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Opportunities and compromise

With Electric vehicles, one of the biggest concerns of the general public is 'Range Anxiety.' There is the perception that if the ICE powered care will do 350 miles on a full tank the Ev car should do the same. Maybe, but maybe not.

With any vehicle it is necessary to trade off weight and power against potential mileage. Ev's are no exception. The heavier the car, the less distance it will travel for a given battery capacity.

As with most 'new technologies,' its generally preferable to start with a new hardware design and not try and squeeze tomorrow's innovation in todays caseworks.

Existing ICE powered platforms are not optimised for traction batteries — either in terms of placement or maximising available space (and hence range.) The most efficient battery solutions are likely to be delivered by vehicles that have a platform specifically designed to take batteries and not shoe-horn them into spaces that used to hold metals containers with fossil fuel.

Weight is always a challenge

The battery of a P100 Tesla weighs circa 544 kg.
Each motor, 2 for the 'D' models, weighs about 45kg.
Power electronics weighs in at circa 45kg.
All up,
Powertrain weight is 679kg.

Compared with an Audi A7 estate car which is roughly in the same price range and trim level as the Tesla.
It has 90kg of differentials, axles and drive shafts.
A 97kg ZF 8hp90 transmission.
A 204kg V8 with the peripherals attached.
Probably 25kg of oil and coolant and transmission fluid.
68kg of turbos and exhaust.
Thats an all up powertrain weight of 484kg.

The Audi Powertrain is nearly 200kg lighter than the Tesla.

Electric vehicle Powertrain is not lightweight!

This is why you need to take the weight out of a vehicle elsewhere. EV conversions of existing platforms are always going to be at a disadvantage.

Battery Types

Lithium Iron

Most modern battery chemistry need specific charging regimes. Its not a matter of stringing them all in series and supplying power to the first positive plate and the last negative plate. Lithium Iron batteries (the most common) need to be charged in groups and under a strict charging regime to maximise the number pf possible charge cycles and minimise heat build up. The faster you try to charge the battery, the more heat is generated.

Nickel Metal Hydride

Cost: Nickel metal hydride batteries are, today, the less-expensive technology. As production of lithium-ion cells ramps up, though, economies of scale come into play and the cost of Li-ion cells should drop. When more vehicles require more batteries, each individual battery becomes less expensive to manufacture.

Weight: NiMH batteries are larger and heavier than Li-ion batteries. Weight matters in hybrid cars. Lighter battery packs with higher energy density make it easier to get the car going.

Power: Li-ion and NiMH batteries can actually hold a similar amount of power, but the lithium-ion cells can be charged and discharged more rapidly. Li-ion also doesn't have as much of a "memory effect," which occurs when a battery is recharged before it is fully empty. This can diminish a battery's capacity. Lithium-ion batteries are less affected by memory effect than NiMH batteries.

Durability: While both types of batteries are durable and both have been in use for years in various applications, this is the one area where NiMH has an advantage. Some Li-ion batteries don't last as long in extreme temperatures, particularly in very hot climates.
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