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That Little Water Pump

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#21
It seems to me that what we call drivetrain 1.0 is more like 1.1, as it has been locked in 2nd gear. I see the possibilities this way:

1) It's a bug that crept in with
1a) Changes to deal with the transmission locked in 2nd gear, or
1b) Changes to the common codebase that deal with drivetrain 1.5
2) It's a band-aid for a problem with the ESS. I don't think this is very likely. Martin doesn't think the ESS needs all that cooling, and I defer to his expertise.

It's amazing how software that should be modular and encapsulated gets interconnected and kludgey over time.
 
#23
bobw said:
It's amazing how software that should be modular and encapsulated gets interconnected and kludgey over time.
Click to expand...

Oh, the stories I could tell...

A lot of this comes from the "waterfall" method of development, where tail-end pressure to fix an avalanche of bugs causes the balance to tip towards expedience vs. correctness. We mostly know better now (only mostly because we still get "cowboy engineers" who game the system to stay in waterfall mode).

Some of the blame also definitely lies with companies who don't look to keep software teams together long-term. Hey, if you're not going to be working on the product in two years, why keep it clean? (He says, having worked on the same product for over 17 years now...)
 
#25
Ah, yes, green field... That trick never works!

I've yet to see a green field rewrite of any sizable project that actually "worked", in terms of being the same project or being any "cleaner". You won't find me saying "Let's rewrite it from scratch"! :)

Anyways, we've gotten off-topic. I sure would be interested in finding out more about the water pump issue, including if it was a software bug.
 
#26
There was a post on the Owner's board this morning from Tesla with regards to the water pump.

The gist is that this behavior is not a bug, but a safety feature. They feel that energy loss is bad, but safety is far more important at this stage of the game. They are currently looking at possible design changes that could cause the water pump to run less in the future.
 
#27
I hope Tesla doesn't mind quoting their posting from the Owner's Board. It was well written, and I consider the informatio a positive for the company. So here it is:

Allow me to explain this behavior. Martin's information on the behavior of the water pump for the battery coolant is accurate. He has spoken with various Tesla employees about this behavior, so much of his information was based on these discussions.

This behavior is as intended and is not a bug. The water pump circulates any time the battery is over 50% charge and does so to ensure that temperatures of the individual cells are balanced against each other. Energy loss is an important consideration, but our safety record is paramount, so in an abundance of caution we have chosen to run the water pump even when the battery is not hot.

We continue to research and test battery behaviors, and are evaluating potential design changes that will reduce the need for the water pump to be turned on. We are also continuing development of the cooling system so that it operates more efficiently than it does currently.

For now this behavior is necessary as a way to demonstrate as near 100% safety as possible. This is critically important for the survival of Tesla, and equally important the survival of the electric vehicle industry. New technologies tend to scare people, which necessitates that safety beyond existing technologies must be demonstrated. We will modify this behavior as we feel appropriate as time and research continues. Calling this energy use a "waste" is ignoring its value.

Regards,
Zak
Click to expand...
 
#28
I had previously posted the following (speculation from me) on Martin's blog:

The “only when above 50% charge” suggestion really points a finger at safety concerns. Being ready to redistribute any heat from a burning cell all around to the rest of the pack. The fact that the A/C compressor doesn’t run suggests it is not about trying to cool the whole pack, but rather just to even out the temperatures. I don’t know if if is for cell failure safety, or just an effort to try to keep the whole pack at uniform temp so that the cells age evenly.
Click to expand...

It is nice to get an 'official' answer, but the roundabout way Martin's questions are asked then answered is peculiar.

#1: Martin posts something on his blog.
#2: A response is put on the owners forum.
#3: Someone copies the answer back over here.
 
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#29
TEG said:
It is nice to get an 'official' answer, but the roundabout way Martin's questions are asked then answered is peculiar.

#1: Martin posts something on his blog.
#2: A response is put on the owners forum.
#3: Someone copies the answer back over here.
Click to expand...

You left out a step:

#1b: One or more owners post to the owners forum expressing interest in the issue.

The core process is that Martin and other owners have a way to talk to Tesla and get answers to issues, both through the owners forum and directly. That seems pretty normal. Steps 1 and 3 are just wrapped around that channel.

Tom
 
#30
Zak's explanation on the Owner's Forum is more detailed than the explanations any Tesla employee gave me, though I did ask why the pump behaved as it did.

Note that I get "special treatment" at the Owner's Forum - Darryl Siry told me that any negative comments that I post there will be deleted. I do not wish to be subjected to scrutiny by Darryl or his special censorship. I have not even logged in since may first post there as a customer was deleted and I was banned from the Forum.

Clearly, safety is very important, but a design that requires constant water circulation is sub-optimal. What happens when my water pump fails from constant use, possibly as soon as next year? (See the last part of my blog, where I talk about pump life.) Is my car then no longer safe? Is it even no longer safe when parked in my garage?

I also wonder if this constant pump energy is accounted for when Tesla computes its energy usage for the EPA-mandated window sticker. I don't think the EPA testing protocol will catch this constant energy consumption. I think that test requires the car to be fully charged, then immediately driven over the specified driving cycle, then immediately charged again to measure its energy usage. If true, such a test would miss something like 22% of the energy consumed by the car under normal usage. (Note that as a very early car, mine came without any window sticker.)
 
