[Jan]

Originally Posted by Jordysport

I assume you have bottom balanced the 3 cells in parallel before assembling...

Won't that happen automaticaly? I asume they are somewhat balanced from the factory. And if they are stressed they will balance prety quickly due to the deeper voltage sag at lower SOC.

[kerrymann]

Originally Posted by danh818

Also, what is supporting the bottom of your module? I have seen the picture on you build thread of the module in the stock fuel tank position; it seems to be hanging. What is keeping the cells from slipping out the bottom other than the tension of the cables?

They are completely supported by the tension. With a couple hundred pounds of force on each rod it will take well above 10gs for these cells to slip. I might add a bottom plate for splash protection though.

Originally Posted by Jordysport

Thanks, looks a good setup, might consider it myself. just a few questions on it sorry to be a pain. I assume you have bottom balanced the 3 cells in parallel before assembling, then you can use the BMS to balance them in series? Do you have any more pics of the BMS system as this is one area i have no clue about atm (sorted controller, cells, motors, etc etc)

Thanks Again
Jordy

All the cells were drained down to the same level as part of the cell testing I did but it isn't necessary for cells in parallel anyway. They will find their own equilibrium. Originally I was going to skip BMS but I need cell monitoring to keep an eye on the gray market cells.

Originally Posted by danh818

Great job Kerry! I think if you posted the video we would all appreciate it.

Any worries about all that conductive metal surrounding the cells?

Thanks. I'll try to get around to it. I have zero video editing software and almost the same amount of time to do it.

The only place where it is physically possible for a short to occur due to movement, is at the last cells. And I am insulating.

[drgrieve]

This looks the easiest build I've seen around. I have a few questions if you don't mind:

1. I'm looking at 5p. Do you think that will still be doable with this design?
2. What is the weight of one of your modules (so I can see how much weight to plan for).
3. From others testing it seems that most of the heat manifests at the tabs. Perhaps allow room for a fan to be added later if needed.
4. Are the cooling fins structural or can they be replace by insulators

Cheers,

David.

PS Another vote for video. You might ask Jack Rickard if he is interested in the videos - not sure how turned off them he is after his mishaps.

[kerrymann]

Originally Posted by drgrieve

This looks the easiest build I've seen around. I have a few questions if you don't mind:

1. I'm looking at 5p. Do you think that will still be doable with this design?
2. What is the weight of one of your modules (so I can see how much weight to plan for).
3. From others testing it seems that most of the heat manifests at the tabs. Perhaps allow room for a fan to be added later if needed.
4. Are the cooling fins structural or can they be replace by insulators

Cheers,

David.

PS Another vote for video. You might ask Jack Rickard if he is interested in the videos - not sure how turned off them he is after his mishaps.

No worries on the questions, by all means.

1) 4p would work but I am unsure about 5p as you would be distorting the top of the cells a lot. I would ask why do you need 5p? That is a lot of capacity. are you running max voltage of your controller? Even with my soliton1 and a ~250VDC pack I will only be pulling 680amps peak for my motor (170v max). I would try to maximize the voltage limit of your controller with cells in series and then add cells in parallel for capacity and current from there.

2) For 72cells it's about 34kg. The parts only weight ~2kg total so just add that to the weight of your cells. The pack system is insignificant to the weight of the actual batteries.

3)I'd be curious to see that data. I have a design that integrates to PC fans into the top cover but I haven't seen anything so far that would convince me I need to do it. There will be plenty of free airflow on it's own.

4) If you don't think you need cooling (say max of 3-4C) then just eliminate the fins all together. But everything I have seen and read shows that you want some cooling to maximize cycle life.

PS. I actually offered to Jack a couple weeks ago as it was the easiest way to share with people. Most of the video I shot 2 months ago but have been too busy to do anything with it. But Jack wasn't interested in the video and suggested I sign up for EVCON (too far of a drive and I have to work anyway).

[MalcolmB]

Hi Kerrymann,

I really like the simplicity of your pack construction.

Originally Posted by kerrymann

3)I'd be curious to see that data. I have a design that integrates to PC fans into the top cover but I haven't seen anything so far that would convince me I need to do it. There will be plenty of free airflow on it's own.

There are a few thermal images of these cells under load here: http://endless-sphere.com/forums/vie...ared&start=105

[drgrieve]

Originally Posted by kerrymann

1) 4p would work but I am unsure about 5p as you would be distorting the top of the cells a lot. I would ask why do you need 5p? That is a lot of capacity. are you running max voltage of your controller?

2) For 72cells it's about 34kg. The parts only weight ~2kg total so just add that to the weight of your cells. The pack system is insignificant to the weight of the actual batteries.

3)I'd be curious to see that data. I have a design that integrates to PC fans into the top cover but I haven't seen anything so far that would convince me I need to do it. There will be plenty of free airflow on it's own.

