Agni motor tuning and racing

[jonescg]

Interesting... I have an audible alarm when a cell drops below 2.5 V, but it doesn't shut the bike down though. Just sounds an annoying buzzer. I could have it shut the contactor on me but in a race environment that would be disastrous. The motors could signal the controller dial back power, and at least that way you can feel it without having to look at something on the dashboard. I'd rather have rolled in to the finish line than DNF, for sure. Let me know when you have that Motor Analyst ready, Steve, I'll happily test it Will contact Kelly too. I don't think I have the option of battery side limit, but the software may have since been updated.

Keep up the good stuff on the first couple of posts. I'm studying it very carefully

 

[Jozzer]

You could work out a way to use that signal to pull down throttle voltage I'm sure..
I'll be back with some more info tomorrow, in the meantime, any requests or suggestions?

 

[jonescg]

One other point might be "The merits of a properly aligned twin motor setup" or "how a dozen armchair experts can still be wrong about flexible couplings" Seriously, I had lots of people telling me I needed a lovejoy or universal joint because my two motors were going to fail if the alignment wasn't 100.0000000% perfect. Simplicity and strength was all it needed.

 

[Tiberius]

You could work out a way to use that signal to pull down throttle voltage I'm sure..

This is what I do with my LVC. Something that just cuts out is a disaster; you want an "analogue" rather than "digital" control. Then you can carry on at whatever throttle setting the system can cope with.

Nick

 

[jonescg]

Found two pretty good patents that show the internals from a few years back. I was surprised to see the cantilevered bearing!

You might also find this interesting. Andy did a bit of a story on the manufacture of motors being made by LEMCO at the time.
http://www.youtube.com/user/evmotorcycle?gl=IE&hl=en-GB#p/u/15/xbVTqkE_F1U

 

[boostjuice]

Exceedingly informative video!

 

[battman]

Hi Jozzer,

Concerning your recommendation of 1MM advance for every 150A. Would you change this rule of thumb if regen were involved? I just use my bike on the street with 250A max motor current and about 2.6kW peak of regen.

I had about 1mm of advance on my previous set of brushes (220A max at that time) and only saw 1500 miles before they had to be replaced. I think I saw a video somewhere that Cedric was getting > 50000 miles out of a set of brushes, so I had high expectations and was rather disappointed to only get 1500 miles, but then I don't know what voltage/ current Cedric's ride was operating at.

 

[jonescg]

Yes the video above includes the statement 50,000 miles, but surely that assumes a 10 amp drain at 2000 rpm. Maybe the fettled (I love that word! :lol brushes would last a bit longer?

 

[Jozzer]

Hi Battman,

Depends what your regen current and duty cycle are like, but if you mean 220A max forward current then you should have seen a lot longer lifespan than that. I would imagine Cedric is running at least 200A peaks, probably a little higher, and uses regen too. I will check what his brush advance was set too, but I'm sure he would have had some advance set.
For myself, with a 400A+ peak and using regen occassionally with 2mm advance, I've certainly done more than 4000 miles without needing to change (less than half worn).
There have been some differnet makes of brushes around over this last, when did you buy the motor/brushes? What vehicle, and how heavy was the use of regen?

Steve

 

[liveforphysics]

There are bikes with 10,000miles on the original brushes. Start with good brushes, and set them up right, and don't over-current the motor excessively, and they hardly wear at all.

Start with bad brushes = death in minutes

Start with badly setup brushes = death in hours

Hugely over current the brushes = death in minutes

Set up good brushes properly = Years of reliable service, then a simple brush swap to replace.

 

[jonescg]

Jozzer - how do you wire up the thermistors on a dual Agni bike? Can they be put in series and wired into the controller? Or do they need to be paralleled? Seems quite an important feature I am yet to utilize properly :S

 

[Jozzer]

Unfortionatly there is no easy way to wire them up in series or parallel, I usually plug mine straight into my "Methods LTC BMS" and program it to cut back at a temperature of my choice
Later this year I'll be offering a gizmo to do this, along with lots of other safety/performance enhancing tasks...I'll be sure to mention it here when it's ready.

Steve

 

[battman]

Hi Battman,

Depends what your regen current and duty cycle are like, but if you mean 220A max forward current then you should have seen a lot longer lifespan than that.
...
There have been some differnet makes of brushes around over this last, when did you buy the motor/brushes? What vehicle, and how heavy was the use of regen?

Steve

Hi Steve,

Yes, 220A max forward current (until I started monitoring brush temperature at around 1000 miles and then upped max a little to 250A). About 32A regen current. I use regen quite heavily, hardly ever touch the rear brake now. The vehicle is a Kawsaki Ninja 250R and weighs 365 pounds.

