Open Source DC controller

Post by **bga** » Thu, 03 Sep 2009, 02:02

Hi Paul,
and welcome to the forums.

Tranzorbs...
Yes, these things work really well against transients.

I've always been surprised that the gate Zener isn't built into FETs, given how sensitive the gate is to transients and static discharge damage.

I was commenting on the diodes because Ian at Zeva managed to toast an older type controller on his direct drive conversion. I recall the the diodes were implicated because of the high torque operation of the direct drive with a big motor and a heavy car putting a lot of flyback current through the diodes at low speed.

In my own smaller DC motor controller designs (12 to 24V and 10 to 20 amps), the diodes get hotter than the FETs.

My search for the device found a different diode with a 15+15 amp rating... Explained by looking at the fuzzy parts list on page 1 - 6002C instead of 2002C would make the difference!

Cheers

Post by **mcudogs** » Thu, 03 Sep 2009, 02:46

My mistake, I could only find an Altium package for the 2002 and I forgot to change the comment, the original bom has the 6002s, schematic has been updated.

Power board

Post by **MPaulHolmes** » Fri, 04 Sep 2009, 10:53

FANCY MOSFETS!

Check out those mosfets! They won "best in show" or whatever at the 2009 mosfet fair or something like that. I was reading about that. Digikey has them for $7 each in quantities of 10, but are out of stock until December. Now, if we could get synchronous rectification working, or some higher amp rated diodes. The controller could become quite a bit more powerful without having to change much.

Post by **Squiggles** » Fri, 04 Sep 2009, 10:59

Paul,
You should contact ixys directly, tell them what you are doing, you have plenty of evidence. Ask them for samples for prototyping.

Some companies are very good in this regard. Worth a try.

Post by **MPaulHolmes** » Mon, 07 Sep 2009, 20:21

I emailed them and asked for 10 samples. We'll see what happens. They also have a new 250v mosfet with an RdsOn of 12.9 mOhms I think. 500v diodes are pretty easy to find, so I think it would be basically the same price for making a 200v controller instead of a 144v. Well, maybe an extra $20 or $30. They even have some that are getting into IGBT territory with still reasonable rdson. Here's what I'm talking about:

mosfet list

Post by **Squiggles** » Tue, 08 Sep 2009, 02:13

With such a range of devices available getting component count down is easy, in terms of current capacity that is. 1000 amps continuous with six FETs is no problem. There is still the issue of heat dissipation. Good gate driver circuit and heat sink design should minimise heat issues. Looks like the capacitor bank is going to be the issue that drives overall size.

Post by **MPaulHolmes** » Tue, 08 Sep 2009, 09:53

Within the space right now, the sixteen 820uF caps I'm using take about 3-4 times longer to precharge than the Curtis 1231c according to Joe. He had to change to a smaller value precharge resistor. There is also another larger cap that's just about 10mm taller but same diameter that we could use without changing the power section etching design. I think that would be fine for 1000 amps. Might need to move to 6-8 ounce copper pcb though. Also something other than a LEM Hass. Fancier LEMs exist, but the price goes up by a factor of 5 or 10 once you get above around 800-900 amps.

Post by **Squiggles** » Tue, 08 Sep 2009, 13:39

How was the optimum capacitance calculated?

Post by **MPaulHolmes** » Tue, 08 Sep 2009, 20:01

I was mainly concerned with ripple current. The EVTech list had also told me that basically the more capacitance and ripple current the better. I went with the approach of getting as much ripple current capability as possible in the space I had in order to keep the caps cool. I didn't do any official calculations. I think it's pretty conservative with how many are being used right now. Too much isn't bad, except for cost.

Joe told me that the capacitors in his controller take quite a while to heat up. They always lag behind the mosfets/diodes. He drove it at a switching frequency of 8 KHz just to see how the reduced switching losses affected the temperature, and suddenly the caps were getting a bit hotter than the mosfets/diodes. The ripple current rating on the caps goes down the lower the switching frequency. So, half as many caps would be too few I think. That's as close to a calculation that was done.

By the way, I'm going to make a little driver board on my new cnc mill.

Post by **BiGH** » Fri, 13 Nov 2009, 04:33

Hi Everyone,
I've been reading slowly through the MEGA thread on ecomodder - if any Australian group buying goes on please let me know i'm definatly interested (only 75 pages to go! LOL)

Haydon.

Post by **bga** » Fri, 13 Nov 2009, 17:30

Got me curious:

Using 16 x 200V panasonic capacitor 820uF (22mm dia x 50mm high)
(the Panasonics are better spec then most on the market)
RMS current rating is 60 Amps (at 10KHz and 3.76A per capacitor)
total capacitance is 13,120uF (0.013F)
ESR is 5.125mR (0.082 ohms at 20 KHz per cap)
so, for 1000A, 5 microsecond pulses:
dvdt = 76mv per usec, or 0.380 V ripple in 5uS
V(ESR) = 5.125V (Equivalent Series Resistance)
Combining these, approximately 5.5V of ripple on the battery.

Consider the ESR of the battery string, probaby 80mR (assuming 160V and 2000A short circuit current) the effect of 5.5 volts of ripple in this will be about 60 Amps of current ripple.

I don't think that any of the above is cause for concern, but the ripple voltage is a bit high and mostly the result of the capacitor ESR.

