Anyone have dealings with VoltPhreaks -- impressive 15C LiFePO4 claims?

[txhokie4life]

VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????

Probably bunk -- but impressive looking cell on "paper".

M

[Ian Hooper-3]

It's not really that unbelievable - the specs are more modest than  
many 18650s I've tested. Pretty good price though, significantly  
cheaper than K2 or PHET. The closeup shows the text on the cell starts  
with abbreviation "HW" - manufactured by Headway perhaps?

On a side note, I imagine it'd be pretty tedious building an EV-sized  
pack from 1100mAh cells!

Ian Hooper
--
"Never doubt that the work of a small group of thoughtful, committed  
citizens can change the world." - Margaret Mead
http://www.zeva.com.au

On 20/07/2008, at 11:11 PM, txhokie4life wrote:

>
>
>
> https://s.p10.hostingprod.com/@.../ssl/catalog/product_info.php?cPath=1_23&products_id=31
> VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????
>
> Probably bunk -- but impressive looking cell on "paper".
>
> M
> --
> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18555346.html
> Sent from the Electric Vehicle Discussion List mailing list archive  
> at Nabble.com.
>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev
>
>

_______________________________________________
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[Roger Heuckeroth]

Interesting that these cells fall short of the manufacturer's own  
ratings according to the curves.  They start to fall off at about 900  
mAh.

On Jul 20, 2008, at 11:11 AM, txhokie4life wrote:

>
>
>
> https://s.p10.hostingprod.com/@.../ssl/catalog/product_info.php?cPath=1_23&products_id=31
> VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????
>
> Probably bunk -- but impressive looking cell on "paper".
>
> M
> --
> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18555346.html
> Sent from the Electric Vehicle Discussion List mailing list archive  
> at Nabble.com.
>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev

_______________________________________________
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[Roger Heuckeroth]

Zeva did a review on some larger Headway cells.  See http://zeva.com.au/tech/headway/ 
   They were not to impressed.

On Jul 20, 2008, at 11:33 AM, Ian Hooper wrote:

> It's not really that unbelievable - the specs are more modest than
> many 18650s I've tested. Pretty good price though, significantly
> cheaper than K2 or PHET. The closeup shows the text on the cell starts
> with abbreviation "HW" - manufactured by Headway perhaps?
>
> On a side note, I imagine it'd be pretty tedious building an EV-sized
> pack from 1100mAh cells!
>
> Ian Hooper
> --
> "Never doubt that the work of a small group of thoughtful, committed
> citizens can change the world." - Margaret Mead
> http://www.zeva.com.au
>
> On 20/07/2008, at 11:11 PM, txhokie4life wrote:
>
>>
>>
>>
>> https://s.p10.hostingprod.com/@.../ssl/catalog/product_info.php?cPath=1_23&products_id=31
>> VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????
>>
>> Probably bunk -- but impressive looking cell on "paper".
>>
>> M
>> --
>> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18555346.html
>> Sent from the Electric Vehicle Discussion List mailing list archive
>> at Nabble.com.
>>
>>
>> _______________________________________________
>> For general EVDL support, see http://evdl.org/help/
>> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/
>> ev
>>
>>
>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev

_______________________________________________
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[Ian Hooper-3]

Yeah.. that was me doing the tests :)

Oh I thought the 38120 Headways were alright.. definitely more  
powerful than ThunderSky LFPs, and significantly cheaper/easier than  
using 26650s, so they have their niche. Rated cycle life of 1000 seems  
a bit low for LiFePO4 (and I didn't do cycle testing), I wonder if  
they're just being conservative or if they do actually cut corners in  
manufacturing which results in a lower cycle life? 1000 is still  
better than most chemistries, of course..

While we're on the subject, is anyone actually running Headways in an  
EV yet? We're currently gearing up for the next conversion project at  
this end and definitely want something more powerful than ThunderSkys..

