Blue Bird Electric Bus Chassis Walk-Around with Hinton Harrison

Blue Bird Electric Bus Chassis Walk-Around with Hinton Harrison

During this live webinar recording Hinton Harrison, a senior technical specialist engineer with Blue Bird, gives an in-depth chassis walk-around of a Blue Bird Corporation’s rear-engine all-electric school bus chassis. This is a must-watch video for any school district considering school bus electrification.

Blue Bird began its journey into school bus electrification during the early 90s and has since perfected both its partnerships and technology to produce and deploy both Type C and Type D buses nationwide. Blue Bird’s Micro Bird Type A school bus is a perfect electric bus option for schools and organizations seeking a small design bus for their fleet. Micro Bird is made possible with the company’s partnership with Girardin. Blue Bird continues to innovate through proprietary technology and strategic partnerships. Blue Bird delivered the company’s first electric bus in 2018. Since then, the electric division of Blue Bird bus has seen exponential growth.

V2G (Vehicle to Grid) for Electric Vehicles

  • Date: October 27th, 2020
  • Time: 11:00 am – 12:00 pm ET
  • Speaker: Marc Trahand with Nuvve



Justyne Lobello (00:00):
Well, welcome everybody to today’s broadcast. We have Hinton Harrison, who is our electric liaison and engineering. And he’s going to talk to us today about the internal components of our electric bus by doing a chassis walk around. So I’m going to go ahead and play a video. And as in past zoom calls that I’ve done, we’re going to go ahead and play the video. And if there’s any lag or fee or bad feedback on your end, we will be sending this video to all of the zoom participants after the call so that you can watch it at your leisure. There will be a Q and a at the end of this call. If you have any questions for Hinton and you can just send me a chat request to the host, that’s me, and I will get those questions related to Hinton. So without further ado, I’m going to go ahead and start the video now.
Hinton Harrison (00:43):
Hi, I’m Hinton Harrison with Blue Bird. And today we’re going to talk about our rear engine electric bus and all of the components that make up that electric bus in order to move it down the road; we’re going to start with the air compressor in order to have the air brakes operate properly, you have to have an air compressor to fill the reservoirs so that the brakes will stop the bus. Here we have a twin cylinder air compressor run by a dedicated 380 volt alternating current motor with its inverter. This compressor puts out 14 cubic feet of air a minute, and it has its own dedicated filter. Since we don’t have a turbocharger and we don’t have an engine with its own filter, we have to use a filter here that’s easily washed and then replaced. And this compressor will fill your reservoirs faster than it will on the diesel because this motor keeps the compressor running at its optimal most efficient speed.
Hinton Harrison (01:51):
Cause we don’t want to have the compressor running any more than what we want to. It also turns itself on and off as needed. So it’s not running constantly. Inside the chassis rails, here we have the electric motor or the propulsion motor. This motor is rated at 315 horsepower and 2,400foot-pounds of torque. Now that sounds like a lot, but when you have your average 660 foot-pounds of torque diesel engine with an Alison transmission and starting off in first gear, that axle sees roughly the same amount of torque through that combination as it does through this motor, which you will see if you’ll notice down in here, we do not use a transmission. It is directly coupled with the small drive shaft. And we do that one to save weight because we just didn’t need a transmission. And two, it also saves on any type of maintenance. There’s not any oil to change, and there are not any internal components on a transmission that has to be maintained.
Hinton Harrison (03:09):
This module back here is what we call our high voltage module. Over on the far left is a junction box. That’s where the batteries are all coupled together, for when you charge the batteries, their current comes into that junction box and then out to the batteries. And then it also acts as a distribution box to send high voltage to all of the accessories, the air compressor. We just talked about the thermal management system or an our power steering pump. In this area right here, there are two DC to DC converters and it takes the 650 volts of DC power from the propulsion batteries and converts that into 12 volts to charge our 12 volt battery. And it’s very similar or to having a 400 amp alternator on your engine because each one is rated at 200 amps. That’s how we’re able to run like a wheelchair lift and not have the bus Owen.
Hinton Harrison (04:12):
But it has to be key to one in order to get the power out of the high voltage batteries. And it keeps the 12 volt battery constantly charged up. Also in this area are AC chargers and there’s three of them inside of here. Now this particular bus has both AC charging and DC charging. So going forward on newly received orders, all Blue Bird electric buses will have the ability to charge with 19.2 kilowatts of AC power and 60 kilowatts of DC. Fast charge. Now you can’t do them at the same time, but it will go through the same plug, which we’re going to see a little bit later.
