[BatMan]

I've been warned from colleagues that I'd be lucky to get 200 cycles, and that was at 0.1-0.2C.

They did find a vendor that guaranteed 1000 cycles with fast charge, but can't remember the name off the top of my head.

Mike

 

[EVfun]

So what brand of Lithium batteries do you sell BatMan?

 

[nimblemotors]

How can any battery company guarantee cycle life??
There is no possible way to determine the number of cycles at the cell level. You would have to sell a fully engineered pack to offer a warranty that isn't just hype and marketing. Otherwise, a battery company would go broke in a hurray, but maybe they don't plan to be around after the sale anyway.

So what brand of Lithium batteries do you sell BatMan?

 

[nimblemotors]

So it appears nobody has done any cycle life testing on Thundersky cells.
I find that quite amazing, given the cost of these cells, the cycle life actually determines how much the cells are worth. At $10k-$20k a pack, that is a lot of cash based on faith and battery salesman claims.

So I'm going to be doing cycle tests, I have to believe you will want to see the results, would you pay $5 to see them? I'd like to propose that I raise a collection for the tests, let's say $500, so 100 people at $5 would cover it, any less I don't publish, you get the $5 back or whatever donation has been given.

The plan is to charge them at 1c, discharge at 3c to empty, and just keep doing it is until they are dead. This takes a long time to run and destroys the cells. At 1c charge, 1 hour to charge, 20 minutes to discharge, time to rest say 10 minutes, so a cycle takes 1.5 hours. That is 16 cycles a day, 480 cycles a month. So to test the claimed 3000 cycles will take almost over 6 months of 24/7 testing.

Another set of parameters will take longer, if discharge is only .5c, it will take 3 hours to do one cycle, so 12 months of 24/7 testing.
And if one tests only discharge to 80% or 70%, another set of cells to destroy and test hardware to build and keep running.

You see this is a significant investment in time and energy to run these tests, and make sure they work property over such a long time frame.
I don't think it is unreasonable to get some financial support to do the tests.

 

[T1 Terry]

I'm interested in the 3C claims, in each direction. A suggestion, the cell discharge is used to recharge a large percentage of the other cell on test. 3 cells will need to be tested at 70% discharge and 3 cells at 80% discharge. The charging and discharging will need to be done via a controlled method with digital recording equipment so charts can be seen as far as voltage sag, and recharging trends indicating changes to internal resistance. The question is, do you have the facilities to carry out this sort of testing?

T1 Terry

 

[nimblemotors]

Certainly the charge/discharge will be controlled and recorded and equipment to do it properly will be built. I have some ultracaps I planned to use to store the discharge and then put it back in, but I could use a second battery as well to toggle the flows and test two at once, will probably complicate the setup, but maybe not too much.

I finally got my cells today. I tore apart one of them to see what's inside, and was thinking I could take some sub-cells out to test smaller Ah, but while the insides are grouped into 20Ah assemblies with 40 .5ah cells,
they are not individually sealed, so its really just one battery, can't take them apart with integrity. I did construct a single .5ah cell, it discharged nicely to power a flashlight bulb.

I'm interested in the 3C claims, in each direction. A suggestion, the cell discharge is used to recharge a large percentage of the other cell on test. 3 cells will need to be tested at 70% discharge and 3 cells at 80% discharge. The charging and discharging will need to be done via a controlled method with digital recording equipment so charts can be seen as far as voltage sag, and recharging trends indicating changes to internal resistance. The question is, do you have the facilities to carry out this sort of testing?

T1 Terry

 

[MN Driver]

nimblemotors

Very interesting, it makes me want to buy a 40Ah battery to pull a sheet and do a capacity test and then if I could find a thermal imaging camera to test it at 10C and see how warm it got and where it gets hot. It seems that the high discharge A123 pouches get hot towards the terminal while the rest of the battery seems to stay cold. It would be interesting to see if we find any hot spots in a single sheet pair or whatever the capacity a single set tests to.

 

[DIYguy]

So it appears nobody has done any cycle life testing on Thundersky cells.
I find that quite amazing, given the cost of these cells, the cycle life actually determines how much the cells are worth. At $10k-$20k a pack, that is a lot of cash based on faith and battery salesman claims.

So I'm going to be doing cycle tests, I have to believe you will want to see the results, would you pay $5 to see them? I'd like to propose that I raise a collection for the tests, let's say $500, so 100 people at $5 would cover it, any less I don't publish, you get the $5 back or whatever donation has been given.

The plan is to charge them at 1c, discharge at 3c to empty, and just keep doing it is until they are dead. This takes a long time to run and destroys the cells. At 1c charge, 1 hour to charge, 20 minutes to discharge, time to rest say 10 minutes, so a cycle takes 1.5 hours. That is 16 cycles a day, 480 cycles a month. So to test the claimed 3000 cycles will take almost over 6 months of 24/7 testing.

Another set of parameters will take longer, if discharge is only .5c, it will take 3 hours to do one cycle, so 12 months of 24/7 testing.
And if one tests only discharge to 80% or 70%, another set of cells to destroy and test hardware to build and keep running.

You see this is a significant investment in time and energy to run these tests, and make sure they work property over such a long time frame.
I don't think it is unreasonable to get some financial support to do the tests.

Here's some advice... don't tell anyone if you do the testing.

 

[nimblemotors]

Here's some advice... don't tell anyone if you do the testing.

I don't get it, you being facetious?

I'm working on the test hardware, trying to figure the best way to do it.

