# Drag car



## Duncan (Dec 8, 2008)

Sounds like a good plan!
I got my Volt battery using - Car-Part.Com


----------



## LOSTHUNTER57 (Feb 21, 2019)

Duncan Thanks for the info


----------



## x.l.r.8 (Oct 20, 2018)

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.


----------



## LOSTHUNTER57 (Feb 21, 2019)

where would ya get them from?


----------



## Duncan (Dec 8, 2008)

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


----------



## x.l.r.8 (Oct 20, 2018)

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.


----------



## Duncan (Dec 8, 2008)

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


----------



## x.l.r.8 (Oct 20, 2018)

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.


----------



## brian_ (Feb 7, 2017)

x.l.r.8 said:


> 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.


----------



## x.l.r.8 (Oct 20, 2018)

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


----------



## LOSTHUNTER57 (Feb 21, 2019)

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?


----------



## brian_ (Feb 7, 2017)

x.l.r.8 said:


> 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.



x.l.r.8 said:


> 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).



x.l.r.8 said:


> 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.



x.l.r.8 said:


> 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.


----------



## Yabert (Feb 7, 2010)

x.l.r.8 said:


> 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).


----------



## x.l.r.8 (Oct 20, 2018)

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.


----------



## dain254 (Oct 8, 2015)

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!


----------



## brian_ (Feb 7, 2017)

brian_ said:


> ...
> Bolt: 96s3p with approx 56 Ah cells (436 kg, 138 Wh/kg) - one pack is 60 kWh / 175 kW and 436 kg





x.l.r.8 said:


> 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.


----------



## brian_ (Feb 7, 2017)

LOSTHUNTER57 said:


> Looking at building a drag car using a awd setup. was thinking of two hsr tesla units running 400volts...





dain254 said:


> 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.


----------



## brian_ (Feb 7, 2017)

x.l.r.8 said:


> 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.


----------



## John Metric (Feb 26, 2009)

Lonestar would supply:
5P96S 25AHr full power for two tesla motors, 160lbs.


----------



## x.l.r.8 (Oct 20, 2018)

brian_ said:


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


The NMC 622 cell chemistry information is available but they are using quite high SOC with relatively low discharge rates. 
If we are accepting the volt gen 2 is able to withstand 20C for short duration's with its 26Ah cells. then using a better designed cell that's used in the Bolt and I-pace with 53Ah cells it would stand to reason that the cost of a bolt pack is actually viable. 
The gen 1 volt cells alone are what 383g per cell, thats 110 kg or 245 lbs for bare cells, a 3s 45Ah brick for want of a better term is 1.146kg
The bolt cells are I believe 820g per cell is 236kg 500lbs for bare cells.
Each brick of 3s would be 159Ah and weigh 2.46kg
3 times the capacity for twice the weight. 
but you would need 2 volt packs, probably gen 2 and they are certainly not $1200, closer to $3000 us 
In a short time I am sure they will be turning up fairly soon and the one pack I have seen for $8000 Cad $6000 US will be common place

Ref for NMC 622 chemistry
http://jes.ecsdl.org/content/164/7/A1361.full
https://www.targray.com/li-ion-battery/cathode-materials/nmc

The cycle life at modest discharge rates 7-10C is amazing, at 20C not so much (86% after 500 cycles), even worse will be the next generation 811, they look to be the cell of choice for the 2020 roadster but again they are going to be super controlled because of the effect of high discharge rates and high cost. 
For now the NMC 622 chemistry (in what ever packet it comes in) seems to be the potion of choice for DIYers to be able to buy freely. Its just a case of working out what you need and buying the cells that fit your application. 
Don't forget to think about charging because just as volatile (maybe even more so) is the danger of charging heated cells, their potential energy will be huge on a fresh charge compared to a depleted pack. I spent as much on the hacked 18kw charger and Tesla master/slave BMS to ensure the pack is not going to be more of a time bomb than it potentially is, especially as cells weaken and internal resistances go up, these choices are probably as important as what battery you are going to use. 

That's just my opinion, there are higher output cell available for much less weight but they would be a lot harder to buy for a DIY build


----------



## rcoffin (Feb 23, 2010)

Matt,
Actually using a road car battery for a drag car is a terrible solution. 
I'll explain:
First, what is a road car battery designed for? One thing: range
Second, what do you want in a drag race battery? Two things: High discharge rate and light weight.