Hinton Harrison (05:00):
This right here is what we call our thermal management system. And we can, I call it thermal management because it controls the temperature of a variety of items, mostly the batteries, because the batteries like to operate right around 70 to 80 degrees. That’s when they’re the most efficient and they take a charge the best and they discharge the best. So we have two heaters in here that will heat the coolant. If you’re in cold new England areas or you’re in the Dakota state or Minnesota, where it’s cold during the school year, we have heaters that will heat the cooling. But if you’re in the deep South South Florida, we also have what’s called a chiller and it will chill that pool it, and it will circulate it to the motors and the batteries, and that will help keep everything cool. There’s a variety of control valves that are on here that divert the fluid to where it needs to none of which the driver has to control it.
Hinton Harrison (06:00):
All. This is all done behind the scenes in order to keep the bus running in its most efficient manner possible and would come on around the back of the bus, we have what’s called our low voltage module. Bus still has to have 12 volts to operate because you still have brake lights, headlights, warning, lights, and all that is controlled inside of here. There’s a series of breakers and circuit breakers and fuses that are inside of here. And, but not really maintainable. This is all done for Cummins, but for 12 volt control this right here. This is the brains of the bus. This is what we call the VCU. It’s a vehicle control unit and it does the exact same thing that an ECU, an engine control unit does on a diesel engine. Now we couldn’t call it an ECU because well, this bus doesn’t have an engine.
Hinton Harrison (06:59):
So we had to rename it to something more applicable. And that’s why we call it a vehicle control unit. This box right here, this is no different than any other Blue Bird bus it’s called our body PDU. So everything feeds into here for the body and then goes right back out and just like any other bus has, we’re going to wait. I want to rail. We have power steering system. This is the reservoir. It uses the same fluid has the same filter and uses the same type of plumbing that any other rear engine type Blue Bird bus has tucked up in here is a 380 volt AC motor with a pump. That’s very similar to all the other Blue Bird steering systems. It puts out the same amount of pressure puts out the same amount of flow. And then once it leaves, this pump is plumbed the exact same way as any other rear engine type steering system.
Hinton Harrison (08:01):
So it comes out of that. Pump, these hoses go up the inside of the frame, rail up to the steering gear and operates no different than any other steering system on a rear engine type bus. Now this, this is all part of the thermal management system. We have a surge tank that uses orange Dex-Cool coolant. And we have to use that on this bus because this type of coolant does not have any type of reaction. When it’s circulating through the aluminum batteries, we use a Ford propane radiator that should the chiller not be able to get the coolant down enough and cool it off enough. It will flow through this radiator and depending on if it really can’t. So if we’re operating like in Miami, we have four fans here that the fans will operate off of a thermal input. And then the VCU that we just talked about will control weather.
Hinton Harrison (09:05):
None of the fans come on or two of the fans or for the fans. And we do that again, just so we’re not using any more electricity than we have to because we want to use all of our battery power to push this bus down the road in order to maximize the range that we can get out of the bus. So we’ll work our way on around. We have one 12 volt battery on this bus. So when you have a diesel engine, this chassis will have anywhere from three to four, 12 volt batteries on it. And you have to have that for cold cranking amps. It takes a lot of current in order to start a cold diesel. Well, we’re not really starting anything. We only have just have a 12 volt battery in order to run the 12 volt accessories that we have that we talked about a little bit earlier, and we have the DC to DC converters that will take the high voltage and keep this battery charge it up properly.
Hinton Harrison (10:06):
So we go from small, regular 12 volt battery to the main event with our bus, which are the 14 high voltage batteries in between the frame rails in between each of these axles, which are encased in the same type of material that we build our crash barriers for our diesel fuel or gasoline and our propane tanks. Now these are divided into two sets of seven. So you have a set of seven in the front, a set of seven in the rear. So we tasked some of them together in series. Then they’re all wired together in parallel. And that’s where we get our 650 nominal volts in order to operate our system. We also tie them together in two separate batteries so that if any one battery has a fault or goes bad, for any reason, you can still operate this bus under full power, full acceleration, just seven batteries is just that the range is cut in half.
