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Hey guys
Looking at building a drag car using a awd setup. was thinking of two hsr tesla units running 400volts. the problem I have is getting batterys. could anyone send me in the right direction. Was thinking three gm volt batterys but im open to ideas.
Thanks Matt
 

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There are a few good options, basically your looking a 96S either pouch or cylinders. There are some great options out there, the pouch cells have a much higher discharge rate so I'd go that route. Most will discharge at 20C so the 45Ah will make 450A. The volt battery is good as it has proven it can discharge at that rate and the liquid cooling helps disperse heat. However drag racing it will make little difference. Using 2 packs will give you 1600A for the duration but at a weight penalty of 400lbs per pack. Still 400lbs less than a 85kw tesla pack. The EV west pacifica modules of 16S will drop 800A apparently, each module is 40lbs, 6 modules will give you 96S so 240lbs gives you the equivalent of the Volt pack. running them in 2P will hit the 1600A at the correct voltage and still only be 480lbs, and would be easy to distribute around the car, thats the route I'm heading down. If something else comes out in the mean time I'll have a new power wall.
 

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Re - 400 lbs for a volt pack - a lot of that is the armoured base piece - I didn't weigh mine but I could pick up each half - so 300 lbs is more like it
 

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I believe thats also dry and not including the water pump and coolant. Out of interest how much fluid is required for 2 volt packs with what I assume a radiator and reservoir also. I really wanted to go that route but the reality is when I use it on the street it will be just to get somewhere and in anger it will be for a short period. I also think the Bolt cells to be an improvement yet again on the 2nd gen volt modules but I don't know if the discharge rate for the Bolt is close to the well documented Volt cells.
The Pacifica modules are available from a seller here, and an ebay seller that will do 12 modules for about $300 a module. You don't state where you are but if shipping to somewhere is involved then the modules will be easier than a volt pack unless you have a scrapped Volt in the area near you. Most people who have to Volt batteries have also had to fabricate a complex way to locate and secure them after they are broken down and reconfigured to fit into available spaces. I am from a motorsports background and weight and simplicity always trump for me. If I was planning on going on car nights or was going to use the vehicle for anything other than drag racing I would want an active cooling/heating management. A long time ago I had to decide if I wanted a road car I race or a race car, If I'm going to be doing 1/4 mile at a time I don't need a battery to perform for 30 miles, 30 minutes or 30 seconds.
If your thinking of driving to the strip/shops/work then a Volt/Bolt battery may well be a better choice.
 

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Volt Battery

Coolant adds maybe two pounds to the weight
I just circulate the coolant between the batteries and the controller - cools the controller and warms the batteries

The armoured base includes that attachment rails - just drill out the spot welds and bingo a flexible attachment system that weighs about 5 pounds

The picture shows me getting the air out of the coolant system - you can see the clamp rails and the 20 mm square tube I welded them to
The straps are just to keep the assembly on the sack barrow
 

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Pleasantly surprising theres only about a litre of coolant in in the battery pack, makes me wonder exactly how efficient the coolant actually is. Do you have inlet and return temps or just using the thermistor built into the pack? I had written a can protocol using my davis craig waterpump to run off the original BS readings but as previously mentioned I only need to monitor the temperature, I wont have enough time to do much about it other than shut down so I decided it was adding complexity to a system that for a drag car didn't warrant it.
 

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I also think the Bolt cells to be an improvement yet again on the 2nd gen volt modules but I don't know if the discharge rate for the Bolt is close to the well documented Volt cells.
A Volt pack only has 18 kWh nominal capacity but needs to put out enough power to run the car for useful period (GM specs 120 kW for 10 s for the second gen), typical of a plug-n hybrid. As a battery-only EV, the Bolt has more than three times the capacity (60 kWh) at the same voltage but only needs to supply enough power for a 149 kW (peak) motor. For any given total mass of battery, the Volt cells may be capable of producing more power, and the Volt cooling system is likely more capable of keeping up with the required heat removal rate and maintaining even cell temperatures.
 

