Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Nissan Leaf/e-NV200 drive stack topics
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Dan--T
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Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Dan--T »

Sorry for a bit of a basic question, I'm muddling through this conversion as a mechanical/automotive guy.

I'm converting a GS450h to EV, and aiming to make hit 150kw power, with roughly 60 miles range.
I'm possibly buying a 24kwh Gen2 Leaf battery.

From what I can see, it is rated to 228A current, so ~90kw @ 400v. - So from this info the answer to my question would be no.

But can I wire up the modules in the pack differently in order to achieve my goal at the expense of range? - More modules in parallel

Thanks
Dan
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by EV_Builder »

No. Thats why the bigger tesla's have bigger batteries.

You do need to look at peak current from a pack for certain seconds..(sustain) to know if it can deliver the power for your engine.
228Amps doesn't sound much, but i'm not a leaf battery expert.
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Bratitude »

Itlll do it. Maybe for a short period of time. Won’t be happy about it. Add liquid cooling. Volt packs are cheap and capable. Or get 2 leaf packs and double the parallels cells.

Changing the pack layout won’t change the amount of energy available, just how it’s delivered
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Dan--T »

OK, 2 leaf packs could probably be found within budget.
I could probably go for one now and get the car running and working then add a second in the boot when I have a bit more confidence.

I read on the wiki that running more cells in parallel within a pack was relatively easy, but running two packs in parallel was much more difficult, why is that the case?
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by johu »

The 24 kWh BMS allows 110 kW discharge power and the 40 kWh allows 125 kW. Not sure about the 30.
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Dan--T
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Dan--T »

johu wrote: Wed Oct 13, 2021 9:24 am The 24 kWh BMS allows 110 kW discharge power and the 40 kWh allows 125 kW. Not sure about the 30.
Ah ok, so the BMS is in control of how much power is drawn, set to a level that's safe for the battery.

So if I did add more modules in parallel to up the power would I have to move to an aftermarket BMS system?
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Isaac96 »

Dan--T wrote: Wed Oct 13, 2021 3:43 pm Ah ok, so the BMS is in control of how much power is drawn, set to a level that's safe for the battery.

So if I did add more modules in parallel to up the power would I have to move to an aftermarket BMS system?
No. The BMS will complain about the excessive power draw but it can't do anything about it as it won't control anything (unless you want it to).
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by ZooKeeper »

Dan--T wrote: Tue Oct 12, 2021 9:24 pm
I'm converting a GS450h to EV, and aiming to make hit 150kw power, with roughly 60 miles range.
I'm possibly buying a 24kwh Gen2 Leaf battery.
That should be doable with the 24kWh pack :D
From what I can see, it is rated to 228A current, so ~90kw @ 400v. - So from this info the answer to my question would be no.
The fusing protects the WIRES and has little to nothing to do with the battery's ability to deliver amperage (see EVBMWs video where he tests a spanner ;) )
But can I wire up the modules in the pack differently in order to achieve my goal at the expense of range? - More modules in parallel
Dan
The primary affect on range is aero and the GS is pretty decent, so if speeds are sane (< 100kph) it should be fine.
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Dan--T »

Ok so now I'm really confused

Again apologies for my lack of electrical knowledge.

I guess my question is, if I hook up the 24kwh leaf battery pack to the gs450h motor (with Damiens VCU board in between). What is the limiting factor for the power output? And what will be the failure mode?

1. The motor will draw more current than the battery can safely supply and something will catch fire?

2. The battery can't supply enough power to the motor and will self limit to whatever power level the battery is capable of supplying?

3. Something else......


Just trying to understand the basics really, this is so far away from injector duty cycle, ignition timing and lambda that I'm used to!

Thanks
Dan
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by ZooKeeper »

Dan--T wrote: Wed Oct 13, 2021 8:28 pm Ok so now I'm really confused

Again apologies for my lack of electrical knowledge.

I guess my question is, if I hook up the 24kwh leaf battery pack to the gs450h motor (with Damiens VCU board in between). What is the limiting factor for the power output?
Not exactly sure what is being asked. Full power is maybe, 30s to terminal speed??? Certainly long enough to hurt the pack, but cause a battery failure, not sure but I do not think so. During normal driving, one does not pull FULL power often, if ever and normal driving is in the 15kw to 30kw range, steady speed. The LEAF pack can sustain that level for over an hour.

And what will be the failure mode?

1. The motor will draw more current than the battery can safely supply and something will catch fire?

2. The battery can't supply enough power to the motor and will self limit to whatever power level the battery is capable of supplying?

3. Something else......
The current to the motor (from the pack) is limited by what you set in the controller. This means the failure mode depends on the controller settings. If you want to protect the pack, make choices based on battery limits; if protection for the motor is desired, focus on limits for it. But whatever is set, make D@MNED SURE the wiring can handle the current and is properly fused!!!!

In my (limited relative experience) damage is done by either not thinking about limits, ignoring them, or forgetting about protecting the cables.
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by catphish »

Dan--T wrote: Wed Oct 13, 2021 8:28 pm What is the limiting factor for the power output? And what will be the failure mode?
What will happen if you ask the inverter to draw more power then the batteries are rated for will depend on how much beyond the rated capacity you go. Here are some things that could happen, in order of how much beyond the rated capacity you go!