4) If you don't think you need cooling (say max of 3-4C) then just eliminate the fins all together. But everything I have seen and read shows that you want some cooling to maximize cycle life.

PS. I actually offered to Jack a couple weeks ago as it was the easiest way to share with people. Most of the video I shot 2 months ago but have been too busy to do anything with it. But Jack wasn't interested in the video and suggested I sign up for EVCON (too far of a drive and I have to work anyway).

1. Ah well I'm trying to save up for an completely over the top build but an unplanned addition to the family and finishing an unnecessary expensive house build is getting in the way.
Anyway the drive train I'm considering is dual Kostov 250v mated to a gear vendors overdrive connected to diff. 5P100S A123 (32 KWh) pack. Dual Soliton 1 controllers. Plan to run at 1800 amps (900 per motor) and over volt motors to 280v (RPM limited). Will charge pack to ~3.45v so under limit 350V Soliton limit. Aiming for peak battery output of 500KW.
If I was to go to 4P then I'd need to up the voltage but the only other option currently would be a Shiva. Which is even more over the top than I need.

2. Awesome!

3. This is from evtv I think - I read a lot so forget the sources. No actual data that I recall, just from the commentary. My boxes will be enclosed so I'll probably need fans.

5. Thought as much. He's gone off A123. But nevertheless he has generated much interest even if he doesn't finished those side projects.

Be sure to send him a spreadsheet of a power run when you get going. He should be jealous of your low voltage sag.

Cheers!

[kerrymann]

Originally Posted by drgrieve

1. Ah well I'm trying to save up for an completely over the top build but an unplanned addition to the family and finishing an unnecessary expensive house build is getting in the way.
Anyway the drive train I'm considering is dual Kostov 250v mated to a gear vendors overdrive connected to diff. 5P100S A123 (32 KWh) pack. Dual Soliton 1 controllers. Plan to run at 1800 amps (900 per motor) and over volt motors to 280v (RPM limited). Will charge pack to ~3.45v so under limit 350V Soliton limit. Aiming for peak battery output of 500KW.
If I was to go to 4P then I'd need to up the voltage but the only other option currently would be a Shiva. Which is even more over the top than I need.

2. Awesome!

3. This is from evtv I think - I read a lot so forget the sources. No actual data that I recall, just from the commentary. My boxes will be enclosed so I'll probably need fans.

5. Thought as much. He's gone off A123. But nevertheless he has generated much interest even if he doesn't finished those side projects.

Be sure to send him a spreadsheet of a power run when you get going. He should be jealous of your low voltage sag.

Cheers!

That is ambitious build! In that case just build 3p packs and connect half of the packs in parallel to get the equivalent of 6p. Or with 2 controllers you could even just run two separate packs so you would even get some redundantancy.

[kerrymann]

Originally Posted by MalcolmB

Hi Kerrymann,

I really like the simplicity of your pack construction.

There are a few thermal images of these cells under load here: http://endless-sphere.com/forums/vie...ared&start=105

Thanks and thanks!

[kerrymann]

Mark II module



The original module design has undergone another change to improve the end plates. I went back to a previous design that uses nice thick 3/8" aluminium plates. I had originally try to keep things as DIY friendly as possible so I used .120" sheet and the L angles. The problems is the sheet is not stiff enough and doesn't do a very good job of distributing the force over the whole face of the cell and I worry if could lead to premature cell failure. Going to 3 channels makes it better but still not as good as I would like. So I am getting quotes on having the plates CNC'd.





I hope to have the parts in a week or two and will update from there. If anyone else is interested in getting in on my CNC order let me know.



In the mean time I am installing my BMS and should have pics of that tomorrow.

[onegreenev]

Just remember that keeping pressure on the plates does not keep them healthy. I had a set of cells that was happy and content visually in the case for the last 3 years and yesterday I decided to pull them out for charging. These had been drained slowly because of a failed BMS system. I am now thinking that the pack had been drained some initially and then driven not knowing that any cells were drained low. The balance was way off and the BMS failure failed to report low voltage cells. The vehicle was driven and then put up because of crappy performance and distance. Still not knowing what actually happened. Just before I pulled the cells they all looked perfect. All snug in a nice tight case. As soon as I pulled them they popped out like fat little pigs. So even after 3 years of being held tight the damage was done and the pressure remained. Pressure won't fix or prevent any thing from happening and only covers a problem.

Don't put too much on clamping the cells. If I could have seen the cells puff from the damage from over discharging them while driving it would have been easy to diagnose a problem.

Don't rely too much on the BMS system either. If you over discharge your cell while driving you WiLL kill the cell, clamped or not.

Just thick flat aluminum ends would work. My idea will only be thick fiberglass reenforced with aluminum. No need for elaborate clamping except to hold them together lightly. I am including a bottom to hold them.


Nice work but where is enough, enough?