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But the Bolt is also a water-cooled system with more emphasis of cooling the modules, if you used the top module base you could place modules with less disruption to coolants. its still a 96S3p with each cell 55Ah, thats over 3 times the capacity of the gen 1 volt configuration. Again I am still looking for discharge ratings, but if the cells can take the same discharge rate as the Volt seems to be able to do 15-20C they are certainly in contention. The 2nd Gen Volt cells i believe were 27Ah cells. Again nothing is free as the weight of the Bolt pack is 960lbs potentially if able to support the same 20C rates will be reaching a staggering 3000A for 10 seconds. Remembering this is a drag car, I'm not looking at longevity or ability to autocross, just potential discharge rates, I have the spec sheets for most cells but theres not a lot out there on the new Bolt cells If they only discharge at 5C then they are of little use to a drag racer
 

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Discussion Starter #12
Thanks everyone for the great info.
The next thing is yes weight. The car we are using i can get to about 1000kg but thats dry and i say after motors and battery i would add the 500kg back in. So what would be the batterys to use and running to motors at 400volt with 800amp in both for 10 sec how much if enough? can we run more cells to add more rang to get a few test runs in?
 

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But the Bolt is also a water-cooled system with more emphasis of cooling the modules...
I'm not sure what that means. The Bolt has a simpler, more compact, and less effective "cold plate" system, compared to the Volt's system which circulates coolant through a "fin" between each pair of cell layers. This is why I would expect the Volt cooling to be more effective at a higher power density.

its still a 96S3p with each cell 55Ah, thats over 3 times the capacity of the gen 1 volt configuration.
  • Volt Gen 1: 96s3p with approx 15 Ah cells (196 kg, 87 Wh/kg) - three packs would be 48 kWh / 330 kW and 588 kg
  • Volt Gen 2: 96s2p with approx 26 Ah cells (183 kg, 101 Wh/kg) - three packs would be 55 kWh / 360 kW and 549 kg
  • Bolt: 96s3p with approx 56 Ah cells (436 kg, 138 Wh/kg) - one pack is 60 kWh / 175 kW and 436 kg
Capacities are nominal. Volt specs from GM. Volt power as rated by GM for 10 seconds; Bolt power is based on motor output power and 85% efficiency, probably good for extended period (so a 10 second rating would likely be higher).

Compared to the Volt Gen 1, the Bolt has over three times the capacity with the same number of cells, because the cells are larger (and possibly more advanced), with over three times the individual cell capacity.
Compared to the Volt Gen 2, the Bolt has over three times the capacity due to 50% more cells and double the cell capacity, because the cells are larger (and possibly more advanced).
In either case, larger cells does not imply a higher tolerable discharge rate in proportion to capacity ("C" rate).

Again I am still looking for discharge ratings, but if the cells can take the same discharge rate as the Volt seems to be able to do 15-20C they are certainly in contention.
But there's no reason to count on the Bolt cells withstanding the same discharge rate (in "C" terms), both because of the cooling difference, and because of the intended application. The Bolt cells might have the same discharge rate performance as the Volt Gen 2 cells, or even better, but they might not.

Again nothing is free as the weight of the Bolt pack is 960lbs potentially if able to support the same 20C rates will be reaching a staggering 3000A for 10 seconds.
The capacity per unit mass is better with the Bolt pack, and some of that will be due to more advanced cell design (especially compared to the Volt Gen1), but some will be due to leaner cooling and packaging.


If it is necessary to go for as large a pack as three complete Volt packs or one Bolt pack, then the Volt Gen 2 would likely handle the most power, but the Bolt would be lightest, and if it is only limited by cooling that limit might not matter for the brief demand of a drag race.

The Bolt modules are a tidier shape, but require a separate cold plate for thermal management, while the Volt modules include the cooling system internally.

A practical consideration is that Volt packs are reasonably available as salvage, but salvage packs from the newer Bolt seem relatively unavailable. New complete Bolt batteries can be purchased, but they're about US$16K list and US$13K retail.


All of these alternatives are 360 volt (nominal). If 400 volts is desired, more modules would be required in series.
 

