[JoeE13]

I am still trying to figure out components and my car is space challenged. It looks like a Hyper 9 motor will be the power, I have read that I may need up to 5 18650's. This is not even a weekend driver it is a race vehicle with a VW transaxle. I need as much torque and rpms as I can get for six (6) 90 second runs in an event and some slow driving to and from actual course. Car will be turned off for about 10 minutes between each run. Can I get by with 3 or 4 ? I could stack 5 if necessary.

 

[john61ct]

Do you know what "a 18650" is?

Tesla has several different pack types now.

I would get a lot more than you think you need, and then see if taking any away makes you go faster by lightening the weight.

 

[JoeE13]

Do you know what "a 18650" is?

Tesla has several different pack types now.

I would get a lot more than you think you need, and then see if taking any away makes you go faster by lightening the weight.

Yes I am aware and they will fit in my car. At $1,500 a piece buying too many isn't an option.
Tesla Model S Lithium Ion Battery 18650 EV Module - 22.8 Volt, 5.3 kWh, EV West - Electric Vehicle Parts, Components, EVSE Charging Stations, Electric Car Conversion Kits

I guess what I am asking is how do I research the relationship of battery type and specs to motor performance both spreed and duration. And from what I have read EV West is not the best supplier but, their web site links a lot of the needed parts together for what required components go together..

 

[Duncan]

A Hyper 9 is expensive and wimpy - NOT what I would want in a race car

 

[JoeE13]

What would you recommend I look at in a 9" motor? I plan on using my driveline transaxle for now it will work they are easy to get gears swapped out. Was is ur 0 to 60 or 100Km time?

 

[Duncan]

I would recommend finding the guys who repair forklifts and visiting with a crate of beer and some folding money

I've got a spare 9 inch I got "just in case" - it cos $100NZ - about 50 quid
If you get desperate I could ship it to you but the shipping costs will be a lot more than that

There is a long thread in the motors section about choosing a forklift motor - worth a quick skim

Acceleration times
A Tesla Model 3 performance is about 0.4 seconds faster than I am to the 1/8th
And they are 3.2 seconds to 60
So I think I am just below 4 seconds to 60

 

[Isaac97]

Definitely take a DC motor over the Hyper 9.
With a Zilla or Soliton it will beat the crap out of most AC motors at low revs. RPMs need to stay lower - see this thread How to get the most out of a Warp9 or M102 motor?
A beat up forklift motor might not be too happy at the highest speeds - @Duncan, how high do you rev? Probably 6000 or so?

Also you'll want to run 144-180V for sufficient power. Tesla modules are not great for that -- lots of amp hours (so long range) but low voltage. Maybe a Chevy Volt pack, split and paralleled, or just half a Volt pack (8Kwh, might not be enough capacity).

-Isaac

 

[Duncan]

Hi Isaac97
I have an 11 inch Hitachi motor - the highest I have taken it is about 5400 rpm - which is 96 mph
Our motor guru - Major - thinks I should be good for 6500 rpm - maybe

You need LOTS of volts to push decent current through a DC motor at high rpms

I'm using most of a Volt pack - 14 kwh - 300v empty 340 volt full
And even with that my controller is maxed out (100%) before the end of the 1/8th mile and the current is dropping

I don't know by how much as my instruments all throw a wobbler at full power (1200 amps) - and I'm too busy hanging on and being afraid to spare any attention

On the road 150 volts is fine
For playing silly buggers on the track you need more

A 9 inch motor may not be as bad but IMHO there are no disadvantages in going as high as you can
The P&S IGBT controller I have is meant to be good for 400 volts

Don't worry about the motor - you can't overvolt a motor - just overcurrent and over rev

 

[dhanushx012]

I plan on using my driveline transaxle for now it will work they are easy to get gears swapped out. Was is ur 0 to 60 or 100Km time?

 

[JoeE13]

Hi Isaac97

You need LOTS of volts to push decent current through a DC motor at high rpms

I'm using most of a Volt pack - 14 kwh - 300v empty 340 volt full
And even with that my controller is maxed out (100%) before the end of the 1/8th mile and the current is dropping


Don't worry about the motor - you can't overvolt a motor - just overcurrent and over rev

I found this for Chevy Volt is this what you are using?

 

[Duncan]

There is a long thread on the Volt battery

2012 Chevy Volt Battery:

Paid $2000 + $150 shipping from a junkyard. It is a work of art. I'll be sad to tear it apart for the cells, but that's life. I'm getting 373 vdc for the battery, and 3.88 vdc per cell. IF there are 288 cells. Already things aren't making sense. I count 72 modules about 1" thick...

www.diyelectriccar.com

The Volt is interesting as it is a hybrid - which means a smaller battery - which means that the battery is designed to produce more power/size

A battery EV (Tesla) has a large battery for the range - which means that the battery is not as highly stressed even with the Tesla power output
A Hybrid has a short range - a smaller battery - so it needs to put out more power compared to its size

The Volt was their first go at the market - I suspect it was also a bit over designed in the battery cooling area - the replacement the Bolt has a much less impressive cooling system

 

[Ladogaboy]

