The Hows and Whys of Battery Relocation or How Battery Relocation Affects Corner Weight!


Steve Mitchell
Steve enters the raw data into an excel spreadsheet to get the weight distribution and cross weight percentage.

Next we moved the battery to the left side of the trunk to see what would happen.

 Left WeightRight WeightBattery LocationFront to Rear Weight PercentageCross Weight
Front Weight686627left rear of trunk52/4850.4%
Rear Weight646567   

Although the weight bias is more to the heavier left side of the car, it is still much better than stock.  The cross weight percentage is even better but this is deceiving, it could easily be zeroed out with some slight adjustments of the coilovers.  The right rear of the trunk is clearly the best place for the battery.

Sometimes you cannot fit the battery in the trunk or you want to keep the cars polar moment of inertia low for quicker transitional handling.  To visualize polar moment of inertia, imagine trying to twist a set of dumbbells back in forth from the handle.  Sort of tough right?  Now imagine trying to twist the same weight in your hand if it was a compact sphere, its easier.  A car with its mass located closer to its center will respond to steering input faster.  So if you want to reduce your polar moment of inertia more than improving your overall weight distribution, you will want to place the battery within the cars wheelbase.

Let’s see what happens when the battery is placed behind the passenger seat.

 Left WeightRight WeightBattery LocationFront to Rear WeightPercentage Cross Weight
Front Weight687651behind front passenger seat53/4750.4%
Rear Weight622567   

The left to right wheel weights are considerably improved and the front to rear weight distribution is still improved by an impressive 1%, equivalent to about a 5” engine setback.  A 1% change in weight distribution is feelable to most drivers.

Placing the battery behind the drivers seat resulted in these weights.

 Left WeightRight WeightBattery LocationFront to Rear WeightPercentage Cross Weight
Front Weight703631Behind drivers seat53/4749.7%
Rear Weight625568   

Not as good but definitely way better than in the stock position.

So you can see that relocating the battery is as good as a lot of expensive fabrication.  What’s stopping you from doing it?

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