Hinton Harrison (11:17):
It’s very similar to if you had a hundred gallon diesel tank and you somehow got a hole up the side, right in the middle, your engine still runs. Everything still operates. You just have half the range. Now on outside of these batteries, we have a couple of safety features and we have some plates for service. So you can, this is what we called our MSD. It’s our master service disconnect. And if you pull those out, that will shut down the high voltage for leaving the batteries and have to, if you remember, we have two sets of seven, so we have one at the rear of the bus, and then we have one at the front of the bus and order to get the power into these batteries. We have to have a receptacle that can handle that type of current going forward on newly ordered bus.
Hinton Harrison (12:16):
All blue birds will have what’s called a C, C S Y a combine charge the system one type receptacle. So if you remember, all of our buses will be able to have level two AC charging or DC charging. So if you’re going to have just level two AC charging, you will use this top piece. And that looks just like any other level to a receptacle. And you will only use the top piece. If you have DC charging and have opted for that, you will use the entire plug. And these bottom two plugs are where the DC current will come in and go directly into the batteries and up to 60 kilowatts an hour. Other than that, the other major components of this bus are no different than any other Blue Bird bus.
Hinton Harrison (13:18):
That was great hint. And thank you for that. I’m going to go ahead and ask you to unmute. Let me find you in my participants panel here, we’ve got a lot of people on the call. So I did actually get a question while we were watching that video. The question was, is there a video on how to drive the bus? And yes there is. And Hinton actually did that a few weeks ago. If you guys are interested, I can just email that to everyone on this call once we’re complete. And I’ll also send you the chassis walk around. I really do enjoy the chassis walk around videos because it gets an inside glimpse of, of how it works and a hint in there, something specific about the chassis that whenever you’re doing technical training, you always point out about that high voltage system and what’s that,
Hinton Harrison (14:09):
Well, we don’t want people going in and just touching the chassis. If you solve those cables quite a few of them were bright orange. And what that represents is a high voltage cable SAE defines high voltage, anything above 50 volts. So it would have that orange color where we’re operating anywhere between 580 570 on the low end of the batteries all the way up to about 698 volts. So they kind of tells you where all the high voltage lines are running. And we don’t want anyone trying service that we do all of our service through the local Cummins dealers. In fact, we don’t even service that. We have an onsite Cummins dealer or Cummins representative that stays on site with us in Fort Valley. So when you have any type of issue or need any type of service, we would ask that you contact your local Cummins dealer that has been trained on the EV and they will come in and handle anything regarding the high-voltage system.
Justyne Lobello (15:21):
So the next question I got is what is the electric vehicle range? And I, the next question is what’s the average school bus distance on a typical school day. And I know that varies quite a bit, but depending on the district,
Hinton Harrison (15:43):
Okay. So, so when we were designing this bus, we looked at in rails and in rails comes up did a study of just under a thousand different routes through various parts of the country. And they determined that the average route of a school bus. And again, this changes whether you’re you’re in downtown Boston or you’re over in Wyoming or Kansas, but they came up that the average route is right around 80 miles a day, but that’s not 80 miles in the morning or 80 in the afternoon. It’s 80 miles total. So you’re looking at like 40 in the morning, 40 in the afternoon. What we have seen with our bus is that under very temperate climates, nor not extremely hot, not extremely cold we’re seeing our buses get right around 90 to 95 miles with some good prudent driving and using a lot of regeneration instead of wheelie and brakes in order to get some electricity back into the batteries.
Hinton Harrison (16:51):
When we go into the cold climates we have one in Fargo, we have four up on long Island. Th those are not getting that kind of range. They’re down into the upper fifties and sixties mostly because one it’s cold they are operating close to zero Fargo will actually operate their bus down to negative 30 and they will operate. It does operate at that temperature. It does not like to take a charge at that temperature. So that’s where the thermal management comes in and assist with that. But in normal cases even when your temperature fluctuates we’re seeing most customers get arrived around 80 to 85 miles on a charge.
Justyne Lobello (17:42):
So if you guys have any more questions, please feel free to send them in the chat box. There was something I wanted to ask you Hinton about the chargers themselves. What’s, what’s unique about our charger right now is that it can do both. And can you speak more to that a little bit?
