Hillhater
100 TW
Arlo1 said:
Good advice, ..but what are the "rated C ratings " for these cells.
Its hard to find official data ..
http://www.eco-aesc-lb.com/en/product/liion_ev/
Nissan Leaf Cells Test Data
- Thread starter icecube57
- Start date
Good advice, ..but what are the "rated C ratings " for these cells.
Its hard to find official data ..
http://www.eco-aesc-lb.com/en/product/liion_ev/
MitchJi
10 MW
Hi,
24kw-h at 4.2v. At 3.6v it is 21kw-h, or about 4C which should be a safe burst rating.
Hillhater
100 TW
MitchJi said:
Im sure that is a safe rating ...
BUT,... Isnt that just what they are being used for, not what their actual capability is ?
I doubt they would be used at anywhere near their maximum rating in a consumer product.
zEEz
1 kW
in the end it all depends on the purpose of the cells. for few time per year drag racing 20 C could be ok, but for long lasting daily use commuter vehicle it should be better to adhere to Nissan usage guidelines ... 3 to 4 C maximum peak.
This is why I decided to leave them 2p intending to use them in a light motorcycle.
Get out of them 50 cycles instead of 2000 is not for me a sensible investment in using Nissan Lipos instead of gas. :?
have fun!
This is why I decided to leave them 2p intending to use them in a light motorcycle.
Get out of them 50 cycles instead of 2000 is not for me a sensible investment in using Nissan Lipos instead of gas. :?
have fun!
John in CR
100 TW
MitchJi said:
I don't know how you jumped to the correct answer.
Assuming the 80kw is peak power draw and voltage sags to the nominal voltage Nissan uses, 360V, then it's 222A drawn through the 2p modules. At 66ah that's 3.4C . I think it's reasonable to assume that's a near continuous rating, since relatively long climbs can be expected.
As always we have the advantage of building for our own use. I love the exhilarating acceleration electrics are so easily capable, so I expect peak current to be only a few seconds in duration. We won't know for sure until we have info on voltage sag, but I hope to hit mine with 8C peak. That's assuming it actually is easy to turn the 2p2s modules into 4s.
Hillhater
100 TW
Exactly John.
We can see what the cells are doing in the Leaf, ..3C+..continuous
We have seen that they can do 10C under test conditions ( but for how long & at what penalty)
FYI .. 10 C voltage sag was posted here..
..And we could infer from data that the cell has potential for 16C ..maybe ?
..but nowhere is there any official data sheet stating the actual tested or recommended performance limits. !
Interestingly, on the same AESC site, they show a smaller cell (4.1Ahr) with test results of a 90Amp discharge ..22C !
Those cells are used in the Nissan Fuga (Infinity 35) , M45h, etc , hybrids.
Maybe you need some of those ! :lol:
We can see what the cells are doing in the Leaf, ..3C+..continuous
We have seen that they can do 10C under test conditions ( but for how long & at what penalty)
FYI .. 10 C voltage sag was posted here..
noahpodolefsky said:
..And we could infer from data that the cell has potential for 16C ..maybe ?
..but nowhere is there any official data sheet stating the actual tested or recommended performance limits. !
Interestingly, on the same AESC site, they show a smaller cell (4.1Ahr) with test results of a 90Amp discharge ..22C !
Those cells are used in the Nissan Fuga (Infinity 35) , M45h, etc , hybrids.
Maybe you need some of those ! :lol:
hillzofvalp
100 kW
I just got a leaf, and I'm trying to figure out the economics of their 60,000 mile battery warranty (if pack goes below 70%, they will replace). Strangely, 60,000/65 (avg trip of 65) yields ~1000 cycles. Looking at other nmc like sony vtc4, if you project the cycle life data for ~4C you get 70% capacity at 1000 cycles. That's assuming its linear. What do you guys think? I'm thinking about using the dc 2C chargers whenever possible to accelerate aging so that in 2-3 years I can get a new pack 
hillzofvalp said:I just got a leaf, and I'm trying to figure out the economics of their 60,000 mile battery warranty (if pack goes below 70%, they will replace). Strangely, 60,000/65 (avg trip of 65) yields ~1000 cycles. Looking at other nmc like sony vtc4, if you project the cycle life data for ~4C you get 70% capacity at 1000 cycles. That's assuming its linear. What do you guys think? I'm thinking about using the dc 2C chargers whenever possible to accelerate aging so that in 2-3 years I can get a new pack
They probably know when you did it. Not sure if warranty will cover that. But looking forward to the 70% degradation in 2-3 years! I guess you will be driving a lot more now compared to ebiking.
hillzofvalp
100 kW
They have a yearly check on your battery which is basically just a print-out star system rating your charge behavior. This is a pre-owned car and it had 4 stars for fast charge, but all other categories (trickle, standard, short cycles) were 5 stars. They actually encourage you to standard charge more than trickle charge, which confused me. Thought that was only true with lead acid.
