current limiting on Curtis and TS cells

AC, DC, amps, volts and kilowatt. It's all discussed in here
Peter C in Canberra
Senior Member
Posts: 494
Joined: Sun, 27 Jul 2008, 04:05
Real Name: Peter Campbell
Location: Canberra

current limiting on Curtis and TS cells

Post by Peter C in Canberra » Thu, 11 Jun 2009, 16:04

Back onto topic...
The last few days have had maxima below 10oC and last night was -4 or -5 depending on which radio you listen to. Cars in the open were frost covered. Mine was under a tiled roof with no sides but had no frost. Still it is about as cold as the cells with ever have to cope with. Yesterday I had the BMS 2.5V alarm go off briefly once or twice with about 250Amps and about 80% full charge and this morning I hit 260 Amps briefly on a full charge and the alarm went off. So, it seems I don't quite get 3C (270Amps) when it is cold but I can generally get sufficient performance from the car within this limit. What I don't know yet is whether performance declines further when the charge is getting low but not yet empty and it is this cold.
Still I think it might be rather nice in a few years (when I can afford it and the price is less, cells smaller, lighter etc) to add a second string of cells, not so much for extra range as lower impedance. I feel the limit on the car's performance is in the cells rather than the Curtis controller or ADC 8" motor, not that I am dissatisfied with the performance.
Peter.
Last edited by Peter C in Canberra on Thu, 11 Jun 2009, 06:06, edited 1 time in total.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

antiscab
Senior Member
Posts: 2490
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

current limiting on Curtis and TS cells

Post by antiscab » Thu, 11 Jun 2009, 18:04

a single string of A123 M1s (45 of them) would increase available current by 50-60A in cold weather, and cost around AUS$400 + AUS$300 for a el-cheapo BMS.

though as you say, if you are satisfied with present performance, id wait.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

Peter C in Canberra
Senior Member
Posts: 494
Joined: Sun, 27 Jul 2008, 04:05
Real Name: Peter Campbell
Location: Canberra

current limiting on Curtis and TS cells

Post by Peter C in Canberra » Thu, 11 Jun 2009, 18:47

Interesting. That is just where my thinking had been going. I was wondering whether there were cells of modest amp-hour rate and modest cost but distinctly lower internal resistance than my TS90s. For brief bursts of power these could supply a disproportionate amount of power, halfway to having some ultracapacitors. As I back off the accelerator they would recharge from the main battery pack. Where can I buy A123 cells? I'll almost certainly wait for a bit since the cupboard is bare just now but I can start thinking...
Thanks,
Peter.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

antiscab
Senior Member
Posts: 2490
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

current limiting on Curtis and TS cells

Post by antiscab » Thu, 11 Jun 2009, 19:06

Royce wood is selling A123 M1 for US$6.50 each + shipping + BMS:
A123 cell source
ive ordered 125 of them for my bike conversion (and may order a few more).
When i get them ill report back if they're the real deal or not.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

User avatar
weber
Site Admin
Posts: 2626
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by weber » Fri, 12 Jun 2009, 02:56

Peter C in Canberra wrote: Back onto topic...
The last few days have had maxima below 10oC and last night was -4 or -5 depending on which radio you listen to. Cars in the open were frost covered. Mine was under a tiled roof with no sides but had no frost. Still it is about as cold as the cells with ever have to cope with.

Hi Peter, do make sure you never charge the battery when it is at 0°C or below. While it will seem to be taking the charge just fine, metallic lithium plates out onto the anode. This is irreversible and not only permanently reduces capacity but it turns the batteries into incendiary devices if they later get overheated or ruptured.

IMHO, LiFePO4 battery chargers should monitor the temperature of the cells as well as the voltage, and shut off automatically if too cold or too hot.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

Peter C in Canberra
Senior Member
Posts: 494
Joined: Sun, 27 Jul 2008, 04:05
Real Name: Peter Campbell
Location: Canberra

current limiting on Curtis and TS cells

Post by Peter C in Canberra » Fri, 12 Jun 2009, 04:23

Hmm. I just went out to check the temperature. At 10PM the battery compartment was 6 degrees when the air was 3 degrees and -4 is the predicted minimum. I had a timer set so the charger would not come on till 9PM so the charger has been running an hour. The battery gauge shows -6Ah so it should have less than half an hour to go charging. I guess it will be alright but perhaps I'll change the timer to allow charging from 8 rather than 9PM. Once we are out of the frosty period I can set the timer for charging in the early hours of the morning. On the way home, up the first big hill with an 80kmph limit I tripped the BMS alarm with ~220Amps so only about 2.5C. I am learning to back off the accelerator pedal as the revs and current rise.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