Ian Hooper
--
"Never doubt that the work of a small group of thoughtful, committed  
citizens can change the world." - Margaret Mead
http://www.zeva.com.au

On 21/07/2008, at 8:33 AM, Roger Heuckeroth wrote:

> Zeva did a review on some larger Headway cells.  See http://zeva.com.au/tech/headway/
>   They were not to impressed.
>
> On Jul 20, 2008, at 11:33 AM, Ian Hooper wrote:
>
>> It's not really that unbelievable - the specs are more modest than
>> many 18650s I've tested. Pretty good price though, significantly
>> cheaper than K2 or PHET. The closeup shows the text on the cell  
>> starts
>> with abbreviation "HW" - manufactured by Headway perhaps?
>>
>> On a side note, I imagine it'd be pretty tedious building an EV-sized
>> pack from 1100mAh cells!
>>
>> Ian Hooper
>> --
>> "Never doubt that the work of a small group of thoughtful, committed
>> citizens can change the world." - Margaret Mead
>> http://www.zeva.com.au
>>
>> On 20/07/2008, at 11:11 PM, txhokie4life wrote:
>>
>>>
>>>
>>>
>>> https://s.p10.hostingprod.com/@.../ssl/catalog/product_info.php?cPath=1_23&products_id=31
>>> VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????
>>>
>>> Probably bunk -- but impressive looking cell on "paper".
>>>
>>> M
>>> --
>>> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18555346.html
>>> Sent from the Electric Vehicle Discussion List mailing list archive
>>> at Nabble.com.
>>>
>>>
>>> _______________________________________________
>>> For general EVDL support, see http://evdl.org/help/
>>> For subscription options, see http://lists.sjsu.edu/mailman/ 
>>> listinfo/
>>> ev
>>>
>>>
>>
>>
>> _______________________________________________
>> For general EVDL support, see http://evdl.org/help/
>> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/
>> ev
>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev
>
>

_______________________________________________
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[Roger Heuckeroth]

Ian,

How much more powerful than ThunderSky do you think the Headways are?  
I know your testing was limited to 3C because your test apparatus was  
designed to test smaller cells.  Just by comparison, It looks like the  
HW 38120 cell sagged to about 2.9-3.0V (its hard to read the scale) at  
3C discharge rate.  What voltage do you think the TS cells would do at  
3C?

BTW.  I want to thank and compliment you on your efforts.  Thank you  
for sharing all this great info with us.

Roger

On Jul 20, 2008, at 10:19 PM, Ian Hooper wrote:

> Yeah.. that was me doing the tests :)
>
> Oh I thought the 38120 Headways were alright.. definitely more
> powerful than ThunderSky LFPs, and significantly cheaper/easier than
> using 26650s, so they have their niche. Rated cycle life of 1000 seems
> a bit low for LiFePO4 (and I didn't do cycle testing), I wonder if
> they're just being conservative or if they do actually cut corners in
> manufacturing which results in a lower cycle life? 1000 is still
> better than most chemistries, of course..
>
> While we're on the subject, is anyone actually running Headways in an
> EV yet? We're currently gearing up for the next conversion project at
> this end and definitely want something more powerful than  
> ThunderSkys..
>
> Ian Hooper
> --
> "Never doubt that the work of a small group of thoughtful, committed
> citizens can change the world." - Margaret Mead
> http://www.zeva.com.au
>
> On 21/07/2008, at 8:33 AM, Roger Heuckeroth wrote:
>
>> Zeva did a review on some larger Headway cells.  See http://zeva.com.au/tech/headway/
>>  They were not to impressed.
>>
>> On Jul 20, 2008, at 11:33 AM, Ian Hooper wrote:
>>
>>> It's not really that unbelievable - the specs are more modest than
>>> many 18650s I've tested. Pretty good price though, significantly
>>> cheaper than K2 or PHET. The closeup shows the text on the cell
>>> starts
>>> with abbreviation "HW" - manufactured by Headway perhaps?
>>>
>>> On a side note, I imagine it'd be pretty tedious building an EV-
>>> sized
>>> pack from 1100mAh cells!
>>>
>>> Ian Hooper
>>> --
>>> "Never doubt that the work of a small group of thoughtful, committed
>>> citizens can change the world." - Margaret Mead
>>> http://www.zeva.com.au
>>>
>>> On 20/07/2008, at 11:11 PM, txhokie4life wrote:
>>>
>>>>
>>>>
>>>>
>>>> https://s.p10.hostingprod.com/@.../ssl/catalog/product_info.php?cPath=1_23&products_id=31
>>>> VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????
>>>>
>>>> Probably bunk -- but impressive looking cell on "paper".
>>>>
>>>> M
>>>> --
>>>> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18555346.html
>>>> Sent from the Electric Vehicle Discussion List mailing list archive
>>>> at Nabble.com.
>>>>
>>>>
>>>> _______________________________________________
>>>> For general EVDL support, see http://evdl.org/help/
>>>> For subscription options, see http://lists.sjsu.edu/mailman/
>>>> listinfo/
>>>> ev
>>>>
>>>>
>>>
>>>
>>> _______________________________________________
>>> For general EVDL support, see http://evdl.org/help/
>>> For subscription options, see http://lists.sjsu.edu/mailman/ 
>>> listinfo/
>>> ev
>>
>>
>> _______________________________________________
>> For general EVDL support, see http://evdl.org/help/
>> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/
>> ev
>>
>>
>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev

