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Might be better on the bottom. See this rollover during testing. https://insideevs.com/four-injured-electric-bus-rollover-inc...

Disclosure< I work for Proterra and our packs are on the bottom.




Bottom seems like the natural place. Can I ask you how you solve the problem mentioned in the article of excess axel weight?

> Mr. Stoddart continued: “Provisions for rooftop battery packs are common across all North American and international bus manufacturers. In fact, heavy-duty transit buses built by other manufacturers with batteries located only under the floor (between the axles) have recently been tested at the FTA Altoona track and have exceeded front axle weight ratings, resulting in a significant limitation to the number of passengers that can be carried on board.”


I went to the test doc at: http://altoonabustest.psu.edu/buses/reports/480.pdf?15190591...

The relevant quote there is:

The interior of the bus is configured with seating for 39 passengers including the driver. Eight seats fold away for 2 wheelchair positions. The manufacturer passenger placard indicates that the test bus can accommodate 42 standing passengers. At 150 lbs per person, this load results in a measured gross vehicle weight of 43,540 lbs which exceeds the gross vehicle weight rating of 42,000 lbs by 1,540 lbs or approximately 10 people. At this load, the front gross axle weight rating is also exceeded. All testing performed under this partial test was performed at a seated load weight of 37,230 lbs.

My read from that is total weight, and only about loading to highest placarded passenger count, which using the govt. weight would overload the axle.

I didn't see anything that would change based on weight location or CG.

As with every EV vehicle it's about weight reduction while maintaining structure and safety margins.


Is that the norm? I guess the floor could be raised with a higher roof to compensate. I’ve noticed that new energy buses are taller (NG and electric) to make room for fuel/battery, but I’m not exactly sure where that is going.


Car batteries in the floors of cars don't seem to have made them any taller.


Buses have different constraints, so I'm assuming they have more battery for more range between recharges.


Depends on the use-case. For fixed-line buses in urban areas, their range requirements could be quite low, especially if high-speed charging is available at the terminal.




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