## How much extra time is saved by starting a lap on a full battery charge?

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
Brenton
11
Joined: Sun Dec 17, 2017 6:28 am

### How much extra time is saved by starting a lap on a full battery charge?

In qualifying they can't do two hot laps in a row, in part because the battery wouldn't be fully charged to start the 2nd lap. Is there a rough estimate as to how much it helps the lap time to start the lap on a full charge plus being able to finish the lap on an empty charge? As opposed to a race setting where they may start a lap at say... n% charge and end the lap at n% (n=any hypothetical percentage like 50%).

Big Tea
69
Joined: Sun Dec 24, 2017 7:57 pm

### Re: How much extra time is saved by starting a lap on a full battery charge?

Does it not also mean they can start with fractionally less fuel weight?
One test is worth a thousand expert opinions

NL_Fer
63
Joined: Sun Jun 15, 2014 8:48 am

### Re: How much extra time is saved by starting a lap on a full battery charge?

Less recovery from MGU-H, must be about 60-70 bhp more. So about 0,6s per lap?

henry
242
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Location: England

### Re: How much extra time is saved by starting a lap on a full battery charge?

Brenton wrote:
Sat May 25, 2019 3:51 pm
In qualifying they can't do two hot laps in a row, in part because the battery wouldn't be fully charged to start the 2nd lap. Is there a rough estimate as to how much it helps the lap time to start the lap on a full charge plus being able to finish the lap on an empty charge? As opposed to a race setting where they may start a lap at say... n% charge and end the lap at n% (n=any hypothetical percentage like 50%).
Judging by the number of replies I think you’ve posed a question to which there is a dearth of answers.

I also don’t know. But I can think of two ways to get at an answer.

One is to look at where the additional energy might be spent and the difference that might make. On a qualifying lap they will start with an extra 4MJ available to consume. In reality I think they start using it on the exit of the corner onto the start finish straight.

I think this is mainly used to implement electric supercharge mode giving 20 to 30kW extra from the PU.

In rough figures:

They can easily recover 2MJ from the MGU-K to the ES during the lap so they have 6MJ to spend. They are only allowed to transfer 4MJ from ES to the MGU-K. If the MGU-H is generating at 60kW then together with 4MJ from the ES they can run the MGU-K for 67 seconds, which is sufficient to cover the needs of most circuits. They then have an additional 2MJ in the ES to spend. At the beginning of each straight they can drive both the MGU-K (120kW) and the MGU-H (50kW) from the ES which is hence being consumed at 110kW more than if it were just driving the MGU-K with MGU-H assistance. They can do that for 18 seconds (using my numbers).

All that remains to do is calculate the time gained by deploying the extra ICE power at the beginning of the straights. That, of course is dependant on the configuration of the track. I’ll leave it to the reader.

A second approach might be to look at the 2 occasions where Gasly has made an explicit attempt on fastest lap at the end of Baku and Monaco. Looking at his fastest lap and his race pace 2 laps later will give a measure for the upper bound of the difference between race and qualifying power. There are lots of other factors, but there are in any attempt to assess the difference a single aspect of performance has.
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus

henry
242
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Location: England

### Re: How much extra time is saved by starting a lap on a full battery charge?

I had an old acceleration simulation which I modified to see if I could get some “meaningful” numbers.

I think the 4MJ ES energy might be worth in the realm of 0.5 to 1.0 seconds.

If I assume 4 medium straights each run with 4.5 seconds of e-boost then when e-boost is turned off the boosted car will have travelled 3.5 metres further and be travelling 3kph faster.

In total a gain of 14 metres for the lap, which at 50m/s average speed (180kph) is 0.28 seconds. Add to that time gained by running faster for the rest of the straight and it’s likely the gain is more than 0.5 seconds but probably not twice that.
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus

hollus
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Location: Copenhagen, Denmark

### Re: How much extra time is saved by starting a lap on a full battery charge?

How much was KERS worth?
Much easier to isolate the effect there.
It is not white, it is not black, it is probably gray.

henry
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Joined: Mon Feb 23, 2004 7:49 pm
Location: England

### Re: How much extra time is saved by starting a lap on a full battery charge?

hollus wrote:
Mon May 27, 2019 4:20 pm
How much was KERS worth?
Much easier to isolate the effect there.
Using the same calculator methodology I get that with 4 1.6 second KERs events the car is 1.6m further and 6kph faster at the end of each KERs deployment. So 0.2 seconds from the extra distance but much more from the extra speed. Maybe up to a second from the extra speed putting the advantage from KERS at 1 to 1.2 seconds.

Anybody remember what it was worth?

Having done a quick search I find that in 2009 motorsport.com was predicting 0.3 seconds per lap.
https://www.motorsport.com/general/news ... ng/317725/. I think they were including a loss of time due to the weight of KERS.

