Do I need a new controller?

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Paul9
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Post by Paul9 » Tue, 29 Mar 2016, 16:48

Hi people,

I have come to a point where I am a bit “stuck” as to what improvements I can do to my EV. It originally (in 2008) was a 96v system using 8 x 12v, 100 ah, lead acids, 300amp 96v controller and 96v Motor DC F series 2800 rpm 8.5kw continuous. I was told this configuration was adequate for city driving. I don’t know which city they were referring to but it certainly wasn’t Sydney! Performance was far short of adequate!

In 2012 the lead acids “konked” out and I replaced them with 34 x 3.2 volt 100ah lithiums thus increasing battery voltage to 109v. I was told, on these forums, not to go too much higher than 109v as the 96v controller may not handle 109v but the motor would. This advice, as I expected, proved correct, as long trips in very hot weather overheated the controller. I have since fitted fans to cool the controller.

I have also done a few aerodynamic modifications, most of which I feel have had little more than an imaginary effect, but one or two of these have definitely improved performance at higher speeds.

Rolling resistance improvements include thin LRR tyres and stripping weight – right down to replacing the 12v auxillary battery (12kgs) with a 12v lithium battery (3.3kgs). I also have a solar panel on the roof, feeding the aux battery so the aux battery doesn’t draw its charge from the main battery bank.

I am now at a point where there are very few aero mods or rolling resistance mods left to do!

The above changes have improved performance to the extent that top speed has gone from barely 70kph to 90kph. Range has improved from around 25kms to probably around 80kms although my longest trip without a charge has been 61kms. The situations wherein the car still does not perform ”adequately” is going up steep slopes at high speed ie. 80kph speed limit, and when starting off at the bottom of a hill. Both of these situations probably show a lack of torque and therefore current but I have no idea whether I am right??

When I am in the above “high load” situations, I normally try to stay in the lowest gear possible. When starting off at the bottom of a hill I use 3rd gear and can barely get above 50kph at the top. Steep slopes at 80kph, I use 4th gear, and even if doing 80kph at the bottom of the hill, I end up doing barely 60kph at the top.

In short, I am wondering if purchasing a new controller, producing higher amps, would help to solve the problem?? Someone who is familiar with my controller said “it is a weak controller”. I am wondering if “weak”, when referring to controllers, is simply a reflection of the amps it will produce without overheating? Is a 600amp controller twice as strong as a 300amp controller? I assume you can’t have “weak” amps or “strong” amps?

Upgrading the motor is probably a no-go as a new motor would require a new adaptor plate and a complete reorganisation of where everything is under the bonnet. A new controller, however, could sit comfortably where the existing controller sits without much fuss.

In case it is relevant, I should add that I also have one lithium battery left over and have space to fit it in the car. Maybe I could add the lithium battery to the car (upping the nominal voltage to about 112v dc) and buy a 120v controller capable of greater than 300amps?

Anybody got any ideas?
Thanks tons,
Paul

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Post by Johny » Tue, 29 Mar 2016, 17:03

Hi Paul. If I remember correctly, your motor is from the "Goombi 96volt kit". This kit was never intended to be a very powerful system to start with. The 8.5kW continuous rating would not be enough to maintain my car at 80km/h. (Mine takes about 11kW input to controller on the flat and level to maintain 80km/h - 1070kg.)

So my initial thought is, no more power. That said, a higher current controller would no doubt give you more torque but I tend to think that the motor would "snuff" it pretty quickly.
Sorry. For more power (I think) you are going to need a bigger motor.

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Post by 4Springs » Wed, 30 Mar 2016, 17:31

Johny wrote:Sorry. For more power (I think) you are going to need a bigger motor.

I tend to agree with Johny. I bought a bigger controller and promptly burnt out my motor. You could get one and try it if you are willing to take that risk.

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Post by Paul9 » Thu, 31 Mar 2016, 00:54

Thanks Johny and 4Springs

I sorta thought a new motor might be necessary! I was just hoping there might be another solution.

I will continue on with any aero mods I can think of and then accept the car for what it is. Developing the car has certainly been an interesting journey.

Obviously if I knew then, what I know now, I would have got a 120v or 144v system.

Thanks
Paul

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Post by Richo » Mon, 04 Apr 2016, 21:18

Unfortunately your system is balanced the way it is.
Change one part and you'll probably need to change another.

Lets say you upgraded you controller to 500A.
This would give you, under ideal situations, more acceleration.
But could your batteries handle 5C?
Could the motor handle the extra current?
In both situations it would be Yes - but not for long.
ie in 6 months you'll either have poor range or a burnt out motor.

Even if you did upgrade your motor for more power, you would then need another controller and different batteries.

