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?