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Again I am still looking for discharge ratings, but if the cells can take the same discharge rate as the Volt seems to be able to do 15-20C they are certainly in contention.
Here a 15C discharge test done in 2014 with my gen 1 Volt battery: https://www.diyelectriccar.com/forums/showthread.php/power-capability-chevy-volt-battery-109698.html

I think the Volt battery is your best low cost/used OEM choice because the Bolt battery are high energy/low power cells (like Tesla battery).
 

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Where are you getting the Bolt cells spec sheet, I have not been able to find anything on the cells. Obviously you cant post it here but if you could PM me the sheet that would be great to have them with the Volt data sheets.

I know they worked on a formula for the Bolt to withstand a lot hotter temperatures but I would still like to see data on the cooling ability of 1 litre of water on 300lbs of lithium discharging at 20C for 10 seconds.

I'm assuming the 400V came from the publicized voltage of the Tesla pack when it would be easier for clarification stating nominal cell voltage and how many cells in series. The industry standard seems to be settling on a 96S pack.

Ive seen one bolt Battery for $8000 Canadian and missed it by 6 hours because I emailed rather than phoned the wrecking yard. I have yet to see Gen 2 volt packs go for less than $3000 US, I believe the price is being held higher as they are so versatile and proven to take a lot of abuse. If I were going that route I would also make provisions to rotate the battery into a domestic power system when it starts to deplete as there is bound to be something better in a few years to replace it with (hoping solid state makes a big leap forward and Graphene doesn't become the modern day asbestos). Only 5 years ago we were ripping Leaf packs apart to power e-bikes, they are old news already.

But the real question is, as capable as the volt pack is, would you recommend it for a drag race application, or put another way is there something better for this particular application. Lonestar is another option however you have to submit them your engineering degree if you want to buy from them so they may or may-not also be a viable option of you want cells that will discharge at 100C I like the idea of balancing my race car for optimum performance rather then just cramming whats available into the space thats available.

To give a better answer the the original question would be what kind of space, what kind of motor and what kind of ability to charge at the track.
 

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The question I always come back to asking is what is your budget for this thing? It sounds like you are starting with a vehicle already.. If you are using a Tesla large drive unit, you are looking at $7-8k/piece to get that and have it be functional. For an 8s pass in my opinion you could get by with two 1st gen chevy volt packs. They will handle nearly 1000A for around 10S before they get unhappy, you should see 800hp from two drive units and two Volt packs easily. They can be found for $1200-1500. I think a person would be better off focusing on weight reduction or fabbing a custom chassis and using a single large rear drive unit. Just my Opinion!
 

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  • ...
  • Bolt: 96s3p with approx 56 Ah cells (436 kg, 138 Wh/kg) - one pack is 60 kWh / 175 kW and 436 kg
Where are you getting the Bolt cells spec sheet, I have not been able to find anything on the cells.
The 96s3p configuration and cooling configuration are from multiple published articles.
The motor power is from all GM specs for the Bolt (including the Chevrolet website's model listing).
I calculated the 56 Ah capacity from the nominal energy capacity and number of cells.
The weight is just converted to kilograms from the weight in pounds posted earlier.
Energy density is calculated from that weight and the nominal capacity.

I haven't seen specifications for the Bolt comparable in detail to the Volt specifications published by GM.
 

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Looking at building a drag car using a awd setup. was thinking of two hsr tesla units running 400volts...
I think a person would be better off focusing on weight reduction or fabbing a custom chassis and using a single large rear drive unit.
While drag racing is normally a RWD exercise, I can only guess that the AWD configuration has been chosen for traction, or for total power... and that implies that the goal is higher acceleration than can be reasonably accomplished with the traction of only the rear wheels, or with the power of a Tesla large rear drive unit. Either way, that's quick - what's the goal?

I realize that the thread's question is about battery, but the performance goal determines the power requirement, which in turn determines the battery current requirement.
 

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The industry standard seems to be settling on a 96S pack.
Yes, but as 96S has become almost standard, larger-capacity EVs are being announced with slightly higher nominal voltage. Both the Audi e-tron and Jaguar I-Pace appear to use 108S 4P packs. Although none of the coming Porsche products are out yet, there seems to be lot of talk of higher-voltage charging (800 V?) and there's no point in that unless the pack voltage is that high... it will be interesting to see.
 
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