Tostino's water cooled 36 fet infinion

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Tostino's water cooled 36 fet infinion

Post by tostino » Sep 01 2012 2:09pm

Hello all! It's been forever since I've been around these parts. Mostly to do with when I had an accident with my old bike, got hit by a lady in a mustang who turned right into me. Had to have knee surgery, bike was totaled (motor had shorted phases, controller blew because of it, frame bent, CA crushed). The only thing that didn't get damaged was my batteries.
I was pretty discouraged with everything and didn't have the energy to get back to re-building (nor the funds, still have an ongoing lawsuit with the insurance co. 2 years later).


A few months ago I switched jobs, and am now making a good bit more than before doing database development. Now it's time to rebuild.

First step in that process is a new controller.

I had a couple 36 fet infinion boards I had ordered from Keywin a long time ago, which I was wanting to build up and water cool.
What I have:
  • 1/8" copper bar for the heatsinks
  • Copper tubing for the water cooling pipes
  • Some nice low esr 160v caps from digikey
  • Project boxes to enclose them in
  • 80 4115 fets
  • 120x360mm radiator and fans
  • Water pump
  • Rubber tubing
I know I should have gone with 4110's, however, I was planning on a 36s setup at the time I ordered. Hindsight is always 20/20 I suppose. Not like I can't switch them later if I feel the need.


My plan was to have the high side fets soldered directly to the copper bar connected to the heat pipe, and the low side fets split into three groups of 6 soldered directly to 3 different copper heatsinks, and then clamp those heatsinks to the larger heatsink connected to the heat pipe.

Today I got motivated and devised a solution to get those fets soldered:
IMG_20120901_120228_es.jpg
What you see above, is the row of 18 high side fets with solder paste on the back of them, clamped to the copper heatsink with an alu-bar on the front to hold them all in place, and smaller copper bars on the back to hold the heat pipes in place.

Next, I stuck them on the burner on the stove, covered the whole contraption with a pan, and set the heat on medium. Only the C-Clamps were in contact with the burner. I kept tabs on the heat of the fets with an IR thermometer, and as soon as the solder on the back of the fets melted, I started cooling everything off.

I kept the temp from getting too high I believe, but I still need to figure out if I ruined the fets before I continue.

Anyways, enjoy the rest of the pictures from today... I'll be continuing with the low side ones now:
IMG_20120901_120305_es.jpg
IMG_20120901_132752_es.jpg
IMG_20120901_132914_es.jpg
IMG_20120901_145929_es.jpg
IMG_20120901_150005_es.jpg

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Re: Tostino's water cooled 36 fet infinion

Post by hjns » Sep 01 2012 3:48pm

Great, I love it! I may try something like that myself. Though I would prefer Oil... Any specific reasons why you want to play with water?
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Re: Tostino's water cooled 36 fet infinion

Post by hillzofvalp » Sep 01 2012 4:10pm

I thought the thermal pad on the back was also the drain or source of the fet.. Which is why we put insulators behind the FETs... Is this not the case with 4115s? Check continuity. You may need to cut that bar into sections

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 01 2012 4:47pm

hillzofvalp wrote:I thought the thermal pad on the back was also the drain or source of the fet.. Which is why we put insulators behind the FETs... Is this not the case with 4115s? Check continuity. You may need to cut that bar into sections
The 4115's are like any other fet. The difference is the layout of the 36 fet controller. All of the high side fets for each phase are in the same row of 18. This means that they are all already connected through the middle leg, even if you insulated the back of the fets, they are still electrically connected with the layout as it is.

So instead, I am utilizing that to my advantage to get the best cooling I possibly can.

The same is true for the low side fets to a point... each phase is grouped together, so you can have all 6 fets per phase connected to the same heatsink directly without any issues. You just then have to insulate the three blocks of 6 fets from one another.

See if this illustration helps at all:
IMG_20120901_173732_es.jpg

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 01 2012 4:49pm

hjns wrote:Great, I love it! I may try something like that myself. Though I would prefer Oil... Any specific reasons why you want to play with water?
Water is pretty easy to work with... Lots of cheap parts that work reliably for computer water cooling. Also holds more thermal mass for the volume that oil if I recall.

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Re: Tostino's water cooled 36 fet infinion

Post by hillzofvalp » Sep 01 2012 5:14pm

Got it. I want to build one f these. What power do you think it'll take with cooling? 25kW?

