old good cells in addition to never fully charging the new ones. if you just put the new 5 in series and charged the string of 23 cells.... then you did not balance at all. Bringing the string of 23 up to 80v means you probably brought the old 18 much higher than you intended, and didn't get much into the new 5.

to make sure ALL the cells in the string are balanced, the best way is to connect them IN PARALLEL and charge with a power supply to your desired vpc. 

If you don't wanna do that, then you'll have to charge JUST THE NEW ONES up to 'full' vpc value if you think all the old cells are full. Then one your first charge you'll have to manually monitor like a bandit to see if the old cells are finishing first and cooking while the new ones are not full....

OR, if you have a variable power supply, you COULD connect to each cell individually in the string and charge to your desired 'finish' voltage vpc, and work your way thru the entire string......


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## spdas (Nov 28, 2009)

All 23 cells are brand new. 18 are still at 3.301 - 3.306v when I returned and 5 went bad to 0.5v.

Francis


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## dtbaker (Jan 5, 2008)

spdas said:


> All 23 cells are brand new. 18 are still at 3.301 - 3.306v when I returned and 5 went bad to 0.5v.
> 
> Francis



ok, not QUITE so worrysome... but the chance still exists that brand new those 5 might have been from a different batch or sitting the shelf or whatever and had 'significantly' different SOC from the others when you unpacked them...

The question remains did you, or did you not, initially wire in parallel and charge to some vpc a little higher than your intended 'finish' vpc when installed in series? or, charge all cells in the string INDIVIDUALLY to some target vpc until 0 amps? if not, then you have not actually top-balanced, which would explain the situation.

the point I am trying to make is that unless you wired the whole string in parallel and charged to a vpc, or charged each cell to a vpc, then you have not top-balanced at all.


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## spdas (Nov 28, 2009)

dtbaker said:


> ok, not QUITE so worrysome... but the chance still exists that brand new those 5 might have been from a different batch or sitting the shelf or whatever and had 'significantly' different SOC from the others when you unpacked them...
> The question remains did you, or did you not, initially wire in parallel and charge to some vpc a little higher than your intended 'finish' vpc when installed in series? or, charge all cells in the string INDIVIDUALLY to some target vpc until 0 amps? if not, then you have not actually top-balanced, which would explain the situation.
> 
> the point I am trying to make is that unless you wired the whole string in parallel and charged to a vpc, or charged each cell to a vpc, then you have not top-balanced at all.


No I did not parallel them. I tested each cell "above the knee" at one point and they all were (I can't remember exactly) about the same 3.5v. There were no cells high or low and they all settled to the same resting voltage as described. The last voltage check right before this happened, while on the charger, they were within .010 volts of each other and the charger was at 0 amps. Resting voltage after a couple hours then was pretty much the same for each cell

As I remember they had sequential serial numbers and the voltage of each cell was quite even when I got them out of the box. I think the point is that the 5 must have been waaaayyy out of balance (I don't think this is the case) or I have some bad cells. 

But if it is necessary to drive the cells to 3.8 to 4.0 to properly activate or balance them, then that is something I do not know about. I feel I got them all even above the knee in voltage though. I did parallel the used TS cells as described as they varied in voltage, but the calbs I did not. Thanks for all the help in this guys. 
Francis


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## spdas (Nov 28, 2009)

dtbaker said:


> ok, not QUITE so worrysome... but the chance still exists that brand new those 5 might have been from a different batch or sitting the shelf or whatever and had 'significantly' different SOC from the others when you unpacked them...
> The question remains did you, or did you not, initially wire in parallel and charge to some vpc a little higher than your intended 'finish' vpc when installed in series? or, charge all cells in the string INDIVIDUALLY to some target vpc until 0 amps? if not, then you have not actually top-balanced, which would explain the situation.
> 
> the point I am trying to make is that unless you wired the whole string in parallel and charged to a vpc, or charged each cell to a vpc, then you have not top-balanced at all.


No I did not parallel them. I tested each cell "above the knee" at one point and they all were (I can't remember exactly) about the same 3.5v. There were no cells high or low and they all settled to the same resting voltage as described. The last voltage check right before this happened, while on the charger, they were within .010 volts of each other and the charger was at 0 amps. Resting voltage after a couple hours then was pretty much the same for each cell

As I remember they had sequential serial numbers and the voltage of each cell was quite even when I got them out of the box. I think the point is that the 5 must have been waaaayyy out of balance (I don't think this is the case) or I have some bad cells. 

But if it is necessary to drive the cells to 3.8 to 4.0 to properly activate or balance them, then that is something I do not know about. I feel I got them all even above the knee in voltage though. Thanks for all the help in this guys. 
Francis


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## dtbaker (Jan 5, 2008)

you don't need to get them up to any particular voltage to 'activate' them, but you DO need to charge them all up to a specific vpc 'above the knee' if you want to be sure they are top-balanced.

