Ultra-Power Lipo Cells Now in Stock USA!

[EVDragRacer]

Allright guys, sorry for jumping in this thread and being behind and missing info , just saw this:

Derek, says I can run the cells for 10 seconds at 250amps (2500amp 10P) with a sag of 3.3volts per cell

250 / 6AH = ~41.66C.

Why are these being advertised as having a 65C burst rate if they can only handle ~41.66C for 10 seconds? Burst rate is defined as what, 2-5 seconds then?

The continuous would be lower then, like 30C..
Or maybe 20C..

Uh yeah, hope you didn't buy too many of these & plan on selling too many.

The Haiyin cells can give you a burst rate of 65C, but the sag is the problem. I would like to keep my sag no lower than 3.3V per cell, so at 250amps per cell I get 3.3volts.

 

[EVDragRacer]

Let's keep in mind that these are similar to what we see in middle-upper RC Lipo cells.

So if you take a 60C continuous cell, you'd not want to run it at more than 30C continuously.
If you take a 20C cell, you don't want to run it at more than 10C continuously.

.... so its disappointing to see the real data from independent tests show they sag below 3V when discharging at their 50C (300A) continuous rating .

Show me another 6AH cell sold in single cells with large tabs that can produce 300amps and not drop below 3volts per cell?

 

[neptronix]

You asked for it..
What competes with your product? buy one of these $23 2S 40C packs and wire the cells up in paralle rather than series ( just flip one cell and solder it in, to get a 10AH "cell" that has better capacity and power output per $ than your cell.

https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16194

If we think of the specs as being what the company advertises ( as you have with your cells ), then this 10AH cell would be capable of 400A and capable of 500A bursts.

You might say that the tabs couldn't handle that power draw, but in this parallel configuration, the power is split 50-50 between the tabs of both cells.

I bet it would perform better. It would be a little heavier and bigger, but you can deal with some extra weight in a car. The extra voltage would make up for it.

 

[Hillhater]

Ron,
Can you show me an example of a nanotech tab that has failed when operating within its specefied range ?
Why do you think it is important to only consider single cells when constructing large packs ??
Why dont you send off some of your old nanotech packs for testing to see how they compare to your Haiyin cells ?

The Haiyin cells can give you a burst rate of 65C, but the sag is the problem....

That is simply not true. At 65C those cells suffer near instant voltage collapse (< 2.5v) and even at their 50C constant rating, will only sustain that for a few seconds with 25% voltage sag. They couldnt really be considered to have even a 50C "burst" rate !

 

[Jozzer]

Hmmm.. http://www.diyelectriccar.com/forums/showthread.php/deal-lifetime-81121.html
There must be a new "best cell in the world" :lol:

 

[Jeremy Harris]

At 65C those cells suffer near instant voltage collapse (< 2.5v) and even at their 50C constant rating, will only sustain that for a few seconds with 25% voltage sag. They couldnt really be considered to have even a 50C "burst" rate !

Simple physics tells you that the heat generated in the cell when it sags to that degree is going to cause a problem, too. That voltage drop is caused by the cell total resistance, so if you're pulling 65C (i.e. 390 A) from the cell, and losing about 1.2V in sag, then the cell is generating around 468 W of heat. Personally the idea of a small cell like this generating that much heat doesn't fill me with joy, especially if you have dozens of them all generating this much heat each in a big pack.

 

[neptronix]

I would not consider a battery shedding more than 10% of it's power as waste heat as an acceptable use of the battery.

If a cell drops from 4.2 to 3.0v during discharge, that's 30% of it's power going to waste heat, and 70% going to whatever it's trying to power. That's not acceptable at all. I've never seen a battery manufacturer rate the 'burst' capability of a cell that high. A cell like this would last under a hundred cycles under this condition.

But hey, overpromising and underdelivering is what wins minds over to the electric side.. right... right?

 

[Hillhater]

.... Personally the idea of a small cell like this generating that much heat doesn't fill me with joy, especially if you have dozens of them all generating this much heat each in a big pack.

Rons own data from his last run recorded a volt drop of over 100v at a pack output of 4000A.
that would suggest heat being generated at the rate of 400 kW !
..It may only be for a few seconds ( 8-10) but that is still a LOT of heat to deal with, and must represent a real risk.
( anyone care to calculate the pack temp rise in 10 sec's ?)
It is ironic that the reason ron ditched his proven successful Turnigy pack was because he felt the Tabs may melt under load,.. but this pack seems to present much greater problems and risks.
However, it seems that (as Jozzer pointed out) .. Ron says he has a different cell supplier for his next attempt.
Lets hope they are better for the application than the Haiyin proved to be.

 

[Hillhater]

.. Ron says he has a different cell supplier for his next attempt.
Lets hope they are better for the application than the Haiyin proved to be.

Oh dear !..Ron has destroyed my hopes !!
He is planning a switch to a LiFepo4 pack of K2 73Ah modules, ...all 1300lbs of it !
That is 800lbs heavier than last years Haiyin pack,
..and best part of 1000lbs heavier than the Turnigy pack he went fastest with.
http://www.diyelectriccar.com/forums/showthread.php/one-shiva-twoi-81941.html