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Re: Tostino's water cooled 36 fet infinion

Post by amberwolf » Sep 01 2012 5:25pm

Just to be sure: You're going to electrically insulate the groups of FETs for each phase from each other, right? ;)

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Re: Tostino's water cooled 36 fet infinion

Post by dnmun » Sep 01 2012 6:43pm

you can test each of these mosfets now after you heated them up. use the diode checker function on your voltmeter and see if they all still read about 530mV or so. i doubt if the gates would be shorted.

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 01 2012 7:32pm

amberwolf wrote:Just to be sure: You're going to electrically insulate the groups of FETs for each phase from each other, right? ;)
Thank you! I didn't know that it was that easy to test. I'll do that asap.
amberwolf wrote:Just to be sure: You're going to electrically insulate the groups of FETs for each phase from each other, right? ;)
Yes I am, see below:

So this is the rest of the progress I have made for the day...
I cut these for each bank of low side fets:
IMG_20120901_182315_es.jpg
I then squared them off:
IMG_20120901_183039_es.jpg
It will look something like this (with insulation between them) when it's done:
IMG_20120901_190800_es.jpg

After I solder the fets to the smaller heatsinks, I need to figure out the best way to attach them to the larger heatsink... Maybe a clamping mechanism of some sort. Not too sure yet.

I'll be using kapton tape as the insulation material.


P.S. Zombies, where did your post go? =p I had just got ready to type up a reply.

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 01 2012 7:53pm

hillzofvalp wrote:Got it. I want to build one f these. What power do you think it'll take with cooling? 25kW?
I do believe it'll do 25kw in short bursts, probably not continuous.

Like I said before, I really should be using 4110's for what i'm doing now, but I don't have any, and instead I have 4115's. So that severely limits the power I can get out of it at the sane voltages I plan on running now.

On that note, if anyone has a batch of 36 4110's they want to trade for 4115's, let me know lol XD.

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 01 2012 10:06pm

Looks like the fets are all good still after soldering. They measure 400 mv.

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Re: Tostino's water cooled 36 fet infinion

Post by zombiess » Sep 01 2012 11:39pm

tostino wrote:
hillzofvalp wrote:Got it. I want to build one f these. What power do you think it'll take with cooling? 25kW?
I do believe it'll do 25kw in short bursts, probably not continuous.

Like I said before, I really should be using 4110's for what i'm doing now, but I don't have any, and instead I have 4115's. So that severely limits the power I can get out of it at the sane voltages I plan on running now.

On that note, if anyone has a batch of 36 4110's they want to trade for 4115's, let me know lol XD.

If you want to be safe figure you can do 40a per fet in a bank while keeping them below 100c and you should be able to do 240a continuously with a very large safety margin. Pushed to their 100c rating they are 71a per fet which is good for 426a. Since you are water cooling you shouldn't have any problems as long as you don't have a really slow switching fet in a bank and push the limits. I ran mine at 125v 120a battery 210a phase and couldn't manage to get it warm.

I'd have no worries pushing mine to 200a battery 350a phase at 125v, but my bike at 120a 210a phase was plenty and hard to ride.

No need to worry much about the advantage of 4110 fets when you put 6 irfb4115s in parallel.
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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 01 2012 11:51pm

Awesome info! Thanks.

At the time I purchased these, no one had a working one. So it is pretty cool to get some real-world numbers.

I just remember through some calculations that at a 50% duty cycle, and 400 phase amps, I would be generating a combined 1550w of heat between the high side and low side XD...
Nothing to shake a stick at. That was estimating a resistance value of 0.002891 mohm for 6 fets. I suppose i'll just have to see what the setup is capable of.

I'll need a different motor before i'm ever going to stress this controller though... My lowly 9c is going to fry =).

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 02 2012 10:33am

Some more progress today. Coming along pretty smoothly if I do say so myself!

