New Tesla P100D Battery Module Walkthrough

8 months ago by George Bower 8

Recently some photos of Tesla’s new P100D module were made available via a very interesting fellow – Jason Hughes (aka @wk057) on his website here. Jason has other very interesting projects as well and has extremely sharp computer skills. Take a look at his solar storage project. Very interesting as the huge battery storage is made from salvaged Tesla packs.

Back to the subject at hand. Before Keith and I present our own interpretation of the new P100D battery photos, a little background.

In an article here we showed by some simple geometric calculations that the cooling ribbon that snakes thru the module wastes a lot of space. Then in a second article we proposed a configuration for the P100D pack. As you may remember the P100D pack uses the same cells as the P90 pack. The increased energy storage is derived from squeezing more cells into the same area.

In order to squeeze in more cells we proposed a thinner cooling fin would allow increased room in the pack. We got that part right. However we were incorrect in proposing that Tesla would use a bottom cooling plate in conjunction with thin solid aluminum cooling fins.

Let’s walk thru the heat transfer aspects of the old and the new cooling scheme as we interpret it from wk057’s photos (here).

Figure 1 shows the old 85 kwh module cooling configuration.

The old 85 kwh cooling scheme used one cooling ribbon which snaked thru the pack

The old 85 kwh cooling scheme used one cooling ribbon which snaked thru the pack

From a heat transfer point of view you can see that the old design would result in cells being warmer that were at the end of the tubing run. This method is simple and cost effective but is not the most efficient way to cool the pack.

Now look at wh057’s photos again. The manifolding in the pack makes it pretty clear that there is now 2 inlets and 2 outlets for coolant instead of just 1 inlet and 1 outlet used in the old design.

Here is our interpretation of wk057’s photos.

It appears that the new pack uses 2 cooling ribbons not 1 as in the old pack design.

It appears that the new pack uses 2 cooling ribbons not 1 as in the old pack design.

Presumably this new, more efficient design has allowed Tesla to make the ribbon thinner, opening up room in the pack for more cells.

This approach is far simpler to implement than a complete pack redesign using a bottom cooling plate. It required less development time and was lower cost way of solving the problem than a complete redesign of the pack cooling architecture. Very smart as usual.

What do you readers think after looking at the photos? Do you agree with our “interpretation”. Certainly a photo can be interpreted in many different ways.

About the authors: George Bower is a retired mechanical engineer with over 20 years experience in gas turbine power systems.

Co-Author of the piece, Keith Ritter is a mechanical engineer, and licensed professional engineer with over 35 years of experience in heating ventilation and air conditioning systems.

8 responses to "New Tesla P100D Battery Module Walkthrough"

  1. no comment says:

    the new interpretation does make sense, and yes, it would make sense that you could use thinner cooling ribbons. my suspicion is that they probably didn’t use the thinnest ribbon possible so that they could allow for performance improvements.

    the previously theorized “heat sink” concept would probably still be an improvement over the twin cooling ribbon approach, but i would imagine that space in the battery cavity is tight, so the heat sink approach would probably require a substantial redesign of the car.

  2. Bill Howland says:

    I don’t know what to think George – No flow information was given. I’m assuming the flow rate in both scenarios was definitely in the Laminar range, and no where near turbulant.

    As a for instance, in their cars Chevy has stated the cooling of the battery is no big deal, since in 2011 they said they were awaiting for aftermarket suppliers to provide ‘up to 14 kw’ of battery chargers since the battery could take it.

    So I’m assuming a plain old 40 amp (roughly 9.6 kw) charger would be a breeze.

    Tesla has a more difficult cooling job as the battery has to be able to be charged, at least for a few minutes at 120 kw.

    So I’d assume that the amount of heat to be removed must be at least an order of magnitude larger, and that cooling glycol pump requirements are larger since the flow rate must be much higher, and the ‘series’ pattern of flow (although 2 pararalled ‘series’ loops now) mean higher pressure drop through the much longer thin loops as opposed to GM products.

    1. no comment says:

      think whatever you may of this, but i’m not following your concept. there is a certain amount of heat generated in the battery per unit time; there is a certain heat absorption capacity of the coolant per unit volume. so you inject a sufficient volume of coolant per unit time to absorb the generated heat. if you split the one loop into two loops, you approximately cut in half the amount of heat that each loop has to absorb. so you could conceivable reduce the diameter of each loop by about 30% when compared to the diameter of the single loop.

      the question in my mind is, would a 30% decrease in loop diameter support a nearly 18% increase in the size of the cells? i haven’t actually calculated it out, but my suspicion is that it is not. in which case, they would have to reduce the diameter of the loops by more than 30%, in which case they would have to increase the pressure in the loops to offset the reduced loop cross section and 18% increase in heat generation. but it doesn’t seem like it would be a ridiculously large increase in pressure.

      1. Bill Howland says:

        What you say is true – I was just comparing 2 manufacturer’s ways of doing things.

        I said to George what I meant – I don’t know what to think (he asked us what do we think?), without more info. I like you, can only make an educated guess.

  3. Jake Brake says:

    It would be really helpful to get new outer dimensions and a mass for this new module to see how it compares to the last version.

  4. tolou says:

    I would think that coolant should be going in to the middle of the pack, and out at the edge as it is bound to be a lot more heat at the center that needs to be transported away.

    1. Me Martin Winlow says:

      Quite right – my immediate thought as well…

  5. JimGord says:

    Can anyone speculate on how Tesla would be able to fit the new 2170 batteries in the pack?