# Finally, the new pack is ready to be installed



## ElectriCar (Jun 15, 2008)

That's about 245 more wires than I have in my 50 cells.  No BMS here but I do have a method to monitor them. And I stop charging at about 3.45V so there's no issue with overcharging them. 

Shunting so you can charge up to 3.8V or so doesn't give you any more energy or mileage than at 3.45 if you allow it to charge to that voltage and hold it until the current drops to zero amps. Yes I realize it may give you a half an Ah or so but still that's basically zero. I top balanced my pack and never go near empty so I leave way more than half an Ah in the pack all the time anyway. 

Now for inspiration. I am driving a ton more now that I can. We go to eat out of town for like 40 mile round trips, some after driving 11 miles home and not recharging. We can cruise around to other places if we like, run the heater and lights with no worries of running out of juice. 

In the last month I've driven about 800 miles which has saved me about $200 in diesel fuel! Still at that rate it will take me about 6 years to recover the money spent on the pack. But what thrills my soul is my money isn't going overseas to people that hate my country and I'm not creating pollution along my driving routes.


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## Mr_tim (Dec 13, 2010)

Not really, I was including the cell interconnects in my wire count ;-) When I get back on the road I'll be using it as my daily driver again. Right now I'm spending about $400 a month on gas. That should put me at the break even point in less than three years, without any increases in the price of gas.
I need to go find someone to lend me a 7/8" chassis punch amongst the thousands of other little things I need to do to get things finished.

Later,

TiM


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## ElectriCar (Jun 15, 2008)

Painful isn't it. You know that's a small car payment right there! Best of luck Tim! Hope you get it up and running soon.


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## Mr_tim (Dec 13, 2010)

Woo woo, first charge on the lithium pack tonight. I need to hit it a little more, I didn't get all of them full yet, though it was like Christmas watching all the lights blinking on the regulators as the batteries filled.
I need to figure out what are reasonable setting for my charger and controller cut outs. What the consensus for CALB 180s? I'm looking for maximum life, not maximum range ;-) As long as I get over 50 I'll be happy. Now tomorrow some more charging and my first Lithium run. I'll need to reprogram my controller. I had to go way low on the voltage limit to get the old near dead lead pack to make it up the driveway.

TiM Back on the road again!


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## ElectriCar (Jun 15, 2008)

I'm charging to about 3.44V. At some point above that you risk overcharging some cells. I've charged to 3.49V but around this point the voltages of each cells start to vary quite a bit. At 3.44 or so they're all very close. Besides at this point it from my unscientific observation, it appears the pack is within half an Ah from being full anyway if your charger is working properly.


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## EVfun (Mar 14, 2010)

I found 3.44 vpc to be a little low for my TS pack. At 3.50 vpc I can get about 90% charged before it hits the charger voltage limit and the current starts falling (at 0.2C charge rate.) At 3.44 vpc I get to about 60% SOC before it hits the voltage limit (at 0.2C charge rate) and the current starts slowly falling. I have handwritten charge logs in the garage from recording both types of charges. The total charge time was about 1 hour longer. I needed to hold at max voltage for about 3.3 hours at 3.44 vpc, versus 0.8 hours at 3.5 vpc, but the constant voltage started about 1.5 hours sooner because it started at a lower SOC. I'm not sure which I'm am going to use long term. I do not have a BMS or any type of monitoring on the pack.


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## ElectriCar (Jun 15, 2008)

If I try to go to 3.5 the voltages start spiking all over the place with very little Ah added. Just not worth the risk IMO trying to go there when basically there's no value in doing so anyway. Also TS recommends 3.8V anyway don't they while Calb recommends 3.6V, a little difference in their chemistry I suppose.


