I don't have an in-depth understanding of the engineering required or the capabilities of a design like this but have you considered using a heat pipe design to remove heat from the Leaf pack? Or piggy back that with the car's air conditioner?
Well yes, there will be a heat exchanger that can be tied into the A/C system. It's not a heat pipe, rather just a branch off the existing piping that drops into the pack. A sealed battery pack without any dedicated way of deliberately moving heat into/out of the pack is never a good idea.
Ive started down this road and its a tough one but to build the leaf battery with Active cooling or heating requires a redesign from the ground up . Its a workable solution but when you consider the cost of the new Alu case ( as aluminium is very heat conductive ) the question is are consumers willing to pay for the cooling ?
We're working within the constraints of the original pack for two big reasons: one is that it allows for relatively easy engineering of the most safety-critical parts, the other is that it saves a lot of cost. That does mean thermal management is going to be somewhat suboptimal, but really... it's not that bad. As soon as you have just any airflow inside the pack, the few hundred watts you're dissipating are very easily transported around.
Then comes the next question how to manufacture it safely and then how to make sure its crash tested ? and safe for passenger vehicles .?
Realistically, for a near EOL vehicle, you're not going to get a new battery shell design approved. Now, fortunately, the battery isn't part of the safety rating (it's not a structural component, crash testing is done with dummy masses instead of the battery) so you could probably get out of this without a bunch of expensive crash testing, but it's much easier to take what's been approved and build on top of that.
To be clear, we're still doing all the appropriate testing and validation to ensure the pack complies with relevant safety regulations - ECE R10, R100, etc.
see the below idea we had the design consideration is that the total pack would have to sit at least 20mm lower to clear the rear passenger foot depression area . This means the overall pack can still be made in the same plane but with a lower height ? in saying this the 62Kwh pack sits 40mm lower so this isnt bad ? maybe some people can comment and give their thoughts . Many ways to achieving this but
@mux would need to Chime in Heating and cooling are Every leaf owners concern .
The lowest point on the leaf is already a bit lower than the battery itself, you can move the floor of the battery down exactly 40mm without needing new certification (that's what Nissan did on the same environmental/safety certificate number with the 62kWh battery - i.e. no need to retest).
So I would ask you to consider liquid thermal management and some insulation on the casing -- heating via the liquid coolant when it's cold and running it through a little radiator with a fan somewhere when it's hot. If it has that in place, then it can later be kitted to make it hot-weather friendly.
Yes we have thermal management as an option*, but you'll still have this problem when the car is sitting idle. No matter how much you insulate the battery, it's eventually going to heat up to whatever the ambient temp is. The only solution to that is letting the car sit in an insulated, air conditioned garage.
I don't have metrics yet (will need to install some sensors to get them), but my plan has been to tap the coolant system (add T connectors) in three places:
1. straight out of the pump,
2. immediately after exiting the motor, and
3. before going back in to the radiator.
The purpose is to 1 use freshly cooled coolant for cooling batteries, 2 to use waste heat from the chopper and motor when it's cold, and 3. to return the coolant. Hoses 1 and 2 would need to have some insulation.
If you're making a custom solution anyway, it's much easier from a pressure management perspective to put a T-valve in front of and after the existing interior evaporator and switch them both over to your own heat exchanger, insulating both lines. Then you have the same performance and pressure drop characteristics (so no problems with the AC Auto Amp throwing errors) and only two cuts/4 joints to worry about.
PS: If you aren't keeping up with the latest SiC power MOSFETs, they are amazing! e.g., Qorvo UJ4SC075008L8S is an N-channel 750V 106A MOSFET with 8mΩ Rds(on)! I was surprised! I could use that to switch the main BMS connection on and off and only loose 0.8% to waste heat. But I've found a diode that might actually work better.
On this entire project: don't consider what happens if things go right, but consider what happens when things go wrong. If that MOSFET fails, it will fail closed and thus explosively. MOSFETs are not a usable high energy contactor. You HAVE to use a mechanical contactor with arc extinguishing features, e.g. TE LEV200.
I am very interested in what you are trailing here. I just sent a comment in via your website to join any mailing list you may have for updates to this story.
You asked for requests. In my case, although I have a Leaf, it currently has good range. My requirement is for another vehicle which is an EV conversion based on a salvage Leaf, using Resolve-EV VCU, so needs a Leaf compatible BMS.
Ideally:
50 - 70kWh
Trusted supplier
Does not require metal case
Decent instructions
Warranty
Option for faster charging - if that’s something that can be added at a later date when funds allow, that would be great as an option.
I look forward to hearing more.
Thanks.
Thanks for the message, you're on the list now. Still working on that website and feature brief, but the kids take up much more time than you'd think!
*(option meaning: we're shipping these as kits, so you need to find somebody who has the equipment to pump out the HVAC system, connect new pipes onto our quick disconnect, test everything and pump refrigerant back in - the rest of the battery is plug and play, HVAC mods obviously arent)
