F1 Energy store density for 2026 and hot swap batteries

[wuzak]

@Wuzak. There is no limit on F1 battery storage. The weight is limited and the discharge per lap.

From the 2022 Regulations:
5.3 Other means of propulsion and energy recovery

Energy Storage
The difference between the maximum and minimum state of charge of the ES may not exceed 4MJ at any time the car is on track.

5.5 Mass and centre of gravity
5.5.3 The total mass of the part of the ES that stores energy, i.e. the cells (including any clamping plates) and electrical connections between cells, must be no less than 20kg and must not exceed 25kg.

The maximum weight defines the maximum possible storage of the ES based on the energy density of the cells.

As I said above, the chart you posted has a range of energy densities for lithium-ion batteries from 100Wh/kg to 275Wh/kg.

From that can be calculated the actual storage.
275Wh/kg * 25kg = 6.875kWh = 24.75MJ.

I used 300Wh/kg to be generous, which gives 7.5kWh = 27MJ.

The effective storage is 4MJ, however.

You cannot ignore the brake recovery if you want to look at the energy input from the fuel. It's straiyht forward that more brake recovery means you can, use that energy from the battery and make do with less fuel.

Precisely.

The fuel used per race is based on there being a certain amount of energy recovery.

My calculation accounts for the brake energy used to make the lesser fuel stretch as much as possible over the race, and the deficit is to be filled in by an additional battery usage.

That is already part of the calculation.

The maximum fuel used per race is currently 110kg. Without brake energy recovery it would probably be more.

[wuzak]

....the loss of fuel energy will be compensated by the reduction in drag from the 2026 chassis ....

how wouldn't this cause a reduction in aerodynamic downforce ? .....
reducing tyre grip and braking force available .....
disproportionately increasing the time for regeneration (at 350 kW) before the grip further reduces .....

this would be a big part of filling the 'energy-gap'

The lap time may be gained by shorter times on the straights compensating for longer time in the corners.

[wuzak]

Front recovery has been disallowed.

In any case, it isn't likely that the energy recovery would be significantly more, since a proposed recovery system with front and rear MGUs had, more or less, the same power as the 2026 regulations.

You mean other than the fact that it's guaranteed to be more than double? Front wheels do most of the braking of course, and right now they exclusively use all that energy to heat up the brake disk to glowing red/orange.

Why would it be double, or more than double?

If the total power for brake recovery remained the same (ie 350kW) but split between front and rear MGUs the energy recovery will be increased, but I am doubtful that it will be double.

The front MGU will extend the time the MGU can extract at maximum power, but only at the slower end of braking. And not all braking takes the car down to the slower speeds where the brake power is reduced so that rear brake power is less than 350kW.

[PlatinumZealot]

@Wuzak. There is no limit on F1 battery storage. The weight is limited and the discharge per lap.

From the 2022 Regulations:
5.3 Other means of propulsion and energy recovery

Energy Storage
The difference between the maximum and minimum state of charge of the ES may not exceed 4MJ at any time the car is on track.

Eaxactly...

Nowhere does it limit the battery capacity. Only two reference points for the state of charge. Different teams may chose to "trim" along anywhere in the state of charge depending on their battery condition to extend life or performance etc.

[wuzak]

@Wuzak. There is no limit on F1 battery storage. The weight is limited and the discharge per lap.

From the 2022 Regulations:
5.3 Other means of propulsion and energy recovery

Energy Storage
The difference between the maximum and minimum state of charge of the ES may not exceed 4MJ at any time the car is on track.

Eaxactly...

Nowhere does it limit the battery capacity. Only two reference points for the state of charge. Different teams may chose to "trim" along anywhere in the state of charge depending on their battery condition to extend life or performance etc.

The weight and energy density of the cells limits the capacity.

In 2026 there is only a minimum weight for the ES (which includes more items).

[PlatinumZealot]

That was addressed in an earlier post.

What everyhting points to so far is that the expected weight and capacity of battery required to make up for 2026 rules and to have some extra race pace if a team chooses to by swapping in a fresh battery mid-race, is viable.

The other design concerns would be the electrical contacts and the chassis design around the space or "bay" allow the hot swapping.

[wuzak]

What everyhting points to so far is that the expected weight and capacity of battery required to make up for 2026 rules and to have some extra race pace if a team chooses to by swapping in a fresh battery mid-race, is viable.

Why would there be extra race pace?

They can only use 4MJ at a time, and recover and, by extension, deploy 9MJ per lap.

How would swapping in a battery help?

The other design concerns would be the electrical contacts and the chassis design around the space or "bay" allow the hot swapping.

The battery is in the middle of the bottom of the car, under the fuel tank.

