[SpeedRacer93]

I working with a small group to build an EV land speed streamline race car. We have done a couple landspeed cars and a couple EV conversions and own factory EVs but this our first race EV.

Like most landspeed cars this is a DIY type build so budget is in play.

We are looking for different battery options.

Some of the specs are 400+ volts, 800 total AMP draw for 90 seconds.

Looking at BMW i3, Nissan Leaf, Volt, ampahaulic sleeper cells, A123 20 Ah and other pouch type cells.

We have ruled out 18650 due to the number of cells needed and RC Lipo due to the AMP load.

RC Lipo look good on paper but when you start looking at AMP loads the wiring from the pre built packs will not hold up. How can they rate a pack for 300+ Amp continuous when the connectors and wires only support spikes of 50-100 amps.

We are limited to 1000 Kg total weight so weight comes into play but we not worried so much about cycle life.

Anyone have any good ideas or suggestions?

 

[SpeedRacer93]

The ampahaulic/John Metric cells are on the list and in the running. Looks like we would need a 110s4p pack of those cells to meet the needs. Cell weight only would be 127 lbs but as stated the $12k price but that is the almost the price of a small block long block less blower/turbos.

Looks like the Volt Gen 1 or Gen 2 battery packs may be able to fit the bill if they can be pushed to 16 C for the 90 seconds. Chevy rates them at 7.8 C. Reports online show they can be pushed to 20 C but length of load test is kind of unknown.

Understand that the 400 V and 800 AMP is the max side. With most landspeed cars getting the power down is the hardest part. We plan on doing AWD/4WD setup with dual motors. Nissan Leaf, BMW i3, Tesla small drive motors are on the list using aftermarket/DIY controllers. Based on the aero numbers, we need 260kw total to reach our goal. So 130k each motor is very do able.

I know some are pushing a single Leaf motor to these levels but using dual motors simplifies the drive train. We looking at toothed/timing/blower belt drive or spur gear box. (no diff needed) We can "gear" the motor the keep it in the high torque area of the motor. Think 1.6:1 final ratio instead of the normal 8:1 EV ratio.

We could do two battery pack (2 x 400V x 400 AMP packs) but weight becomes an issue. Also a high parallel count of a single pack will help with the amp draw and voltage sag.

 

[SpeedRacer93]

Our cells are for real high power to weight ratio OR low heat build up. "Long course" land speed racing is a lot like hill climbing... long sustained high power.

We looking at doing "long course" land speed racing.

I would suggest 4P108S about 128lbs about 1.5 cubic feet.

This matches up exactly with my spreadsheet. I think I have 4P110S to make them the same voltage as other cells in the spreadsheet. This is a good sign my spreadsheet is looking good.

You guys going to have a transmission? I would be happy to sharpen the pencil.

We are thinking about trying to be first to 300mph on the Texas Mile LSR course. I have a plan.

Based on 2 mile, 3 miles, 4 miles and 5 miles calculations we will be able to meet our goals running a direct drive with a 1.5 to 1.6 final "rear end" ratios.

Give the Taxas Mile a go!!!

 

[SpeedRacer93]

Does anyone have details on the Hitachi pouch cells used in the 2016+ Chevy Malibu ECO?

Looks like the cells are 5.2 aH, 3.7 Volts, 240 Grams and 5000 W Output Density (W/kg). Looks like that would be about 1200 Watts per cell. Which would be 324.4 Amps so about 62C Max (10 seconds)?????? (I have been in the sun all day so my math may be off)

Hitachi Automotive Systems cells spec:

Item Specification
Size (mm) 120×80×12
Weight (kg) 0.24
Average Voltage (V) 3.7
Capacity (Ah) 5.2
Output Density (W/kg) 5,000
Energy Density (Wh/kg) 80

1.5kwh, 115 volt, 32 cells in total pack

https://insideevs.com/hitachi-delivers-5000-wkg-prismatic-lithium-ion-cells-chevrolet-malibu-hybrid/

http://www.hitachi.com/New/cnews/month/2015/05/150519a.pdf

I know the old round cells before 2016 does not give the old round cells good marks.

https://www.energy.gov/sites/prod/files/2014/02/f7/battery_malibu_3800_0.pdf

 

[SpeedRacer93]

We used a123 pouch cells a123 32157 ? cells volt batteries
Then we bit the bullet and got johns cells they are hands down the best
for racing light and powerful.
Dont do like i did and spend money on cells that will not work for racing
All batteries will work just some not for long ,or as good.
If i added all the money and time on all the other batteries i bought it was
less than i paid john for good ones.
RACING QUESTION = HOW FAST DO YOU WANT TO GO ??
ANSWER = HOW MUCH MONEY YOU GOT !!!!!!
Just my 2 cents

John's cells are at the top of my list but other team members want to looking at other options so we put together a list of hybrid/EV cars so I have been pulling specs on their cells and Hitachi ones jumps out.

 

[SpeedRacer93]

110 in series by 4 in parallel of these cells (for nominal 407 V and nominally 8.4 kWh) would be 106 kg and 51 litres of volume... plus wiring and packaging. 800 amps total or 200 amps per cell would be 38C. That doesn't sound bad, but it's five and half Malibu packs to find, tear down, and reassemble.

Since the Malibu Hybrid is produced by GM there are number of them available. I found 2 at local salvage yards so going to give them a call tomorrow. Based on searches the 2016+ Malibu hybrid packs are going for $500 to $1000.

We are looking at a high load battery test setup right now.