Full Electric Drive Conversion of Tri-Axle Coach 21700 or prismatic? Battery cycle Testers..?

[AkivaAld]

Hi all,
I’ve been browsing for a few days and have just purchased some GEB21700 battery’s in small quantity for testing.

Firstly I ask of you if there is any decent charge/discharge cycle testers that I can purchase for a reasonable price. To be able to check capacities of cells.

I’ve considered Lifepo4 as a potential battery source, however the weight difference will be close to 1T. For around 550-600kwh

I’ve decided at the moment to purchase some 21700 batteries in small quantitys and test the capacities.

Build is an Austral Tour-Master and will most likely see an Axial Radial Flux motor from Emerax producing 400kw peak and 500nm torque mated to the original gearbox.
Solar will be a fold out system comprising of triple the roof space and coming close to 20kwh on the rooftop.
These will most end up as SunMan flexible lightweight cells.

Bms will be broken into small 12v Modules. This will let the bms system stay lightweight. Each 12v system will have an active balancer attached in conjunction with a 12v bms.

Being 12v they can then be balanced with off the shelf 12v balancers, one to the other simply. If one bms drops it will through sone fancy electronic relay wizardry, drop the contactor and protect the HV battery pack. (Custom PCB) I will design.
This being an easy way of building a full battery management system.

I will most likely build the packs in smaller 12v cells and capacity test/balance and match them to lessen cell drifting. Also making failures fare more easy to access and repair.

She is old but perfect donar vehicle, the money saved on buying a bus that needs work allows a roof rebuild, probably half the cost of the battery.

 

[Nobodybusiness]

Hi all,
I’ve been browsing for a few days and have just purchased some GEB21700 battery’s in small quantity for testing.

Firstly I ask of you if there is any decent charge/discharge cycle testers that I can purchase for a reasonable price. To be able to check capacities of cells.

I’ve considered Lifepo4 as a potential battery source, however the weight difference will be close to 1T. For around 550-600kwh

I’ve decided at the moment to purchase some 21700 batteries in small quantitys and test the capacities.

Build is an Austral Tour-Master and will most likely see an Axial Radial Flux motor from Emerax producing 400kw peak and 500nm torque mated to the original gearbox.
Solar will be a fold out system comprising of triple the roof space and coming close to 20kwh on the rooftop.
These will most end up as SunMan flexible lightweight cells.

Bms will be broken into small 12v Modules. This will let the bms system stay lightweight. Each 12v system will have an active balancer attached in conjunction with a 12v bms.

Being 12v they can then be balanced with off the shelf 12v balancers, one to the other simply. If one bms drops it will through sone fancy electronic relay wizardry, drop the contactor and protect the HV battery pack. (Custom PCB) I will design.
This being an easy way of building a full battery management system.

I will most likely build the packs in smaller 12v cells and capacity test/balance and match them to lessen cell drifting. Also making failures fare more easy to access and repair.

She is old but perfect donar vehicle, the money saved on buying a bus that needs work allows a roof rebuild, probably half the cost of the battery.

Dang, That is a huge undertaking.

I wish you luck and send pictures when finished!!

 

[SolarRich]

What's the projected cost to do this?

 

[Batvette]

Go big or go home just got bigger.

 

[kromc5]

This will be very interesting to follow, battery size seems great and is not to far from from the tesla semi. I have been research premade geb based packs for atv/utv conversion for awhile.

 

[yabert]

the weight difference will be close to 1T. For around 550-600kwh

I did many EV conversion since 2009 and it's my full time job now. My advice: Don't mess a single second with cells of any chemistry. Start a complex conversion by building a huge battery from cells is the better way to never finish this conversion or/and have an unreliable conversion.

The best way to do this IMHO: Use the knowledge of thousands of engineers by reusing EV parts coming from crash cars.
By example, reuse battery modules coming from Tesla model 3 long range will save you an insane amount of time and you will start with quality cells.

 

[Lt.Dan]

Yeah I'm not too sure on using thousands of smaller cells, rather than maybe a hundred (or two) of larger prismatic cells.

More cells = more work in a LOT of ways.

Preexisting packs like mentioned above do take a lot of work off your plate, but could cost more.