Anyways, I'm not DC charging with my own rig.. I'm using nissan/blink chademo 50kW chargers most of the time.
I have not ridden my MB for a while. It's going to have to fight for love now between it, Kickr skateboards, and the Leaf. Boy is WOT on the leaf fun! up until about 35 mph, anyways.. After that it is pretty slow... My MB would destroy it to 60. When the general warranty is out I'll try making some changes :wink: :wink:
I don't think I would really care THAT much if I didn't get a replacement battery under warranty, because likely the replacement packs are just as diminutive. I'd like to build a solid 40kWh pack when the time is right, but by that time I may be in the market for a Model 3.
Anyways, I'm not DC charging with my own rig.. I'm using nissan/blink chademo 50kW chargers most of the time.
I have not ridden my MB for a while. It's going to have to fight for love now between it, Kickr skateboards, and the Leaf. Boy is WOT on the leaf fun! up until about 35 mph, anyways.. After that it is pretty slow... My MB would destroy it to 60. When the general warranty is out I'll try making some changes :wink: :wink:
I don't think I would really care THAT much if I didn't get a replacement battery under warranty, because likely the replacement packs are just as diminutive. I'd like to build a solid 40kWh pack when the time is right, but by that time I may be in the market for a Model 3.
Deanwvu
100 W
What would be the best way to connect multiple packs if the copper bus bars have been removed from the packs?
I have individual cells I'd like to wire in series, but all the copper bus bars have been removed.
Thank you.
I have individual cells I'd like to wire in series, but all the copper bus bars have been removed.
Thank you.
zEEz
1 kW
veloman said:
I suggest you to ask for a complete piece of 4 modules by 2 mounted on the specific subframe, as found in the Leaf.
In this way you will avoid any damage due to transport. Having said this, I can confirm that I received 2 boxes of 4 and 3 modules, shipped internationally, in pretty good shape. Good luck!
heathyoung
100 kW
I'll let you know when mine arrive at my doorstep, expecting 19 for the Vectrix, they are already in the country
No more thundersags! Yay...
No more thundersags! Yay...
agniusm
1 MW
I got 8 modules. Problem is I cant get 67.2V waterproof on board charger for them. How much capacity is there from 4.12v to 4.2v? I could get one with max 66V and it is 35A charger. Would it be ok if I am using whole modules, for 2p charging?
zEEz
1 kW
agniusm said:
I guess you want to bulk charge, not using a Bms, so that option is far better than Boom
Not to mention that you will get more cycles before degradation of cells!
Capacity in that range is in the graph of the test, at beginning of the thread, less than 1Ah, not much in my opinion, if you factor in the safe factor, but probably, just opening the charger and tweaking a pot or soldering a resistor you could get to the exact wanted value. Put a link to the charger to confirm and have opinions from other members!
have fun!
icecube57
10 MW
13s
agniusm
1 MW
Not exactly. I want to use BMS and a charger. Not using BMS is a bit silly. Been using one for 3 years without issues. I have thought about it and will get proper voltage charger, off board cause those are 8kg. Thanks for the info
BigRider
10 mW
Hi all.
I had it pointed out to me in PM that I speak authoritatively on Li batteries. So I'm a noob here in all ways but one .... I know way more than I ever wanted to know about lithium batteries due to part of my work responsibilities. But, hey, I can contribute and not just be a sponge!
Couple golden rules on Li batteries
1) Never charge above the rated voltage. If it's a 4.2V cell never charge above that. (more below)
2) Never below 2.7.... or really about 3V. The lower you take it the more stripping you're doing of the copper of the anode, causing plating (capacity loss) and dendrite growth (can lead to a puncture and safety problem).
3) Limiting to 3.5V and 4.1V will greatly improve your cycle life. I've read of EV makers who limit their stuff to the middle third of available capacity to greatly increase cycle life.
4) Not using a BMS is dangerous.
This is actually a great summary of all the issues and at least the first couple pages match what I know.
http://www.mpoweruk.com/lithium_failures.htm
The reason for overcharging being an issue. Cell manufacturers are judged by their maximum capacity combined with reliability, but the first-most spec they get judged on ... what gets them in the door, is their energy density. To do that they push the voltages up as far as they can and have a reasonable 500 cycle life. There are various tradeoffs for safety, capacity, and lifetime. Some cells are better at some than others.