Since road car manufacturers are shooting for range, the only way they get a lot of current for rapid acceleration is to use far to many cells than you need for a drag race. This make it overly heavy. What you want is a battery that can develop that current for a short period of time. With the right kind of cells this can be done with a battery that's less than 1/4 the weight of a road car battery. You can't get a battery designed for a race car from GM, Tesla, Toyota, etc. or out of a recycler.

I build affordable race car batteries and can build you the battery you need. I just have to know how much current you want and at what voltage to give you an estimate of the weight and volume.


----------



## x.l.r.8 (Oct 20, 2018)

Wow! Opinion or sales pitch?


----------



## rcoffin (Feb 23, 2010)

For the past 18 months I've been developing high discharge rate batteries for motorsports applications. The reason for this is simple: I have an application and there were no good solutions for it, so I developed my own. There are good battery cells available, but suitable packaging that can handle the high discharge currents and the physical demands of motorsports was lacking. 

What I am making are modular parallel packs that can utilize any 26650 cell. For motorsport, we like the LiFePo4 chemistry because it's rugged. The packs are intended to be used in an array by way of an innovative mounting arrangement to accommodate building batteries with whatever current or voltage is desired. For safety, fusible buss bars provide the interconnection between packs. There are no welded nickel strips between cells in each module, thus the cells can be replaced when their life cycle has been expended. The desired discharge rate and Ah capacity (or kWh) dictates the C rating and storage capacity of the specific cell to be used. 

We are a couple of months away from production. At the moment, all components are machined from solid materials, but that's why prototyping something as complex as this is such a big commitment. Soon our injection mold tooling will be built (another big commitment) and piece prices will drop dramatically. At that point, patents will be filed, a web site will be put up and pricing will be established.


----------



## x.l.r.8 (Oct 20, 2018)

so something like the a123 that has a 48C discharge rate would require 13p96s . 360v 1500Amps 80g per cell is only 100 kg or 220lbs which is pretty damn good. There may be a lot better cells out there as its been many years since I looked at that format but 1248 cells at a conservative $10 a piece is $12,500 I don't know if you get one hell of a discount of even %50 but its still over $6000 for the cells alone. Is this the kind of figures you are talking about, i know once I get mine up and running the packs will have their limitations and at some point I will be looking for more power and light weight but I have to prove the car first. I may be eligible for the lone star cells by then but if your in the same bracket its a thought. What kind of cycle rates do you think you would achieve at 48C? I would think around 500 maybe if allowed to cool between runs and charging. I would like to know more about your format and pricing and cell spec.


----------



## rcoffin (Feb 23, 2010)

Thanks for your reply x.l.r. 8. You are slightly off about the cell count and calculated mass since LiFePo4 cells are a nominal 3.3V. For 360V (and to have a bit of "headroom") I suggest a 15P110S configuration which would require 1650 cells. The mass per cell is ~ 85G so we are looking at about 140 kg (355lb) for the cell mass and about 90 lb for the packaging. As far as cell cost, buying direct from A123 would be an expensive proposition. Nearly all the cells are made in China and the suppliers I have vetted can provide equivalent cells in the $2-5 ea. (my bulk cost) range. Of course, right now the import duties have driven the cost up a bit, but I expect that to change in the long term.

We are talking about a bespoke motorsports qualified battery here, not some re-purposed power source designed for a commuter appliance. As far as cycle life is concerned, it is a very robust cell. If you stay within the manufacturers discharge (and charge) specification they will meet their published specs. That said, it's entirely dependent on how much abuse you put the equipment through. That's why I suggest some extra cells for "headroom". Let's not forget, it's racing... the purpose is to win, not finish last for a very long time. 

As the saying goes.."Speed costs money. How fast do you want to spend?"

Seriously, once production is ramped up, this will provide a good solution for the racing applications that some in the DIY community are interested in.


----------



## brian_ (Feb 7, 2017)

rcoffin said:


> Thanks for your reply x.l.r. 8. You are slightly off about the cell count and calculated mass since *LiFePo4 *cells are a nominal 3.3V.


