seeking advise - EV batteries oriented towards performance

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HindooCow
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seeking advise - EV batteries oriented towards performance

Post by HindooCow » Sun, 12 May 2019, 21:28

Hi guys, looking for your help and expertise...

I've been researching the best options regarding batteries in a performance-oriented EV, and thought you could help. Ive been researching EV's for the past 3 years or so, but still have some holes in my knowledge RE battery tech(chemistry/physics)

In general Lifepo4 seems like a solid option RE performance, however some of the other options seem to be worth considering:

:lead, -heavy, -short life, +cheap, -probably physically too big for my required power
:lifepo, + good all-rounder, +battery life, -expensive
:something weird like salt water batteries?
:NiCAD / NiMH?
:Tesla modules +power to weight, -expensive, -integration
:other EV manufacturer batteries such as Chev/Mitsubishi/Toyota
:your recommendation?

Its still early days. Im looking for something that wont break the budget but is capable of delivering the goods when I upgrade from my petty 25hp 8" DC to a high powered AC motor(the most likely next step).

My, vehicle is a 1989 daihatus charade, pre converted to a budget EV. It should end up at about 1000kg once all the mods are complete. Im willing to slowly improve handling/brakes/reliability/power until everything is sorted. I've sold my previous hot hatch(renault megane R.S. - approx 270Hp) to fund this project. Im chasing a very solid power to weight ratio.

The renault was great, but to be honest I had become bored with it at 1330kg/270Hp. The daihatsu is to be road registered as a semi-daily driver with a focus on hillclimb motorsport events.

Not too concerned with range, as ill only require about 60ks (although Im expecting anything that can output the required power will probably have a larger range than that?)

Im willing to buy second hand batteries.

most of the options i've looked at seem to have too little voltage(with too much capacity, ie weight) for my needs. Is this just a shortcoming of current battery tech? My rudimentary knowledge suggests that voltage will be a shortcoming and can not be tweaked / increased for a given battery pack that I choose?

Any advice or gap-fills you could offer me would be greatly appreciated.

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jonescg
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Re: seeking advise - EV batteries oriented towards performance

Post by jonescg » Sun, 12 May 2019, 21:45

What's your budget? I build high powered LiPo battery packs which deliver crazy power, and have respectable energy density (160 Wh/kg) but as a built pack are about $1250/kWh.
So definitely not cheap, but they will be fairly light and even the most powerful inverters and motors would struggle to keep up with them.
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HindooCow
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Re: seeking advise - EV batteries oriented towards performance

Post by HindooCow » Thu, 16 May 2019, 21:26

Hi Chris,

That does sound like respectable energy density. Is there somewhere where I can get some more info on your packs? Im trying to avoid buying batteries, then upgrading everything else, then buying a second lot of batteries to cope.

Cheers,
Ross.

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jonescg
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Re: seeking advise - EV batteries oriented towards performance

Post by jonescg » Thu, 16 May 2019, 22:07

Probably best place to see what I've built is on this thread over at Endless-Sphere: https://endless-sphere.com/forums/viewt ... 0#p1398812
Lots before and after, but it's a good place to start.
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Re: seeking advise - EV batteries oriented towards performance

Post by Scotty T » Fri, 17 May 2019, 12:52

@jonescg Because I am not good at math, how do your packs compare price wise and density wise to the ElMofo packs? Those things look pretty amamzing but also pretty expensive. Yours look pretty damn nice too.

https://www.elmofo.com.au/lithium-batteries.html

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Richo
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Re: seeking advise - EV batteries oriented towards performance

Post by Richo » Fri, 17 May 2019, 12:56

jonescg wrote:
Sun, 12 May 2019, 21:45
I build high powered LiPo battery packs which deliver crazy power
jonescg from some other forum wrote: Technically they are a 2C continuous, 5C peak
Yep that's crazy power. :roll:

:?:
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Re: seeking advise - EV batteries oriented towards performance

