[Yabert]

Originally Posted by eman.cardona

The Fiat 126 is keeping well with traffic!

Awesome!
Please share more details about the Alltrax setting.

Motor Amps
Motor Volt
Battery Amps

And what about top speed?

[eman.cardona]

Alltrax settings of the new SPM controller.. 72% max voltage output curve (sags to 48V), motor current 400A max, battery current 250A maximum. Top speed is still not clear but till now I saw 85kph which is above the national speed limit. I think I can go up to 90-95kph with the wind in favor

[SamSpade]

Nice drive through the city!

I'm very interested in the performance of these new cells as I'm planning to purchase them too.

Can you please check the voltage sag at 60A (1C), 120A (2C) and 180A (3C) battery current? For example, if starting from 78.0 V does 180A (3C) current result in <66V total pack voltage (15% voltage sag or more)?

Thanks!

[eman.cardona]

Hello SamSpade,

Interesting question which I never took into consideration. I attached a laptop and took some readings.

Please note that I took this data when the batteries were on the low charge and I think it will be better with charged batteries.

2C - 10% voltage sag
3C - 15% voltage sag
3.5C - 20% voltage sag

Do you think that this is normal or maybe I have something missing in my calculations?

Cheers.

Eman

[Yabert]

Originally Posted by eman.cardona

Do you think that this is normal or maybe I have something missing in my calculations?

Temperature! 25°c or 5°c? That can do a big difference.


Thank a lot to share all details.
It's really interesting to know than a small car can probably hit 100 km/h with only 72v. It will be interesting to know how many Kw is need to maintain high speed.

About battery, the calculated impedance from your data is pretty bad. That give 2.7 mohm for those 60Ah cells and the Calb 70Ah claim to be under 1 mohm.
Do you consider 3.2v (76.8v) like 100%?

[SamSpade]

Originally Posted by eman.cardona

2C - 10% voltage sag
3C - 15% voltage sag
3.5C - 20% voltage sag

Thanks for the info.

There's little data that others post about voltage sag. But based on a few posts (tomofreno, etc.), 10%-15% at 3C seems to be the range for the Chinese prismatics. With 10% being good and 15% acceptable. Low temperatures make it worse.

Originally Posted by Yabert

About battery, the calculated impedance from your data is pretty bad. That give 2.7 mohm for those 60Ah cells and the Calb 70Ah claim to be under 1 mohm.

Comparing internal resistance (mohms) is problematic. First, the ESR is non-linear and the datasheets don't say at what currents those were taken. If the CALB data was true then those 70Ah cells would only have 6% sag at 3C. Second, most people get confused comparing the resistance of low capacity cells with higher capacity ones. Quoting voltage sag at several Cs would give a better picture.

So based on first glance I would rate these cells as an improvement on energy density (100 Wh/kg and 189 Wh/liter), but with minimal improvements on power density (because of the lighter weight and volume) and no improvements on performance. I define 'performance' as voltage sag under a given current, closely related to power density. Of course, the lower the sag, the better the performance, the higher C discharge possible.

[Yabert]

Originally Posted by SamSpade

Second, most people get confused comparing the resistance of low capacity cells with higher capacity ones.

I compared with 70Ah calb because they seem to be the news 60Ah cells (more energy, similare shape to old 60Ah cells).
A bit like the 60Ah cells of eman is the new 60Ah cells because older model was taller and heavier.

Comparing internal resistance (mohms) is problematic. First, the ESR is non-linear and the datasheets don't say at what currents those were taken. If the CALB data was true then those 70Ah cells would only have 6% sag at 3C

Yes, but that don't include the loss in contact connections between cells and others loss who aren't included on laboratory test.
Real data are precious!..

[drgrieve]

Those voltage sags are not very good. For a small cell I'd expected half the sag you are getting at those C rates.

For comparison have a look at this thread.

http://www.diyelectriccar.com/forums...ute-62326.html

For example the calb 100 gives 8C at 20% sag and the calb 180 5.5C @ 20% sag - these are pack readings.

So either these cells have rubbish power density (but excellent energy density) or your readings are wrong somehow or you have loose / bad connection somewhere.

Maybe check that you are not getting hot / loose connections or hot wiring?

[SamSpade]

Thanks for the link drgrieve. Please keep updating that thread.

Apart from connections, his numbers were also affected by the low state of charge. And a few cells already on the knee would contribute to that even more. Would be good to get the numbers when the pack is fully charged.

[dladd]

I'll add my personal observations from the last month or so... temperature has a HUGE influence on pack sag. My 48 130ah CALB cells are limited to 135v by my controller, on a cold morning when the car has been outside all night long (battery cases around 34F) I only get around 200a at that sag. On a warm day, it's more like 400 amps. Same car, same cells, same everything, except temperature.