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Coming soon

Not autobiography but biographies

Steve jobs by Isaacson

Elon musk by ashlee vance

The everything store

Books on startup by entrepreneurs

Books by Richard branson

Zero to one by Peter theil

The hard thing about hard things by ben Horowitz

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23/M/India and its neighbours: looking to talk to people who are way too enthusatic about something but have nobody to share their interests with

I am a 23 year mechanical engineer who works on electric cars. I just graduated college couple of months ago and moved to New Delhi and I don't really have anyone to talk to.

I love reading non-fiction books. Currently I am reading Ask an astronaut by Tim peake. I love astronomy, science and technology. I also listening to podcasts. I do watch a lot of tv shows and the last one I watched was the expanse.

I work in startup so the hours are little longer but I really love my job because I actually get to build something. And because of this, I don't get to go out and meet new people so here I am.

I am looking to talk to more women. I can talk email, reddit mail or whatever you like. The reason why I mentioned India and its neighours as I would also love to meet someone in real life (but only after we have talked online for a little while). But that's not really a requirement. I have also lived in Sri Lanka too!

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23[M4F] India and its neighbours: looking to talk to people who are way too enthusatic about something but have nobody to share their interests with

I am a 23 year mechanical engineer who works on electric cars. I just graduated college couple of months ago and moved to New Delhi and I don't really have anyone to talk to.

I love reading non-fiction books. Currently I am reading Ask an astronaut by Tim peake. I love astronomy, science and technology. I also listening to podcasts. I do watch a lot of tv shows and the last one I watched was the expanse.

I work in startup so the hours are little longer but I really love my job because I actually get to build something. And because of this, I don't get to go out and meet new people so here I am.

I am looking to talk to more women. I can talk email, reddit mail or whatever you like. The reason why I mentioned India and its neighours as I would also love to meet someone in real life (but only after we have talked online for a little while). But that's not really a requirement. I have also lived in Sri Lanka too!

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Structurefree for mechanics

Brian Douglas for automatic control

AvE for tool reviews

You can also use NPTEL (those indian professors on youtube) where you can find almost all engineering courses. Everything is free as it is funded by Indian government

Buy her a copy of ignition: an informal history of rocket fuels

I work in an EV startup as a mechanical engineering intern (which will turn into a job by the end of month) and I do all the things you mentioned. I design, analyse, find vendors, talk to vendors (negotiation done by the seniors because I suck at this), build prototype, test prototype and in future manufacturing for large scale. I also learn something new everyday since I am responsible for the whole thing. So for instance, for one week, I was working on calculating the heat transfer and then the next week, I am studying material science and than the next week, chemistry of making dispersion. I have no idea what I will have to learn in the future. It's a really fullfilling job. I have both independence and tons of responsibilities. Forget about being part of a team, you will be the team.

However, the pay is lower and hours are long. Also, having this much responsibilities at such young age is daunting. And there the inherent risks assioated with startups. But you do learn a ton in a very short amount of time.

Also, startups can be forgiving of grades and degrees. I have failed tons of courses (failed chemistry twice and got D in heat and mass transfer) and yet nobody really cared (nobody asked so I didn't tell anyone).

If you wanna find a job in startups, try angelist which is like linkedin but for startups. You can also just google search "aerospace startups" and just mail them.

Do remember that startups are very diverse and risky so be careful. if you feel something is off about the founders, don't join them.

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What is the easiest way to bend an aluminium tube?

I need to make small bends in these aluminium tubes or as they are called "Multi-port extrusion tube"( they are used in heat exchangers) in a shape like this:

https://drive.google.com/file/d/1klPkOorCqWFOqDAj-s2jlHMXAVjBm67B/view?usp=sharing

Diameter of bends is 20 mm. The dimensions of the tube are flexible. The wall thickness is about 0.5-1.5 mm. The height is about 40-60 mm and the width is about 4-5 mm.

The dimensions : https://drive.google.com/file/d/1pXbjzoijSuJdsEgG2Vq4KMrIWQKj46il/view?usp=sharing

So what is easiest way to achieve these bends? I have been told by a radiator guy that only an expensive machine can do it. I would also like to know the name of the machines that can do this.

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How do you create a Phase change slurry from microincapsulated PCM powder? (X post from r/chemistry

I am working on thermal management system for EV battery packs and I want to use mPCM slurry as a coolant. However, the only company in my country that could possibly supply that is BASF that has sold its buisness to an american company. So I am wondering if I can just take any mPCM powder and simply mix it in water/glycol to get a PCM slurry? Can I mix multiple mPCMs in one solution (I have read a paper that did this but they didn't mention the method of preparation)? I know that the powder is created by drying the dispersion solution.

