Feature requests/input for MUXSAN 45kWh replacement LEAF battery

[blooot]

Would there be a business case proposal for dropping the intended capacity in half?

All of these solutions seem to focus on massive packs compared to the Gen1 leaf.

Here’s what I see.
Better density would give a lower overall weight, improving performance
Lower weight may contribute to reduced consumption, possibly equaling the original 24kwh range
Extra space inside the pack allows for passive air cooling and less loading
Costs would be dropped, and a better economic calculation to improve an older car vs a complete vehicle upgrade - which in most cases is simply cheaper overall.
Shipping costs reduced
Tax costs reduced
Lastly - the range offered by a light weight 20kwh pack would be better than double the range of the vast majority of Gen1 owners who might consider this. If 50m/80km is working for them now, getting back to near double that is a great bonus and extends the life by at least another 10yrs

This is what I want. A light 20kWh pack (also capable of 160kW ), but I see you covered this -- I will continue to hunt for a 12 bar 24kWh pack.... @mux what's the projected weight of this 40kWh unit?

 

[ginetto]

Hi @mux IMHO any new battery pack should not rely completely on internal passive BMS to balance cells. Use cases for the battery are so many that a BMS that is good for normal commuting use does not work for a taxi use.
So the feature request is to:
1) move BMS outside the pack in a water proof place
2) having the BMS accessible without take down the battery
3) having the BMS accessible, for Taxi use case, make sense to periodically apply active balancing instead to rely on passive BMS that does not work well, or becouse it is faulty or because can't work well in case of many QCs.

The only way to allow the BMS to work is to charge really slowly and after a strong unbalance, it is necessary to vaious cycle of discharge and charge slowly to allow a good capacity count and a good balancing. Something really hard for a taxi.

My 2c.

 

[Joeaverage]

This was pretty cool. Maybe useful for heat management in the battery.

 

[danielsantos]

I'm sorry for not responding, but I lost my mother last month and we were very close, so I've been grieving and recovering from her loss.
As ever, thank you for your thoughtful responses!

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.

Yes, which is the reason for involving the AC system below.

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.

So I think you misunderstood or I wasn't clear enough (and didn't use the right terminology), or your suggesting I go another route. I meant to add a T-valve to the "HCO" (High Voltage Cooling System) here:



Then replace or modify this "low pressure pipe" (I don't have a heat pump, so this is the exploded view with "no heat pump" )



...into a counter-flow heat exchanger (low pressure refrigerant on one side, HCO coolant on the other) to bring it below the ambient temperature (presuming the AC is running) and cool the battery with that.

But I think you're suggesting to just modify the AC (with heat pump) system so that I can exploit the heat pump for efficient battery warming as well, then I won't need an insulated pipe to the battery compartment (refrigerant is already cooled close to ambient temperature anyway, just an expander and heat exchanger there? Of course, I prefer my low pressure coolant lines to be insulated, which they currently aren't. Otherwise, we're soaking up additional heat unnecessarily, which means more work for the compressor, etc.

That's very interesting, thank you!

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.

Well I feel fortunate to have encountered an EV charging expert at my local makerspace!!! I'm hearing a lot of the same advice. He added that MOSFETs are better suited for a situation where it must be compact and suggested I look into IGBTs. And much of the same cautionary advice. He was apparently hired to clean up after a disaster caused by a pair of PhDs fresh out of school (but still lacking practical experience) where many, many ground-based batteries blew up due to some unexpected oscillation caused by the capacitance of the MOSFET gates or some such. Of course, switching on or off is when things are hottest. He said it was a major fire event.

*(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)

Well if I can come up with a pair of (one for heat pump, one without) of clamp-on heat exchangers, then it's possible for it to be fairly plug and play. It would still require draining the HCO coolant and replacing two hoses with the T-valve hoses.

I still need more time to consider the mechanism you've suggested -- modifying the HVAC system.

The other draw-back is the requirement for the vehicle to be in the "on, but charging" state (I'm not sure what the official descriptor for that state is). At least that state doesn't waste power on power steering. After you reach 80% or 100% (top of level) in this state, the high-voltage battery remains connected and the charging system appears to provide exactly the same amount of power you're drawing, though I've seen it creep up beyond 80% sometimes. It stays in this state until you turn off the compressor.

ADENDUM: For the sake of others, I feel like I should add that just cooling the battery to the outside ambient temperature would be a HUGE boon for battery life! My obsession with better cooling is mostly related to brutal summers in Texas, though I will assert that it can improve battery life (over mux's proposed product) in any region where the average high temperature exceeds 80°F / 26°C (Dallas is 96°F / 35.5°C).