Anyone have any ideas on how to attach these individual phase heatsinks to the larger heatsinks?
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Re: Tostino's water cooled 36 fet infinion

Post by zombiess » Sep 02 2012 11:51am

Buy a sheet of good electrical insulating material, make sure both surfaces are flat, drill several holes and attach each with many nylon screws or regular screws run through some sort of plastic sleeve. I've used nylon screws in several of my controllers to attach fets to the heat sink with no issues. Since you now have all the tabs connected you should look at supplying b+ directly to the high side and attaching each low side to each phase. I used buss bars to do this with great success and have run as high as 110a battery current 135a phase through my eb318 4115 controller. If you search I have a few threads with pics in the tech section.
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Re: Tostino's water cooled 36 fet infinion

Post by scriewy » Sep 02 2012 2:12pm

So you were horseless since the accident ?! That bitch.

i pray for you my child that no fet pops on you, coz then it's gonna be a mess replacing any fet, aspecialy if 1 pops on high side.

i usually k.i.s.s thermal paste & screw mount my heatsinks.
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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 03 2012 11:54am

zombiess wrote:Buy a sheet of good electrical insulating material, make sure both surfaces are flat, drill several holes and attach each with many nylon screws or regular screws run through some sort of plastic sleeve. I've used nylon screws in several of my controllers to attach fets to the heat sink with no issues. Since you now have all the tabs connected you should look at supplying b+ directly to the high side and attaching each low side to each phase. I used buss bars to do this with great success and have run as high as 110a battery current 135a phase through my eb318 4115 controller. If you search I have a few threads with pics in the tech section.
Do you have any suggestions for nylon screws/nuts and bolts? I don't quite know what size i'd need, and where to get high quality ones...

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Re: Tostino's water cooled 36 fet infinion

Post by dnmun » Sep 03 2012 12:06pm

you could clamp them together. use a legal papers type of paper clip that will span the back of the tube to the front of the mosfets so the clamp would be on the face of the mosfet. your insulating layer is between the two, the clamp would be at the same potential as the tubing so the paper clip would be at that potential. the plastic case of the mosfet should provide the needed electrical isolation, you even spread out he force by using some kinda plate under the clamp on the surface of the case of the mosfet and the paper clip on the outside of that to spread the force, and use some of the silicone type hot glue they use in the new headway BMS to carry the heat from the mosfets through the face of the package to the heat sink above.

or you can use zip ties, pull them around the entire assembly as tight as possible but leave the tail on in case you need to tighten it again later if they stretch.

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 03 2012 2:41pm

Well, zip ties are what I had available. So here is my progress.

I think i'll put a dab of epoxy in between the fet blocks to keep them from moving around and touching.
Attachments
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Re: Tostino's water cooled 36 fet infinion

Post by zombiess » Sep 03 2012 6:24pm

Figure something else out instead of zip ties and make sure you have some sort of isolator between the blocks in case they move. What are you using to electrically isolate each phase to the water block on the back?

I'd probably use nylon nuts and bolts myself. Bigger is stronger.
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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 04 2012 7:27am

zombiess wrote:Figure something else out instead of zip ties and make sure you have some sort of isolator between the blocks in case they move. What are you using to electrically isolate each phase to the water block on the back?

I'd probably use nylon nuts and bolts myself. Bigger is stronger.
I am using kapton tape as the insulator.

Yeah, I wasn't quite happy with the zip tie solution for holding things perfectly in place. A little too loose tolerance for my taste.

Edit: I am a little weary about drilling holes, simply due to the water pipes on the back. I just have a feeling i'll screw up.
Probably just irrational fear.
Last edited by tostino on Sep 04 2012 7:46am, edited 1 time in total.

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 04 2012 7:33am

scriewy wrote:So you were horseless since the accident ?! That bitch.

i pray for you my child that no fet pops on you, coz then it's gonna be a mess replacing any fet, aspecialy if 1 pops on high side.

i usually k.i.s.s thermal paste & screw mount my heatsinks.
Completely and utterly (electric) horseless =(. I still had my dirt bike at least so I had some two wheel fun.

And yeah, it won't be fun if any of the fets blow. I may cry. That's why I need to work as hard as I can to keep the suckers nice and cool!

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 06 2012 12:47pm

I picked up some of these for trying to clamp. I'll see when they come in how they work.

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Re: Tostino's water cooled 36 fet infinion

Post by tostino » Sep 18 2012 8:45am

I'll cut to the good stuff... a bunch of new pictures.
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Re: Tostino's water cooled 36 fet infinion

Post by dnmun » Sep 18 2012 9:20am

i use milk jugs to proved the insulating layer sometimes. the poly plastic of the milk jug is thick, and sometimes the curves help, not so sure about the rubber felt you used there. looks like it is really compressed under the clamp. you can use hot glue on the ends too since it won't be that hot. way cool.

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