This isn't a big deal, but I find it a little disturbing that someone who commercially builds battery packs doesn't know it's LiFePO4, rather than LiFePo4.  That's one phosphorous (P) and four oxygen (O), not four polonium (Po).



rcoffin said:


> For 360V (and to have a bit of "headroom") I suggest a *15P110S *configuration which would require 1650 cells


That means 15 strings of 110 cells per string, with the strings in parallel. Do you really mean that? Wouldn't it be groups of 15 parallel cells, with 110 groups in series... which would be 110S15P, following the common notational convention?



rcoffin said:


> Let's not forget, it's racing... the purpose is to win, not finish last for a very long time.


 Clever, but the original remains true: _to finish first, first you must finish_.


----------



## Batterypoweredtoad (Feb 5, 2008)

If someone wants to buy batteries for their drag car without going the OEM route: http://www.ampahaulic.com/ It is owned by a high level EV drag racer. They sell really high performance built to order battery packs. He has several cars into single digit 1/4 mile times and has sold batteries to others doing similar things. The prices are not bad if you consider the power they make.


----------



## rcoffin (Feb 23, 2010)

Well, it's clear that by posting here I've opened the door to unlimited harassment, but I expected that. I'm sure that there are those who will find fault with my other typos too. From my exposure to battery nomenclature, the "P" comes first, followed by the "S". So yes, fifteen 26650 LiFeP04 cells in parallel with 110 packs of those in series is what I suggested. Now, that said, I don't really know what the actual current requirement is. I was shooting from the hip, going by the suggestion in the post by x.l.r.8. Maybe it could be done with fewer cells, but at 360V, not with fewer than 110 LiFeP04 packs. 
Another thing I want to be clear about is this: I don't claim to be the only one to provide a good solution. There may be others who can do better or be more cost effective. I am not disparaging anyone else's effort, I'm just saying, for a motorsport application, and drag racing specifically, what I've designed is a helluva lot better choice than any road car battery.

Now, something about me. I'm no scientist or battery chemistry expert. I am a toolmaker, machinist, successful inventor, small business owner, family man and motorsports enthusiast. I set out to make suitable batteries for a specific motorsport application (which I will eventually disclose at the proper time). All I've done is design a unique battery cell packaging system (and mounting system for the packs) that enables these amazing cells to discharge at their maximum rate without frying the conductors and wasting a lot of power. Along the way it became apparent that what I invented would likely be useful for other applications. I might be right about this, I might be wrong. Time will tell. It works great for the purpose I designed it for.


----------



## brian_ (Feb 7, 2017)

rcoffin said:


> First, what is a road car battery designed for? One thing: range
> Second, what do you want in a drag race battery? Two things: High discharge rate and light weight.


I agree that different goals lead to different design choices. Among production road vehicles, battery-only vehicles are biased to high energy density (and their batteries are so large that their power output is adequate) and hybrids are biased to high power density (since their batteries must be small).

There are multiple reasons for the popularity of the Chevrolet Volt (a plug-in hybrid) as a source of salvaged battery modules, including relatively high power density for DIYers with limited battery space.



rcoffin said:


> Since road car manufacturers are shooting for range, the only way they get a lot of current for rapid acceleration is to use far to many cells than you need for a drag race.


No. The number of cells is irrelevant; the required capacity can be built up with many small cells or fewer larger cells. The largest pouch cells in production EVs have about 20 times the capacity of the smallest cells in production EVs (18650's in Tesla Model S/X). Perhaps the intended meaning was that production EVs have larger capacity than needed for drag racing?



rcoffin said:


> What I am making are modular parallel packs that can utilize any 26650 cell.


26650 (26 mm dia by 65 mm long) cells are much smaller than the cells in any production EV other than those from Tesla. So, it's not about cell size...

I do understand the logic of using cylindrical cells in custom packs. Their cylindrical shape and metal case make them self-containing, unlike pouch cells or even prismatics that need to be clamped in stacks, making the mechanical assembly easier to design and more flexible to configure.


----------



## brian_ (Feb 7, 2017)

rcoffin said:


> Well, it's clear that by posting here I've opened the door to unlimited harassment, but I expected that.


I didn't mean to "harass" anyone, but I think that the standards for someone offering a commercial product should be very different from hobbyists discussing their hobby.



rcoffin said:


> Another thing I want to be clear about is this: I don't claim to be the only one to provide a good solution.