One note of caution is that the ESR causes heating in the capacitor, so for a 1000A motor current, about 5000 watts during the 'on' part of the switch cycle. This is probably 500 watts for a typical 10% duty cycle. The capacitors are going to get hot fairly quickly, boil the electrolyte and explode if this is sustained for more than a minute or so.
You'll be picking bits of paper, goo and foil out of the (probably dead) controller for hours.

Measuring the capacitor temperature rise during a full torque at stall test would indicate what the limits actually are. The Panasonics are rated for 105 deg.C

Post by **polo-ev** » Sat, 14 Nov 2009, 19:52

Hi Haydon
I was part of the original Aust buy group. I have spare copper bars, circuit boards, hardware kits, controller components & the like.
One of the group members has one working on the bench already & another several are in construction stages.
Regards
Ian

Post by **mcudogs** » Sun, 13 Dec 2009, 02:52

Latest pics for Cougar Controller with Ian's custom case.

Cougar Pics

Post by **Yogibear** » Sun, 13 Dec 2009, 03:04

Appreciate the photo's Don, as Iam not far behind you, the heat sink and fans look great

Post by **Yogibear** » Sat, 26 Dec 2009, 21:55

Pleased to let you know that my cougar was fired up today and was even more than i expected, Looks good and the speed control was very smooth, I really believe that the cougar is a winner.. Thanks guys for pointing me this way..

Post by **Digger11** » Mon, 15 Mar 2010, 20:09

Anyone actually built one of these ? 144V 500A is probably good enough for me - would prefer 1KA, but for only about $250 USD this seems like good value (if it works).

What would be the operational differences between this Open Source Kit and say a Curtis or Zilla controller of similar rating ???

Post by **BiGH** » Mon, 15 Mar 2010, 20:16

You might want to hold off then. Paul is working on a 1000a synchronous rectification based controller at the moment. The alternate is that you could use igbts insted of mosfets for the power stage. This drives the cost up slightly but makes for an easier build. Two users in the thread have gone the igbt route using surplus igbts off eBay

Post by **Digger11** » Mon, 15 Mar 2010, 20:22

thanks BIGH,

I'm still in the planning stages but most likely going rear wheel direct drive (an old 190E Merc I have) and have read that 1000A is probably better as the Merc is a bit heavy (but a nice car).

TransWarp 11 to provide the power (yes, I'm saving the $'s).

Post by **BiGH** » Mon, 15 Mar 2010, 20:26

Your welcome. Mmm direct drive. That's gonna need a LOT of batteries! Hav you worked out what your max speed is likely to be? If I was going to do direct drive I'd be very much considering an AC drive.

Regardless. Transwarp 11 I'm jelous.

Post by **Digger11** » Mon, 15 Mar 2010, 21:59

I see 3,000 RPM for 100kmh currently. Not sure DC will be that happy at that constant speed. Maybe AC will be better - still in the brainstorming stage.

Post by **antiscab** » Mon, 15 Mar 2010, 22:54

BiGH wrote: Your welcome. Mmm direct drive. That's gonna need a LOT of batteries! Hav you worked out what your max speed is likely to be? If I was going to do direct drive I'd be very much considering an AC drive.

Regardless. Transwarp 11 I'm jelous.

going direct drive has little effect on how much battery you need.

more battery = more range + more *max* power

for direct drive you will need a bigger controller.

more controller = more torque = more acceleration.

Matt

Post by **BiGH** » Tue, 16 Mar 2010, 01:31

antiscab wrote:
going direct drive has little effect on how much battery you need.

more battery = more range + more *max* power

for direct drive you will need a bigger controller.

more controller = more torque = more acceleration.

Matt

bigger controller = pulls more amps at high load situations (ie taking off) = increased battery usage. was what I was referring to.

Post by **Digger11** » Tue, 16 Mar 2010, 14:54

One more (theoretical question). If I do go Direct Drive with say a Netgain Warp 11 motor, would I be better off using 2 smaller Warp 9's instead ?
The Warp 9's appear to be made to connect up in series quite easily - so I assume for a heavy little Mercedes, this might give more torque to get the thing going.

Other than the additional cost (about $1k more than a single Warp 11) would there be any other disadvantages in the twin motor setup ?

I have seen a couple of dual motor installs, where the tailshaft is left at stock length and the rear motor becomes quite hidden in the transmission tunnel. This appeals to me, as it gets some of the weight low and as far back as possible.

I would probably prefer a manual gearbox set-up. but my 190E is an Auto (like many of them are), so Direct Drive seems to be the way to go.
My theory is to spend up big on quality motors (and maybe controller) but not too many batteries initially (due to the cost) and then extend the range when LiFePo4 cells become cheaper (say in 5 years).

I only need 10km return to get to the shops and 35kms return to get to the Golf Club. For longer journey's I will have to use the smelly ICE 4WD.
I like the 9 series Volvo that has been converted - and will use this as a starting point.

Post by **Johny** » Tue, 16 Mar 2010, 15:03

You would also have extra cost in getting the motors joined to each other unless you are doing it yourself. Other than that, the 2 motor set up is better IMO. It also gives you series/parallel options to better utilise what power is available from the controller.
Even in a heavyish car, 2 Warp 9's is going to launch it pretty fast...

Post by **BiGH** » Thu, 18 Mar 2010, 18:17

mcudogs - the link to the 2D schematic is broken, could you provide a new link? Also what differences are there to the 2c one?