VX1 Battery Currents

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R
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Re: VX1 Battery Currents

between 2000 and 8000 miles would probably represent a truer figure.
Well Laird, that was true with the pre oct2008 software. However after the new software with EQ, many people hanging around in catalunya reported decreased range in the beginning, but that range was steadily increased as months went by, and the bikes seem to be stable by now.

The only batteries that failed where those with old software (some owners refused new SW due to initial decreased range), or those batteries damaged by unattended long storage period.

In this forum there is a guy with 30.000 km on his vectrix, 20.000 km with the last battery, and his battery seems stable. If the eq is done properly, and the battery is not stressed by hi temperatures, the bikes can easely last 40.000 km or 50.000 km. My bike is now reaching 20.000 km, 12.000 km with the last battery. I can easely travel 70-80 km on a single charge... it wont last as long long as it should, because is very difficult for me to do EQ (I can't leave the bike plugged in the middle of the street!), but I'm sure I'll manage to reach at least 30.000 km, around 14.000 miles with one battery...

Mik
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Re: VX1 Battery Currents

Here is another way to roughly estimate the current draw:

Range at 100km/h is about 20km (not tested by me).

100km/h = 1.666km/min

20km / 1.66km/min = 12 min to empty battery at 100km/h.

30Ah / 12min = 150A (this number will be too high because of the Peukert effect, particularly at this >3C discharge rate).

Now look at the current in X-Vectrix' graph between 21.1s and 24.1s: It's around 120A, fluctuating a bit as it does at full throttle. That means you can only get 80% of the total 30Ah out of the battery if you discharge it at full throttle; an entirely plausible result!

This information may be used entirely at your own risk.

There is always a way if there is no other way!

AndY1
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Re: VX1 Battery Currents

I think the graph is self explanatory, what is going on with the battery:
//visforvoltage.org/sites/default/files/u4117/VX1%20current.jpg)

Let's assume, that the X-axis represents time x/10= seconds. The ride begins with a bit of speed and comes down to a stop at 4.1 seconds. Voltage is high, current is at 0, speed is at 0.
Then full throttle is applied:
- voltage drops due to increasing power demand
- current is increasing
- speed is increasing

A red line jumps from 0 to 100 exactly where the current reaches 125A. I think that the RED LINE represents fuse overload.
As the speed increases linearly up to 13 seconds, acceleration is constant, current increases linearly, up to 250A. That is a reasonable value, since 250A * 110V(at that time) = 27.5kW minus losses on the way to the electric motor.
After the 13th second, the acceleration slows down (no more linear increase in speed, but still an increase, slower), obviously a limitation by the software, less current is needed UNTIL...

... the bike hits 62 mph at 20 seconds, where it stops accelerating completely and holds steady 62 mph:
- Voltage stabilizes
- current drops to a steady value

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Re: VX1 Battery Currents

It's around 120A, fluctuating a bit as it does at full throttle.

X-Vectrix mentioned, that the measurement was made by driving uphill with a headwind and 120A and for such condition it's the right value.

By my aproximate calculations, these are the battery currents on a flat terrain with no head wind:
- 70km/h = 1C = 30A
- 80km/h = 1.5C = 45A
- 100km/h = 3C = 90A

And this corresponds with the aerodynamic drag formula. There's also a rolling resistance, but I don't know it's value.
In above case, for a speed increase from 70km/h to 80km/h (14% speed increase), you require 50% more power.
For a speed increase from 70km/h to 100km/h (less than 50%), you require 200% more power.

So, take care of you battery by trying to drive no faster than 70km/h for a long time, since the power requirement increases immensely above 70km/h without any mention of losses due to Peukert value, which drops the useful capacity of the battery even further and creates additional heating of the battery.

R
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Re: VX1 Battery Currents

Range at 100km/h is about 20km (not tested by me).

I don't agree...