It was the original set of brushes that were fitted to the motor that wore out in 1500 miles. I bought the motor in June 2009.
My current set look like they will wear out in about 1500 miles too. I bought those in February this year. For each set I made sure I advanced them by turning the brush holder in the opposite direction to motor rotation. With the second set I verified that the alignment marks were indeed correct by following the section near the end of the workshop manual titled "Finding the correct brush holder adjustment". Brush holder doesn't seem loose, so no need to wrap tape round it.

I don't believe I'm overheating the brushes since I monitor brush temperature and stop the bike if they reach 80C (which only happens if I ride WOT in 45C Arizona heat). Agni recommend 90C max for the brushes, but I find that even after stopping the bike, the temperature
measured at the brushes continues to rise a bit as heat continues to leave the motor core. So 80C seemed like a reasonable maximum in my situation.

Unlike a lot of Agni powered motorcycles I have seen, I have the motor placed just behind the front wheel with full frontal assault of anything thrown off the wheel. So I don't know if that, combined with desert conditions is resulting in a lot of dust being ingested. I don't see any dust accumulating in the brush holder though other than lots of carbon (which I blow out every few hundred miles). Other than that, I'm kind of stumped why I'm getting worse wear than other folks.

Barron

 

[battman]

One other thing (and maybe this is close to the root of my problem!) is that I measure 8.3KOhm between the perforated metal case (and mounting holes) and each power terminal on the motor. Chris Jones kindly made the same measurement on his motors and had values in the megaohm range.

The 8.3KOhm measurement also means that my chassis is unfortunately somewhat live ...

 

[Jozzer]

Hi Battman, that doesnt sound good, can you confirm you made that measurement with the controller DISCONNECTED from the motor? A short would definitly explain fast wearing brushes!

Steve

 

[battman]

Hi Battman, that doesnt sound good, can you confirm you made that measurement with the controller DISCONNECTED from the motor? A short would definitly explain fast wearing brushes!

Steve

Yes - controller was disconnected. Resistance measurement was the same regardless of motor rotation.

 

[Jozzer]

I'd write to them explaining this, Cedric may ask you to take some readings to confirm this, but if it has a short they will probably replace it for you immediatly. Be patient with them, they will catch up with your message and reply after a while, they do have a lot going on right now (anyone seen the price of magnets lately!?). I'll mention it next time I speak to them to make sure they are aware..

Steve

 

[battman]

I'd write to them explaining this, Cedric may ask you to take some readings to confirm this, but if it has a short they will probably replace it for you immediatly. Be patient with them, they will catch up with your message and reply after a while, they do have a lot going on right now (anyone seen the price of magnets lately!?). I'll mention it next time I speak to them to make sure they are aware..

Steve

Thanks for your help Steve. I'll write to Agni. I could post results/ resolution of the issue here if you felt it wasn't hijacking this thread (any further :lol: ).

Barron

 

[Jozzer]

It's a relevant topic, just the kind of thing that might catch one of us out and all adds to the experience.

 

[jonescg]

Could you not make the Agni a SepEx motor by using electromagnets instead of PMs?

Sorry, hijack, but always looking at ways of reducing costs of things.

I've not heard back from Agni since I said "I'll take two!" But I gather they are scrambling to produce more motors with the cost of resources and the fact that most of their motors are being used / burned out on racetracks right now :lol:

 

[Jozzer]

I guess Zero are hogging most of the available stock whilst they are still trying to get a stabilised supply of endplates. There are a batch due in very soon, they will share them out as best the can.
Cedric is looking into alternatives, but my bet is that the rare earth situation will come to an end in due course as mines reopen all over the world and China is forced to deal with global competition again..

 

[jonescg]

Just on the subject of thermistors - if you could use a circuit like this:
http://www.technologystudent.com/elec1/therm1.htm

You might at least be able to have two big red LEDs on the front panel that light up your face when the brush temperature is too high. At this point you can back off to save your motors.

What I don't know is the R value of the Agni thermistor, or what the preset resistor value should be. I guess 95'C would be a good place to back off?

Edit: Just read that it is 20-40 kOhm at ambient temperature, and 2 kOhm at the maximum acceptable temperature. So I'd need to make sure that the preset resistor was at or below 2 kOhm? I'm no good at electronics

 

[battman]

What I don't know is the R value of the Agni thermistor, or what the preset resistor value should be. I guess 95'C would be a good place to back off?

Agni told me that 90C was the maximum allowable temperature measured at brushholder and I've noticed that after stopping bike temperature continues to rise a bit as heat continues to be released from motor core.

 

[liveforphysics]

I'm personally hogging all the Agni's.

 

[jonescg]

Well Luke, you can kindly put two aside for me, preferably matched for kV and brush resistance thanks!

No seriously :? , I hope I can get two motors delivered before September, or I'm shit out of luck.