I have a motor controller I built to run my electric outboard that could handle 48v and 200 amps, I sold my sailboat a long time ago, so I can repurpose it for this testing. 3C for a 40Ah battery is 120amps.

It looks like I will need about 70 of my 2600F caps to hold the discharge, but I'm not certain if that will work, because of the voltage mismatch between battery and caps

 

[DIYguy]

I don't get it, you being facetious?

I'm working on the test hardware, trying to figure the best way to do it.

I have a motor controller I built to run my electric outboard that could handle 48v and 200 amps, I sold my sailboat a long time ago, so I can repurpose it for this testing. 3C for a 40Ah battery is 120amps.

It looks like I will need about 70 of my 2600F caps to hold the discharge, but I'm not certain if that will work, because of the voltage mismatch between battery and caps

Actually, I wasn't. Lots of people have invested lots of $ and time to post information of value on this site. Comments like "so 100 people at $5 would cover it, any less I don't publish, you get the $5 back or whatever donation has been given" rub me the wrong way.
You don't publish? Look buddy, do it or don't do it. But if you do it and don't share it.... it may not go over so well. So, my advise is...if that's your game... don't tell anyone. Or, like the rest of the people on this site....share your information.

 

[nimblemotors]

I share plenty of information, I'm sharing how I'm going to run these tests.
You can then build and buy the parts and run them yourself.
Seeing as nobody has, what could be the reason?

Actually, I wasn't. Lots of people have invested lots of $ and time to post information of value on this site. Comments like "so 100 people at $5 would cover it, any less I don't publish, you get the $5 back or whatever donation has been given" rub me the wrong way.
You don't publish? Look buddy, do it or don't do it. But if you do it and don't share it.... it may not go over so well. So, my advise is...if that's your game... don't tell anyone. Or, like the rest of the people on this site....share your information.

 

[DIYguy]

I share plenty of information, I'm sharing how I'm going to run these tests.

oh,...well, that's rocket science.

Seeing as nobody has, what could be the reason?

It's a conspiracy. Everyone secretly knows that these cells only get 500 cycles. We all work for the Chinese on commission. When they sell to "the people who don't really know", we all get some good $$ . So ...shhhhhh.

 

[DavidDymaxion]

One thought is to get Headway or A123 or similar cells. You could then do much higher currents, and get ~4 times as many cycles in the same time. The cost would be much cheaper, for both the cells and the equipment.

 

[brainzel]

Jack Rickard did some testings but not over such a long period of time.
I have to say that I am skeptical that your collected data will fit the interest of all the 100 donors.

I would support the meaning of DIYguy, I blowed up some things, I got the wrong parts, replaced others and all of these experiences I would give to the community for free, because they helped me for free.

If anyone is so grateful and full of overwhelming gratitude, he could donor my project via PayPal ... if not, no problem.
I do it for hobby, not for dollars

 

[F16bmathis]

Its not scientific and half of it is for Lead acid, but my trucks been running over two years, 10400+ miles, mostly highway, which means high amps with my Zilla, but I track evey bit of juice pushed in, and so it gives cycles also. Just got the Thundersky's in Oct 10?

www.evalbum.com/1752 There's a picture of my excel chart.

I haven't bought gas since early Dec 2010!

 

[nimblemotors]

Rickard just published data obtained from Thundersky.
He did do 400amp tests that killed a cell.

No one needs to run these tests to get a EV working, which is why they are not done. It is usually a university or national lab that does these kinds of tests, funded by your tax dollars.
In my opinion, knowing how to treat these cells to make them last is very important information. If you and the useless DIYGUY don't think $5 is worth finding out, then so be it. I will know how to make my EV last a long time.

Jack Rickard did some testings but not over such a long period of time.
I have to say that I am skeptical that your collected data will fit the interest of all the 100 donors.

I would support the meaning of DIYguy, I blowed up some things, I got the wrong parts, replaced others and all of these experiences I would give to the community for free, because they helped me for free.

If anyone is so grateful and full of overwhelming gratitude, he could donor my project via PayPal ... if not, no problem.
I do it for hobby, not for dollars

 

[nimblemotors]

I am interested in the Thundersky cells specifically (Calb appear to be essentially the same) these are a bit different than the headway and certainly the A123. But really when testing the C rating, it takes just as long to do 2ah as 200ah, it is just that 2ah is a lot less current, 6amp vs 600amps, a lot easier to deal with. I've got 40Ah cells which is the smallest thundersky makes, so 3C is 120amps for 20 minutes.

I don't see much issue draining the cell into the ultracaps, but charging the cell back from them will be the harder part. I will need to have a DC-DC conversion to constainly raise the voltage level up to the charge voltage. Not so simple for just 2-4volts.

One thought is to get Headway or A123 or similar cells. You could then do much higher currents, and get ~4 times as many cycles in the same time. The cost would be much cheaper, for both the cells and the equipment.

 

[DIYguy]

Rickard just published data obtained from Thundersky.
He did do 400amp tests that killed a cell.

No one needs to run these tests to get a EV working, which is why they are not done. It is usually a university or national lab that does these kinds of tests, funded by your tax dollars.
In my opinion, knowing how to treat these cells to make them last is very important information. If you and the useless DIYGUY don't think $5 is worth finding out, then so be it. I will know how to make my EV last a long time.

Careful there sunshine. Personal attacks only demonstrates a weak argument. There is a vendor section if $ is your game..

 

[Jan]

Useless diyguy.