Range at 90-100 km/h is around 35 km. Tested by me with my V. ;-)

95km/h = 1.583km/min
35km / 1.583km/min = 22.11 min to empty battery at 95km/h.
30Ah * (60 min/1h) / 22.11 min = 1.357 = 81 A.
81 A at 125V nominal = 10.125 watts,
10.125w/3.750wh nominal capacity = 2,7C<3C...

I suspect this 20 minutes trip at 100 km/h is from a battery with reduced capacity...

Mik
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Re: VX1 Battery Currents

I think the graph is self explanatory, what is going on with the battery:
//visforvoltage.org/sites/default/files/u4117/VX1%20current.jpg)

Let's assume, that the X-axis represents time x/10= seconds. The ride begins with a bit of speed and comes down to a stop at 4.1 seconds. Voltage is high, current is at 0, speed is at 0.
Then full throttle is applied:
- voltage drops due to increasing power demand
- current is increasing
- speed is increasing

A red line jumps from 0 to 100 exactly where the current reaches 125A. I think that the RED LINE represents fuse overload.
As the speed increases linearly up to 13 seconds, acceleration is constant, current increases linearly, up to 250A. That is a reasonable value, since 250A * 110V(at that time) = 27.5kW minus losses on the way to the electric motor.
After the 13th second, the acceleration slows down (no more linear increase in speed, but still an increase, slower), obviously a limitation by the software, less current is needed UNTIL...

... the bike hits 62 mph at 20 seconds, where it stops accelerating completely and holds steady 62 mph:
- Voltage stabilizes
- current drops to a steady value

I like the fuse overload as the meaning for the red line! Well done!

The only thing that I think is wrong with your explanation is the reason for the flattening of the acceleration curve after the current peak at 76km/h (13sec). The flattening is in my opinion due to the exponential growth of kinetic energy with speed: E=1/2mV^2 and the increasing back-EMF as the motor speeds up towards it's maximum RPM (when torque would theoretically be zero).
The linearity of the acceleration curve before the current peak is the result of software regulation (to protect the IGBTs, I think).

But I might be way off with these guesses, I still don't understand how the battery current and motor phase currents relate to each other.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

SVX
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Re: VX1 Battery Currents

X Vectrix's post of the graph shows a current drawn which exceedes 200 Amps indeed, it shows a maximum of 250 amps, assuming that the scale on the left represents the current in Amps. Unfortunately there is no indication of the X-axis scale (the horizontal scale) which rather leaves the graph as being worse than useless in this context. I suspect that the current curve is actually that of one of the motor phases, probably over a short time period of milliseconds. I will no doubt stand corrected in due course.

You really think the Vectrix tested did 0-62 in 0.148 seconds? Looks like the scale is in tenths of seconds (as others have also figured out). Current shown is battery current.

Now, if we can return to the question of 'how much current does the vectrix draw from the batteries' which was Paul's original post. I think that the answer is "up to 120 Amps, probably not more than 110 Amps".

Maximum battery current is about twice that, ~250amps.

X Vectrix
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Re: VX1 Battery Currents

VX1 current2.jpg

Hows this. It starts at 450 seconds because its part of a much larger graph. Very interesting but too long to print.

The Laird
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Re: VX1 Battery Currents

All corrections are welcome,

I didn't see the speed curve in the original graph and took the word 'speed' as being related to the red box in some way. I also noted the current line dropping from 20 amps down to zero in the first 21 horizontal units, this does look odd if you discount the speed curve. Sorry, I did say 'I shall no doubt stand corrected'.

I have returned to my drawing board and done some calculations. I calculate that the Vectrix acceleration is around 0.3G at an all up weight of 700Lbs. This requires an increasing power output from zero speed=zero power (it's all torque until the bike moves), at 15 MPH the power required is 6.8kW (135volts @50Amps). At 30 MPH the power required is 13.9kW (135volts @ 100Amps). At 45 MPH the power required is 20.8kW (135volts @ 150 Amps) and at 60MPH the power required is 27kW (135volts @ 200 Amps). And these figures do not take electrical and mechanical losses into account. Will I ever be forgiven?