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## cruisin (Jun 3, 2009)

EVfun said:


> I found 3.44 vpc to be a little low for my TS pack. At 3.50 vpc I can get about 90% charged before it hits the charger voltage limit and the current starts falling (at 0.2C charge rate.) At 3.44 vpc I get to about 60% SOC before it hits the voltage limit (at 0.2C charge rate) and the current starts slowly falling. I have handwritten charge logs in the garage from recording both types of charges. The total charge time was about 1 hour longer. I needed to hold at max voltage for about 3.3 hours at 3.44 vpc, versus 0.8 hours at 3.5 vpc, but the constant voltage started about 1.5 hours sooner because it started at a lower SOC. I'm not sure which I'm am going to use long term. I do not have a BMS or any type of monitoring on the pack.


You are at risk of loosing your expensive cells relying on just the logic in the charger to avoid overcharge. I could show you many examples of students systems failing due to the best of charger failures. A secondary system as in BMS, etc. needs to be in place to avoid such failures. The cells need to be taken up to 3.6 (CALB) and taper off for a long time for cells to balance. The charger will do that better than the BMS. Where is your protection for undercharge? If one cell takes a dump, how will you know. I would take a real hard look at what you are doing to avoid a big mistake. Many have been there and done it.


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## ElectriCar (Jun 15, 2008)

cruisin said:


> You are at risk of loosing your expensive cells relying on just the logic in the charger to avoid overcharge. I could show you many examples of students systems failing due to the best of charger failures. A secondary system as in BMS, etc. needs to be in place to avoid such failures. The cells need to be taken up to 3.6 (CALB) and taper off for a long time for cells to balance. The charger will do that better than the BMS. Where is your protection for undercharge? If one cell takes a dump, how will you know. I would take a real hard look at what you are doing to avoid a big mistake. Many have been there and done it.


Not the place for this debate but since you asked, I must oblige... I run a Zeva plus fuel guage driver and an Ah counter, the Cycle Analyst. The Zeva is calibrated with the CA such that it operates a low fuel light with a rather large % of the available Ah remaining and shows E with still a large amount of Ah remaining. THIS will prevent all but idiots from taking the cells too low. Lots of people run out of gas pushing it, even airplane pilots, often to their death. 

However unlike in a vehicle where you can just pull over and fill up about anywhere, prudent people won't go somewhere without KNOWING they can make it back to their charging location. And your BMS isn't going to allow you to go further necessarily, if anything it may make you "feel safe" by thinking you can take it lower than I can but if you miscalculate your range, it will shut you down while you try and make it back. 

That's for the low side. For the high side and it's detailed in my upgrade thread, I use a voltage monitoring relay to prevent the charger from over charging, should it fail. The other means to prevent that is to not try and squeeze every possible Ah into the pack. I stop at about the knee before the cell voltages begin to diverge. At that point I could put in maybe a half an Ah or so to my 200 Ah pack. Even if it were 2Ah, that's only 1% and totally insignificant as it amounts to less than a mile on a 100 mile approximate range.

I also have a split pack voltage monitor which will show you a over/under charged cell AND a bad connection in the pack which I think your BMS will not. Your BMS may see a high resistance connection as a cell going too high as the voltage builds across the connection when current is flowing and start shunting while you're driving. I don't know if a BMS will do that but suspect it's not intelligent enough to know not to thus it will. If you're on a trip that you need most of your Ah, you could be in big trouble as all the while you're driving, that cell is shunting and losing SOC. At some point you're going to be shut down on the side of the road calling for a tow. If you continue to drive after the BMS reduced that cells capacity, it also may not trip on LV as the current flowing in the circuit through the bad connection makes still makes it appear that the cell has more voltage than it has. As you continue to motor along thinking all is good, that cell finally goes empty without you or the BMS knowing. And you know what happens when a cell continues to have current pulled through it once it's empty. 

If you were in my truck you could have stopped and checked for the bad connection, repaired it and been on your way. Not sure this is a valid scenario or not as I'm not a BMS expert but I suspect many if not most BMS are not so sophisticated and simply can't detect a bad connection like that.


