Battery temperature makes a huge amount of difference in an electric car. If the batteries are too hot or too cold, performance suffers, range suffers and the battery is more likely to fail prematurely.
In an electric car, a huge amount of effort is devoted to maintaining the battery temperatures at an optimum figure so that this is not a problem. However, not every manufacturer gets it right - I've driven a prototype electric car a few months ago with a summer range of 85 miles which drops to nearer 35 in really cold winter conditions. Since then, this particular car has had a battery pack redesign in order to incorporate battery heating to resolve this particular problem, so it should not be an issue when it is launched at the end of this year.
So it is unlikely that you'll have these sorts of problems with a Nissan LEAF, because all these sorts of issues should have been ironed out by now. However, if you are ever in a situation where you're driving an electric car and the battery temperature warning light comes on, here is what to do:
If battery temperatures are too hot:
Switch off anything that you don't need - including air conditioning and radio, and switch to eco mode whilst you find somewhere to pull over safely.
Pull over as soon as possible and let the batteries rest and cool down. Allow at least twenty minutes and preferably longer.
When you start driving again, drive slowly and gently, using eco mode only and using as few other facilities in the car in order to protect the batteries.
When you get to the end of your journey, let the batteries cool down for several hours before plugging the car in to recharge again.
Call your dealer - you could be looking at a faulty battery cell.
If battery temperatures are too cold:
Drive slowly and gently, using eco mode only and using as few other facilities in the car in order to protect the batteries.
As you continue your drive, the battery temperatures should increase again. Once the battery warning light goes off, you can drive normally, which will increase battery temperatures even more.
When you get to the end of your journey, plug the car in to recharge immediately.
To be honest, most people never have temperature problems with their electric car batteries. But if you end up being one of the unlucky ones who do, now you know what you can do.