 

[400bird]

Bms will be broken into small 12v Modules. This will let the bms system stay lightweight. Each 12v system will have an active balancer attached in conjunction with a 12v bms.

Being 12v they can then be balanced with off the shelf 12v balancers, one to the other simply. If one bms drops it will through sone fancy electronic relay wizardry, drop the contactor and protect the HV battery pack. (Custom PCB) I will design.
This being an easy way of building a full battery management system.

I will most likely build the packs in smaller 12v cells and capacity test/balance and match them to lessen cell drifting. Also making failures fare more easy to access and repair.

I love the bus conversion plan! I hope you have deep pockets and a full wallet, because otherwise this project won't go far.

But, your plan on the multiple 12v battery thing is a terrible idea. You are introducing so many more failure points. Also, I don't think I've ever seen a 12v BMS rated to be in a 400+ volt series.

I think you'd be better off paralleling 5 full EV packs to get to your desired kWh capacity.

 

[400bird]

Here's a forum dedicated to DIY electric conversions. They can be very direct/harsh on any poor plans.
They will crap all over the 12v battery plan, possibly other portions too.

DIY Electric Car Forums

A forum community dedicated to DIY electric car owners and enthusiasts. Come join the discussion about electric vehicle conversions, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!

www.diyelectriccar.com

 

[xjaw4]

Imagine charging an electric vehicle at a campground using a 50 amp 240V outlet.
50 AMPS * 240V = 12,000 watts assuming a power factor of 1.

1 gallon of diesel = 138,700 BTU

1 kwh = 3412 BTU

So 1 hr of charging at 50 amps x 240 = 40945 BTU or 40945 /138700 the same energy as 0.29 gallons of diesel.

If your outlet can only supply 12KW it would take about 50 hrs to pull 600 KWH worth of energy.

A 600 KWH of battery capacity would be the same energy as 14.76 gallons of diesel.

To be fair any engine can only convert a % of the chemical energy of the fuel into useful mechanical power, the remainder is heat, some % of which could be usable for cabin heat and heating water for showers etc. This is one of the reasons why electric vehicle range drops more rapidly in cold weather than a fuel powered vehicle.

A 5 passenger electric vehicle might use .340 KWH per mile or 1160 BTU
You might have to burn 3 times as many BTU of diesel fuel to get that same amount of mechanical power. That would translate to a vehicle getting 35 MPG.

A diesel semi truck sized vehicle might get 6 - 10 MPG

How many kwh per mile it would use and how quickly a battery pack would be depleted are left as an exercise to the reader.

 

[Lt.Dan]

I would estimate it being in the 1.5-2kWh per mile range considering the size/weight of the vehicle. Best case scenarios for small compact electric vehicles are near the .180-.200kWh per mile.

But even if you drove to your campground and stayed there for 2-3 days, charging the entire time, then who cares how long it takes? You get to charge for free (most of the time), and in 48 hrs, you could add 480kWh, if charging at a more reasonable 10kW. Add in solar charging on top of that, etc. Its kind of viable actually

 

[740GLE]

I would estimate it being in the 1.5-2kWh per mile range considering the size/weight of the vehicle. Best case scenarios for small compact electric vehicles are near the .180-.200kWh per mile.

But even if you drove to your campground and stayed there for 2-3 days, charging the entire time, then who cares how long it takes? You get to charge for free (most of the time), and in 48 hrs, you could add 480kWh, if charging at a more reasonable 10kW. Add in solar charging on top of that, etc. Its kind of viable actually

The camp ground will care ?

Just cause it’s rated at 50a doesn't mean their set up is designed for 100% duty cycle.

 

[Lt.Dan]

The camp ground will care ?

Just cause it’s rated at 50a doesn't mean their set up is designed for 100% duty cycle.

Hence the more reasonable 10kw (~41amp).

Hell even if you pull 30-35a, thats still a considerable amount of energy over 2-3 days.

 

[OffGridForGood]

A 600 KWH of battery capacity would be the same energy as 14.76 gallons of diesel.

