johu wrote: ↑Sat Jul 27, 2024 4:03 pm
Tell me more about making an air chiller! If I could produce air with lower temperature than ambient plus improve air flow it could at least allow for one full charge session per day, equating to 500-600 km relaxed driving.
Going back to air cooling the Nissan pack which wasn't fully encapsulated (thus making me nervous in heavy rain) and was fitted with a small fan stopped overheating. In a way it had better long range ability than the MEB pack, because it cooled down 10-15°C between charge sessions.
Well...
The idea with the room was to have so much alu fins to create slots where air would move with really high velocity. At the same time the slots would reduce in size to cause the air layers to compress which would increase the air speed even more (at constant pressure). Air moving so fast would remove temperature from the fins and at the end of the room there would be large heat exchanger (medium unknown) which would interface with other room where the products requiring would be.
In your case i would imagine the chilling medium would be simply air. I have recomendations:
1. Create slots over your battery modules with
clear air path on two oposite sides of the battery from intake to exhaust.
On intake side slot would be maybe
3cm wide 1cm. On the exhaust i would imagine
2cm 1cm or even less.
EDIT: for construction stifness i would use longerons in the direction of air travel which would be riveted to aluminum cover. I dont know about the side of the modules. I imagine air should be traveling over modules directly. In that aspect you could even install the air duct to the battery cover directly. If you think of your battery box structure as carrying then you should build the air duct inside your box and fasten it to the box with opening for intake and one slot for exhaust on the other side.
2. On each intake you would want to place one or more centrifugal blowers and form the slots to be connected to blowers exhaust as directly as possible. Centrifugal blowers should be of a sealed type so you could install them under chassis.
So as to be no misunderstanding, i do not imply you should make slots on our box where air would enter directly while driving! Not at all! Blowers should provide air motion and slots should be sealed by rubber seals.
3. On the slot exhaust side you could create a downward facing hatch so any moisture freewheeling there would be deflected downwards/outwards.
In any case i would suggest to have this system operating whenever you would be driving or charging so as to remove moisture from the battery as much as possible.
Whenever you use air it is inevitable you would get moisture inside your system. To fight that you could seal the modules BMS connector slots with silicon goo or that black engine head gsket goo...
EDIT: I would think one does not need to get lower than outside air temp, simply lower than 42deg that battery chemistry finds offending. This means you need to counted the temperature gradient towards the battery center with one towards the outside.
For that i would think best way would be to fit the air slots to the bottom and the top side of your pack. Keep the air moving fast and along the whole side of the pack. Then exit from a slot that is downward angled at your current inox wall. You would need to play with angle grinder to create the slots at the front and back. But you need to make some standoff fittings on the sides so you can raise and lower the top nd bottom sides. Would that be doable?
. With 255W/256000g * 0.9 * 2h I arrive at 6.4°C rise in 2 hours, of course neglecting heat exchange with the environment.
It's super hard to get everything out again.