There’s also an interesting article by @Steven on this site. https://www.f1technical.net/features/18642. I’m not sure I completely agree with the analysis but it has some similar numbers to my calcs.

I could try adding the weight effect but in reality weight is probably more significant in the corners than on the straights.
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus

saviour stivala
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Joined: Wed Apr 25, 2018 11:54 am

### Re: How much extra time is saved by starting a lap on a full battery charge?

Are formula 1 cars back to using KERS again?

henry
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Joined: Mon Feb 23, 2004 7:49 pm
Location: England

### Re: How much extra time is saved by starting a lap on a full battery charge?

saviour stivala wrote:
Mon May 27, 2019 7:16 pm
Are formula 1 cars back to using KERS again?
No
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus

wuzak
356
Joined: Tue Aug 30, 2011 2:26 am

### Re: How much extra time is saved by starting a lap on a full battery charge?

henry wrote:
Mon May 27, 2019 3:35 pm
In total a gain of 14 metres for the lap, which at 50m/s average speed (180kph) is 0.28 seconds. Add to that time gained by running faster for the rest of the straight and it’s likely the gain is more than 0.5 seconds but probably not twice that.
henry wrote:
Mon May 27, 2019 6:44 pm
hollus wrote:
Mon May 27, 2019 4:20 pm
How much was KERS worth?
Using the same calculator methodology I get that with 4 1.6 second KERs events the car is 1.6m further and 6kph faster at the end of each KERs deployment. So 0.2 seconds from the extra distance but much more from the extra speed. Maybe up to a second from the extra speed putting the advantage from KERS at 1 to 1.2 seconds.
KERS, with 80hp and 400kJ, had more effect than the current ERS, with 160hp and 4,000kJ?

Look at it this way.
The current cars use ~2kg per lap in a 50 lap race.

Assuming a calorific value of 45MJ/kg for fuel and an average efficiency of 45% the amount of energy used to make speed is around 40MJ.

The battery storage is 4MJ, so 10% of the useful energy from the fuel.

Assuming a square relationship between lap speed and energy, you would get approximately 5% improvement in lap time. Or about 4s over a 90s lap, compared to not using the ERS at all.

That assumes that you only use the 2MJ in the lap, where the reality is they probably use >4MJ over a lap, regardless of what they start the lap with.

henry
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Joined: Mon Feb 23, 2004 7:49 pm
Location: England

### Re: How much extra time is saved by starting a lap on a full battery charge?

wuzak wrote:
Fri May 31, 2019 6:42 am
henry wrote:
Mon May 27, 2019 3:35 pm
In total a gain of 14 metres for the lap, which at 50m/s average speed (180kph) is 0.28 seconds. Add to that time gained by running faster for the rest of the straight and it’s likely the gain is more than 0.5 seconds but probably not twice that.
henry wrote:
Mon May 27, 2019 6:44 pm
hollus wrote:
Mon May 27, 2019 4:20 pm
How much was KERS worth?
Using the same calculator methodology I get that with 4 1.6 second KERs events the car is 1.6m further and 6kph faster at the end of each KERs deployment. So 0.2 seconds from the extra distance but much more from the extra speed. Maybe up to a second from the extra speed putting the advantage from KERS at 1 to 1.2 seconds.
KERS, with 80hp and 400kJ, had more effect than the current ERS, with 160hp and 4,000kJ?

Look at it this way.
The current cars use ~2kg per lap in a 50 lap race.

Assuming a calorific value of 45MJ/kg for fuel and an average efficiency of 45% the amount of energy used to make speed is around 40MJ.

The battery storage is 4MJ, so 10% of the useful energy from the fuel.

Assuming a square relationship between lap speed and energy, you would get approximately 5% improvement in lap time. Or about 4s over a 90s lap, compared to not using the ERS at all.

That assumes that you only use the 2MJ in the lap, where the reality is they probably use >4MJ over a lap, regardless of what they start the lap with.
I think both our calculations are flawed.

I did a bit more research and redid my calculations.

For the 2009 KERS cars the main difference was that there was a weight penalty, estimated at 35kg. When I factored that in and repeated the calculations I found that a non KERS car at the weight limit and a KERS car 35kg heavier would traverse a 1km straight in pretty much the same time. It’s possible that a KERS equipped car was potentially slower over a qualifying lap than a non KERS car.

I can recall that some teams resisted using KERS and these figures illustrate one possible reason.

My error was twofold, one I didn’t take the weight into account and two I assumed that the speed advantage gained from initial deployment, even with the weight penalty, would persist for the rest of the straight. That speed difference in my calc is about 3kph.

I also calculated the benefit of KERS if the two cars were the same weight in that case the KERS car would gain about 0.3 seconds for 4 deployments of 60kW for 1.6 seconds each at the beginning of a straight.