Lets consider:
600kWh is 4.58 x the F150 131kWh pack. so we will compare to 14.76 gallons/ 4.58 = 3.22 gallons.
A 131kWh F150 Lighting has 300 miles range.
A diesel F150 3.0L powerstroke using 3.22 gallons (the same energy content) has a range of 97 miles.
ICE are very low energy efficiency (typically in the 30% range) , while electrical motors are extremely high energy efficiency (typically in the 92% range). That said,
You can add 3.22 gallons of fuel to a tank a lot faster than you can add 131kWh to a battey pack.

 

[Nobodybusiness]

Lets consider:
600kWh is 4.58 x the F150 131kWh pack. so we will compare to 14.76 gallons/ 4.58 = 3.22 gallons.
A 131kWh F150 Lighting has 300 miles range.
A diesel F150 3.0L powerstroke using 3.22 gallons (the same energy content) has a range of 97 miles.
ICE are very low energy efficiency (typically in the 30% range) , while electrical motors are extremely high energy efficiency (typically in the 92% range). That said,
You can add 3.22 gallons of fuel to a tank a lot faster than you can add 131kWh to a battey pack.

I guess you could run a Hybrid bus?
Maybe keep fuel tank and run a 4 cylinder diesel directly connected to generator?
Like an locomotive.

It makes my brain itch trying to figure out how to power that monstrous bus.

 

[OffGridForGood]

But a hybrid solution feels like we quit before we even tried to solve this puzzle.
The first thing to consider is the doner-vechicle: in conversions they list out all the light-weight cars ever made and use these as the starting point.
The bus is not a light weight doner, and I feel we have already hooped ourselves by choosing this as the starting point. It is too heavy.
We should start with a pickup, and modify it into a coach. Keep the weight down to what is really needed. I am thinking something in the size of an F-450 maybe a good starting point.

 

[toms]

There were a few projects in Australia (not sure if any are still operating) making electric busses. They used large LiFePO4 cells for their batteries.

Do a bit of google research on AVASS electric bus manufacturer.

 

[400bird]

You realize the OP was a one post and gone type of member?

The bus is not a light weight doner, and I feel we have already hooped ourselves by choosing this as the starting point. It is too heavy.

I've got it!
Fill the tires with hydrogen! That will save some weight. I wonder if you could fill the cabin with some helium too. Replace the nitrogen with helium, leave the 21% oxygen and have 78% helium. I'm sure that will help ?

 

[Nobodybusiness]

You realize the OP was a one post and gone type of member?

Sure seems like it.

I was like dang dude you picked one hell of a goal there.

It would take a lifetime just to built the cells out of 21700s.

More power to him but it’s way beyond my scope.

 

[OffGridForGood]

There were a few projects in Australia (not sure if any are still operating) making electric busses. They used large LiFePO4 cells for their batteries.

Do a bit of google research on AVASS electric bus manufacturer.

Sure, and there are lots of electric busses in China as well.
A city bus needs to be able to carry all those passengers, and needs a heavy frame/chasis. The OP is doing a conversion of a hwy bus to a coach for personal use/travel/camping and it likely doesn't need the same heavy undercarridge of the original purpose. It would be a lot more efficient if they start with a lighter undercarridge, and build what they need, using a lot fewer batteries (less costly).
Looking back at Ford, first they developed a lighter weight truck frame and aluminum body panels, then they applied the EV technology to this lighter starting point.
Could a personal travel camper be built from a hwy bus, sure, but it seems like it will be fantastically expensive. Even a schoolie seems like an easier starting point.

One post and gone? Maybe we will see him on the DIY Electric Car Forum?

 

[Tecnodave]

BYD produces electric transit busses in Lancaster California, USA , up to 60 feet articulated powered by LFP cells
Used in over 50 cities and transit agencies in America and Canada

First bus ever to pass NTSB requirements at 1st pass!

 

[OffGridForGood]

BYD produces electric transit busses in Lancaster California, USA , up to 60 feet articulated powered by LFP cells
Used in over 50 cities and transit agencies in America and Canada

First bus ever to pass NTSB requirements at 1st pass!