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[Stephen West-2]

On 23/07/08 8:36 AM, "Roger Heuckeroth" <rheuckeroth@...> wrote:
> What voltage do you think the TS cells would do at 3C?

I've heard reports that 3C takes TS cells down to 2.6-2.7 Volts.

Steve West



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[txhokie4life]

When someone says it takes X cell down to Y volts -- at what point are you looking,

I have a spice simulation of an older LiFePO4 cell and the voltage looks like an S curve lying on its side.

I interpret the bottom of the S as the ESR effect, then a gradual slope, almost like a time-constant decay,
then a breakdown curve ~80 DOD.

I'm not a battery guy -- so my interpretations are purely mathematical......

Mike

Stephen West-2 wrote:

On 23/07/08 8:36 AM, "Roger Heuckeroth" <[e-mail]> wrote:
> What voltage do you think the TS cells would do at 3C?

I've heard reports that 3C takes TS cells down to 2.6-2.7 Volts.

Steve West



_______________________________________________
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[Stephen West-2]

> When someone says it takes X cell down to Y volts -- at what point are you
> looking,

If not specified I would assume the median, or failing that 50% SOC. At 3C
LiFePO4 seems to have a pretty flat discharge curve. eg
http://www.yesa.com.hk/uppic/200710/2007101113592887292.jpg

That could be due to rising internal temperature during the discharge
reducing the internal resistance just enough to balance the natural "gradual
slope". Notice at 5C the voltage actually increases some of the time.

Steve West

On 23/07/08 10:27 AM, "txhokie4life" <mseningen@...> wrote:

>
> When someone says it takes X cell down to Y volts -- at what point are you
> looking,
>
> I have a spice simulation of an older LiFePO4 cell and the voltage looks
> like an S curve lying on its side.
>
> I interpret the bottom of the S as the ESR effect, then a gradual slope,
> almost like a time-constant decay,
> then a breakdown curve ~80 DOD.
>
> I'm not a battery guy -- so my interpretations are purely mathematical......
>
> Mike

_______________________________________________
For general EVDL support, see http://evdl.org/help/
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[Ian Hooper-3]

Yep I agree with Steve West, in my experience the TS cells sag to  
about 2.6-2.7V at 3C. Varies with temperature and SOC of course, but  
that's a fair ballpark.

One of the important differences is that the low voltage cutoff for  
ThunderSkys is 2.5V, whereas the Headways are 2.0V. I hear ThunderSky  
do something a bit strange with their manufacturing process (can't  
remember the specifics) which results in higher max and minimum  
working voltages - though the same nominal voltage. So you get less  
leeway for voltage sag if you want to keep them above their minimum  
discharge voltage at all times; you won't be able to pull much more  
than 3C from them.