Increasing your voltage will get you closer to the breakdown of the FET's in your current controller - which will make it hotter quicker and burn that out sooner.

To me it appears you have 30kW battery, ~30kW peak motor and 30kW controller - balanced.

So to me I see you have a couple of options:

1. Sell the eV as is and start again with higher specs 50-60kW.
2. Sell off just the motor and controller and get different ones and either add batteries or change them too.


The next size up motors that has realistic prices are the Motenergy motors.
The liquid cooled would have better continuous rating for going up hills.

Changing just one part of your system would just be a temporary band-aid solution.
Probably not cost effective for the long term.
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Post by Paul9 » Tue, 05 Apr 2016, 03:09

Thanks Richo,

It was only after reading your reply that I remembered that the 100ah batteries are rated for a max 3C discharge which obviously means that a 500a controller would "stuff" them up quickly.

A 500a controller would require a bigger motor and different batteries which, all up, almost amounts to a total new rebuild (as you say).

I posed the question hoping there may be a simple fix. I think I will just stick with what I have and accept it for what it is!

Thanks again,
Paul

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Post by Peter C in Canberra » Wed, 03 Aug 2016, 04:06

Paul9 wrote: Thanks Richo,

It was only after reading your reply that I remembered that the 100ah batteries are rated for a max 3C discharge which obviously means that a 500a controller would "stuff" them up quickly.
l

Not necessarily. A controller will put out a higher current at lower voltage than the battery. It acts like a sort of DC transformer. With a series DC motor (is that what you have?) torque increases with the square of current. My car dramatically improved performance with a controller that puts out 800A compared with the original that was rated for 500A (and declined to do only 400A). That is from a 90Ah LFP battery rated to 3C. If I put my foot down hard I can pull almost 500A albeit with sagging voltage. At that point I expect I have hit 800A to the motor.
A higher current controller might help but make sure it is limited to the maximum peak current the motor is rated for.
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Post by Paul9 » Wed, 03 Aug 2016, 17:32

Thanks Peter,

I just checked the manufacturer's website and the motor is rated as 100-200 amps continuous but the label on the motor says 110 amps continuous.

The website's spec for the motor says it is capable of handling 3 times the continuous rating for up to one minute ie. 330 amps (depending on whether I believe the website or the motor's label).

I note in your reply that when you are pulling 500 amps from the battery, the motor is getting 800 amps? Is that correct?

If so maybe I shouldn't pull more than about 200 amps from the battery to give me the 300 amps at the motor? Have I got that logic correct? After all, I can't measure motor amps only battery amps so I suppose I need some way of estimating motor amps from battery amps drawn?

Thanks
Paul

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Post by Peter C in Canberra » Wed, 03 Aug 2016, 18:13

Ideally you would have a controller that is capable of delivering over 330A and then have it limited to 330A max. Mine, for example, is rated at 1000A but electronically limited to 800A, the short term rating of the motor. Mine is a Kelly brand which has a port to plug in a PC to adjust such settings as current and voltage and throttle response.
You are correct that you could have 300A at the motor but 200A from the battery. The volts would be in the same proportion the other way around (minus some slightly losses).
If you have a programable controller that can take higher volts than the motor, you can also limit the max volts that the controller will show the motor.
However, it sounds like you might not have a lot of scope to beef up the controller before you hit the motor limits.
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Post by Johny » Wed, 03 Aug 2016, 18:25

Hi Paul.
Reading back on your original post it looks like the area you are most concerned about is motor power at higher speeds - and you really want to move forward (no pun) in some way.

While I tend to agree that the Goombi controller probably doesn't deliver the full current that the motor can handle, it may only solve some of your problems. More motor current without any other change will only give your marginally more top speed - but WILL improve low (motor) speed acceleration - possibly at the expense (pun) or the motor life.

Lets take this a little bit at a time.
At some particular speed, your motor will reach a point where the torque begins to "drop off".
This point is related to the motor design and overall gearing of your system. The drop-off point can be raised with more battery voltage. I.E. More battery voltage will give you an increase in speed by increasing nominal motor current(torque) to a higher RPM.

I note that Peter has already responded with a controller suggestion and I totally agree. A programmable current controller would be a good next step.
Since the controller is also the reason why increasing battery voltage might be a problem (controller voltage rating is very real, motor not so), a better controller with higher voltage rating (and a few more cells) would be the way to go.
A reputable controller capable of around 400-500Amps but configurable would be my choice. Limit the current to 300A as Peter says and see what it has bought you.

So to sum up.
- Increase your battery voltage.
- Change to a higher voltage controller with known output rating.
(The motor will be fine with 20 or so more volts - it's not that sensitive.)

