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Discussion Starter · #1 · (Edited)
I have my Tesla drive-unit mounted in the Rx7 and now comes the big battery decision. My goals are simple - killer performance with enough range to get to a road where I can have fun. I have a 40 mile loop from my house, but assuming I'm hammering it I need a battery that has a decent amount of range.

I was set on the Pacifica batteries but those appear to be impossible to find.

One big question - are the i3 batteries appropriate for a Tesla drive unit? I haven't seen much talk about them but the prices have really come down. For ~8k I can get to 42 kWh. They appear to be a bit heavier than other options, but the price might be right.

Thoughts?

Updated on 11/4:
120735


120736
 

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I would consider Kia soul. They use SK innovation cells. You can pull very high C-rate without big voltage drop.
Power wize this cell is great. Energy dense its okay. You can get a 27-30kWh battery fairly easy.
Theres very good live usage from teslacobra user.
 

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There was a lawsuit from LG recently regarding the Pacifica Hybrid batteries. The supply is now gone. :( I have 6 batteries, was going to expand to 12 later if it became necessary. The i3 seems reasonable, and has SimpBMS support. The Electric GT stuff looks promising, but is just a little too much for their Energy line. If they could get it to $500/module instead of $600/module, that'd be where I go - but 400A current limit (10 seconds) is a bummer. Their Power line is nice, but pricey. 42 kWh (96 cell) with 900A max current is $846*16->$13536. That's $322/kWh.

The upside is they are brand new batteries, and 42 kWh is nothing to sneeze at in terms of range!

-Matt
 

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That is a great spreadsheet!

Mattsawesomestuff is dead on. I am no help but will be using your spreadsheet for lots of daydreaming!

I assume the packs are from salvaged vehicles? How do you verify useful remaining life, miles on the pack?
 

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Discussion Starter · #6 ·
There was a lawsuit from LG recently regarding the Pacifica Hybrid batteries. The supply is now gone. :( I have 6 batteries, was going to expand to 12 later if it became necessary. The i3 seems reasonable, and has SimpBMS support. The Electric GT stuff looks promising, but is just a little too much for their Energy line. If they could get it to $500/module instead of $600/module, that'd be where I go - but 400A current limit (10 seconds) is a bummer. Their Power line is nice, but pricey. 42 kWh (96 cell) with 900A max current is $846*16->$13536. That's $322/kWh.

The upside is they are brand new batteries, and 42 kWh is nothing to sneeze at in terms of range!

-Matt
Another thought is resale value of the batteries in a few years. The Tesla batteries seem like they will always have good demand because people are building so many uses around them. I don't think the ElectricGT batteries would have near the resale value unless they take off and people start using them to build powerwalls and such.
 

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Which Tesla Drive Unit do you have mounted on your RX-7 ?

Any one know if there is a performance advantage (hp / kW) to running 16 modules of Tesla 5.6kWh battery pack vs the 5.3kWh in a small drive unit ? The small DU is rated at about 300 hp . But I’m not sure if that is a battery , hardware and or software restriction/limit?
 

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I think in your chart you should include the maximum or peak current amps. From what I found:

BMW i3 = 409 A
LG Chem = 800 A
Tesla Model S = 750 A
Chevy Volt Gen 2 = 430 A

Nissan Leaf = 540 A

Any reason you didn’t consider NissanLeaf? It’s rated at 540 A compared to the 409 A BMW i3

Data Source:

BMW i3 & i8
https://wiki.aalto.fi/download/atta...rsion=1&modificationDate=1398446470505&api=v2

Nissan Leaf:

Tesla Model S:

LG Chem:

Chevy Volt Gen 2:
 

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Discussion Starter · #12 ·
I would consider Kia soul. They use SK innovation cells. You can pull very high C-rate without big voltage drop.
Power wize this cell is great. Energy dense its okay. You can get a 27-30kWh battery fairly easy.
Theres very good live usage from teslacobra user.
Thanks - I've added it in the updated chart. The Kia Soul batteries seem to have a really great price with reasonable weight and size. They seem to be harder to come by on copart but not impossible.

I think in your chart you should include the maximum or peak current amps. From what I found:

BMW i3 = 409 A
LG Chem = 800 A
Tesla Model S = 750 A
Chevy Volt Gen 2 = 430 A

Nissan Leaf = 540 A
Thanks - added the data. This is definitely a key piece that was missing.
 

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Discussion Starter · #13 ·
I updated the chart in post 1 with more data. If anyone has something I have wrong or need to add please point it out. There are so many good options now, but of course with an Rx7 I'm size limited.

Based on my current research here are the batteries that seem to stand out to me:
1. ElectricGT - These are new so they are on the higher-end price wise but the customization may make them easier to fit into smaller cars. I need to explore how much the cooling solution will add to the price.
2. Tesla batteries - If I had a bigger car, honestly I would probably buy the full pack. Ya they're expensive but I think you can account for having a good resale value on these over the next couple of years so they really aren't as expensive as they look.
3. Kia Soul - Cheap, reasonable size and weight, and we've seen them perform well for teslacobra.
 

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Also I think you keep in mind those current ratings are for certain time in seconds. I’ve seen the Tesla also rated at some sites 1000 Amps for 10 seconds and 1500 amps at 3 seconds etc. I’m not sure at what time duration the 750 amps EV west is rating it .

 

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@rjmcdermott81 - Thanks for starting this thread and summarizing all of this information in a spreadsheet.

I am having trouble finding current specs for the 24 kwh or 30 kwh Nissan Leaf battery packs. I'm wondering if they would supply enough power to run the 220kw Tesla small drive unit? I've heard they will not due to current limitations, but in the thread above, it was mentioned that they could supply 540 Amps? It looks like that's only for the newer 2018+ 40kwh packs.

I'm also doing a swap into a smaller car, a Porsche 996, and I'd like something around 30kwh. The BMW i3 pack is looking good, but also doesn't seem to meet the current requirement of the Tesla small drive unit. If I'm thinking about this right, P = IV, so if I want to run 220kw, and most packs are 360V, I'd need 220kw/360V = 611 Amps of peak current capability from the pack.

The Volt and the BMW I3 packs have been recommended to me for this project, but both have peak current around 400 Amps. Does this mean, I'd only be able to run the Tesla drive unit at 2/3 it's power capability?

Thanks anyone and everyone who can shed some light for me.
 

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Sustained current draw for an i3's 0-60 sprint will likely be double the period of yours, so sounds like it may be in the ballpark for your setup to me. You really need the 10s C draw spec for the cell and not a systems spec.
 

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I think in your chart you should include the maximum or peak current amps.
I'm pretty shocked the volt's peak amps is listed at 430amps, that seems incredibly low given how powerful builds are which use them. That R32 skyline comes to mind...

I wonder if that 430a number is extremely conservative on purpose, much like how Chevy put huge top and bottom charge buffers on the volt but didn't really need to....whereas the actual safe peak amps is more like 800
 
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