I only tested the HW 38120s to 3C due to limitations of the testbench,  
but at that rate they were significantly better than TS, and had  
similar performance to the K2 26650EV which I did test up to 10C  
continuous. So all other things being equal, the HWs would probably  
be ~2.4V at 10C. Heating would be an issue of course, you wouldn't  
want to maintain 10C in them for too long! But I do believe the power  
would be there if you needed it.

OTOH, the 1000 cycle rating of the Headways (vs ThunderSky's  
independently confirmed 2000-3000 cycles) does change the economics a  
bit, especially if you're a charge-every-day type person. But if you  
only need to charge twice a week, calendar life will the limiting  
factor with either cell.

Ian Hooper
--
"Never doubt that the work of a small group of thoughtful, committed  
citizens can change the world." - Margaret Mead
http://www.zeva.com.au

On 23/07/2008, at 4:36 AM, Roger Heuckeroth wrote:

> Ian,
>
> How much more powerful than ThunderSky do you think the Headways are?
> I know your testing was limited to 3C because your test apparatus was
> designed to test smaller cells.  Just by comparison, It looks like the
> HW 38120 cell sagged to about 2.9-3.0V (its hard to read the scale) at
> 3C discharge rate.  What voltage do you think the TS cells would do at
> 3C?
>
> BTW.  I want to thank and compliment you on your efforts.  Thank you
> for sharing all this great info with us.
>
> Roger
>
> On Jul 20, 2008, at 10:19 PM, Ian Hooper wrote:
>
>> Yeah.. that was me doing the tests :)
>>
>> Oh I thought the 38120 Headways were alright.. definitely more
>> powerful than ThunderSky LFPs, and significantly cheaper/easier than
>> using 26650s, so they have their niche. Rated cycle life of 1000  
>> seems
>> a bit low for LiFePO4 (and I didn't do cycle testing), I wonder if
>> they're just being conservative or if they do actually cut corners in
>> manufacturing which results in a lower cycle life? 1000 is still
>> better than most chemistries, of course..
>>
>> While we're on the subject, is anyone actually running Headways in an
>> EV yet? We're currently gearing up for the next conversion project at
>> this end and definitely want something more powerful than
>> ThunderSkys..
>>
>> Ian Hooper
>> --
>> "Never doubt that the work of a small group of thoughtful, committed
>> citizens can change the world." - Margaret Mead
>> http://www.zeva.com.au
>>
>> On 21/07/2008, at 8:33 AM, Roger Heuckeroth wrote:
>>
>>> Zeva did a review on some larger Headway cells.  See http://zeva.com.au/tech/headway/
>>> They were not to impressed.
>>>
>>> On Jul 20, 2008, at 11:33 AM, Ian Hooper wrote:
>>>
>>>> It's not really that unbelievable - the specs are more modest than
>>>> many 18650s I've tested. Pretty good price though, significantly
>>>> cheaper than K2 or PHET. The closeup shows the text on the cell
>>>> starts
>>>> with abbreviation "HW" - manufactured by Headway perhaps?
>>>>
>>>> On a side note, I imagine it'd be pretty tedious building an EV-
>>>> sized
>>>> pack from 1100mAh cells!
>>>>
>>>> Ian Hooper
>>>> --
>>>> "Never doubt that the work of a small group of thoughtful,  
>>>> committed
>>>> citizens can change the world." - Margaret Mead
>>>> http://www.zeva.com.au
>>>>
>>>> On 20/07/2008, at 11:11 PM, txhokie4life wrote:
>>>>
>>>>>
>>>>>
>>>>>
>>>>> https://s.p10.hostingprod.com/@.../ssl/catalog/product_info.php?cPath=1_23&products_id=31
>>>>> VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????
>>>>>
>>>>> Probably bunk -- but impressive looking cell on "paper".
>>>>>
>>>>> M
>>>>> --
>>>>> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18555346.html
>>>>> Sent from the Electric Vehicle Discussion List mailing list  
>>>>> archive
>>>>> at Nabble.com.
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> For general EVDL support, see http://evdl.org/help/
>>>>> For subscription options, see http://lists.sjsu.edu/mailman/
>>>>> listinfo/
>>>>> ev
>>>>>
>>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> For general EVDL support, see http://evdl.org/help/
>>>> For subscription options, see http://lists.sjsu.edu/mailman/
>>>> listinfo/
>>>> ev
>>>
>>>
>>> _______________________________________________
>>> For general EVDL support, see http://evdl.org/help/
>>> For subscription options, see http://lists.sjsu.edu/mailman/ 
>>> listinfo/
>>> ev
>>>
>>>
>>
>>
>> _______________________________________________
>> For general EVDL support, see http://evdl.org/help/
>> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/
>> ev
>
>
> _______________________________________________
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> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev
>
>

