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How to cool an electric car battery

What is a manufacturer to do about electric car batteries susceptibility to heat? As it turns out, the answer depends on what the warranty says, not so much on what the owner’s manual warns you not to do, Finley writes.

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Simply put, the Nissan engineers have fine tuned their software, battery limits, and car performance in such a way as to not need a heavy, complex and expensive, active liquid cooling system. Leaf drivers rarely notice the performance changes happening to keep the battery pack cool. I’ve never noticed my battery temperature gauge moving at all.  It is in some ways analogous to the fine tuned design of the Prius which remains unmatched for gas mileage performance after all these years. The consistent high ambient temps in the Southwest punched through the Leaf’s design envelope for a small number of drivers. They’ll get it under control, possibly with this new battery:

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From Green Car Reports:

 Nissan is testing a revised lithium-ion cell chemistry for its Leaf electric car that the company says appears to be as durable in sustained extreme heat as its current battery is under normal conditions.

 If tests confirm that the new cells degrade at no more than the standard rate, even at high temperatures, the company hopes to have battery packs using those cells available next April.

 Those packs would become the replacement for any current Leaf batteries replaced under warranty for loss of capacity.

 Hayes said Nissan has thus far replaced only 22 batteries for capacity loss in extremely hot climates–less than 0.1 percent of the 31,200 Leafs sold in the U.S. through July.

I suspect that the Leaf may very well prove to be the Prius of the electric cars. The Leaf solution to controlling battery temperatures is actually technologically superior in just about every way to the primitive, ham-fisted system of hoses, pumps, fans, valves and radiators used in cars since the Model T … and in WW II era fighter planes I might add.

Every aircraft I have ever flown, or have ever been a passenger in, uses passive (requiring no moving components) air cooling for the engines (no fans, pumps, liquid coolant, hoses, or radiators), except one, a WW II era P-51 mustang fighter I once hitched a ride in. I had an old professor who had helped to design the system of shut off valves for that plane to prevent loss of coolant from bullet holes. Unlike the air cooled fighters and bombers, a single hole in the cooling system could bring a Mustang down.

So, obviously, if  aircraft use passive air cooling, it must not only be adequate for cooling, it must also have some advantages over active liquid cooling systems in some applications. For commercial aircraft the two overarching reasons are:

  1. Less weight which translates into greater efficiency (the compact four passenger Volt weighs over 400 pounds more than a mid-sized five passenger Leaf, although not entirely due to its cooling system).
  2. Greater reliability via less complexity (fewer components like hoses, connectors, pumps, valves, and radiators to fail). The Volt has five radiators.

For the Leaf, you can add to that list, less cost.

In my life I have experienced dozens of instances in my cars or in the cars of people I know, of failures in the coolant system. One failure like that with a battery that relies on a pumped coolant is likely to permanently damage it, or at least to cause the computers to shut it down.

Source: Testing the Electric Car Battery Warranty Waters

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