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#31
Martin, I am a bit surprised that this whole situation is a surprise to you now. As far as I know, you were very involved with the whole ESS design. Was this "pump always on above 50%" an engineering decision that was made after you were no longer with the company?

----

With regards to EPA mileage: It wouldn't surprise me if this sort of thing does NOT count against it. Some people (particularly taxis, police cars, and such) will spend a lot of time parked and idling... Using some gasoline. The EPA tests don't take into account how much fuel is used going nowhere when people decide to use their energy storage while parked. People in very hot climates may sit in their car with the engine running and the A/C on and they are using gas at 0MPG, but again, the EPA wouldn't take that into account.

Some old VW microbuses had gasoline powered heaters - again, I don't think that would count against MPG. So, I don't think electricity used while parked for long periods of time is going to affect the sticker. Still it seems like a perfectly valid point of discussion particularly since the whole EV movement is trying to solve the "big picture" problem, not just get some EPA number.

Now on my RangerEV, even though everything shuts down when the truck is off and not plugged into a charger, it still "leaks" energy over time. Li-Ion itself is actually good at holding charge for a long time, but NiMH is worse about just self-draining over time. For the most part, EVs work out better in applications where they are driven frequently and not left to sit for long periods of time. Then there is the whole situation of battery conditioning. Some EVs will self-drain the cells and recharge them repeatedly in an effort to get the different cells more in balance. This is another (arguably) necessary waste of electrical energy.

I wish I had some simple answer to make this all seem great, but we are back to that old adage "it's all about the batteries".
(And then there is this version)
 
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#32
TEG,

It's been more than a year since I was relieved of control at Tesla. Lots and lots of technical decisions have been made since then. When I left my post as CEO, we were not yet ready to ship the car; there were many technical issues left to resolve. Were I still there, I would have influenced the resolution of these issues with my own perspective and my own attention to what I considered to be important - for example, energy efficiency.

There have been 3 CEOs now since I left that post, and they each have directed Tesla in their own directions, each has left his mark. The shipping car bears the marks (if you will forgive the pun) of all 4 CEOs.

To your second point, yes, the EPA test does not cover extreme, non-typical driving patterns like NYC taxis. Yes, they also don't account for minor losses like the self-discharge in your Ranger EV. But the EPA tests try (successfully or not) to capture something that resembles typical vehicle usage and typical fuel consumption as a result of such usage.

Note that the EPA recently changed its calculation methodology to more closely capture typical energy consumption for gasoline cars, because it became apparent that the old way was failing to do so.

My driving is fairly typical - perhaps 10 miles per day more than average, perhaps a tad more hills and aggressiveness than average. But this energy lost to the 24/7 pump is a loss that every single owner will experience, and the percentage of energy consumption lost to the pump will actually go up for folks who drive fewer miles or drive less aggressively.

If the EPA tests miss 22% of the energy consumed by typical drivers then it is failing in its mission.
 
#33
Well, obviously it is a bummer that the pump is left running like that. Conserving energy is certainly an appeal of the Roadster, and anything that cuts into that tarnishes the image.

Whether you stumbled onto it recently as an "new item of concern", or knew about it for a while and had hoped they would find a better way doesn't matter I suppose. It is what it is. Hopefully "drivetrain 2.0" includes a way to avoid having this 'parasitic loss'.

In the mean time some owners might want to only ever charge the Roadster half way up if their daily driving is under say 100 miles total.
 
#34
TEG said:
Well, obviously it is a bummer that the pump is left running like that. Conserving energy is certainly an appeal of the Roadster, and anything that cuts into that tarnishes the image.

Whether you stumbled onto it recently as an "new item of concern", or knew about it for a while and had hoped they would find a better way doesn't matter I suppose. It is what it is. Hopefully "drivetrain 2.0" includes a way to avoid having this 'parasitic loss'.

In the mean time some owners might want to only ever charge the Roadster half way up if their daily driving is under say 100 miles total.
Click to expand...

Unfortunately, it takes extraordinary action to charge to 50% - the "normal" charge takes to to well above 80%. Also, it kind of takes away the point of the fancy battery pack if you only charge it half way. Part of the point of a 200+ mile driving range is that you don't have to worry about taking an unplanned trip - you get invited out to dinner in the City and you leave straight from work, for example.
 
#35
Well, yeah - obviously keeping under 50% is an inconvenience and reduces the flexibility - but some people are very much running a set routine and drive the same trip every weekday without fail. Doing a pre-set 1 hour charge each night during the week, and then a full charge Friday night for the weekend could possibly work for some subset of owners. Certainly not ideal, but just a thought as to a possible way to avoid the excessive pump action.
 
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#37
TEG said:
Some people (particularly taxis, police cars, and such) will spend a lot of time parked and idling... Using some gasoline.... People in very hot climates may sit in their car with the engine running and the A/C on and they are using gas at 0MPG, but again, the EPA wouldn't take that into account..... So, I don't think electricity used while parked for long periods of time is going to affect the sticker
Click to expand...

I think the difference here is choice. Martin's Tesla runs down without him choosing to do any of the above energy wasting practices.
 
#39
Does anyone know who makes the Roadster water pump? Is Büehler also the manufacturer of the Roadster part?

Edit: to change the spelling of the company. Their PDF spells it Bühler, the press release: Buehler. I compromised with Büehler.
 
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