1) Everything will be fine, the manufacturers are probably conservative in their specifications, because they have to guarantee them.
2) The batteries will run a little warmer than they should, reducing their overall lifespan.
3) The batteries will run much warmer than they should, causing immediate damage and potentially fire.

Most likely you would not notice this happening, as the batteries will be able to provide much more power than they should. There is generally no self-limiting, so you need to make the decision, and make sure your inverter enforces that decision. You also need to be mindful about how long you can draw the power for.

If you want to go beyond the manufacturer's guaranteed specifications, you will have to go on anecdotal evidence of how much power you can draw per kwh of capacity, for each type of battery pack, and each type of cooling solution.
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Alibro »

If using two leaf packs in parallel as was suggested there should be no issues as each is perfectly happy to deliver 80kW.
Packing two leaf batteries into the car might be a different issue.
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by celeron55 »

Dan--T wrote: Wed Oct 13, 2021 8:28 pm I guess my question is, if I hook up the 24kwh leaf battery pack to the gs450h motor (with Damiens VCU board in between). What is the limiting factor for the power output? And what will be the failure mode?
This is a very complicated question and an accurate answer would require specific experience with the 24kWh Leaf battery.

In short, as long as you're not driving a battery into a literal short circuit, and you don't drive it so hard it develops an internal short circuit, you don't get a battery fire.

I believe the Leaf battery doesn't use a particularly fire prone chemistry, so as long as you monitor the battery temperature and keep it reasonable, let's say 70°C is already stretching it, it will be fine-ish. The Leaf pack is of course known to overheat and age prematurely even in a Leaf itself.

When you exceed the battery manufacturer's specification, you can expect excessive voltage sag, which limits high speed performance, decreases efficiency and makes it more difficult to monitor state of charge. The extreme is a short circuit: you get 0V output which is totally useless.
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Dan--T »

Thank you everybody for the really informative and understandable replies, this was just what I needed to know.

Ok so I now understand that basically it will be my "tuning" within the setup of the VCU controller which will be ultimately responsible for how much current is drawn from the battery and therefore the balance of motor power vs battery temperature/longevity is in my hands.

I will definitely ensure all wiring is over spec'd for the current demand (future proofing). And will start off with one leaf pack in the front, running ~90kw and monitoring battery temps, then later adding more modules in place of the old hybrid battery pack in the boot in parallel to try to safely reach my desired power output.

Thanks
Dan
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by arber333 »

Dan--T wrote: Wed Oct 13, 2021 8:28 pm Again apologies for my lack of electrical knowledge.

I guess my question is, if I hook up the 24kwh leaf battery pack to the gs450h motor (with Damiens VCU board in between). What is the limiting factor for the power output? And what will be the failure mode?
Its no lack of knowledge, more like actual experience, and i dont whish that on anyone.
I have some experience with Lipos and LiFePos

LiFePo failure mode with overcharge
If too much voltage/charge is applied for too long they will slowly raise temperature and cooke themselves untill the first one starts to reach some temperature and two adjacent cells cem be fused together from the heat. At the time cells emmit vapors and hiss omniously. You can still cool down the pack with lots of water.
LiFePo failure mode with overdischarge
If too much power is applied repetteadly you may notice decreased range with several of your cells will drop under 2.5V at EoC. Rest will follow soon. I have never seen total death as in 0V on a LiFe battery during use!

Failure mode in LiPo Kokam cells is twofold:
I dont know what happens in overcharge and i really dont want to find out. This is why i only change up to 4.0V per cell.

In case of overdischarge i have seen cells get bloated on the next charge after overdischarge event. They would swell and damage adjacent cells. After i tested them i found out they could still hold some charge, but not for car application.

There is another failure mode and i am not sure why it comes about, but i am sure is part of design. It happened on the road at 120km/h! A cell blew violently, but my car still had power. When i inspected damage i saw the top of the cell vented pressure away and cell was hot to touch (several adjacent cells). Also that cell was at 0V! Mystery why i was able to still drive was solved when i plied off the plastic on top to see the contacts.
It seems Kokams have copper meshed into polymer and at high temperature it can fuse into thin copper band that will short terminals and provide connection for the rest of the pack. Safety feature? I was just happy i could drive home...
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by dougyip »

Just ran across this thread. People seem to be underestimating the capabilities of the Leaf pack. I have enclosed some data from a test report by Idaho National Labs under the DOE Advanced Vehicle Testing Activity Program. They tested every EV pack (except Tesla) up to about 2016 with very detailed capacity, charge, and discharge information. A GOOD 24kwh Leaf pack is capable of over 200kW discharge power for a 30 second burst right down to 20% SOC. However, it appears that there is relatively fast degradation, so a high mileage pack will not achieve that. We used the DOE data to choose the pack (Kia Soul EV) for our 1st generation race car. The DOE data was bang on. I have included a couple of screen shots and will try to upload the PDF. The data should still be available on the DOE site.
24kwh_1.JPG
24kwh_2.JPG
batteryLeaf9270.pdf
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Re: Extracting 150kw from a Leaf 24kwh Gen2 Battery - Possible?

Post by Bratitude »

dougyip wrote: Sun Oct 17, 2021 9:39 pm Just ran across this thread. People seem to be underestimating the capabilities of the Leaf pack.
I think what everyone is pointing out is it lacks proper thermal management resulting in rapid degradation. The chemistry appears to be quite similar to volt packs. No doubt they can deliver the juice.

Thanks for the review data, I’ll add it to the wiki
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