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Post by Paul9 » Wed, 03 Aug 2016, 19:55

Thanks tons Peter and Johny,

At the moment I am running at a battery voltage of 113v max (about 109v nominal). The 96v controller has once gone into thermal cutback and I was therefore worried that adding two more cells to take me to 115-116v nominal may overload the controller on a hot day. I have since fitted two fans to the existing controller but have not tested it on a very hot day.

As I always try to buy Australian made, I intend getting the ZEVA MC600 at about 120v, from Ian Hooper, and I hope he may be able to "dumb" it down to about 300 amps max, prior to sending it to me. I will also fit fans to it.

I have fitted fans to blow air into the vents on the motor as well in an effort to help air circulate within the motor thus reducing (be it ever so slightly) the average motor temps.

I will get the EVPower BMS (Aussie made obviously) reprogrammed to account for the higher voltage.

Thanks muchly!
Paul


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Post by Johny » Wed, 03 Aug 2016, 20:01

Paul9 wrote:...I intend getting the ZEVA MC600 at about 120v, from Ian Hooper, and I hope he may be able to "dumb" it down to about 300 amps max, prior to sending it to me. I will also fit fans to it.
It sounds like you have it all under control Paul. The MC600 is motor current configurable so he will be able to set it for you.

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Post by Peter C in Canberra » Wed, 03 Aug 2016, 20:10

Johny wrote:
Paul9 wrote:...I intend getting the ZEVA MC600 at about 120v, from Ian Hooper, and I hope he may be able to "dumb" it down to about 300 amps max, prior to sending it to me. I will also fit fans to it.
It sounds like you have it all under control Paul. The MC600 is motor current configurable so he will be able to set it for you.

Good that you are getting a controller capable of feeding a beefier motor which is where you might end up. For now this might be a worthwhile upgrade. I certainly had not appreciated how much my controller had been the performance limit in my car till I replaced a slowly dying Curtis 500A controller.
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Post by Paul9 » Wed, 14 Dec 2016, 14:51

Hi people,

Have just finished the upgrade we have been discussing in this thread and thought I would let you know how it went and thank you for your help! There is however one issue remaining which I would very much like some advice on.

I took the car down to my mate's mechanic workshop and we immediately took the BMS off and sent it to EVPower to get it reprogrammed for 36 cells. I had already purchased 2 new cells to add to the existing 34 cells. I ordered a new MC600 Controller from ZEVA and Ian configured it to provide about 400amps max.

We fitted the new cells, the reprogrammed BMS and the new controller and nothing happened!It appears that the 96v contactor kept tripping when we put 122v through it. Also the old throttle would not work with the new controller. Solution was simple - buy a hall effect throttle and a beefier contactor.

Fitted hall effect throttle and new contactor and still nothing happened! Emails back and forth to Ian Hooper and it appears the throttle manual is "wrong"! Ian described the problem as follows:

"It's easy to get this mixed up because the arm presses the switch when it's in the off position, so the "normally closed" terminal ends up behaving like normally open in this case. The controller will give a throttle error if the switch doesn't seem to match the pot arm position, so this is one of the more common reasons for throttle errors."

So we wired the throttle up as per Ian's advice and finally the car worked! "Worked" except for a constant "Battery Fault" message from the BMS. The problem - I had loosened a battery terminal when fitting the new batteries and had forgotten to tighten it back up! You can't teach stupid!

Of course in the middle of this process, one of the workshop's other customers had reversed into my car while talking on his mobile. Another two and a half week delay while the car was repaired!

The end result has been that the car performs much better than before!! On the way home from the workshop I got the car up to 105kph on a slight downhill but what pleased me was that on the next uphill it only slowly went down to 95kph. Acceleration is much improved. While the controller is limited to 400amps, the most I have had it up to is 185amps from the batteries. I have refitted the fans to the new controller. I have only had the car back for a few days so I haven't had a chance to push it on long trips.

The only remaining problem is that somehow it appears we have (or the new equipment has?) connected the traction pack voltage to the body of the car! While this doesn't effect the operation of the car, it is a problem I need to fix. We spent an hour or two trying to disconnect/reconnect various wires and cannot get the traction pack voltage to NOT connect with the car body.

Eventually we had to give up as we ran out of time. After all the guys in the workshop were doing almost all of their work for me for free. They said to me that it may not be our rewiring that causes the problem as both the controller and the new contactor appear to be initialised from the 12v system unlike the old controller and contactor which were both initialised from the 96v traction pack.

My question is - to identify this problem are there more likely culprits than others? My electrician brother and his electrician mate are going to come over to my place and the three of us try to identify where this HV to car body comes from. To save them time I would like to say to them "The people on the internet said we should try this, this and that first as those are the most likely causes".

