F1technical.net

henry wrote: ↑

30 Sep 2019, 10:22

Juzh wrote: ↑

30 Sep 2019, 09:19

another thing i've noticed is that ferrari tends to harvest a lot of energy at the end, particularly russian main straight was very obvious. They're dropping ~5kmh before braking zones (325 down to 320), compared to mercedes 0 kmh (320) and red bull 1 or 2 kmh (320 down to 318 just before braking). Interesting. Possible reason would be their ICE is so much better they can afford to do some harvesting in such places, since they're arriving at faster speeds anyway, and then use that energy in better places. Double whammy.

I agree. I first noticed this at Hochenheim last year, when AMUS published some end of straight data about Ferrari and Mercedes. I made a model and the only way I could make it fit the data for Ferrari was to have them switch to charging the ES simultaneously from MGU-K and MGU-H at the very end of the straight.This means a charge rate of around 180 or even 190kW. That’s similar to the discharge rate in electric supercharge mode. My understanding is that high charge rates are harder to manage than high discharge. Maybe this is what Ferrari get from their unusual battery configuration?

For completeness I found Mercedes switching off the MGU-K drive earlier than Ferrari and charging the ES with the MGU-K for longer, and obviously at a much lower rate.

I also note that WilliamsF1 have recently announced a battery package with two different chemistries which they claim can handle higher charge rates than a single chemistry. It’s a 200MJ unit and the claimed rates are 550KW for 20 seconds discharge 550kW for 10 seconds charge. They are lower relative rates than F1 where I think the ES is around 20MJ.

If Ferrari were using a two part battery they would probably need to have a battery management system that moved charge between the two parts. It could be that they would use the power management components in the control Electronics to do that. This would mean power flowing across the FIA monitoring sensor but not going to the MGU-K but instead returning to the ES. This would certainly look anomalous to the FIA and might prompt an investigation. There was one and the FIA were happy.

stevesingo wrote: ↑

02 Oct 2019, 12:08

...

Could the twin battery arrangement be a thermal management solution? If they are using high charge rates, the charge/discharge cycle could be alternated between batteries giving a period of cool down between charge/discharge events. Given that a full discharge or charge is unlikely on one acceleration or braking zone.

NL_Fer wrote: ↑

02 Oct 2019, 17:57

Maybe someone help clearing out this theory in my head.

Could it be within the rules, to charge one battery during the lap, while using the other to deploy? Than switch the roles of the two batteries the next lap?

And would that lower the thermal stress on the batteries?

henry wrote: ↑

02 Oct 2019, 17:38

That is a possibility. When the twin battery thing was being discussed Charlie Whiting suggested that an issue was that they had “virtual” batteries. So perhaps they can look at cell temperatures and select the set of cells at the best temperature for the next cycle. I would expect each virtual battery to be fairly large, most of the physical battery capacity, to keep the C-rate down.

I think any advantage gained would show up most in the race rather than qualifying.

sosic2121 wrote: ↑

02 Oct 2019, 21:12

henry wrote: ↑

02 Oct 2019, 17:38

That is a possibility. When the twin battery thing was being discussed Charlie Whiting suggested that an issue was that they had “virtual” batteries. So perhaps they can look at cell temperatures and select the set of cells at the best temperature for the next cycle. I would expect each virtual battery to be fairly large, most of the physical battery capacity, to keep the C-rate down.

I think any advantage gained would show up most in the race rather than qualifying.

I was thinking a lot about this and IMO non of the explanations make any sense.

Wouldn't it be better to just use all cells all of the time!? This way peak temperatures will be lower.

Same with combining Li-cells with super-capacitors. One of those two will be inferior, so any combination of two would be inferior to "pure" battery.

Only reason for 2 virtual batteries (I can think of) would be voltage manipulation, and I'm not convinced this make much sense either.

Zarathustra wrote: ↑

02 Oct 2019, 23:20

How does the discharge of the battery work?

Do they ‘spread’ the discharge evenly over all ‘group of cells’ all at once...?

Or do they discharge each ‘(group of)cell(s)’ after the other; so when one (group of)cell(s) is depleted you go to the next (group of)cell(s)?

Dr. Acula wrote: ↑

03 Oct 2019, 03:20

For instance at the start you discharge cell 1,2,3 and 4. let them cool down but now for charging the system can only use cell 1,2 and 4 for instance cell 3 hasn't cool down enough, so the system removes cell 3 from the group and adds cell 5 which is already cool enough to be used again.
Atleast that's how i imagine the system could work.

henry wrote: ↑

02 Oct 2019, 22:01

Another feature I have seen offered as potential is that when they are being charged cells benefit from short rest periods, some BMS do this. They might cycle through cells allowing brief rest periods for some while the others deal with the charge.

sosic2121 wrote: ↑

03 Oct 2019, 09:17

Dr. Acula wrote: ↑

03 Oct 2019, 03:20

For instance at the start you discharge cell 1,2,3 and 4. let them cool down but now for charging the system can only use cell 1,2 and 4 for instance cell 3 hasn't cool down enough, so the system removes cell 3 from the group and adds cell 5 which is already cool enough to be used again.
Atleast that's how i imagine the system could work.

But wouldn't having 5 batteries all the time lower individual amperage by 20%, and by conscience reduce temperature and increase efficiency of whole system.

Also voltage drop would be lower, so IMO this would lead to higher efficiency later in the system which would lead to lower demand on the battery which would lead to even higher efficiency.

So there are cumulative penalties for not using all cells, or at least I see it that way.

Brake Horse Power wrote: ↑

03 Oct 2019, 12:35

One supercap manufacturer said they can make the formula-e battery 1/3 lighter when applying (combining?) supercap. The internal resistance is really low, so low cooling demand, high efficiency and you can really abuse these things with extremely high charge and discharge rates.