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## cruisin (Jun 3, 2009)

ElectriCar said:


> Not the place for this debate but since you asked, I must oblige... I run a Zeva plus fuel guage driver and an Ah counter, the Cycle Analyst. The Zeva is calibrated with the CA such that it operates a low fuel light with a rather large % of the available Ah remaining and shows E with still a large amount of Ah remaining. THIS will prevent all but idiots from taking the cells too low. Lots of people run out of gas pushing it, even airplane pilots, often to their death.
> 
> However unlike in a vehicle where you can just pull over and fill up about anywhere, prudent people won't go somewhere without KNOWING they can make it back to their charging location. And your BMS isn't going to allow you to go further necessarily, if anything it may make you "feel safe" by thinking you can take it lower than I can but if you miscalculate your range, it will shut you down while you try and make it back.
> 
> ...


You are right, this is not the place to debate, which wasnt my intention but yours, it is to help each other which you dont seem to appreciate. You are dead wrong on the BMS ussage. I will watch for your posting about a bad cell or something even worse.


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## DIYguy (Sep 18, 2008)

cruisin said:


> You are right, this is not the place to debate, which wasnt my intention but yours, it is to help each other which you dont seem to appreciate.


 fail.........



cruisin said:


> You are dead wrong on the BMS ussage. I will watch for your posting about a bad cell or something even worse.


don't hold your breath dude. . . he's got a fine system, no worries.


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## dtbaker (Jan 5, 2008)

cruisin said:


> You are at risk of loosing your expensive cells relying on just the logic in the charger to avoid overcharge.



I would say 'unlikely' if the pack was well top-balanced and the balance was not changed with any active shunting BMS, AND 100% DOD was avoided at the botom end by responsible drivers not trying to see how far they can go without dying.

I could be wrong, and await correction, but I have not seen any thread where a well top-balanced pack relying on charger pack management of the end-o-charge has gone out of balance and fired anything where thee wasn't some parisitic load from some partial BMS somewhere unbalancing things.....


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## EVfun (Mar 14, 2010)

cruisin said:


> You are at risk of loosing your expensive cells relying on just the logic in the charger to avoid overcharge. I could show you many examples of students systems failing due to the best of charger failures. A secondary system as in BMS, etc. needs to be in place to avoid such failures. The cells need to be taken up to 3.6 (CALB) and taper off for a long time for cells to balance. The charger will do that better than the BMS. Where is your protection for undercharge? If one cell takes a dump, how will you know. I would take a real hard look at what you are doing to avoid a big mistake. Many have been there and done it.


Yeah, about 1/2 the Lithium users on this list are at risk of loosing our expensive cells that way. The other half risking loosing cells from failures in BMS modules or wiring. You pays your money and you takes your choice.


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## Mr_tim (Dec 13, 2010)

The EV grin is back! the pack is in, it runs and it accelerates much better and faster than it used to. Of couse you'd expect that after loosing 1400 pounds. I don't want to start a BMS debate in this thread, there are plenty of other threads for that ;-) I chose to use one for my reasons. Of course I have about 50 or 60 questions about the proper way to set it all up and I'll have to wait until Monday and they're back in the shop. Of course they"re also having a "Cyber Monday" sale so I might have to wait until Tuesday to talk to someone in person. In the meantime I'll keep my cycles short. I'll reprogram things for 3.45V per cell. I have almost all the cells at 3.5V right now. 1 or 2 are holding out.
I programed my SOC to read empty at 80% of 180, as that's what my cells are rated at, though they tested out much closer to 200. I figure that should give me plenty or room for error no? Now if i can just figure out how to get the BMS and the charger on the same page. Tooooooo much fun I tell you!

TiM


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## ElectriCar (Jun 15, 2008)

Awesome! Now if you have a 500A controller and go to 1000A, that grin will quickly change to ! I did and I love it, absolutely NO comparison to the original controller!