It would be fair to say that the 120 Amp fuse in the Vectrix hardly qualifies for the title 'fuse'. If it can carry a 150% overload for periods of up to ten and twenty minutes at a time (acceleration and Hill climbing) and do this repeatedly, exactly what current will it take to blow it in a hurry such as when something goes short circuit? Maybe a fire extinguisher would make a handy and useful accessory.

These revelations concern me. This battery (built by G.P. Batteries - Gold Peak Group-Data sheet for model 10GP30EVH) has an internal resistance of (they say) below 12 milliohms. Vectrix, at some point, quoted 2 milliohms. The Cell dissipation at 200 Amps will be between 80 Watts Per cell (using Vectrix's figures) and 480 Watts per cell (using G.P. figures of 12 milliohms). Expanding these figures to the whole battery, all 102 cells, the total heating effect of 200 Amps is 8.1KWatts (Vectrix figures) or 48.9KWats (G.P. figures). The battery is also being discharged at 6.66C (6.66x it's capacity) which is way above the 'High Rate Discharge' figure of 2C shown on G.P's data sheet. A 2C discharge rate would produce 43Watts per cell as against 480Watts per cell at 6.66C (using G.P's figures),

Is it any wonder that Vectrix have been having problems with battery heat? It would be interesting to know how much heat it takes to raise the battery by 1 degree C. and thereby how much heat needs to be dissipated by the plenum chamber and, of course how much energy is wasted heating the battery.

So, it's back to the problem. What is the problem? Does anyone know where we are up to? Is it Friday and can I go home now?

Peace be with you (and me too);-)

The Laird

MikeB
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Re: VX1 Battery Currents

So, it's back to the problem. What is the problem? Does anyone know where we are up to? Is it Friday and can I go home now?

I think the problem was figuring out the sustained and peak discharge rates that a replacement battery pack would be subjected to, thereby eliminating certain battery configurations or chemistries from consideration, and making progress towards specifying an actual replacement pack. And yea, it's Friday somewhere.

My electric vehicle: CuMoCo C130 scooter.

AndY1
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Re: VX1 Battery Currents

Yeah, but remember; with lighter battery pack, one could accelerate faster or accelerate the same with lower power needed for that weight.

Mik
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Re: VX1 Battery Currents

I measured the internal resistance of individual Vectrix cells as about 1.2 to 1.4mOhm. This is very stable across most of the SOC range, it only rises towards empty state.

P=I^2*R makes 250^2 * 0.0013 = 81.25W per cell during full throttle up a very long, steep hill if the Vectrix can just manage to reach 76km/h.

So your calculations there are correct, I think.

But the GP specs are for a module of 10 cells I would assume, which brings it to the 1.2mOhm per cell which I mmeasured.

At 100A (lets asume that is about the current draw at 100km/h on flat ground) we get:

100*100*0.0012= only 12 Watt heat production per cell. Always amazing what effect exponential functions have!

But that is still 1.2kW for the entire battery at maximum speed.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

antiscab
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Re: VX1 Battery Currents

It would be fair to say that the 120 Amp fuse in the Vectrix hardly qualifies for the title 'fuse'. If it can carry a 150% overload for periods of up to ten and twenty minutes at a time (acceleration and Hill climbing) and do this repeatedly, exactly what current will it take to blow it in a hurry such as when something goes short circuit? Maybe a fire extinguisher would make a handy and useful accessory.

Oh it qualifies as a fuse.
for power electronics, the fuses have nothing to do with protecting the hardware, that is the role of the software and other hardware.
the role of a fuse is to prevent a fire or other truly catastrophic failure.

unless the hardware after the fuse is truly overkill,
by the time any fuse has blown, the controller is long dead.
no fuse can protect power electronics from failure.

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

Mik
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Re: VX1 Battery Currents

This thread has been added to the Vectrix Collaborative Handbook, please stay on topic!

This information may be used entirely at your own risk.

There is always a way if there is no other way!

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