Post by jonescg » Fri, 17 May 2019, 15:32

Richo wrote:
Fri, 17 May 2019, 12:56
jonescg wrote:
Sun, 12 May 2019, 21:45
I build high powered LiPo battery packs which deliver crazy power
jonescg from some other forum wrote: Technically they are a 2C continuous, 5C peak
Yep that's crazy power. :roll:

:?:
Two different cells in operation ;)

The 30C/60C cells are 160 Wh/kg

The 2C/5C cells are 208 Wh/kg
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jonescg
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Re: seeking advise - EV batteries oriented towards performance

Post by jonescg » Fri, 17 May 2019, 15:36

Scotty T wrote:
Fri, 17 May 2019, 12:52
@jonescg Because I am not good at math, how do your packs compare price wise and density wise to the ElMofo packs? Those things look pretty amamzing but also pretty expensive. Yours look pretty damn nice too.

https://www.elmofo.com.au/lithium-batteries.html
Pricewise, my packs are a bit cheaper than that, even with the liquid cooling plate. I haven't put my modules through the same testing though, so there are a few unknowns as to how it performs in very wet or high vibration environments. Also I source cells form mainland China, which is not as reputable as Korea but so far my bench testing is showing they are good for 800 to 1000 cycles.
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Re: seeking advise - EV batteries oriented towards performance

Post by francisco.shi » Sat, 18 May 2019, 11:25

High C cells tend to have shorter life especially if you run them hard. That is why Tesla has such big batteries for the higher performance models. The roadster has a very large battery for the size of the car so they can draw more power without reducing the life of the battery.
When you choose the size and type of cell you have to consider what the aim is. If you are using it for a race car and performance is the most important then use a smaller battery with higher C rating. It will not have a long life but it will be lighter and if you only race it once a month then it will be fine.
If you are using the car day to day and want more performance use a lower C cell and put more of them. It will be heavier but will last longer. Also the high C cells are much more expensive than the lower C cells so you will get more kwh/$ for the lower C rating.

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Re: seeking advise - EV batteries oriented towards performance

Post by francisco.shi » Sat, 18 May 2019, 11:35

My Pajero will have 400kw ( 530hp) peak the battery pack will be 70kwh so at peak power it will draw 5.5C. I am not using it for racing so it is unlikely the cells will see much more than 2C peak during normal day to day.
The cells weigh about 350kg.
If I replaced them with the 30C cells I would only need a 13kwh battery which would weigh 80kg for the cells but it is unlikely they will survive 500 cycles.
So you need to decide what your priority is.

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Richo
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Re: seeking advise - EV batteries oriented towards performance

Post by Richo » Mon, 20 May 2019, 12:36

jonescg wrote:
Fri, 17 May 2019, 15:32
The 30C/60C cells are 160 Wh/kg
Hey now you're talkin :mrgreen:
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jonescg
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Re: seeking advise - EV batteries oriented towards performance

Post by jonescg » Mon, 20 May 2019, 15:27

Richo wrote:
Mon, 20 May 2019, 12:36
jonescg wrote:
Fri, 17 May 2019, 15:32
The 30C/60C cells are 160 Wh/kg
Hey now you're talkin :mrgreen:
Yeah, but as Francisco mentioned the cycle life suffers with these cells. The layer of active material is so thin it's prone to structural failures, limiting the amount of charge which can be stored in the matrix. Cooling will definitely help push that right out past 1000 cycles though.
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mikedufty
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Re: seeking advise - EV batteries oriented towards performance

Post by mikedufty » Mon, 20 May 2019, 17:40

I think I have 30C cells on my ebike, I'm having to replace them at under 10,000km, which seems OK for a pushbike, but probably not a car. Probably be acceptable for a race car though.

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Re: seeking advise - EV batteries oriented towards performance

Post by Richo » Tue, 21 May 2019, 12:45

Well as long as they have crazy power right.
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