# What is the weight of the batteries on the e-Fan?

Airbus' own (early) page with technical data about the e-Fan provides some information about the batteries.

It can, for instance, be calculated that they hold approx. 19kWh of energy if you accept a somewhat simplistic calculation by multiplying number of cells (120) with capacity (40A ) and voltage (4V).

What I can't find is information about the weight of these batteries. Is this information available somewhere or can it be reasonably estimated?

The weight of the battery is mentioned here:

Power is provided by 127 kg. of 250-volt lithium-ion polymer batteries from Kokam in South Korea built into the wing.

A slightly different weight is specified here:

... E-Fan has two lithium-polymer battery packs weighing 65 kg each.

I could not find which Kokam battery is being used on the e-fan, but this page has specifications for all of their batteries.

Slightly adjusting your energy estimate (3.6V × 40A × 120 Cells = 17280Wh vs original 19000 Wh), taking an energy density of 125Wh/kg for a high quality battery, it can be estimated:

$$\frac{17280}{125}=138\text{kg}$$

which I think sounds reasonable for a plane with a empty weight of around 500kg.

• Matching this with Farhan's answer, I'd say that's a pretty close estimate! – kevin Jul 16 '15 at 15:32
• Nice estimate and thanks for the link, very interesting. – Monolo Jul 16 '15 at 16:45