Here's a good article on that (and OMG did my head hurt reading that whole site):
http://batteryuniversity.com/learn/article/safety_of_lithium_ion_batteries
There are newer charging voltages in the market. 4.25V, 4.3, 4.35 and I recently saw projections of 5V. There's new cathode materials in development such as silicon based. But all of these trade off against longevity. Initial silicon packs are awesome... till you've cycled them about 100 times. Then they're trash (silicon lattice is too brittle and the intercalcuation of lithium ions forces the lattice to expand and break down your cathode material).
(for a 4.2V cell - and keep in mind this is what you're supposed to do, not what you can get away with ... I can drive my car at 100mph and get away with it ... usually)
I made an analogy in my head to help remember the effects. Think of your battery as a bus. There's only so many seats. If you charge to only 4.1V there's enough seats left that you can leave it there all day long and no problems. In a 4.1V charge you don't need to terminate because everyone on the bus is just so happy.
Now, if you fill every seat you start getting people mad. Some of them react by not behaving like you expect ever again (capacity loss due to plating and general wear of anode / cathode). But this is the normal and it's designed to handle that. You can do it safely. But eventually you need to shut off the doors to keep people from getting too many in the bus and causing problems. Thus, if you're charging to capacity it's important to do battery cut off.
Now ... just why don't you ever charge to above .... sure, you've got some more people on the bus but you do it at the cost of making a lot more of your people permanently mad (more of that plating of the aluminum from the cathode as well as the lithium plating - both permanent capacity loss). But there's a worse side effect. You can have a riot and meltdown of general order. That metal stipped out of the cathode (for overcharge, anode for overdischarge) ends up growing dendrites, or little metal spikes. Those spikes slowly grow and it's possible to push through the separator and short anode to cathode. Then you have a hard short inside the can .... and ... bad things happen then. The bigger the battery the bigger the problem. There are lots of YouTube videos on people who decided it was a good idea to create that short the hard way (nail). It's not pretty.
Anyway, hopefully this can help someone.
I had it pointed out to me in PM that I speak authoritatively on Li batteries. So I'm a noob here in all ways but one .... I know way more than I ever wanted to know about lithium batteries due to part of my work responsibilities
. But, hey, I can contribute and not just be a sponge!Couple golden rules on Li batteries
1) Never charge above the rated voltage. If it's a 4.2V cell never charge above that. (more below)
2) Never below 2.7.... or really about 3V. The lower you take it the more stripping you're doing of the copper of the anode, causing plating (capacity loss) and dendrite growth (can lead to a puncture and safety problem).
3) Limiting to 3.5V and 4.1V will greatly improve your cycle life. I've read of EV makers who limit their stuff to the middle third of available capacity to greatly increase cycle life.
4) Not using a BMS is dangerous.
This is actually a great summary of all the issues and at least the first couple pages match what I know.
http://www.mpoweruk.com/lithium_failures.htm
The reason for overcharging being an issue. Cell manufacturers are judged by their maximum capacity combined with reliability, but the first-most spec they get judged on ... what gets them in the door, is their energy density. To do that they push the voltages up as far as they can and have a reasonable 500 cycle life. There are various tradeoffs for safety, capacity, and lifetime. Some cells are better at some than others.
Here's a good article on that (and OMG did my head hurt reading that whole site):
http://batteryuniversity.com/learn/article/safety_of_lithium_ion_batteries
There are newer charging voltages in the market. 4.25V, 4.3, 4.35 and I recently saw projections of 5V. There's new cathode materials in development such as silicon based. But all of these trade off against longevity. Initial silicon packs are awesome... till you've cycled them about 100 times. Then they're trash (silicon lattice is too brittle and the intercalcuation of lithium ions forces the lattice to expand and break down your cathode material).
(for a 4.2V cell - and keep in mind this is what you're supposed to do, not what you can get away with ... I can drive my car at 100mph and get away with it ... usually)
I made an analogy in my head to help remember the effects. Think of your battery as a bus. There's only so many seats. If you charge to only 4.1V there's enough seats left that you can leave it there all day long and no problems. In a 4.1V charge you don't need to terminate because everyone on the bus is just so happy.
Now, if you fill every seat you start getting people mad. Some of them react by not behaving like you expect ever again (capacity loss due to plating and general wear of anode / cathode). But this is the normal and it's designed to handle that. You can do it safely. But eventually you need to shut off the doors to keep people from getting too many in the bus and causing problems. Thus, if you're charging to capacity it's important to do battery cut off.