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[Roger Heuckeroth]

Just eyeballing at the middle of the S.  Sorry, not really precise.  
They all start at about 3.5ish and end about 2.1-2.5ish, but near the  
middle that is what I was referring to.


On Jul 22, 2008, at 6:27 PM, txhokie4life wrote:

>
>
> When someone says it takes X cell down to Y volts -- at what point  
> are you
> looking,
>
> I have a spice simulation of an older LiFePO4 cell and the voltage  
> looks
> like an S curve lying on its side.
>
> I interpret the bottom of the S as the ESR effect, then a gradual  
> slope,
> almost like a time-constant decay,
> then a breakdown curve ~80 DOD.
>
> I'm not a battery guy -- so my interpretations are purely  
> mathematical......
>
> Mike
>
>
>
> Stephen West-2 wrote:
>>
>> On 23/07/08 8:36 AM, "Roger Heuckeroth" <rheuckeroth@...>  
>> wrote:
>>> What voltage do you think the TS cells would do at 3C?
>>
>> I've heard reports that 3C takes TS cells down to 2.6-2.7 Volts.
>>
>> Steve West
>>
>>
>>
>> _______________________________________________
>> For general EVDL support, see http://evdl.org/help/
>> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev
>>
>>
>>
>
> --
> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18600123.html
> Sent from the Electric Vehicle Discussion List mailing list archive  
> at Nabble.com.
>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev

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[Roger Heuckeroth]

Ian,

I just finished reading a thread on the Headway Batteries.  It started  
with testing on the P model, and then progressed to testing on the L  
model.  Near the end of the thread someone got a batch of 100 L models  
and they all tested really badly.  They were all way underperforming  
both in Ah and in internal resistance.  The early cells had an  
internal resistance of around 6 mohm, and the batch of 100 were  
looking worse than TS at around 30+ mohm. They were barely able to do  
1C without sagging to 2.5V.  The thread if your interested is:

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=3374&st=0&sk=t&sd=a&sid=42a9e8c937df6dc7ad9b6dbce0ba76c5

BTW they refer to your testing quite a bit.

Roger

On Jul 22, 2008, at 9:32 PM, Ian Hooper wrote:

> Yep I agree with Steve West, in my experience the TS cells sag to
> about 2.6-2.7V at 3C. Varies with temperature and SOC of course, but
> that's a fair ballpark.
>
> One of the important differences is that the low voltage cutoff for
> ThunderSkys is 2.5V, whereas the Headways are 2.0V. I hear ThunderSky
> do something a bit strange with their manufacturing process (can't
> remember the specifics) which results in higher max and minimum
> working voltages - though the same nominal voltage. So you get less
> leeway for voltage sag if you want to keep them above their minimum
> discharge voltage at all times; you won't be able to pull much more
> than 3C from them.
>
> I only tested the HW 38120s to 3C due to limitations of the testbench,
> but at that rate they were significantly better than TS, and had
> similar performance to the K2 26650EV which I did test up to 10C
> continuous. So all other things being equal, the HWs would probably
> be ~2.4V at 10C. Heating would be an issue of course, you wouldn't
> want to maintain 10C in them for too long! But I do believe the power
> would be there if you needed it.
>
> OTOH, the 1000 cycle rating of the Headways (vs ThunderSky's
> independently confirmed 2000-3000 cycles) does change the economics a
> bit, especially if you're a charge-every-day type person. But if you
> only need to charge twice a week, calendar life will the limiting
> factor with either cell.
>
> Ian Hooper
> --
> "Never doubt that the work of a small group of thoughtful, committed
> citizens can change the world." - Margaret Mead
> http://www.zeva.com.au
>
> On 23/07/2008, at 4:36 AM, Roger Heuckeroth wrote:
>
>> Ian,
>>
>> How much more powerful than ThunderSky do you think the Headways are?
>> I know your testing was limited to 3C because your test apparatus was
>> designed to test smaller cells.  Just by comparison, It looks like  
>> the
>> HW 38120 cell sagged to about 2.9-3.0V (its hard to read the scale)  
>> at
>> 3C discharge rate.  What voltage do you think the TS cells would do  
>> at
>> 3C?
>>
>> BTW.  I want to thank and compliment you on your efforts.  Thank you
>> for sharing all this great info with us.
>>
>> Roger
>>
>> On Jul 20, 2008, at 10:19 PM, Ian Hooper wrote:
>>
>>> Yeah.. that was me doing the tests :)
>>>
>>> Oh I thought the 38120 Headways were alright.. definitely more
>>> powerful than ThunderSky LFPs, and significantly cheaper/easier than
>>> using 26650s, so they have their niche. Rated cycle life of 1000
>>> seems
>>> a bit low for LiFePO4 (and I didn't do cycle testing), I wonder if
>>> they're just being conservative or if they do actually cut corners  
>>> in
>>> manufacturing which results in a lower cycle life? 1000 is still
>>> better than most chemistries, of course..
>>>
>>> While we're on the subject, is anyone actually running Headways in  
>>> an
>>> EV yet? We're currently gearing up for the next conversion project  
>>> at
>>> this end and definitely want something more powerful than
>>> ThunderSkys..
>>>
>>> Ian Hooper
>>> --
>>> "Never doubt that the work of a small group of thoughtful, committed
>>> citizens can change the world." - Margaret Mead
>>> http://www.zeva.com.au
>>>
>>> On 21/07/2008, at 8:33 AM, Roger Heuckeroth wrote:
>>>
>>>> Zeva did a review on some larger Headway cells.  See http://zeva.com.au/tech/headway/
>>>> They were not to impressed.
>>>>
>>>> On Jul 20, 2008, at 11:33 AM, Ian Hooper wrote:
>>>>
>>>>> It's not really that unbelievable - the specs are more modest than
>>>>> many 18650s I've tested. Pretty good price though, significantly
>>>>> cheaper than K2 or PHET. The closeup shows the text on the cell
>>>>> starts
>>>>> with abbreviation "HW" - manufactured by Headway perhaps?
>>>>>
>>>>> On a side note, I imagine it'd be pretty tedious building an EV-
>>>>> sized
>>>>> pack from 1100mAh cells!
>>>>>
>>>>> Ian Hooper
>>>>> --
>>>>> "Never doubt that the work of a small group of thoughtful,
>>>>> committed
>>>>> citizens can change the world." - Margaret Mead
>>>>> http://www.zeva.com.au
>>>>>
>>>>> On 20/07/2008, at 11:11 PM, txhokie4life wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> https://s.p10.hostingprod.com/@.../ssl/catalog/product_info.php?cPath=1_23&products_id=31
>>>>>> VoltPhreaks 1.1Ah 10C continuous 15C max 18650 cell????
>>>>>>
>>>>>> Probably bunk -- but impressive looking cell on "paper".
>>>>>>
>>>>>> M
>>>>>> --
>>>>>> View this message in context: http://www.nabble.com/Anyone-have-dealings-with-VoltPhreaks----impressive-15C-LiFePO4-claims--tp18555346p18555346.html
>>>>>> Sent from the Electric Vehicle Discussion List mailing list
>>>>>> archive
>>>>>> at Nabble.com.
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> For general EVDL support, see http://evdl.org/help/
>>>>>> For subscription options, see http://lists.sjsu.edu/mailman/
>>>>>> listinfo/
>>>>>> ev
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> For general EVDL support, see http://evdl.org/help/
>>>>> For subscription options, see http://lists.sjsu.edu/mailman/
>>>>> listinfo/
>>>>> ev
>>>>
>>>>
>>>> _______________________________________________
>>>> For general EVDL support, see http://evdl.org/help/
>>>> For subscription options, see http://lists.sjsu.edu/mailman/
>>>> listinfo/
>>>> ev
>>>>
>>>>
>>>
>>>
>>> _______________________________________________
>>> For general EVDL support, see http://evdl.org/help/
>>> For subscription options, see http://lists.sjsu.edu/mailman/ 
>>> listinfo/
>>> ev
>>
>>
>> _______________________________________________
>> For general EVDL support, see http://evdl.org/help/
>> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/
>> ev
>>
>>
>
>
> _______________________________________________
> For general EVDL support, see http://evdl.org/help/
> For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ 
> ev