Note: Explain to me in the simplest terms because I am mechE engineering intern that failed chemistry twice.

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3 points · 13 days ago

mPCM formulations go back decades.

Microtek doesn't have the corner on them by any stretch. There are a lot of academic papers that show a number of approaches, and some of them are easy or at least straightforward to execute yourself without fancy equipment or significant difficulty.

I once had a spray dryer/sol gel vendor produce material for one of my projects successfully based only on a paper from 1996 for an orbital platform STTR. The performance was both comparable and similar in composition to stratospherically priced commercial solutions, which made me realize why they were also so paranoid about even letting me buy theirs without all kinds of utterly ridiculous agreements in place before I could even get my hands on their versions...they were far from novel.

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Original Poster1 point · 13 days ago

Interesting. My problem is that no such vendor is available in my country India. Even if they could do that,they won't unless we give them a huge order. I have found a lot paper that using/studying mPCM but not that many on exact preparation.

2 points · 13 days ago

Ok. Look for "Hawlader" and "PCM".

The approach is to use a paraffin bath with a mixture of gum arabic or acacia. You heat the mixture to the fusion temp, and then use a sonicator (ultrasound) to emulsify the mixture. It will turn pearlescent white. Good temp control is required, and an agitator to continuously churn the mixture.

You introduce the hot emsion into a common spray paint gun that is heated to the same temperature as the mixture. The air supply goes through a heated bath to warm it to a temperature just below the critical temp. You determine those temp by trial and error.

The spray will enter the collection vessel (I used a 50 gallon barrel), with enough cool air circulating to keep the powder from sticking to itself. In my case, I used a lot of room temp compressed air and adjusted it just until clumping did not occur.

I used a xylene wash to get rid of the unencapsulated powder...roughly half of the mass. Any contamination of my cooling system would have been bad during the test.

After we verified our glycol/encapsulated paraffin mixture worked extremely well, I had a vendor who did spray drying do a much better job with much higher yields that actually did not require a solvent wash prior to use. His usual products were specialty art pigments.

Our latent heat capacities by volume were almost 2/3 of the paraffin in our pumped system, nearly as good as many commercial products. I did all of this in a matter of days in terms of actual work to mix, process, and clean the powder. Thise is why I'm saying this is something you can do yourself if you needed to.

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Original Poster1 point · 13 days ago

Thanks for your comment! I think I will be able to ge mPCM powder but my only challenge is to get a stable solution that can flow at low rates in channels. I started studying about it and I feel like with some trial and error, I would be able to figure it out.

Really appreciate the help here!

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How do you create a Phase change slurry from microincapsulated PCM powder?

I am working on thermal management system for EV battery packs and I want to use mPCM slurry as a coolant. However, the only company in my country that could possibly supply that is BASF that has sold its buisness to an american company. So I am wondering if I can just take any mPCM powder and simply mix it in water/glycol to get a PCM slurry? Can I mix multiple mPCMs in one solution (I have read a paper that did this but they didn't mention the method of preparation)? I know that the powder is created by drying the dispersion solution.

Note: Explain to me in the simplest terms because I am mechE engineering intern that failed chemistry twice.

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Why isn't everyone copying tesla's thermal management system for battery packs? (X post from askengineers)

This is a simple schematic of it: http://insideevs.com/wp-content/uploads/2015/12/Tesla-gm-cooling-gb-slide-3.jpg

It's literally a slotted radiator tube bent in a proper shape. You can find the tube on alibaba (https://alibaba.com/product-detail/Flat-aluminum-radiator-core-material-tube_60514244117.html?spm=a2700.7735675.2017115.113.m32RQG&s=p ).

It's really simple and cheap and its really effective. So why aren't others copying it? Leaf's pack's cooling system was probably designed by an intern. Other battery packs with active cooling use cooling plates with large format prismatic cells even though 18650s are cheaper, safer and offer a higher volumetric efficiency. I see research being done on Phase change materials or other "exotic" ways but I still can't argue against tesla's system.

Are there any issues with tesla's design that anyone else knows that I am not aware of?

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16 points · 16 days ago · edited 16 days ago

It's really simple and cheap and its really effective. So why aren't others copying it?

Because it's not particularly great. For example, Direct Expansion (BMW i3, Chevy Bolt?, some others) is generally better than Tesla's solution.

https://www.hybridcars.com/bmw-and-lg-chem-trump-tesla-in-battery-thermal-management/

Other battery packs with active cooling use cooling plates with large format prismatic cells

That's true, but generally performance of that solution is pretty close to what Tesla's 'cooling tube' design is. There would be no reason to "copy Tesla" just to get roughly the same performance they already have.