Hinton Harrison (18:00):
Yeah, so right now we are the only EV manufacturer school bus manufacturer that offers both AC and DC charging as standard there’s a manufacturer that can only do DC charging. There’s other manufacturers that you pick one or the other, but we are capable of doing both AC and DC on the bus as standard. You don’t even have to ask for it. And the reason we did that is because the AC charging cost is right around two to $4,000 to procure the equipment in order to get the 19.2. And we understand that not every school district is going to have unlimited funds. You might say, whereas DC charging that equipment can can approach $70,000 for one piece of equipment. Now that only gets you the piece of equipment put into the parking lot.
Hinton Harrison (19:02):
It does not include the infrastructure that it takes in order to wire that up. So if a customer has those types of funds and has access to grants, then yes, then that would be great. And they would use it, same plug. But if that bus has to go to a maintenance facility or get somewhere that it needs, some work in a DC charger is not available. And that’s the only thing that’s available as DC charging. Well, that bus has kind of stuck. So we made it available so that we could use our bus through AC charging, and you can plug your, that charger into a 240 volt welding outlet that most maintenance facilities hay up. And you’d be able to charge the bus up it’s anywhere between 12 to 19 kilowatts an hour, depending on how much current is coming to that plug. So, so we open up a lot of doors and make it so that the bus is not tad to arrange with only one type of a charger. Could, could we realize that these buses operate in many different types of environments, and we didn’t want to make it so that the bus couldn’t operate at all, should it have to get out of its certain range or get to a different maintenance facility?
Justyne Lobello (20:17):
Right. And actually one of the questions that was submitted to me while you were speaking is is there an appropriate school bus, electric charging system in place nationally? And also the other question I got was what model the chassis is. It’s a T3RE or an All-American rear engine electric bus that we were looking at.
Hinton Harrison (20:37):
So is there a national charging? Well, the, the level two charging with the 19.2 kilowatts that uses the same plug is a lot of what you see on your Chevy volts your Leafs and those types of chargers. Now, yes, it will plug it in, yes, the bus will charge, but those types of chargers are usually rated down right around 2.3 kilowatts to five kilowatts an hour. Well, we’re at 155 kilowatts. So if you do the math, you’re looking at quite a bit of time and in order to get that get the bus charged back up. So the answer is, yes, it would plug in. Yes, it could charge. But what I like to equate that to it’s like trying to fill a swimming pool with a garden hose, you can do it, but you better leave a lot of time in order for it to happen as compared to the 60 kilowatts.
Hinton Harrison (21:36):
No, there’s not a, a national standard for that just yet. Some people think that that Tesla with their superchargers would be able to use that, but no, we can’t do that. They use a different plug and they have a communication protocol that has to be met when, when a Tesla backs up to which charger. And we don’t have that. So, and that’s why another one of the reasons we use both types of charging systems on the bus. So it just provides more of an opportunity to the customers in order to charge the buses in different places.
Justyne Lobello (22:12):
So another question that I got is they just want a clarification. Did you say that you use a regular 240 volt welder plugin?
Hinton Harrison (22:22):
Yes. So as long as it’s an L5 or an L6 50 type plug, so what we’re looking for in the perfect world, if we’re going to work with a customer and install the infrastructure for this, we would have them wire up a totally separate 240 volt, a hundred amp circuit. So in order to get to the full 19.2 kilowatts that charger, or it’s really the EVC electric vehicle supply equipment in order to get the 19.2, it would need 80 amps, but we asked to have it fused at a hundred. So it wouldn’t even be 80 amps at 240 volts. And that would give you your 19.2. Now using the same plug, most welders will pull about 50 amps. So we can use, as long as you had the same L5 or L6 type plug, you could plug that into a welder type plug.
Hinton Harrison (23:19):
That’s 240 volts, but most of those are right around 50 amps. So you’re going to get about a 12 kilowatt per hour charging grade instead of the full 19. So again, yes, it will charge. It’ll just charge it a little bit slower, right. But if you already had those plug around your shop and the bus is only going to be there every now and then it would just be fine to plug that in at the end of the day if the bus had to leave say tomorrow after you’ve finished your maintenance on it today, let it charge overnight. And the bus will be charged back up in the morning, ready to go.
Justyne Lobello (23:55):
And another thing, couple of people are commenting on this, that temporary installations of the plugs require plug that’s less than three feet in length. So I’m not sure what that, what that means for this.
