Energy Usage of electric cars

[Fantomas]

I recently looked at the fuel economy results of FS Uk of the electric cars and noticed a difference.
Looking at the FS UK numbers (divided by 0.65, because of the conversion factor given in the rules), it seems like any single car used more energy than it had sitting around in their accumulator compared to the given numbers for accumulator capacity in the FSG Program Magazine.
Furthermore three of them, Zurich, Eindhoven and Zwickau, used more energy than allowed by the FS UK Class1A rules for the maximum accumulator capacity. Why were they not disqualified?
As far as I know you can never use all the energy from a battery without destroying it.
Anyone knows what happened? Or are the numbers given by the teams in the FSG Program Magazine just nuts and cannot be trusted?

Fantomas

[Fantomas]

I recently looked at the fuel economy results of FS Uk of the electric cars and noticed a difference.
Looking at the FS UK numbers (divided by 0.65, because of the conversion factor given in the rules), it seems like any single car used more energy than it had sitting around in their accumulator compared to the given numbers for accumulator capacity in the FSG Program Magazine.
Furthermore three of them, Zurich, Eindhoven and Zwickau, used more energy than allowed by the FS UK Class1A rules for the maximum accumulator capacity. Why were they not disqualified?
As far as I know you can never use all the energy from a battery without destroying it.
Anyone knows what happened? Or are the numbers given by the teams in the FSG Program Magazine just nuts and cannot be trusted?

Fantomas

[TommKG]

As far as I know, the data in the result sheet is the actual kWh each team used.

E.g. Delft used 4,1 kWh, Zurich 5,5. etc.

So you don't have to divide it by 0,65.

Furthermore the data from UK seems a little bit high, I know that some guys from Zurich calculated their needed energy with roughly 4,5kWh, so the energy meter wasn't that accurate... As far as I know, all numbers on the FSG Magazine about energy storage were correct.

[Fantomas]

But in the Class1A rules and in the published scoring/result sheet it says that it is calculated by the amount of CO2 generated in kg e.g. Minimum Volume (kg) 4,119

Confusing...
Can anyone of the participating teams comment on that?

Fantomas

[JasperC]

I heard from someone on our team that the listed data are indeed the usage in kWh, even though the score sheet itself indicates otherwise.

Cheers,
Jasper
DUT Racing Team 2008-2010
Delft University of Technology

[Yannick]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Anyone knows what happened? </div></BLOCKQUOTE>

The number are, as far as we know, the kWh of energy used. We think that our "fuel" consumption was measured wrong. Our own measurements matched those of FSA and FSE at the respective competition, so we think we had it also right in Silverstone.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Or are the numbers given by the teams in the FSG Program Magazine just nuts and cannot be trusted?
</div></BLOCKQUOTE>

The amount of energy stored in the accumulator given in the FSG program is the nominal amount (nominal voltage times nominal capacity). It's not a random number in our case. I don't know for other teams, but I'd say they also put the real value. However, the nominal ammount of energy is not a very helpful number, think of it.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">As far as I know you can never use all the energy from a battery without destroying it. </div></BLOCKQUOTE>

Yes, in the case of LiPo cells, I think you should not discharge them lower than 2.8 V or you will damage them (some unwanted chemical reactions will start). But look at a Voltage/Capacity chart, and you will see that there is not much energy stored after this voltage anyways.

I'm not an accu guy and if I told some BS please bear with me

Bye

[Fantomas]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The number are, as far as we know, the kWh of energy used. We think that our "fuel" consumption was measured wrong. Our own measurements matched those of FSA and FSE at the respective competition, so we think we had it also right in Silverstone. </div></BLOCKQUOTE>

Did you hand in a protest?
I had a quick look at the specifications of the EnergyMeters of both competitions. FS UK uses a current transducer and transmits the signal over an analogue connection, which should be prone to pick up a lot of noise. The shunt used at FSG and FSA seems to be better suited for this application.

Have you had the chance to have a look at the data recorded during Endurance to see, if noise was the problem?

Fantomas

[Yannick]

I am not sure if a protest was handed in. It would not have altered the result anyway (we still would have used more than Delft, and they were way ahead of us). Keep in mind that in Silverstone it is a fuel economy competition, not efficiency like in FSA or FSE.

I was at the parc fermé when the data was read out from the energy meter. Noise was not an issue, but their voltage measurement on (our) device had an offset. They said that the measured average voltage was around 160 V. Fully charged our voltage will be 152 V, so this is not possible.

Yannick

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Fantomas:
I had a quick look at the specifications of the EnergyMeters of both competitions. FS UK uses a current transducer and transmits the signal over an analogue connection, which should be prone to pick up a lot of noise. The shunt used at FSG and FSA seems to be better suited for this application. </div></BLOCKQUOTE>
A shunt would also use an analogue signal, in fact I know of no way of measuring current 'digitally' without some form of analogue to digital conversion. Presumably the FSG shunt has to be wired into the high-voltage cables and actively cooled? If I understand correctly the FSUK sensor is just looped over the wires in a non-contact way?

Regards, Ian

[Fantomas]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">A shunt would also use an analogue signal, in fact I know of no way of measuring current 'digitally' without some form of analogue to digital conversion. Presumably the FSG shunt has to be wired into the high-voltage cables and actively cooled? If I understand correctly the FSUK sensor is just looped over the wires in a non-contact way? </div></BLOCKQUOTE>

The shunt used by FSG is directly bonded to a PCB which carries an ASIC to digitize the measured current. This leads to an analogue signal wire which is only some millimeters long instead of being routed through the whole car.

The FSG EM specification says that the shunt is only 50µOhm, therefore it should not need active cooling.

The FSUK sensor uses a current transducer, but these do not only catch the field of the measured current, but also all other fields and are therefore less accurate in general. Furthermore the analogue signal is not directly digitized at the sensor, but routed through the car to the logger as far as I know.

Fantomas