The 2026 energy store enclosure must include:

ES (ie the cells) and HV elements as defined.
HV safety elements and sensors
Any DC-DC converter and its connection to the ES HV DC bus. Including active parts, enclosure, brackets and supports.
CU-K (MGUK control unit). Including active parts, enclosure, brackets and supports.
HV DC connections between ES and CU-K/DC-DC converter. Including all conductors, insulation, EMC screening, mechanical and thermal shielding.

And may include:
Low voltage Power Distribution Board (PDB).
PU Electric pump Driver units.
Low Voltage systems passive protection devices - Fuse box.
Low Voltage looms exclusively used: for PU functionalities or power supply chassis devices.
Any Electronic Box devices exclusively used for PU functionalities.

So, are you swapping all that too?

Are you going in from the side or the bottom?

Note that to change a current ES the car is lifted onto stands, the floor is removed, and then the ES is removed/installed. It is not the work of a moment.

And for 2026 the MGUK may also reside in the same defined volume, which means the ERS enclosure would have to be built around it.

This may well preclude extracting the ES from the side.

[PlatinumZealot]

What everyhting points to so far is that the expected weight and capacity of battery required to make up for 2026 rules and to have some extra race pace if a team chooses to by swapping in a fresh battery mid-race, is viable.

Why would there be extra race pace?

They can only use 4MJ at a time, and recover and, by extension, deploy 9MJ per lap.

How would swapping in a battery help?

The other design concerns would be the electrical contacts and the chassis design around the space or "bay" allow the hot swapping.

The battery is in the middle of the bottom of the car, under the fuel tank.

The 2026 energy store enclosure must include:

ES (ie the cells) and HV elements as defined.
HV safety elements and sensors
Any DC-DC converter and its connection to the ES HV DC bus. Including active parts, enclosure, brackets and supports.
CU-K (MGUK control unit). Including active parts, enclosure, brackets and supports.
HV DC connections between ES and CU-K/DC-DC converter. Including all conductors, insulation, EMC screening, mechanical and thermal shielding.

And may include:
Low voltage Power Distribution Board (PDB).
PU Electric pump Driver units.
Low Voltage systems passive protection devices - Fuse box.
Low Voltage looms exclusively used: for PU functionalities or power supply chassis devices.
Any Electronic Box devices exclusively used for PU functionalities.

So, are you swapping all that too?

Are you going in from the side or the bottom?

Note that to change a current ES the car is lifted onto stands, the floor is removed, and then the ES is removed/installed. It is not the work of a moment.

And for 2026 the MGUK may also reside in the same defined volume, which means the ERS enclosure would have to be built around it.

This may well preclude extracting the ES from the side.

I aready said for the topic to be viable the battery capacity and the deployment per lap would be substantially increased as the objective is to add an additional strategic layer to the racing. That is swap batteries by sacrficing pit stop time but gain a lasting advantage via longer lasting deployment for some number of laps.


As for the battery supporting connections etc. Please look at the existing batteries when they are changed out. The whole point would be engineering all that to happen in two to four seconds.

[mzso]

Why would it be double, or more than double?

If the total power for brake recovery remained the same (ie 350kW) but split between front and rear MGUs the energy recovery will be increased, but I am doubtful that it will be double.

The front MGU will extend the time the MGU can extract at maximum power, but only at the slower end of braking. And not all braking takes the car down to the slower speeds where the brake power is reduced so that rear brake power is less than 350kW.

Well, as I said, instead of wasting energy as heat now you would recover via the front wheels. Which are also the more significant wheels in doing the braking.
Well, double might be too much since I wasn't thinking about the recovery limit. But still the front wheels bare most of the braking load, and it can saturate the 350kW recovery for far longer. And since everyone's complaining that it's not possible to recover near the allowed amount of via the back wheels only, it's clear that recovery is needed.
Sure it won't help much on the few circuits where you barely need to to brake, but on other tracks it should bring a lot.

[PlatinumZealot]

It's a conservate approximation of 1megaJoule of total braking energy during a braking event. Put 60% of that on the front wheels and multiply by the number of braking events per lap.

[wuzak]

It's a conservate approximation of 1megaJoule of total braking energy during a braking event. Put 60% of that on the front wheels and multiply by the number of braking events per lap.

Not all braking events are the same.

1MJ @ 350kW recovery is less than 3s. So the total braking energy of a heavy braking zone is >> 1MJ.

What you have to figure is how much extra time recovery at all 4 wheels gives you at the set recovery rate of 350kW.

Is it 3/4 of the braking event at maximum power with all 4 wheels vs 1/2 with only the rear wheels?

[wuzak]

Oh, and many tracks have no more than 3 or 4 heavy braking zones, some only 1 or 2.

So if the recovery for each of them is 1MJ, you are still a long way short of 9MJ in a lap.