Peter C in Canberra
Senior Member
Posts: 494
Joined: Sun, 27 Jul 2008, 04:05
Real Name: Peter Campbell
Location: Canberra

current limiting on Curtis and TS cells

Post by Peter C in Canberra » Mon, 15 Jun 2009, 15:58

Is there some definitive source of info on the LiFePO4 charging chemistry and temperature? As far as I can tell my battery has been charging just fine at temperatures above zero, but not by very much. Zero is a suspiciously round number so it would be nice to know some further details. Does the lithium plating issue come on gradually at lower and lower temperatures so it could be happening to some slight extent above zero?, or does it only occur after some phase change that only occurs at some precise temperature?
On discharge performance, I am now getting the BMS alarm (2.5V on at least on cell) going off with currents around 220Amps more often now with colder weather having set in.
The more I think of it, the more I like the idea of a string of not too expensive, high current/low capacity cells in parallel with the main set of expensive lower performance/higher capacity cells.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

User avatar
weber
Site Admin
Posts: 2626
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by weber » Mon, 15 Jun 2009, 17:30

Most people respect the information from "Battery University". Search for the word freezing on this page.
http://www.batteryuniversity.com/partone-5A.htm

It is apparently the case for all lithium-ion types, not only LiFePO4.

I read somewhere that for fast charging you should ensure the cell temperature is above 5°C. Eventually googled it again. Also at Battery University. Search for lithium in this page.
http://aimeiz.homeip.net/pub/modelarstw ... atures.htm

And I note that charging actually absorbs heat at first, and so may chill the cells further.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by coulomb » Fri, 19 Jun 2009, 02:31

acmotor wrote: Weber, if you still have your test rig together, can you repeat the 3C esky test with the top open to 1) natural airflow and 2) fanned airflow both with a typical BMS board and wiring mounted. I think your 'heat out of the terminals' idea will control cell temperature quite well.
(BTW, having no insulation underneath will make little difference to a heating test Image )

Acmotor was kind enough to send us one of his BMS boards. Weber and I have done the test. The results were ready near the start of the cold, dark AEVA outage (brrr Image ), so I didn't have any incentive to type in the results, then I got the flu, and the dog ran away with my homework.

Well, it's here now. First the setup:

Image
Note the breeze on the paper.

The data:
Image Image Image
Edit: 2 sets of glitches with the old (no fan) data fixed.

The last image has the new temperature and temperature from a similar run without the fan (old run in gold). The temperatures track very closely for a while; the differences could be attributed completely to the difficulty of keeping the load around 120 A. The cell wasn't quite fully charged this setup, so really the gold graph should be moved a minute or two to the right, making it line up rather well until the load is removed.

At that point, the curves diverge markedly, and the battery cools. So it looks as though when the load is on, the fan can't cope with cooling the battery down, but when the load is off, it is able to cool the battery.

I've forgotten what we were trying to prove; something about the terminals being the primary cooling for the battery. So this is a good double blind test: I double don't remember what the outcome is supposed to be, so I can't have influenced the results! Image

For comparison, here is the earlier data on its own:
Image

It's a pity that we didn't keep the temperature data going a bit longer last time.

Edit 1: Weber had the bench setup picture in his camera.
Last edited by coulomb on Sun, 21 Jun 2009, 18:32, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

current limiting on Curtis and TS cells

Post by Johny » Fri, 19 Jun 2009, 03:00

It DOES prove that air flow helps markedly in removing heat once that load on the batteries drop. A concern earlier is that once you fang it a few times you were risking the pack if you didn't stop somewhere and have a cup of coffee. It now looks like you could cool it down ready for the next intersection...
Did the BMS board make any difference - I couldn't see it?
Did the homework excuse ever work for you? I didn't sense any commitment to the truth about the dog - do you even have a dog?

User avatar
acmotor
Senior Member
Posts: 3603
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

current limiting on Curtis and TS cells

Post by acmotor » Fri, 19 Jun 2009, 03:54

Interesting data coulomb.
So in my case where I plan average 1C, max 3C discharge, then I am unlikely to have battery temperature issues. However some forced airflow around terminals/BMS board (once cells are warmer than say 25°C ?) would be quite suitable for pack temperature control.i.e. no side or base cooling required. Yes ?