There is a long thread on the Volt battery

2012 Chevy Volt Battery:

Paid $2000 + $150 shipping from a junkyard. It is a work of art. I'll be sad to tear it apart for the cells, but that's life. I'm getting 373 vdc for the battery, and 3.88 vdc per cell. IF there are 288 cells. Already things aren't making sense. I count 72 modules about 1" thick...

www.diyelectriccar.com

The Volt is interesting as it is a hybrid - which means a smaller battery - which means that the battery is designed to produce more power/size

A battery EV (Tesla) has a large battery for the range - which means that the battery is not as highly stressed even with the Tesla power output
A Hybrid has a short range - a smaller battery - so it needs to put out more power compared to its size

The Volt was their first go at the market - I suspect it was also a bit over designed in the battery cooling area - the replacement the Bolt has a much less impressive cooling system

The Gen 1 Volt's battery cooling system definitely was overdone. The Gen 2 Volt has half as many cooling plates, IIRC. Still though, for the OP's purposes, Volt batteries would be far better than the Tesla 18650 cells, which are more prone to voltage sag. I'm not sure what exactly the Volt cells are rated for in terms of discharge, but it's at least 7 C.

Sasha Anis was able to produce over 400 kW using two Chevy Volt battery packs (32 kWh): Blue Lightning | Mountain Pass Performance

 

[Hollie Maea]

Personally, I would wait until you have at least designed the rest of your system, preferably until you are well into your build before buying batteries. Three reasons:

1. Batteries are a rapidly evolving sector, much more than other components. What is a great option today might not be considered very good in a few years. Not long ago, everyone on here swore by CALBs. Now no one uses them.

2. If you change your mind on what motor/controller you are going to use, this could effect your battery choice due to different voltage requirements.

3. Batteries don't really like to sit around. Even if you choose, say, Volt batteries today and don't ever change your mind, it's better to buy ones that are fresh rather than putting in ones that have sat around in your garage for a few years. Decent chance they'll be cheaper then too.

 

[brian_]

The Gen 1 Volt's battery cooling system definitely was overdone. The Gen 2 Volt has half as many cooling plates, IIRC.

Both generations have the same design: a cooling fin every two pouch cells, so every cell has one cooled face. The second generation is a 2P configuration, so it has two-thirds as many cells and two-thirds as many cooling fins as the 3P first generation.

 

[brian_]

Joe, I assume that John asked if you knew what "18650" meant because it looked like you didn't... and apparently you don't. That's okay - we can fix that.

"18560" is industry terminology for a single cylindrical call which is 18 mm in diameter and 65.0 mm long. What you linked at EV West is a Tesla Model S/X module which incorporates many 18650 cells, with groups of dozens of cells in parallel and six of those groups in series. Other modules built with 18650 cells have different configurations.

The voltage you need to operate your chosen motor properly does determine how many cells in series you need. Those Tesla modules have 6 cell groups in series (6S) so given their chemistry they have a nominal operating voltage of 22.5 V. So, five modules in series would give you about 113 volts.

 

[remy_martian]

You CAN mod the Tesla modules to double the voltage and halve the current, but it's a non-trivial mod and requires gonads you carry around in a wheelbarrow.

There's also a Tesla module used in the Smart ForTwo cars that already has double the voltage. That might work nicely as "sills" or as an "F-18-style conformal fuel tank" in your race car. At that point, you need to be concerned about crushing or puncturing the modules in an incident.

 

[Ladogaboy]

Both generations have the same design: a cooling fin every two pouch cells, so every cell has one cooled face. The second generation is a 2P configuration, so it has two-thirds as many cells and two-thirds as many cooling fins as the 3P first generation.

Ah, for some reason I thought they reduced it further (Gen 1 Volt having each side of each cell cooled), but that makes more sense.

 

[brian_]

You CAN mod the Tesla modules to double the voltage and halve the current, but it's a non-trivial mod and requires gonads you carry around in a wheelbarrow.

I agree that this modification makes sense to enable some desired configurations, but is a bold move.

There's also a Tesla module used in the Smart ForTwo cars that already has double the voltage. That might work nicely as "sills" or as an "F-18-style conformal fuel tank" in your race car. At that point, you need to be concerned about crushing or puncturing the modules in an incident.

Those might be a good fit, and I like the side pod idea (and the F-18 comparison), but those Tesla modules for the Smart are a fascinating case - the electric Smart based on Tesla components was short-lived (only the W451 model 2008-2011), with only about 2,000 cars built, yet the modules seem to be everywhere. I'm not sure if they made way too many of the modules, or Tesla/Panasonic continued production for the aftermarket after the car was out of production, or just that the same handful of modules have been offered for sale - with no one buying them - for a decade. It would make me nervous to base an entire conversion around modules which I may never be able to get another one of, although this car is more amenable to later modification than a street car body.

 

[brian_]

Personally, I would wait until you have at least designed the rest of your system, preferably until you are well into your build before buying batteries.

I like this logic.

The choice which I think needs to be made reasonably early is the approximate operating voltage, since essentially every component which has an electrical connection is affected by that. Whatever battery system is chosen, it can be configured to some extent for different voltages.

 

[Duncan]

The problem with doing the batteries LAST is that for a small car - like a race car - you need to decide what you are going to do early - so that you can fit the things nice and low down
Design the car around the batteries

One of the things I regret is going for the Lotus 7 look - I should have gone for more of a C Type Jag look with nice long WIDE sills to put the batteries in