When I looked back at the current cars calculation I had made the assumption that all the 4MJ would be deployed in e-boost mode. It is likely some would be deployed at the end of straights allowing full KERS deployment for the whole of every straight if needed. However I still think that most of the 4MJ in the ES at the start of lap would be deployed as e-boost and this would discharge the ES at an additional 110kW for an increase of power at the road of about 20kW.

This is because if they didn’t use e-boost they would be discharging at 60kW with a further 60kW to the MGU-K from the MGU-H. Instead there is 120kW from the ES to the MGU-K and 50kW to the MGU-H to drive the compressor.

I believe the rules about energy paths mean that you can’t just add 4MJ to the energy deployed by the ICE and calculate pro-rata across the lap. It is likely that 2 or 3 MJ would already deployed by the normal ES charge and discharge paths meaning that it is not possible to deploy the whole of the 4MJ SOC to the MGU-K , probably much less than half. The rest would need to be deployed in e-boost which is much less efficient and gives quite a small benefit.

Notwithstanding the inefficiency of e-boost I suggest that the 4MJ is probably worth 0.3 seconds if deployed as four 4.5 second bursts in a qualifying lap.

I’m sorry for the complexity of my post. I blame the complexity of the rules that, IMHO, make it impossible to answer questions such as in the OP without recourse to simulations.
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus

wuzak
356
Joined: Tue Aug 30, 2011 2:26 am

### Re: How much extra time is saved by starting a lap on a full battery charge?

henry wrote:
Mon Jun 03, 2019 4:50 pm
I think both our calculations are flawed.
Agreed.

henry wrote:
Mon Jun 03, 2019 4:50 pm
For the 2009 KERS cars the main difference was that there was a weight penalty, estimated at 35kg. When I factored that in and repeated the calculations I found that a non KERS car at the weight limit and a KERS car 35kg heavier would traverse a 1km straight in pretty much the same time. It’s possible that a KERS equipped car was potentially slower over a qualifying lap than a non KERS car.
The weight limit was raised to account for KERS, so the teams using KERS didn't have a weight disadvantage, as such. Teams not using KERS had a significant advantage in using ballast, however.

So the gains from KERS would be, partially or wholly, offset by losses in cornering.

henry wrote:
Mon Jun 03, 2019 4:50 pm
When I looked back at the current cars calculation I had made the assumption that all the 4MJ would be deployed in e-boost mode. It is likely some would be deployed at the end of straights allowing full KERS deployment for the whole of every straight if needed. However I still think that most of the 4MJ in the ES at the start of lap would be deployed as e-boost and this would discharge the ES at an additional 110kW for an increase of power at the road of about 20kW.

This is because if they didn’t use e-boost they would be discharging at 60kW with a further 60kW to the MGU-K from the MGU-H. Instead there is 120kW from the ES to the MGU-K and 50kW to the MGU-H to drive the compressor.

I believe the rules about energy paths mean that you can’t just add 4MJ to the energy deployed by the ICE and calculate pro-rata across the lap. It is likely that 2 or 3 MJ would already deployed by the normal ES charge and discharge paths meaning that it is not possible to deploy the whole of the 4MJ SOC to the MGU-K , probably much less than half. The rest would need to be deployed in e-boost which is much less efficient and gives quite a small benefit.

Notwithstanding the inefficiency of e-boost I suggest that the 4MJ is probably worth 0.3 seconds if deployed as four 4.5 second bursts in a qualifying lap.

I’m sorry for the complexity of my post. I blame the complexity of the rules that, IMHO, make it impossible to answer questions such as in the OP without recourse to simulations.
It's hard to know exactly the strategy used on qualifying type laps. Whether there is any recovery, or not.

I'd suggest that there is and that the teams would probably use more than 4MJ to the K over the lap.

michl420
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Joined: Sun Apr 18, 2010 4:08 pm
Location: Austria

### Re: How much extra time is saved by starting a lap on a full battery charge?

I assume your Question ralates to a Qualy lap.There will be 4 MJ to mgu-k from ES. Whatever you can Harvest from mgu-k under braking (circuit depending 1-2MJ). All other Energy can be generated by mgu-h direct for mgu-k or for storage in ES to use it for e-Turbo boost. A other Option (Maybe a better one) is part trottle mgu-k Harvest. On some tracks, like Monaco, the 4 MJ from ES will be almost enough. Tracks like Spa are way more tricky. I have not calculated anything but would guess 1-3seconds per lap, compare to normal race mode and of Course track depending.

saviour stivala
-13
Joined: Wed Apr 25, 2018 11:54 am

### Re: How much extra time is saved by starting a lap on a full battery charge?

During a qualifying lap the driver will be in qualifying mode. In this mode maximum power unit output is used with no worry of fuel consumption. When at maximum output both ‘H’ and ‘K’ will be sharing ES power. ‘H’ will be spinning the turbo in electric supercharging mode.