Additionally, you are comparing 2011-2014 era EV designs to Tesla's 2017-2018 designs, which isn't exactly fair. Other EVs have moved past cooling plates in their designs, without using the Tesla strategy. Which is part of the reason why they aren't using Tesla's design.

https://www.hybridcars.com/2017-chevy-bolt-battery-cooling-and-gearbox-details/

Leaf's pack's cooling system was probably designed by an intern.

Yeah, absolutely. Tesla has cooling, which is obviously better than not having any cooling (like a Leaf, or a Ford Energi Hybrid)

But that's a crazy low bar to set.

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Original Poster0 points · 16 days ago

I have looked into direct expansion. it just replaces the coolant, why not make it flow through the tesla tubes?

EVs have moved past cooling plates

Which ones? The example you showed is still using the cooling plates.

Got an example of an nmc pouch with higher than 260wh/kg? I work with these cells, and I'm not aware of one

Cooling pouches, you cool the exact prismatic cross section of the cell rather than just the outside. There's a temperature gradient to the core, but it's less bad than for cylindricals.

Chevy bolt uses this, whereas the volt uses the architecture you're describing. not sure of other examples I can talk about due to nda

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Original Poster2 points · 16 days ago

In order to cool those pouches, they use cooling plates with internal tubes for coolant. That itself is heavy. And its pretty expensive.

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Why isn't everyone copying tesla's thermal management system for battery packs?

This is a simple schematic of it: http://insideevs.com/wp-content/uploads/2015/12/Tesla-gm-cooling-gb-slide-3.jpg

It's literally a slotted radiator tube bent in a proper shape. You can find the tube on alibaba (https://alibaba.com/product-detail/Flat-aluminum-radiator-core-material-tube_60514244117.html?spm=a2700.7735675.2017115.113.m32RQG&s=p ).

It's really simple and cheap and its really effective. So why aren't others copying it? Leaf's pack's cooling system was probably designed by an intern. Other battery packs with active cooling use cooling plates with large format prismatic cells even though 18650s are cheaper, safer and offer a higher volumetric efficiency. I see research being done on Phase change materials or other "exotic" ways but I still can't argue against tesla's system.

Are there any issues with tesla's design that anyone else knows that I am not aware of?

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It's just a heat exchanger, made into the appropriate shape. Nothing special about it, whatsoever. Doesn't even employ phase change, by the look of it. No special materials, either. Anyone could design it.

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Original Poster1 point · 16 days ago

I know. That's what I said. The questions is: Why aren't others using it?

btw, phase change is worse.

Well, what are others using, in comparison? And what problem do you have with phase change, in general?

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Original Poster1 point · 16 days ago

Well others are using cooling plates with large format cells. They are more expensive and bulkier.

PCM is lot more experimental. the only practical pcm for this temp range are Paraffins which are flammable (while flash point is higher, it still more flammable than copper tubes) and their cycle life is limited. While the weight is lower, the volume is quite large which means you need to make your car bigger which leads to other issues.

But the bigger issue is that you still need to get heat out of the pcm. In small packs, heat sinks would do the job. But in large packs, you will need an active system which just defeats the purpose.

I can see their applications as a replacement of liquid coolant. But I reckon the pump work would be high.

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I work in an EV startup and people here do all that regardless of their job title (thete are only 3 people including me)

So if you wanna do it all, go for that. But it's a different lifestyle so it may or may not suite you

> that the country needs a modern, safe and fast railway system

Isn't that bullet train? Safety and speed costs money regardless of what you call it. I am not a huge fan of bullet train project either but I don't think this "modern, safe and fast railway system" will be cheap either.

As far as modernising railways goes, they are already working on it:

http://pib.nic.in/newsite/PrintRelease.aspx?relid=177578

http://indianrailways.gov.in/Railways%20Presentation.pdf

https://thenewsminute.com/article/indian-railways-completely-automate-signalling-system-soon-75509

3 points · 21 days ago · edited 17 days ago

lookup structurefree on youtube. he must have a video on that

look up Jack rickard on youtube. He has extremely detailed videos about breaking down tesla battery packs. Way more detailed than anybody else

Anybody here working on Phase change materials?

Again, showing how your parents pay for everything. The thought of having to spend your own money on food and rent is foreign to you. Lol

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Weird. I explained to you how you can't make money by internship here and yet ypu are going on and on about me being Rich.

Again, op is asking about work experience that will help him land a job. Not about money. So how i paid for food and rent is irrelevant here.

*how your parents pay for your food

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And you know that because?

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You can try joining a startup. I just joined an EV startup and my job is to design thermal solution for a battery packs. I am also supposed to build, test and do everything else too. And I just finished Btech 3 weeks ago. I don't even remember anything from heat and mass transfer!