Just to be clear, I made other comments about another poster, who runs a website showing products that he doesn't sell, and makes unreasonable claims. Those comments were not directed to rcoffin!
_*Edit note* (2019 Sep 16): The other post was recently deleted, so I have deleted my response to it._



rcoffin said:


> From my exposure to battery nomenclature, the "P" comes first, followed by the "S". So yes, fifteen 26650 LiFeP04 cells in parallel with 110 packs of those in series is what I suggested.


There's no absolute rule for the notation, which is why I asked for clarification - thanks for that. 

In the conventional notation, it isn't "P first", it's in the order of the pack assembly, with the lowest level last (like the least significant digit of a number being last, or the smallest unit of time being last in "hours:minutes:seconds"). The lowest level in this case is the parallel connection of 15 cells, which is why it would be 110S 15P. For example, in the Chevrolet Volt pack the cells are also parallel at the lowest level, so Chevrolet reports this as "96S 3P" or "96S 2P" (depending on generation).

Some people do actually connect cells in series strings, then parallel those strings... usually in the case of salvaged modules being built into larger packs in a way not intended by the module manufacturer. That's why I asked - it can be done both ways, even though only one makes sense in most cases if building from scratch.


----------



## rcoffin (Feb 23, 2010)

Yes Brian, that was what I meant. More battery mass, not necessarily more cells.
I looked at larger cells and settled on the 26650 for a number of good reasons.


----------



## rcoffin (Feb 23, 2010)

Ok, understood. I learned something.Thank you.
One thing that battery experts have advised me is it's not a good idea to connect series strings in parallel due to possible (or likely) differences in potential of the strings causing large currents between them... any comments?


----------



## brian_ (Feb 7, 2017)

Batterypoweredtoad said:


> If someone wants to buy batteries for their drag car without going the OEM route: http://www.ampahaulic.com/ It is owned by a high level EV drag racer. They sell really high performance built to order battery packs. He has several cars into single digit 1/4 mile times and has sold batteries to others doing similar things. The prices are not bad if you consider the power they make.


Yes, John already posted in this thread, with the proposed configuration from Lonestar/Ampahaulic:


John Metric said:


> Lonestar would supply:
> 5P96S 25AHr full power for two tesla motors, 160lbs.


----------



## x.l.r.8 (Oct 20, 2018)

redundant post


----------



## brian_ (Feb 7, 2017)

rcoffin said:


> One thing that battery experts have advised me is it's not a good idea to connect series strings in parallel due to possible (or likely) differences in potential of the strings causing large currents between them... any comments?


Balancing parallel strings is certainly an issue. They will discharge slightly different amounts, resulting in different cell voltages when the discharge stops, so then the higher-voltage strings will discharge into the lower-voltage strings (possibly with high current, given the lack of resistance between them). When cells are connected in parallel first (at the lowest level) imbalances between cells are handled at the single-cell level, so large voltage differences don't occur.

The other issue with parallel strings is that if you want a BMS to monitor the cell level, you need another BMS for each string, instead of just one set of BMS inputs for each level the pack. That might be a more significant practical issue.


----------



## Batterypoweredtoad (Feb 5, 2008)

brian_ said:


> Yes, John already posted in this thread, with the proposed configuration from Lonestar/Ampahaulic:


My apologies. I didn't catch that the first time through.


----------



## rcoffin (Feb 23, 2010)

Very correctly said.


----------



## kablammyman (Mar 16, 2017)

Duncan said:


> 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
> ...


Im using the same batteries, but I dont have the coolant line elbows. how hard are they to get, or should I try to make my own so I too can run coolant with my batteries/


----------



## Duncan (Dec 8, 2008)

The darker coloured elbows are part of the Volt battery - all of the elbows on the actual battery are from the Volt

The white ones are simple plumbing parts


----------



## x.l.r.8 (Oct 20, 2018)

I got a few endplates and elbows, I brought them when I thought I was going that route. The are relatively inexpensive. Do you already have the metal endplates. PM me if you need some, I'll dig out my box of 'parts I buy without thinking first'.


----------



## brian_ (Feb 7, 2017)

Since this thread included consideration of the Bolt battery, this recently updated discussion should be of interest:
Modified Bolt Pack for Tesla Cobra EV Race Car

This race car has a large Tesla drive unit, and is now using essentially two-thirds of a Bolt battery in 96S2P configuration. It is having difficulty with heating, but is used over a much longer period (20 minutes) than a drag race requires.


----------