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## Mr_tim (Dec 13, 2010)

Already did the 1000 amp controller upgrade. I've programed it for a max battery side of 500. I don't want to spin off my rear end ;-)

TiM


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## tomofreno (Mar 3, 2009)

> I'm charging to about 3.44V. At some point above that you risk overcharging some cells. I've charged to 3.49V but around this point the voltages of each cells start to vary quite a bit. At 3.44 or so they're all very close. Besides at this point it from my unscientific observation, it appears the pack is within half an Ah from being full anyway if your charger is working properly.


 I'd say that is about right, maybe 3/4 Ah. I had a cell (CALB 180Ah) that was at 3.993V when others were at 3.455V, so I charged it with a DC power supply. It took about 3A for 25 minutes, about 1 1/4Ah, to bring it to 3.441V.


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## ElectriCar (Jun 15, 2008)

What I don't understand is how some cells will spike rapidly once they reach a certain point while others will sort of slowly rise...and they all start at the same point! I can top balance them and yet certain cells still spiral out of control much quicker than the rest of the pack.


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## EVfun (Mar 14, 2010)

Mr_tim said:


> Already did the 1000 amp controller upgrade. I've programed it for a max battery side of 500. I don't want to spin off my rear end ;-)
> 
> TiM


I should point out that your peak torque is set by your motor amp limit. If you are greatly concerned about your clutch or rear end you should limit motor amps to something you feel results in an acceptable peak torque.


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## GizmoEV (Nov 28, 2009)

ElectriCar said:


> What I don't understand is how some cells will spike rapidly once they reach a certain point while others will sort of slowly rise...and they all start at the same point! I can top balance them and yet certain cells still spiral out of control much quicker than the rest of the pack.


Is this while the charging current is quite low or is it relatively high? I've seen this happen just about the time the charger begins to taper but then the high cells would drop back as the current decreased. I have assumed this may be due to a difference in internal resistance. FWIW, I only saw this when charging to more than 3.5vpc.


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## GizmoEV (Nov 28, 2009)

cruisin said:


> You are at risk of loosing your expensive cells relying on just the logic in the charger to avoid overcharge. I could show you many examples of students systems failing due to the best of charger failures. A secondary system as in BMS, etc. needs to be in place to avoid such failures.


Lots of possible variables there with student's systems isn't there?



cruisin said:


> The cells need to be taken up to 3.6 (CALB) and taper off for a long time for cells to balance. The charger will do that better than the BMS. Where is your protection for undercharge? If one cell takes a dump, how will you know. I would take a real hard look at what you are doing to avoid a big mistake. Many have been there and done it.


And many have been there and not done it. We'll see in time but so far balancing only needs to be done about once per year, likely longer. I'll let you know in July 2012 how things are going now that I have removed the BMS boards so they can't be used as a reason to imbalance my pack.


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## ElectriCar (Jun 15, 2008)

GizmoEV said:


> Is this while the charging current is quite low or is it relatively high? I've seen this happen just about the time the charger begins to taper but then the high cells would drop back as the current decreased. I have assumed this may be due to a difference in internal resistance. FWIW, I only saw this when charging to more than 3.5vpc.


While charging is where it appears and it doesn't come back down until after driving it. 

I have 5 rows of 10 cells. When first charging I kept an eye on each row, looking for the high cell and marked them. To this day those same 5 cells still behave that way and there are a couple more. I've bled off the voltage to bring them back into the fold and get them all to the same voltage. Then after putting a few cycles on the pack those same ones will show up high again.  

The key though is keeping the voltage below the knee and when I do that the entire pack reads the exact same voltage on each cell down to .001 volt range on my meter. So now I just charge to 3.44VPC or so and all is well. From all I've read by JRP3, you and others as well as my own observations there's no need to go higher for a trivial amount of extra charge. In fact I could go lower I think with only a trivial amount of ah lost but at this voltage I like the way they behave.


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## GizmoEV (Nov 28, 2009)

I don't remember, did you top balance or bottom balance? The behavior I noticed was with a top balanced pack.