So yeah, if you are a risk taker and really love engineering, try finding an early stage startup. You can use angelist fir that.

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How does regenrative braking charges Li-ion batteries in EVs and hybrids?

During regenerative braking the current produced must be quiet high. It's also going to be generated for a short amount of time. However, Li-ion battery packs can only be charged with CC-CV cycle. So how does this unstable current from regen braking is used to charge the packs? Is there a different kind of charging cycle used for this application? Are there any special circuits for this? and what if current is too high?

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If you are gonna do IB , You can forget about JEE. Been there done that

As far as "IT is dying" is concerned, well the "infosys, tcs, wipro "L garbage is definitely dying . But the computer engineering is definitely not dying. I mean, JP Morgan offered 30 LPA package at my college.

But if you are into maths and the parents are hell bent on engineering, go for CS and focus on machine learning which is just applied math.

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What are some good textbooks on building electric car chargers?

What are some good textbooks on building an electric car chargers?

I am a recent MechE graduate who just started interning in an EV startup. While my job is about battery packs, I want to learn more about workings of electric car chargers (Level 1,2,3) , their constructions, all the standards etc. So I am looking for Textbooks, MOOCs, journals or videos etc that are on this topic.

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5 points · 1 month ago

Are you more interested in how they come together as an educational exercise, or are you thinking that you’d save some money by DIY-ing it?

If you’re interested in the latter, you’ll likely end up spending ~20% more in tools, materials, and trips to the store. Additionally, if anything goes wrong, no insurance will cover anything as a result.

If you’re curious about the bits and pieces of a charger supply, I can only think of https://openevse.com as a place to start.

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Original Poster3 points · 1 month ago

It's both. But I do want learn enough about them so maybe I could design them or atleast work on them in the future. I live in India so the Idea of buying it from the store goes out of the window as they don't exist here.

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What are some good textbooks on building an electric car chargers?

I am a recent MechE graduate who just started interning in an EV startup. While my job is about battery packs, I want to learn more about workings of electric car chargers (Level 1,2,3) , their constructions, all the standards etc. So I am looking for Textbooks, MOOCs, journals or videos etc that are on this topic.

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Which part? The charge controller or the tranformer/power handling stuff? Charging lead acid or lithium ion? From house hold circuits or some other source? Sorry for all the questions.

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Original Poster1 point · 1 month ago

Information on both will be great. But since I am interested in charging station, I guess I will be more into power handling stuff

That's a very open question, you can ignore the parts you already know.
The Batteries, including Li-ion page has some info, and that chemical voodoo language halfway down that page decides if you have 'power' or 'energy' cells.
It is a bit jumping to and fro, http://batteryuniversity.com/ is another very useful site.

To keep the batteries safe during charge/discharge you can do "Coulomb counting" to keep track of the SoC but is somewhat complicated, a simple Volt-meter is easy but you need to account for temperature in your head.

For an electronic reference https://www.allaboutcircuits.com/education/ might help.

To charge batteries from the grid you first need a rectifier to convert the grid's 120/230/400V alternating voltage into a DC voltage, followed by a (complicated) "DC-DC converter" (Google is your friend), the complication is that a 'normal' DC-DC converter produces a fixed voltage, a battery charger must take the variable battery voltages and charge currents at each stage into account, while not overloading the grid supply.
Level 1,2,3 is an indication of how much power it can take from the grid (and the needed wire thickness and fuse the electrician has to install from the service panel), some EV manufacturers have dedicated web pages for that.

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Original Poster1 point · 1 month ago

Thanks for the sources!

No lander on this mission (would it even be physically possible to do a lander in the mass/volume constraint of a cubesat?). Lunar Flashlight is just a flyby

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Original Poster1 point · 2 months ago

Paul Bookout:  Yeah, still.  It's called OMOTENASHI.  It's another Japanese CubeSat. 

Host:  Okay. 

Paul Bookout:  And, their mission is to land on the moon. 

Host:  Oh. 

Paul Bookout:  Can you imagine a small little CubeSat, you know, a little bit larger than a shoebox, land on the moon?  Of course, and the big thing about it is that they're going to be using a solid rocket motor to slow down to be able to land on the moon.  So, that's one of the things on EM-1 that we're offering that previous commercial launch vehicles and that don't offer propulsion systems for secondary payload to be able to utilize that.  That's one thing EM-1 and SLS is allowing.  So, that's a huge deal. 

Host:  Yeah. 

Paul Bookout:  For those.  So, if OMOTENASHI is successful at landing on the moon, they'll be the fourth nation in the world to have actually land and do some science on the moon. 

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