[sunworksco]

Originally Posted by winzeracer

Sun,

Hyperion would be nice but at over 3X cost I will play Roulette
http://www.allerc.com/hyperion-g3-vx...ck-p-5118.html

You get what you pay for.

[winzeracer]

Ya I hear ya just can't see spending over 5k on batts for a Kart.

Anyway... I have been cycling my 6s Turnigy bricks and have found that they are doing well. IR ( calculated by PL8) is always between 1.7mOhm 1.9mOhm.
I just discharged at 5+C and set to LVC to 3.4v, this let 4.7Ah out of the pack and after resting for 5 min the High Cell was at 3.602v and low cell was at 3.482v which I was happy with. I may raise LVC to 3.5v and retest to see how much capacity vs. voltage spread that yields. I also had some Batt boxes build but they were to heavy, I am now looking into building a Kevlar sidepod/battery box which would be very nice both form and function wise. In the way of function, if there was ever a crash no metal could penetrate cells and cause a fire, and it would not be that heavy. This would also give a nice professional finish look to the Kart as a whole.

[sunworksco]

Try to get your hands on some Alulight aluminum sandwich panel.

[winzeracer]

So I did another higher discharge test at 8C with LVC set to 3.5v, 4.5ah cap out so that went to 90% DOD and still had a 100mv spread in the cells. Cell number 2 had a lower IR of 1.4mOhm where the rest were between 1.6-1.8mOhm

More testing coming soon.

[winzeracer]

So after quite a bit of battery testing I have decided on a method that I am going to test all batteries with Charge to 4.190v at 15amps(3C) Discharge to 3.55v at 40amps( sometimes limited by supply voltage ) this generally discharges
4.5ah with about 50-70mv spead between cells. I will post all data when complete.

[DIYguy]

It seems that they guys who have had the most trouble with the RC cells are the ones that pushed them too close to their max Crate without some pack "overbuild". These ones tend to cause greater imbalances and can even cause thermal runaway. (a fire you can't put out).
Sorry if I didn't read all your specs. . . but if you test current level are anything close to your racing current levels, that seem like a very comfortable margin. Maybe even more than you need. I would ask Steve about this also. John Metric has had some good success with keeping the Crate lower. I know Olley just burned Black Current 111 to the ground with Flight power cells. This sounded like thermal runaway, not the balance wires issue he had last year.

[winzeracer]

Originally Posted by DIYguy

It seems that they guys who have had the most trouble with the RC cells are the ones that pushed them too close to their max Crate without some pack "overbuild". These ones tend to cause greater imbalances and can even cause thermal runaway. (a fire you can't put out).
Sorry if I didn't read all your specs. . . but if you test current level are anything close to your racing current levels, that seem like a very comfortable margin. Maybe even more than you need. I would ask Steve about this also. John Metric has had some good success with keeping the Crate lower. I know Olley just burned Black Current 111 to the ground with Flight power cells. This sounded like thermal runaway, not the balance wires issue he had last year.

My racing current levels will be a bit more extreme, but there is still quite a bit of head room. The current the motor will see is 400amps thus the batteries will see a bit less, lets say that they saw the full 400amps then they would be at 13.33C a level that I am quite comfortable with. I have emailed with Steve, and he was comfortable with these levels. The "bricks" are rated to 35C constant under RC conditions and I am well under half their rating at my max current.

As for BMS as you had previously brought up, I looked into different types and almost bought one but after talking with Steve he just runs Methods HVC/LVC on pretty much all his lipo, with the controller cutting voltage at 3.5v which is what I plan on doing. I will have plenty of hardware with me at the track for checking and balancing cells if it needed.

I appreciate you looking in on the build, and encouraging me to seek the expertise of others.

Thanks!

[DIYguy]

Originally Posted by winzeracer

My racing current levels will be a bit more extreme, but there is still quite a bit of head room. The current the motor will see is 400amps thus the batteries will see a bit less, lets say that they saw the full 400amps then they would be at 13.33C a level that I am quite comfortable with. I have emailed with Steve, and he was comfortable with these levels. The "bricks" are rated to 35C constant under RC conditions and I am well under half their rating at my max current.

As for BMS as you had previously brought up, I looked into different types and almost bought one but after talking with Steve he just runs Methods HVC/LVC on pretty much all his lipo, with the controller cutting voltage at 3.5v which is what I plan on doing. I will have plenty of hardware with me at the track for checking and balancing cells if it needed.

I appreciate you looking in on the build, and encouraging me to seek the expertise of others.

Thanks!

Oh. . my pleasure. Sounds like you are doing it right. For relative short durations, like racing, I think that is a good way to go for Poly. Im not the biggest fan of li-poly for a daily driver, but for racing it makes the most sense. Pretty much what all the RC guys do also (balance charging after a run). I think u r going to make out just fine

Lowell Simons just burn up his battery pack in Black Perl and sounds like BMS may have been part of it.. I think he was pushing it pretty hard also.