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## ElectriCar (Jun 15, 2008)

Top. JRP3 and you maybe are the ones who talked me into it. And it made sense so I did. Did it a couple of times also. I take a peek at them once in a while but they're still all right there within a thousandth of a volt until approaching the knee where those bad guys start to shoot up.


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## GizmoEV (Nov 28, 2009)

That is really strange. I don't see that behavior with mine ending at 3.465vpc average. My last check showed a low of 3.455 and a high of 3.483V. I wonder how much the difference you are seeing is due to different temperatures between batteries. Mine are all in one box.


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## ElectriCar (Jun 15, 2008)

It is weird and I've not seen any explanation for it. I'll check it again next week but since lowering my charge voltage I likely won't see much if any difference.


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## Mr_tim (Dec 13, 2010)

ElitriCar, what are you using for your low vloltage limit on your Calbs? I'm still trying to figure out my BMS and SOC settings. For some reason the SOC is seeing negative current when charging and it's supposed to be positive. Grrr. It's wired per the specs, so maybe the specs have a type? I'll be calling in the AM.

_-- Sent from my Palm Pre using Forums_


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## tomofreno (Mar 3, 2009)

> I have 5 rows of 10 cells. When first charging I kept an eye on each row, looking for the high cell and marked them. To this day those same 5 cells still behave that way and there are a couple more. I've bled off the voltage to bring them back into the fold and get them all to the same voltage. Then after putting a few cycles on the pack those same ones will show up high again.


 I don't think this is unusual at all. I have seen the same on a number of cells. The cells can behave quite differently on the exponential part of the curve, likely I think due to quite different internal resistances there. Some take off, others take much longer to move up. It's funny to me that we balance on this part of the operating curve since they are so squirrely there. I would guess it might depend on structure of the films on the electrodes, and how that effects internal resistance when the cells are almost fully charged, or maybe differences in SEI. There is only 1/2 to 3/4 Ah or so on this exponential part though, so no need to worry about it. Because they are so sensitive there, a 1/4 Ah difference in balance in a cell and the others can make it behave quite differently, whereas down below 3.44V they may all measure the same to within a few mV even while charging. I suspect a good part of the imbalance seen on the exponential part of the curve is due to differences in internal resistance there and not capacity. But what the hey, they probably shunt balance to within a 1/3 Ah or so of each other even if that is the case.


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## GizmoEV (Nov 28, 2009)

Wouldn't the effects of differences in internal resistance diminish with lower current? Maybe this is why I haven't seen it much since when I was top balancing to 4.00V  the current was well below 0.5A on a 200Ah pack. I don't lose much if any capacity charging to 3.465vpc and very low ending current now. I probably am gaining a much longer pack life, however.


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## ElectriCar (Jun 15, 2008)

Mr_tim said:


> ElitriCar, what are you using for your low vloltage limit on your Calbs? I'm still trying to figure out my BMS and SOC settings. For some reason the SOC is seeing negative current when charging and it's supposed to be positive. Grrr. It's wired per the specs, so maybe the specs have a type? I'll be calling in the AM.
> 
> _-- Sent from my Palm Pre using Forums_


I have a relay with two outputs used for precharge. Once the main contactors are all on if the pack voltage drops below a certain point, the 2nd contact on that relay opens, killing the controller. I just used the hysteresis setting on the relay for that and I think it kicks on around 3VPC. I also used the timer feature to give it a little delay so it doesn't kick out on a sudden momentary drop, ie a quick tap of the throttle when at a low SOC. As of yet it's never kicked in as my voltage only gets near that area while driving at a very low SOC.


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## tomofreno (Mar 3, 2009)

> Wouldn't the effects of differences in internal resistance diminish with lower current?


 Yes. My charger is usually at about 2 - 4A when the highest cells get to the start of the exponential part of the curve, around 3.44 - 3.45V. The current drops fairly quickly once some cells start up this part of the curve increasing pack V. The better the balance the more quickly it cuts back.


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