Sure, and they are now making Tesla Semis too, and I am sure the electric transit bus is pretty pricy for that 60-foot articulated version. We know all that, and it (still) misses the point: The OP is not trying to run a new transit line, carrying 50 passengers at a time. The post is about building a camping travelling personal-use vechicle from a hwy bus. From the website for Grey Hound, the flagship buses start at just over 18 Tons curb weight. A typical Schoolie (I am told) is about 12.5 tons, and from Ford, the F450 curb weight is 8600lbs (about 4.3 Tons)
I am sure, if one wanted to, and had unlimited budget, they could convert a Cat 797 Rock truck to EV, the point was, if the goal is to build an EV motor-home it may be best/economic to start with a lighter doner.

 

[Tecnodave]

Sure, and they are now making Tesla Semis too, and I am sure the electric transit bus is pretty pricy for that 60-foot articulated version. We know all that, and it (still) misses the point: The OP is not trying to run a new transit line, carrying 50 passengers at a time. The post is about building a camping travelling personal-use vechicle from a hwy bus. From the website for Grey Hound, the flagship buses start at just over 18 Tons curb weight. A typical Schoolie (I am told) is about 12.5 tons, and from Ford, the F450 curb weight is 8600lbs (about 4.3 Tons)
I am sure, if one wanted to, and had unlimited budget, they could convert a Cat 797 Rock truck to EV, the point was, if the goal is to build an EV motor-home it may be best/economic to start with a lighter doner.

I think that my point was that they use LFP......not Lithium ion.....for safety!
Also Gillig and Crown use only LFP in their busses

Looking further you will find that all the tugger trucks at the ports of Los Angeles, Long Beach , and Oakland are electric and all that I have looked at are LFP, Deisel powered tuggers are no longer legal under California law.
Tugger trucks are those that move shipping containers within the ports. The cross country trucks can no longer enter the ports, They transfer containers external to the ports

In my opinion the NMC battery packs are way too complex for such a large vehicle, the Tesla fire bombs are a perfect example of that. I am experimenting with an electric bike conversion and it does have 18650 and 20700 NMC power packs but no way in hell am I going to keep that inside my house or garage. The battery packs are removable easily and are stored in a safe spot, far from my safe spot....

 

[AkivaAld]

What's the projected cost to do this?

So far projected costings (quoted) 400kw/1000nm torque, motor + controller combo is $33,000 Aud (weight 65kg)
400kwh of 21700 cells at $0.80c Usd is around $25933 Aud + shipping and import tax (1.1T aprox weight)
Bms/balance is expected at $2000 Aud possibly double if I split it into 2 batteries.
still need to consider 3d printing houses, Alloy bus bars ect.
Nickel strip Cell fused 21700 at $65 usd per kg (need to figure out how much required) auto cad drawings plus copper for collectors.
25kw of solar for the roof around $6000 aud for the wafers (I am building custom panels and covering with ETFE coating) to maximise the space.
Air actuators and relays around $1000
Alloy for the roof (imported by me) around $1500 aud
CanBus dash, fully Solid state relay box, Data acquisition units for wiring + components at around $5000 Aud
900v input Mppt solar Dc/Dc 750v buck stepdown bi directional 20kw Also AC/DC converter. $2000 Aud

Its at $76,433 Aud right now.

Will also need Engineering cost, about to start the process of that when I am home.
Also bellhousing adaptor to the new electric motor.

There is a company here that offer a swap for $160,000 Aud with no battery....


If I went with Lifepo4 batteries at $114USD each 304 that would equate to 411Cells@$114USD=$46854USD
$70281AUD without shipping (@2.178T of weight) not quite fair compared to just the cells of the 21700 but I know the packs will be a lot lighter.

 

[AkivaAld]

I love the bus conversion plan! I hope you have deep pockets and a full wallet, because otherwise this project won't go far.

But, your plan on the multiple 12v battery thing is a terrible idea. You are introducing so many more failure points. Also, I don't think I've ever seen a 12v BMS rated to be in a 400+ volt series.

I think you'd be better off paralleling 5 full EV packs to get to your desired kWh capacity.

Ahh they won't be a bms between the 12v modules, a 10 amp balancer will be installed. If the voltages of one of the bms on the 12v modules is out it will pull the contractors for charge and discharge. All the modules will be tested matched (parallel) before building the string. Smaller modules will be able to balance the whole easier.

Each 12v module will come out to a bus bar then the next will come off of that (maintenance) problem diagnostics. Final setup will be tuned as it becomes closer to being a reality. (+ once its drawn in fusion 360)