by The_Toecutter » Tue 16 Aug 2005, 21:32:32
$this->bbcode_second_pass_quote('', 'A')nd is 3kWh system usefull? I mean your car has what, 50kW power? Or much more if it's SUV? You can assume that reasonably powerfull car (can run uphill with cargo) needs some 20-30kW ...
And with 3kWh battery thats about 6 minutes of power
A 3 kWh system is actually quite small for a battery. That would take an electric car 10-20 miles depending on whether it was a large truck or an efficient midsize car with proper attention paid to aerodynamics.
Most home-built EVs are using 8-12 kWh systems of lead acid batteries, which give them 30-60 miles range average, some more, some less.
To charge an 'empty' 8 kWh battery system from a 110V 20 amp outlet with a charger 92% efficient and lead acid battery 80% efficient will take 5 hours. In an efficient EV that consumes 150 wh/mile of travel, this 8 kWh pack would give a little over 50 miles range. If you go to a 220V 200 amp outlet and have a powerful enough charger and the batteries which can handle being charged that fast, that 50 mile range pack would be charged in 15 minutes!
To cruise at 60 mph, a Toyota Prius sized electric car with clean aerodynamics(About a .26 cD) will take about 12 kW of power from the batteries to cruise. This is 200 wh/mile energy consumption. 20-30 kW or more would be about the peak power usage under sane driving, the average would be more or less about 9-12 kW considering most driving is not high speed. With hard 200 kW accelerations if you give the car a powerful motor/controller/battery combination, yes, efficiency would drop quite a bit, but only under these abusive(but damn fun) driving conditions.
$this->bbcode_second_pass_quote('', 'I')f cars were specifically designed to have the battery pack removed, switching them out would be no problem. They could drop out of the bottom of the car with their own casters and jacking system or something.
No problem, until the battery interconnects fail without anyone knowing, or the companies start monitoring customer driving habits being fearful of battery abuse(and the resulting implications to ones privacy), or people are given dud packs that break down 20 miles into their trip...
And one size does not fit all. What about those with a desire for more power or more range?
I can assure you, batteries will last a lot longer if each individual car has their own pack that is not interchanged. They will be moved around much less, vibrated less, their interconnects will stay clean, complex diagnostics wouldn't be needed everytime someone 'refueled', it would be infinitely much less hassel to simply own your battery pack and not rent and swap constantly. Quick charge stations will also be much cheaper to implement, and won't require nearly as much money to maintain due to the fact that your average moron is well capable of simply plugging an appliance into an outlet with no hassel.