I think your best option at this point it to either re-wire the string in parallel and charge to a vpc, or apply a power supply to each cell to a vpc before attempting another series charge.


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## JRP3 (Mar 7, 2008)

T1 Terry said:


> Were all these cells pre condition charged? I've just been through the process of condition charging a pack of 16 x 90ah Winston cells and the requirement was to charge to 4v per cell and maintain that voltage till the current dropped to 1% of the 0.5C rating, in my case 360ah x 0.5c = 180amps X 1% =1.8amps (4 cells inparallel X 4 sets to make a 12v battery pack). It took a long time because my charge rate was low but a further 120ah went in between 3.4v and 4v, 28ah from 3.8v to 4v. After they settled for 24hr I recharged them to 4v per cell and only an additional 1ah went in but the terminal voltage has remained at ranging from 3.720v to 3.700v after a further 24hrs. I'm thinking you haven't fully charged those cells, let's hope you haven't damaged them.
> 
> T1 Terry


As I've said before I think this "preconditioning" notion is incorrect information left over from a mistranslation and misunderstanding of the charge procedure. We know for a fact that cells are already fully charged and discharged at the factory. They have to be to check actual capacity and resistance. Therefore there is absolutely no reason to charge them to 4.0 volts again, (previously it was 4.25 volts and equally unnecessary.) Finally CALB cells mention nothing of the sort with the same basic cell chemistry.


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## JRP3 (Mar 7, 2008)

Regarding the idea that the only way to balance a pack is to parallel all the cells, what's the logic behind that? Charging all the cells to the same voltage in the knee of the curve at the same current will top balance your pack, that's how all the top balancing BMS's work, without paralleling. They just use shunt bleeding to keep the smaller cells from over volting while the larger cells continue to fill up. You can do the same thing manually by topping off the low cells individually. There is no magic in paralleling the whole pack.


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## spdas (Nov 28, 2009)

JRP3 said:


> Regarding the idea that the only way to balance a pack is to parallel all the cells, what's the logic behind that? Charging all the cells to the same voltage in the knee of the curve at the same current will top balance your pack, that's how all the top balancing BMS's work, without paralleling. They just use shunt bleeding to keep the smaller cells from over volting while the larger cells continue to fill up. You can do the same thing manually by topping off the low cells individually. There is no magic in paralleling the whole pack.


Paralleling would really make sure that the pack is even in voltage, but as you say you could top balance as you describe above. I have charged a cell to 3.7 and another to 3.5 and both basically came down to the same resting voltage. In my case I do not feel that I was off in top balance as the 5 cells would all have to be about 3.25 and the rest of the pack 3.35 to kill the 5 and still have a good % SOC left in the rest of the pack. Keegan is very helpful and is sending a note to the factory. 
Francis


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## EVfun (Mar 14, 2010)

Please don't wire the cells in parallel until you have verified that the 5 low voltage cells will hold a charge. Those 5 should not be in parallel as they may prove to be a dump load. They should not be charged unattended as the current may go wild. Abused cells have been known to short out or have very fast self discharge rates.


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## spdas (Nov 28, 2009)

EVfun said:


> Please don't wire the cells in parallel until you have verified that the 5 low voltage cells will hold a charge. Those 5 should not be in parallel as they may prove to be a dump load. They should not be charged unattended as the current may go wild. Abused cells have been known to short out or have very fast self discharge rates.


The fab 5 are being finished charged individually to bring them up to the rest of the pack. They are at about 3.00 each now. I am going to put a load on one or more with my CBA to see if my amperage is still up there.

Francis


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## dtbaker (Jan 5, 2008)

JRP3 said:


> Regarding the idea that the only way to balance a pack is to parallel all the cells, what's the logic behind that?


the logic is that with a given string of cells, if they are in parallel and charged to some voltage, they will all be the same SOC 'full'. ;0 now, if some of the cells having been damaged previously, have wildly unmatched IR, or some other anomaly, then perhps they would not remain 'balanced.' Given NORMAL cells under normal circumstances in parallel charged to some voltage.... then they will by definition be balanced.


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## dtbaker (Jan 5, 2008)

spdas said:


> I have charged a cell to 3.7 and another to 3.5 and both basically came down to the same resting voltage.


exactly why you cannot look at resting charge after a day and have much idea whether cells are closely balanced or not. The point is that you have to catch them s close to the end of charge as possible to know if they will all finish charge as close to the same time as possible. an extra couple minutes on one cell can be a big stressor if it is .5v above all the rest, and it will look the same after resting!


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## spdas (Nov 28, 2009)

dtbaker said:


> exactly why you cannot look at resting charge after a day and have much idea whether cells are closely balanced or not. The point is that you have to catch them s close to the end of charge as possible to know if they will all finish charge as close to the same time as possible. an extra couple minutes on one cell can be a big stressor if it is .5v above all the rest, and it will look the same after resting!



