I would like to start with a new project to convert a conventional school bus (approx 50 seater) to electric. The idea being that most School buses in my region are diesel which is ofcourse going to die in a few years. I would like to use the same bus body but convert it into a electric bus with a range of around 80-100 kms. Considering that a typical school bus runs for a maximum of 2 hours in the morning and then again 2 hours in the evening, giving it ample time for a good enough re-charge during the school hours. It would be a cheaper option (in the long run) for the schools as well as good for the environment. I need the community's opinion about the idea and I would be really grateful if you could point out the things I need to be careful about and what it would cost me(approximately) for this conversion assuming that the school bus to be converted would be made available free of charge.
closed as too broad by Rory Alsop, JPhi1618, Chenmunka, tlhIngan, MooseLucifer Jan 17 '18 at 20:22
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Diesel is not going to die in heavy vehicles. There is no other option. Large diesel engines are very energy efficient, and diesel has a much larger energy density than batteries. Also, cleaning the exhaust gases is more feasible in large vehicles when compared to small vehicles.
If you'd like to do the conversion, consider how much diesel the bus uses (30 L/100 km)? Consider then how long you want it to go (100 km)? So, 30 L of diesel is required. This is about 40 MJ/liter, or 1200 MJ or 333 kWh. Have you seen a 333 kWh battery pack? I certainly haven't but have seen much smaller battery packs, and even they are HUGE.
About 7 kg gives you 1 kWh, so you need more than 2 tonnes of batteries for your idea. Cost is $400 / kWh, so you need more than $100 000 for your idea. In contrast to this, 30 liters of diesel is 25 kg, about one hundredth of the weight of your batteries. A 30 liter diesel tank costs much less than $100 000. And I'm pretty sure your bus has more diesel than 30 liters.
My opinion: not worth it! (And before somebody complains, I picked up the 30 L / 100 km figure out of thin air. If somebody has more accurate figure, feel free to edit my answer.)
Edit: forgot that efficiency of large diesel engines is 33%, so you could divide the battery size by 3. But it's still quite a lot. So I remain unconvinced.
It's certainly feasible, but whether it's cost effective is another matter. Electric buses are readily available, and becoming more common in European cities, while trolleybuses (buses powered by overhead wires) have been in use since the 1880s.
The challenge, as @juhist says, is getting enough batteries. You need to consider the range you need. 2 hours in urban traffic is, I'm guessing, around 60 miles/100km? A bit of googling suggest 6mpg for a London double-decker, or 39L/100km, so juhist's figures aren't far off...
Wikipedia (https://en.wikipedia.org/wiki/Electric-vehicle_battery) suggests that the cost of batteries in 2016 was $145/kWh, so you're still looking at around $50k just for the batteries (I suspect the rest, motors, electronics, etc is cheap in comparison)
Of course, this cost will drop dramatically over the next few years as they become more common...