Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Doug S]

There's no particular merit to high voltage over high current, or vice versa. You can design an electric motor to run on higher voltage at lower current, or lower voltage at higher current, and both motors will work fine. Battery cells can also be connected in series/parallel arrangements with higher voltage and lower amp-hour capacity, or lower voltage and higher amp-hour capacity, giving the same energy storage capacity, and either of those will work fine. Neither configuration has any inherent advantage over the other. Neither is guaranteed to get you more range, or save weight, or package better, or have any other clear-cut advantage.

Each configuration does have small advantages and disadvantages. The high-voltage configuration, since it uses less current to deliver the same power, might weigh a bit less because the wiring doesn't have to be as heavy-duty. You might save a couple of pounds of copper by using smaller-gauge wiring. (But maybe not, since it might require heavier insulation to be safe at the higher voltage.)

Lower voltage is definitely safer. I imagine most of us Americans have been zapped by 115VAC line voltage, which isn't pleasant but it generally doesn't do any permanent damage. The Zero's 116VDC battery would do about the same if you inadvertently came into contact with it. But the 350VDC Tesla battery pack could do some serious damage, could even kill under the right (wrong) circumstances. My understanding is, that's why Zero designed for lower voltage and higher current -- it's demonstrably safer, to service personnel and rescue personnel in the event of an accident.

As far as fast-charging harming batteries, that used to be pretty universally true. But battery technology is moving forward very fast, and there are a lot more fine points to the story now. Li-ion batteries have a lot longer lives, and can tolerate much higher charge and discharge rates than they could even just a few years ago. This study:

http://www.greencarcongress.com/2014/09/study-finds-rapid-charging-and-draining-doesnt-damage-lithium-ion-electrode-as-much-as-thought-.html

seems to show that the damage to Li-ion cells by fast charging isn't as great as we once thought, or maybe as it once was. Granted it's a four-year-old study, but the point is we just don't know everything about the newest generation of batteries yet. I seem to recall seeing a study with similar conclusions about fast-charging Teslas a while back, but I can't find it now.

BTW, this article:

https://insideevs.com/lets-look-at-tesla-model-s-x-battery-degradation/

shows that Tesla, in the real world, is managing to provide some outstanding battery life, presumably with a mix of supercharging mixed in. These ain't your daddy's batteries.

[T.S. Zarathustra]

Well put Doug.

As for fast charging (sorry), there are many different chemical mixtures and battery management systems. Some rare more sensitive for fast charging than others. The reason fast charging damages batteries (that Lithium Ions don't go into the electrode, but get stuck on the surface during fast charging) was explained to me in a way that makes me still follow the rule to not fast charge unless necessary. I also avoid storing fully charged or nearly empty batteries.

[NEW2elec]

I like cookies.  Hmmmm
It's all a bit frustrating because the "rules" seem to keep changing.  I read, saw reports the fast charging can even be good for Li-ion because it reduces the build up of dendrites.  So we'll have to agree the jury is still out on the effects.
I for one feel better about my little quiq charger helping out so my onboards don't have to work for 5 or 6 hours.

Now I have heard the basic specs for the new electric Porsche Taycan and they seem to support the idea for high voltage.
800 volt system (yeah that'll kill ya)
300ish miles of range
3ish seconds to 60mph
600 HP
15 min recharge.
That's game changing in my eyes.  Of course my eyes are watering at the price but you can't get it all.

Doug my understanding (limited) was that basically high voltage gave you speed for an electric motor and amps gave you your run time or range in our case.  I wouldn't want to give up my range so that got me thinking of a way to have both.  Can't have my cake and eat it too I guess.

[NEW2elec]

And from my last comment here is the new Porsche:

https://www.autoblog.com/2018/08/15/porsche-taycan-ev-prototype-frunk-video/?ncid=edlinkusauto00000021&yptr=yahoo

[Richard230]

And from my last comment here is the new Porsche:

https://www.autoblog.com/2018/08/15/porsche-taycan-ev-prototype-frunk-video/?ncid=edlinkusauto00000021&yptr=yahoo

800 volts (and who knows how many amps) ought to get your attention when working around that vehicle. But then at the prices that Porsches sell for, that is nothing that I will be worried about.