Echo of Johny's question. Did the BMS board make any difference ?
iMiEV MY12     110,230km in pure Electric and loving it !

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by coulomb » Fri, 19 Jun 2009, 04:29

Edit: I've corrected a small glitch in the data; all that happened is that the moderate kink just after load removal is now more subtle.

Edit 2: The data was shifted, and I included some interpolated data points from Weber.

Was:
Stop press! Weber has pointed out that I screwed up the data a little; the wobble just after the load comes off is because the X values of the plots are different. I'll see if I can do better. But it just distorts the X positions; the eventual temperature (and hence internal termerature some time back?) is lower with the fan, I'd say.
Last edited by coulomb on Sun, 21 Jun 2009, 18:31, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by coulomb » Fri, 19 Jun 2009, 04:56

Johny wrote: Did the BMS board make any difference - I couldn't see it?
Err, we didn't do a run with and without the BMS, if that's what you mean. I guess we can do another one without the board.
Did the homework excuse ever work for you? I didn't sense any commitment to the truth about the dog - do you even have a dog?

I do have a dog, and he's always chewing things. Even after he tripped the RCD one time chewing a power cord. I thought that the shock would be enough to stop him chewing anything, but it only seems to be power cords that he doesn't chew now Image

As for the excuse: no, it never works, but I think it's a great line.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

antiscab
Senior Member
Posts: 2490
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

current limiting on Curtis and TS cells

Post by antiscab » Fri, 19 Jun 2009, 08:39

Johny wrote: A concern earlier is that once you fang it a few times you were risking the pack if you didn't stop somewhere and have a cup of coffee. It now looks like you could cool it down ready for the next intersection...


I do note the test was for minutes, and most of the charge had been depleted before the cell rose 20 deg C.
when accelerating hard, a minute is an eternity.....it might be an issue if we are making burn out machines, but how many of us are seriously planning on running at maximum power for several minutes?

it is interesting seeing the results of the testing.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

current limiting on Curtis and TS cells

Post by Johny » Fri, 19 Jun 2009, 14:03

Yes Matt, I agree - I was being facetious but it didn't come across the right way. It's good that cooling makes a difference though.
coulomb, I must have been hyper yesterday - didn't mean to grill you about the dog. I should have put a Image in the post.
I think I'll just read them today...

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by coulomb » Fri, 19 Jun 2009, 14:09

Johny wrote: didn't mean to grill you about the dog.

Oh, no taken that way. All good fun.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Gow864
Groupie
Posts: 202
Joined: Sun, 27 Jul 2008, 04:37
Real Name: (John) Gary
Location: Bellingen NSW

current limiting on Curtis and TS cells

Post by Gow864 » Fri, 19 Jun 2009, 17:17

coulomb I'd be interested to see what happens to the voltage if you were to chill the cell down to something like 16 degrees before you run the test. it would be nice to have a picture of how much temp affects the cells output capabilities.

Gow.
If you are not part of the solution, you are part of the problem.

User avatar
weber
Site Admin
Posts: 2626
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by weber » Fri, 19 Jun 2009, 18:02

Gow864 wrote: coulomb I'd be interested to see what happens to the voltage if you were to chill the cell down to something like 16 degrees before you run the test. it would be nice to have a picture of how much temp affects the cells output capabilities.

We could do a test where we start with the cell about 80% charged and pull 3C for 10 seconds and see how low the voltage goes, and we repeat this at maybe 3 different temperatures and plot low voltage against temperature.

From that you could calculate how many "C" of current you could draw without pulling it below 2.5 V at a given temperature.

Do you want to suggest any changes to that? It can take up to an hour to stabilise a cell at a new temperature, so we'd prefer to do few temperatures and use a test we've already done at 20 to 25°C.