Thanks in advance,
Paul

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Post by Johny » Wed, 14 Dec 2016, 15:38

Hi Paul
If it were any other controller other than Zeva's I'd be looking there - but not in this case.
It's more likely that:
They said to me that it may not be our rewiring that causes the problem as both the controller and the new contactor appear to be initialised from the 12v system unlike the old controller and contactor which were both initialised from the 96v traction pack.
is the culprit. Not much help though - sorry.

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Post by Richo » Wed, 14 Dec 2016, 20:31

Mmmm process of elimination.

The first thing is HOW do you know that the traction pack is connected to the chassis?
If it is, as you say shorting, you should be able to find at which point in the pack the short is occurring.

Oddly I would probably check the hall sensor as these, depending on controller, can be floating with the traction.
Disconnect it from the controller and see if the problem goes away.

Next disconnect the BMS.
Then parts of the controller...
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Post by Peter C in Canberra » Wed, 14 Dec 2016, 21:11

I found that my first Kelly controller was shorted to the chassis. Then, that its replacement was deliberately referenced to the chassis via (from memory) an internal megohm resistance. Documentation of later versions of the same controller had increased this to 10 megohm (from memory). With this came an instruction to connect the negative pole of the battery to the controller before the positive and vice-versa for disconnecting.

Perhaps something like that?
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Post by jonescg » Wed, 14 Dec 2016, 22:34

The onboard charger is also a common source of chassis leaks. Likewise the DC/DC converter.
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Post by Paul9 » Thu, 15 Dec 2016, 14:35

Thanks Johny, Richo and Peter,

We will try your suggestions.

Richo, to answer your question as to how I know the HV is connected to the body is that one of us was leaning on the compliance plate of the car (connected to the body) and touched a terminal and got zapped. I had disconnected the rear battery bank (24 cells) so the front 12 cells were all we got zapped with. This prompted us to put the multimeter on a positive terminal on the front bank connected to the negative of the auxillary battery. It read plus 40volts.

When we reconnected the rear battery bank the same set up gave a reading of minus 80volts. I found this odd as the entire bank is 36cells x 3.2v = 115 volts at least. I also found it odd that we were getting minus readings. We then started disconnecting all wires and reconnecting one by one and continually got this minus 80 volts.

Of course the difference between plus 40 volts when the big red button is pressed and minus 80 volts when I lift my big red button is the 120v my pack is. I am confused but I do get that way easily!!

Does the above info help in any way?

Thanks a lot!
Paul
Last edited by Paul9 on Thu, 15 Dec 2016, 05:27, edited 1 time in total.

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Post by Johny » Thu, 15 Dec 2016, 16:30

It only takes a few milliamps for a human to feel "zapped". It sounds like either leakage or controlled leakage (deliberate low current path to ground). As Chris says, charger or DC-DC could be it. As much as it's a pain, disconnect charger then, if not it, DC-DC - both sides of supply and recheck. If you have the means, place a 4.7K 5W resistor across where you are measuring (pack + to ground) and you may see the voltage drop to near 0.

When you say the rear pack was disconnected, was that BOTH sides of the rear pack and BMS/Charger/DC-DC connections - like it was removed?

(ground = vehicle chassis).

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Post by Paul9 » Thu, 15 Dec 2016, 17:03

Thanks Johny,

When I say the rear pack was disconnected I mean that I had depressed my big red button between the seats inside the car. I had made no other "disconnects" between front and back.

Thanks
Paul

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Post by evric » Thu, 15 Dec 2016, 17:03

Hi Paul,
Are you still using the original motor? If so there may be a carbon build-up from the brushes.
Blow it (the commutator end) out with a compressor and test again.

I had this problem with about 27 K ohm leakage via the motor to ground after blowing it out it went to around 27 Megohms.
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Post by Paul9 » Thu, 15 Dec 2016, 17:43

Thanks Evric,

When the car was at the workshop I actually used the fact that it was up on a hoist to do exactly what you suggest! I had heard about carbon dust build up and took the opportunity to use their compressed air gun. One of the rare instances of me doing something sensible!

Thanks
Paul

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Post by Richo » Thu, 15 Dec 2016, 20:45

Paul9 wrote: I know the HV is connected to the body is that one of us was leaning on the compliance plate of the car (connected to the body) and touched a terminal and got zapped.


Thought as much Image

So what you want to do is measure with a DMM from the Chassis / Aux batt neg TO EACH traction battery terminal to find the closest to ZERO volts.

This will be where the leak / short link is.

This should hopefully narrow down what is causing the problem.
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Post by Richo » Thu, 15 Dec 2016, 20:48

Oh and be careful...
Image
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