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[Stephen West-2]

> Yep I agree with Steve West, in my experience the TS cells sag to
> about 2.6-2.7V at 3C.

Have you carried out tests on the TS cells similar to those you carried out
on the K2 and Headways?

> One of the important differences is that the low voltage cutoff for
> ThunderSkys is 2.5V

Are you this low voltage cutoff applies during heavy discharge? I would have
thought the 2.5V refers to the resting voltage, and that during 3C draw a
cutoff like 2.0V would be more appropriate.

Steve West

On 23/07/08 1:32 PM, "Ian Hooper" <evdl@...> wrote:

> Yep I agree with Steve West, in my experience the TS cells sag to
> about 2.6-2.7V at 3C. Varies with temperature and SOC of course, but
> that's a fair ballpark.
>
> One of the important differences is that the low voltage cutoff for
> ThunderSkys is 2.5V, whereas the Headways are 2.0V. I hear ThunderSky
> do something a bit strange with their manufacturing process (can't
> remember the specifics) which results in higher max and minimum
> working voltages - though the same nominal voltage. So you get less
> leeway for voltage sag if you want to keep them above their minimum
> discharge voltage at all times; you won't be able to pull much more
> than 3C from them.
>
> I only tested the HW 38120s to 3C due to limitations of the testbench,
> but at that rate they were significantly better than TS, and had
> similar performance to the K2 26650EV which I did test up to 10C
> continuous. So all other things being equal, the HWs would probably
> be ~2.4V at 10C. Heating would be an issue of course, you wouldn't
> want to maintain 10C in them for too long! But I do believe the power
> would be there if you needed it.
>
> OTOH, the 1000 cycle rating of the Headways (vs ThunderSky's
> independently confirmed 2000-3000 cycles) does change the economics a
> bit, especially if you're a charge-every-day type person. But if you
> only need to charge twice a week, calendar life will the limiting
> factor with either cell.
>
> Ian Hooper
> --
> "Never doubt that the work of a small group of thoughtful, committed
> citizens can change the world." - Margaret Mead
> http://www.zeva.com.au
>

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[Ian Hooper-3]

Oh dear, sorry to hear it! Thanks for letting me know, too. It's  
important that I keep those testing pages up to date if cell quality  
is changing over time. So hard to find good batteries these days.. Its  
no wonder most people just go with the tried and trued battery  
solutions, with such a large financial investment on the line.

I'm just about to take the plunge and go with K2 26650EVs for my next  
EV project, and perhaps become a reseller for K2 here in Australia..  
anybody heard any bad reports about them!? They will work out rather a  
lot more expensive than ThunderS