Hinton Harrison (24:10):
Okay. So on the, on the EVs E the supply cord is right around three to four feet long, but the cord that feeds into the bus is going to be 25 feet long. Can’t be any longer than that, because then any longer than that, the cord would have to get larger. And we have to watch the voltage drops for anything large smaller than that, or longer than that for that type of cable. So you don’t have to get the bus super close, as long as you’re within like 25 to 30 feet of that outlet, you should be able to plug your bus in and be okay. Hinton Harrison (24:49): Lots of more questions coming in. So what is the full battery capacity in kilowatt hours?
Hinton Harrison (24:58):
The full battery capacity is 155 kilowatt hours. Now, what we like to do is we like to be completely open and honest with this. So we do not, and no battery manufacturer, no electric school bus manufacturer can do this either. You do not get to use the full amount of what those batteries are rated at. So our batteries have a useful kilowatt hours of right around 125. And the reason we do that is that lithium-ion batteries do not like to be fully discharged and they do not like to be overcharged. So in order to preserve the life of the battery and to extend the life of those batteries, which was right around eight to 10 years as a school bus usage, we cut off about 10, 15 kilowatts at the bottom of the batteries, and then reserve another 15 kilowatts at the top.
Hinton Harrison (26:02):
So even though the, you might see on your cluster that you had zero state of charge left that’s all that’s available to the bus, but there’s actually 15 kilowatts left in the batteries and that’s to preserve the batteries and to maintain their life and to keep proper maintenance on the batteries. So we have them last as long as possible, the same way as on the upper end. We don’t go to a full charge. So, so it may say a hundred percent state of charge on the cluster. It’s actually stopping into about 15 kilowatts before it gets to that, because in chargers, take a little bit longer in order to react. So you may end up doing a little bit of an overcharge, and that’s why we stop at that 15 kilowatts to allow for that overcharge and then for the chargers to turn themselves off and get back into a trickle or maintenance type charging in order to, so we don’t overcharge overheat or cause any type of catastrophic event with the batteries.
Hinton Harrison (27:10):
When I asked what is the least amount of kilowatts, the AC charger will accept
Justyne Lobello (27:20):
W ell, the chargers in that case, the charge, it doesn’t receive kilowatts, it would receive amperage. So it was as long as you had the 240 volts and then we altered the amperage coming in that is going to determine how many kilowatts actually go into the batteries at a level two. So like we’re saying, if we were setting you up from scratch, we would want an 80 amp service at 240 volts single phase. And that would give us the 19.2 kilowatts. If we were at 50 amps, that would give us right around 12 kilowatts. And then again, it’d be started backing that down and it’s a pure mathematical. If we get down even lower with with the amperage, say you had 25 amps coming in at the 240 volts, then you’re only looking at about six kilowatts. So that’s where it gets into that is your voltage with level two, as long as that stays right around 240 then your amperage coming into it is going to dictate how much, how many kilowatts are actually going into the batteries.
Justyne Lobello (28:31):
So when you run out of time, we’ve got quite a few more questions. If you, if you guys have any additional questions that maybe weren’t answered on this call, feel free to email us. When I leave you guys with the, the video that we showed you today, and I’ll be sure to get those to Hinton, but before we adjourn, a couple of people were asking like, overall, just, you know, do we help schools transition their fleet to electric? And yes, we will help a school determine if electric is right for them. You know, our, our sales team is very experienced in electric and we have some great experts here, like Hinton who can look at your route and look at your infrastructure that you currently have. And a couple of people were mentioning that, you know, the charge, this especially the, you know, in the service space, obviously any kind of infrastructure or charging equipment, it’s always good to contact a professional or an electrician to help you with those installations.
Justyne Lobello (29:26):
We work with lots of different installers for the, for the charging stations and et cetera. So we definitely can help you out. And any, again, any additional questions that you have weren’t answered today, just feel free to email me and I’ll get those to Hinton or the sales team. We’ll be sure to answer them for you. Our next event is going to be a week from today. We’re actually going to be talking about Vehicle-to-Grid, which does involve that DC fast charge that Hinton was talking about. And it’s a way that your school could transition to electric and actually not only save money on electric, but make some money as well. So we hope to see you at that call. Hinton, thank you for your time. Really appreciate it. And thank you everyone this today. And if you have any questions, again, feel free to contact us and we hope you have a great day.

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