[powerhouse]

Originally Posted by Bowser330

Super excited to hear more about your build.

Has the S2000 been replaced by the Exige?

Unfortunately no.
The exige deal didn't work out, it was a salvage, and the owner lied saying it had no frame damage. It did though, so I backed out.
On another note, the exige has even less space for batteries, I dont think it would have worked out having 1000 headways in there.

[Bowser330]

Originally Posted by powerhouse

Unfortunately no.
The exige deal didn't work out, it was a salvage, and the owner lied saying it had no frame damage. It did though, so I backed out.
On another note, the exige has even less space for batteries, I dont think it would have worked out having 1000 headways in there.

1008 headways @ 300g each = 665lbs, not too shabby for 26kwh and 2000A capable!

[x88x]

Congrats!

Originally Posted by powerhouse

The batteries are rated at 25c continuous, so I figured that they should be able to handle 28c for 3 seconds!

You sure about that? According the the specs Headway list on their own store site, they're 15C continuous, 25C burst. Though, who knows how long that "continuous" or "burst" actually are... On their site, CurrentEVTech lists them as 5C continuous, 15C for 4 minutes, or 20C for 3 minutes.

Sorry, not meaning to rain on your parade, just don't want you to blow up $13,000 of batteries. Speaking of which, that's a great price for them! Where'd you find that?

Another thing to keep in mind is that if you only take them to 80%DOD they should last for another 500 cycles. Just something to keep in mind once you're driving around on them; it'd be worth it, imo, to spend a little time planning your drive in exchange for increasing the life of your pack by 30% (though 1500 cycles still might last you the life of the vehicle...).

[x88x]

Well, either they improved their chemistry or they have multiple translators.

Anyways, I would recommend monitoring the cells heavily before pushing them to those levels. I look forward to seeing that S2000 move!

[Tesseract]

Originally Posted by powerhouse

...
either way, if it doesnt work out, can always just add an extra battery to each series, which will make 2000amps at 25c, as opposed to the 28c for 9 in parallel!

Rebirth Auto just shipped a Jaguar XK8 conversion to a client in the Netherlands that used a 10p95s pack of Headway 8Ah "power" cells. Scanning through a logfile from one of the test drives shows the pack sitting at 311V when pulling 20A from it then dropping down to 266V when battery current increases to 900A, giving a total sag of 45V (for a total resistance in the battery circuit of 50 milliohms).

Keep in mind that 900A from an 80Ah pack is only ~11C... sag at 25C will be closer to 100V.

Assembling a ~1000 cell Headway pack is a formidable task. Here's the one that is going into the Porsche 911 that Rebirth Auto is converting right now:

[Bowser330]

Originally Posted by Tesseract

Rebirth Auto just shipped a Jaguar XK8 conversion to a client in the Netherlands that used a 10p95s pack of Headway 8Ah "power" cells. Scanning through a logfile from one of the test drives shows the pack sitting at 311V when pulling 20A from it then dropping down to 266V when battery current increases to 900A, giving a total sag of 45V (for a total resistance in the battery circuit of 50 milliohms).

Keep in mind that 900A from an 80Ah pack is only ~11C... sag at 25C will be closer to 100V.

Assembling a ~1000 cell Headway pack is a formidable task. Here's the one that is going into the Porsche 911 that Rebirth Auto is converting right now:

That's really interesting data......I believe CroDriver's Headway pack saw a similar amount of sag, its just with such a high starting voltage, it still allows for a lot of power output out of this Jesus motor.

[lonestarrpm]

Originally Posted by Bowser330

That's really interesting data......I believe CroDriver's Headway pack saw a similar amount of sag, its just with such a high starting voltage, it still allows for a lot of power output out of this Jesus motor.

100V sag at 1000A -- isn't that 10kW of heat to dissipate?

That sounds like a problem in of itself.

With most things they get more resistive with age and heat --
is this true with these batteries as well?

mike

[Tesseract]

Originally Posted by lonestarrpm

100V sag at 1000A -- isn't that 10kW of heat to dissipate?

It's actually 100kW, but 100V of sag would occur at 25C, or 2000A from a 80Ah pack, and that would be 200kW of loss. Note that the maximum power from a battery pack (or any other source, really) occurs when the load resistance and internal resistance are the same (ie - the pack voltage has sagged to 1/2 its nominal value) but that means that an equal amount of power is dissipated inside the pack as in the load (motor).

And it is, indeed, a problem. This is more or less what limits the maximum C rate from a cell (more specifically, the amount of heat produced from the internal resistance vs. the surface area to dissipate it).

I don't have enough data on these cells to say for sure whether their internal resistance increases with age; it definitely increases with abuse (over charging or discharging).

[lonestarrpm]

Originally Posted by Tesseract

It's actually 100kW, but 100V of sag would occur at 25C, or 2000A from a 80Ah pack, and that would be 200kW of loss. Note that the maximum power from a battery pack (or any other source, really) occurs when the load resistance and internal resistance are the same (ie - the pack voltage has sagged to 1/2 its nominal value) but that means that an equal amount of power is dissipated inside the pack as in the load (motor).

And it is, indeed, a problem. This is more or less what limits the maximum C rate from a cell (more specifically, the amount of heat produced from the internal resistance vs. the surface area to dissipate it).

I don't have enough data on these cells to say for sure whether their internal resistance increases with age; it definitely increases with abuse (over charging or discharging).

Yeah I can't do simple math :-)

But my point is that's a lot of heat to dissipate in the batteries.

Mike

[DavidDymaxion]

I did a quick back-of-the-envelope... 2200 Amps (200 Amps, or 25C per cell). If you assume the batteries are all water, and run at 25C until 8 Ahr is gone... I get a temperature rise of about 48C. If your batteries are cool to start with they might survive that...

Originally Posted by lonestarrpm

... my point is that's a lot of heat to dissipate in the batteries. ...

Love that Porsche pic -- are there more pics of the batteries in front or back?