Now ... just why don't you ever charge to above .... sure, you've got some more people on the bus but you do it at the cost of making a lot more of your people permanently mad (more of that plating of the aluminum from the cathode as well as the lithium plating - both permanent capacity loss). But there's a worse side effect. You can have a riot and meltdown of general order. That metal stipped out of the cathode (for overcharge, anode for overdischarge) ends up growing dendrites, or little metal spikes. Those spikes slowly grow and it's possible to push through the separator and short anode to cathode. Then you have a hard short inside the can .... and ... bad things happen then
. The bigger the battery the bigger the problem. There are lots of YouTube videos on people who decided it was a good idea to create that short the hard way (nail). It's not pretty.Anyway, hopefully this can help someone.
John in CR
100 TW
BigRider said:
If you run conservative top of charge voltages and more conservative DOD's, then by simply monitoring voltages as the cell level you can be a better human BMS than those failure prone electronics can ever dream of. BMS's and drain down resistors on controllers kill more batteries than humans do.
oatnet
1 MW
John in CR said:
+1.
BigRider, while there is a whole range of skill sets here, you may be underestimating the knowledge and experience of your target audience. There are many threads and posts detailing Golden Rules for LiCo with more conservative voltage clamps than yours, and a few more rules thrown in. I don't have an adequate place to store LiCo safely, and I don't have a design criteria that drives me to need the 15% weight savings over a123 LiFePO4, so I don't use it and my experience is with LiFe and LiMn varients.
It sounds like you have some good experience with LiCo chemistry, but maybe not as much with other Li chemistries or building series traction packs for EVs? Your generalizations about Li batteries seem appropriate to LiCo variants, but not LiFePO4 or LiMn which are also Li cells. For example, LiFe/LiMn peak charge to 3.65v, not the 4.2v you mentioned. Both have inert cathodes so they are not subject to thermal runaway like LiCo, and the consequences of many failure modes are less dire. Over the past 8 years I've lost LiFe cells in a handful of traction packs up to 175v, and the only impact I've experienced was a decrease in voltage and capacity.
I have been stranded by faulty BMS and have lost more cells to faulty BMS than anything else, so I stopped using them 6-7 years ago. The cost of the cells I have lost to my own stupidity is a tiny fraction of what I would have paid for BMS's for all the packs I have built. A BMS is useful for HVC, LVC, and balancing; while it requires a certain situational awareness that would not work for everyone, here is the non-BMS strategy I have developed over 100+ EV builds:
HVC/balancing: The LiMn I've used is self-balancing. I periodically balance my LiFe packs with a banks of single cell chargers, and I have found there is so little drift that monthly balancing is good enough for 3c-5c LiFe, and maybe quarterly for quality 20c powder like a123. SSC's provide HVC on the balance charge, and like John my bulk charges are low (to 3.50v-3.55v/cell) so I could lose (2) cells during a charge before it becomes a concern, and (4) cells before it becomes an issue. Here is the original thread on SSC (single cell charging): https://www.endless-sphere.com/forums/viewtopic.php?f=14&t=2586
LVC: I build my packs with a good safety margin of excess capacity, so I rarely get to a DOD that would prematurely age an unbalanced cell, let alone take it below a critical voltage. I mostly use a123 cells these days, which are rated to a 100% DOD anyhow.
-JD
BigRider
10 mW
Gotcha. I'll go back to lurking-ish. Or sponging anyway .
Just trying to be helpful in the one area I can contribute on.
.Just trying to be helpful in the one area I can contribute on.
zEEz
1 kW
I have possibly found a cheap way to charge 4x Leaf modules connected 16s1p at cell level.
In case I will go for this configuration for a light e-moto build, I plan to semi-bulk charge using
4x brick power supply at 7 A and 16,5v each, one per module, plus 2 CellLogs 8m, connected
to the pack with the HVC alarm line used to trigger off the charger in case any cell is going higher
than 4.2V. In that way the process should be quite failure proof. 8)
In the end it is a 400W charger, top up in 5 hour, plus CellLogs 8m as Bms, and you can buy
everything for less than 100 € shipped ... suitable to the cheapness of Leaf modules
Clearly, once per month or when needed, the cell level monitoring can suggest wich cell is worth
to be individually charged a bit more in order to keep the pack happily balanced ... using an RC charger.
have fun!
In case I will go for this configuration for a light e-moto build, I plan to semi-bulk charge using
4x brick power supply at 7 A and 16,5v each, one per module, plus 2 CellLogs 8m, connected
to the pack with the HVC alarm line used to trigger off the charger in case any cell is going higher
than 4.2V. In that way the process should be quite failure proof. 8)
In the end it is a 400W charger, top up in 5 hour, plus CellLogs 8m as Bms, and you can buy
everything for less than 100 € shipped ... suitable to the cheapness of Leaf modules
Clearly, once per month or when needed, the cell level monitoring can suggest wich cell is worth
to be individually charged a bit more in order to keep the pack happily balanced ... using an RC charger.
have fun!