Might be easiest to do it at whatever ambient happens to be on the day, and then after a few hours in the fridge.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

Peter C in Canberra
Senior Member
Posts: 494
Joined: Sun, 27 Jul 2008, 04:05
Real Name: Peter Campbell
Location: Canberra

current limiting on Curtis and TS cells

Post by Peter C in Canberra » Fri, 19 Jun 2009, 19:25

I also would be interested in a plot of max current at 2.5V for various temperatures down to barely above zero degrees. In the last week or two I have been driving my car with cells at temperatures between 5 and 15 degrees. I now have a little max/min thermometer in there to keep track. I would suggest that there would be sufficient info if brief current measurements were done with a cell equilibrated to (say) ~4 degrees (domestic fridge), the ambient 20-25 you have, and two points between, say about 10 and 15 degrees. Keeping the tests brief will minimise self-heating.
From the last few weeks of driving experience I would suggest that I hit 2.5V at 2.2C (BMS alarm goes off, 200Amps on TS90s)for at least one of the 45 cells if the cells are at single digit temperatures.
Peter.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

Gow864
Groupie
Posts: 202
Joined: Sun, 27 Jul 2008, 04:37
Real Name: (John) Gary
Location: Bellingen NSW

current limiting on Curtis and TS cells

Post by Gow864 » Fri, 19 Jun 2009, 19:27

Coulomb/PeterThat all sounds great.

Gow.
If you are not part of the solution, you are part of the problem.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by coulomb » Mon, 22 Jun 2009, 04:38

For the purists, the Thunder Sky 40 Ah 3C discharge-with-fan graph has had the older (temperature with no fan) data corrected a second time. The data was shifted, and I incorporated some interpolated data from Weber.

That horrible deformity near the end of the discharge is now gone. The two graphs start diverging about 5 minutes after the load is removed, not immediately after the load was removed as it appeared before.

Link to the data (updated graph is the gold line about 3/4 down this long post):
viewtopic.php?p=14135&t=1178#p14135
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by coulomb » Thu, 25 Jun 2009, 17:47

Peter C in Canberra wrote: I also would be interested in a plot of max current at 2.5V for various temperatures down to barely above zero degrees.

Well, we have close, but for 40 Ah. After being in the freezer overnight, the thermometer reading -4°C, we got these figures for our TS-LFP40AHA:

3.26 V dropping to 2.11 V with 98 A load, for 12 mR internal resistance. That's about 3-4 times the internal resistance when warm (30°C say).
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Peter C in Canberra
Senior Member
Posts: 494
Joined: Sun, 27 Jul 2008, 04:05
Real Name: Peter Campbell
Location: Canberra

current limiting on Curtis and TS cells

Post by Peter C in Canberra » Thu, 25 Jun 2009, 18:07

thanks for that. I would expect a domestic freezer to be -20oC though. A domestic fridge should be +4oC. Anyway, your finding that they barely manage 2C for an acceptable voltage drop when close to zero degrees is consistent with my experience in the car in cold Canberra weather.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

User avatar
weber
Site Admin
Posts: 2626
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

current limiting on Curtis and TS cells

Post by weber » Fri, 26 Jun 2009, 01:21

Peter C in Canberra wrote: thanks for that. I would expect a domestic freezer to be -20oC though. A domestic fridge should be +4oC.

Yes. It should be at least -15°C in a freezer. But it took some time for us to get it insulated and bolted into the test rig. And once it was bolted in, it lost coolth rapidly through the cables. So all you can say for sure is that it was below -4°C internally.

Some graphs here that may or may not be indicative.
http://data.energizer.com/PDFs/BatteryIR.pdf
http://www.mpoweruk.com/performance.htm
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

Peter C in Canberra
Senior Member
Posts: 494
Joined: Sun, 27 Jul 2008, 04:05
Real Name: Peter Campbell
Location: Canberra

current limiting on Curtis and TS cells

Post by Peter C in Canberra » Tue, 21 Jul 2009, 05:11

I went driving up various local hills while my daughter hung her head over the back seat to view the BMS LEDs in the hatch area (safely through a perspex cover!). She could see most of the green LEDs go out together as I floored it. There were a few she could not see. As I persisted I got more and more current out till I was getting over 3C again. I guess this suggests that I don't have one dodgy cell, rather, lots, most or all are hitting 2.5V at about the same time. Perhaps it is the TBS guage reading a little high or the BMS tripping/LEDs going out at slightly above 2.5V on each cell. I had assumed I had one cell at 2.5V when the gauge said I had an average of about 2.8V. In any case, this result is more consistent with chilly cells being uniformly a bit sluggish rather than one dodgy cell or connection.
Thanks for you helpful comments.
Peter.
Last edited by Peter C in Canberra on Mon, 20 Jul 2009, 19:23, edited 1 time in total.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

Post Reply