I am not so sure if I agree with the above. (actually re-reading it I do see your point).
I am more comfortable with counting ah or watts....using voltage readings especially above the knee seems unreliable. For example, I could put 5ah into 2 different cells starting at 3.45v. One then may indicate 3.60 and the other may indicate 3.64. I would then not want to put in some more ah to the 3.60v cell to balance it with the 3.64 cell. 
Better then as you say to parallel charge and I would not consider the actual voltage readings above the knee

Francis


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## dtbaker (Jan 5, 2008)

spdas said:


> Better then as you say to parallel charge


that would be the best aprox of 'top balance' and get cells actually at the same voltage as far up the knee as you feel good with. The further up, the closer balanced.

AFTER they are balanced, then you can count ah in and out all you want to figure out if cells are ok or damaged. 

Or, in your case you might want to charge a cell individually once, and discharge to some below the knee voltage to see if you still have anywhere near the ah you are supposed to. 

regardless of whether capacity has been damaged, the best top balance requires putting cells in parallel at some constant voltage above knee, until amps drop.....


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## spdas (Nov 28, 2009)

Yeah, if all goes well, I still may be faced with "will I get 300 charges or 3000 charges out of these 5 cells.

Francis


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## JRP3 (Mar 7, 2008)

spdas said:


> I am more comfortable with counting ah or watts....using voltage readings especially above the knee seems unreliable.


Actually the further into the knee you get the MORE reliable voltage is in relation to SOC, same is true on the other end on discharge. Tapering current into the knee and holding voltage is how you top balance cells.


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## tomofreno (Mar 3, 2009)

Boy, lot of confusion here. Francis, if you verified that all CALB cells were charged to 3.5V then there is no way the 5 were overdischarged due to imbalance when the others still have so much charge left. There is hardly any capacity above 3.5V for CALB cells. I have the same 180Ah cells, and there is only a fraction of an Ah above that voltage. I would be less worried about capacity loss than increased cell resistance due to overheating of the electrolyte and plating of the electrodes if the cells got hot. Check voltage sag under a high load. I would be very cautious about reusing those 5. If they develop high internal resistance they could overheat and vent.


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## GizmoEV (Nov 28, 2009)

Francis,

Do you have an Ah counter in your car? If not, get one! If you are not going to get one then by all means bottom balance your pack so all cells hit bottom at the same time and you won't kill some off when you discharge so much. The CycleAnalyst is inexpensive and well worth the features. Check it out at ebikes.ca. It runs on pack voltage so it won't unbalance your pack.


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## tomofreno (Mar 3, 2009)

> I tested each cell "above the knee" at one point and they all were (I can't remember exactly) about the same 3.5v.





> All 23 cells are brand new. 18 are still at 3.301 - 3.306v when I returned and 5 went bad to 0.5v.



Francis, for the first 6 months or so I drove my car I recorded cell rest voltages after each charge and discharge, and Ah used after discharge. According to my data 3.3V is about 40% - 45% SOC. That combined with the fact that you charged all cells to 3.5V which is well up the exponential part of the curve for CALB cells, indicates the 5 low cells were defective. They would have to have been out of balance by around 50Ah or more relative to the other cells to discharge to 0.5V when the others are at 3.3V. No way that could be the case if they were all charged to 3.5V.


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## JRP3 (Mar 7, 2008)

If they were defective from the factory that's a major miss for CALB QC, it should have shown up in the initial charge/discharge cycle at the factory. I wonder if something else could have cause higher discharge rates for those cells, high resistance connections, or something draining only those cells?


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## EVfun (Mar 14, 2010)

A high resistance connection could get them real hot when driving. I wonder if that would show up after a short time as a dramatic loss of capacity?


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## Beemer (Jun 2, 2011)

You have a mixed pack of calb's and ts's? That is a severe "no no". There is slight operational differences in working voltages, internal resistance and capacity.

It's not all about capacity. For a matched pack the other axis on the graph is internal resistance. A cell with a lower "IR" will charge up and discharge quicker even whilst in series with others.

If you charge a cell to its upper knee it has to be left to settle for a couple of hours because of its internal capacitance.

"When I got home I found 5 cells in mid pack in a row at .3 to .5 Volts (yes 1/3 to 1/2Volt) and they were warm!"
Herein is lesson number one to Li cells; Temperature! The ultimate red light condition. You might find them bricked or so severely hurt as to not match their peers again. I'm presuming no air flows between the cells to normalise temperatures across the pack?

Top balancing is fine if you never attempt to use your EV for maxing any distance.

What is both nice and nasty about these cells is the quite flat Voltage zone through most of the cells charge. One cannot honestly tell if the new cell that is being added is really at the same state of charge unless bottomed or topped independently and at the same temperature as the others.

I'm sorry for the bad news. All the best for next time? 
Andy.


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