Search found 2727 matches

by weber
Fri, 01 May 2009, 22:56
Forum: Electric motors and controllers
Topic: Ultracap addition idea to AC controller
Replies: 49
Views: 8430

Ultracap addition idea to AC controller

what if you use your BMS to shunt the battery pack under regen to dump more charge into the capacitors? (obviously you'd need a fairly tough BMS to handle much current, but it could at least push the capacitor's storage percentage up a bit. The energy stored in a capacitor is half capacitance times...
by weber
Fri, 01 May 2009, 20:06
Forum: Electric motors and controllers
Topic: Ultracap addition idea to AC controller
Replies: 49
Views: 8430

Ultracap addition idea to AC controller

Is the charge rate of the capacitor linear? Is the current constant? The beauty of the above argument is that it doesn't matter how the current or capacitor-voltage change with time (provided they aren't changing so fast, or your cables are so long, that propagation at 0.6 of the speed of light bec...
by weber
Fri, 01 May 2009, 18:10
Forum: Electric motors and controllers
Topic: Ultracap addition idea to AC controller
Replies: 49
Views: 8430

Ultracap addition idea to AC controller

The distribution of energy between ultracap and battery is simple when they are in series. Internal resistances (i.e. ESR's at DC) are irrelevant. Since they are in series they must both receive exactly the same charge. Call it Q. Assuming the capacitor starts from zero volts, the energy into the ca...
by weber
Fri, 01 May 2009, 15:26
Forum: Electric motors and controllers
Topic: Ultracap addition idea to AC controller
Replies: 49
Views: 8430

Ultracap addition idea to AC controller

ESR of battery is also frequency dependent to a lesser extent. It is usually quoted at 1kHz for no good reason other than it is lower than at DC ! Sorry, that's not ESR either. That's battery impedance . 15,900 google hits. http://forums.aeva.asn.au/smileys/smiley1.gif Weber, using google hit count...
by weber
Fri, 01 May 2009, 05:03
Forum: Electric motors and controllers
Topic: AC motors, multipoles, torque
Replies: 549
Views: 80348

AC motors, multipoles, torque

Hey Johny, I think I just understood something you wrote earlier. We don't need the motor manufacturer to apply for exemption under AS/NZS 1359.5:2004 section 1.2 (d) because we're automatically exempt under section 1.2 (e). See earlier message in this thread. This has nothing to do with the fact th...
by weber
Fri, 01 May 2009, 04:14
Forum: Electric motors and controllers
Topic: Ultracap addition idea to AC controller
Replies: 49
Views: 8430

Ultracap addition idea to AC controller

Isn't ESR still ESR regardless of what it is in? The operation of the cap and battery ARE different but a series resistance is still a series resistance. acmotor is quite right. But there's another aspect. ESR (capacitor) is frequency dependent. I don't mean impedance which of course is frequency d...
by weber
Wed, 29 Apr 2009, 23:18
Forum: Electric motors and controllers
Topic: AC motors, multipoles, torque
Replies: 549
Views: 80348

AC motors, multipoles, torque

Cool, it's available in custom voltages, so 0.5^0.5 turns of 2^0.5 thicker wire = 208V Star / 120V Delta 4 pole => 11kW x 2 x 3.7 x 3^0.5 = 142kW. Weeeell, we might be forced to go that route. But I find the idea of a 3.4 times overvoltage a bit scary. Has anyone done it? I think 208 LFP40s will ju...
by weber
Wed, 29 Apr 2009, 21:42
Forum: Electric motors and controllers
Topic: AC motors, multipoles, torque
Replies: 549
Views: 80348

AC motors, multipoles, torque

Tmax/Tn is about 3.52. Right. I mistakenly typed 225 into my spreadsheet instead of 255. Duh. Tn is 72.28, Tmax is 255 but these figures are probably woefully inaccurate at 100Hz. At 100 Hz the charts in ABB catalogs show continuous torque as being 90% of what you'd expect from a simple linear rela...
by weber
Wed, 29 Apr 2009, 18:56
Forum: Electric motors and controllers
Topic: AC motors, multipoles, torque
Replies: 549
Views: 80348

AC motors, multipoles, torque

Johny, Thanks for that. That's excellent information. You didn't say how many poles your Taiwanese motor is. I'm assuming it's 4-pole with Tmax/Tn ~= 3.1. Are you getting a flange as well as feet? Woody, Coulomb and I are planning to use a 2-pole motor in 240 V delta and feed it 415 V, i.e. overvolt...
by weber
Wed, 29 Apr 2009, 17:08
Forum: Electric motors and controllers
Topic: AC motors, multipoles, torque
Replies: 549
Views: 80348

AC motors, multipoles, torque

After my ex-employer nagged his ABB reseller every week or two on my behalf for the past month or two, we finally got a response regarding the 22 kW x 3.8, 2-pole 132-frame motor in the General Performance Motors (GPM) catalog . See part number 3GAA 131 008-••E in the middle of page 4. Their respons...
by weber
Tue, 28 Apr 2009, 20:31
Forum: Batteries, charging, management and monitoring
Topic: Battery Heat
Replies: 9
Views: 1997

Battery Heat

This doesn't explain why a dead lead acid battery recovers some charge after a short rest though. Hi woody, That can be understood by recognising that all parts of the plates are not equally accessible to the electrolyte and it takes time for ions to diffuse to deeper layers. Rapid discharge result...
by weber
Mon, 27 Apr 2009, 18:28
Forum: Technical and conversion discussion
Topic: reverse cycle air conditioning
Replies: 44
Views: 11564

reverse cycle air conditioning

coulomb, If you're thinking of doing this on the MX-5, forget it. I'm no refrigeration mechanic either, but from a bit of googling: If the system wasn't designed to be reverse cycle from the start it looks like it would be a nightmare to make it so. You may remember there's a skinny pipe coming from...
by weber
Mon, 27 Apr 2009, 16:41
Forum: Batteries, charging, management and monitoring
Topic: Battery Heat
Replies: 9
Views: 1997

Battery Heat

there is a well known battery industry rule which says "for every 10 degrees C above 25 degrees C the battery life is halved". Yes. That relates to Arrhenius equation which approximates the rate of all chemical reactions. http://en.wikipedia.org/wiki/Arrhenius_equation However there is nothing spec...
by weber
Sun, 26 Apr 2009, 18:15
Forum: Members Machines
Topic: VOLVO 960
Replies: 10
Views: 2371

VOLVO 960

I found this patent http://www.freepatentsonline.com/4384608.pdf It references other that might help. I'm pretty sure that running the compressor in the reverse direction will make no difference. I think it is usually done by valves that divert the refrigerant to flow in the reverse direction. Not s...
by weber
Sun, 26 Apr 2009, 04:19
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 399518

Weber and Coulomb's MX-5

Here's the Dodgy Brother's charging setup for our testing of a single LiFePO4 cell. 24 A max (0.6C for the 40 Ah cell). http://forums.aeva.asn.au/uploads/690/ChargingSetup.JPG A recent addition is a kelvin sense wire (the skinny fused wire on the right) to improve voltage regulation at the cell term...
by weber
Sat, 25 Apr 2009, 14:46
Forum: Batteries, charging, management and monitoring
Topic: Battery Heat
Replies: 9
Views: 1997

Battery Heat

Not taking things too far at all Woody. I^2R power losses apply. The resistance is real. The internal ideal voltage source doesn't instantly reduce in response to increased current drain. The internal ideal voltage source is essentially constant, being affected only in minor ways by temperature and ...
by weber
Fri, 24 Apr 2009, 16:42
Forum: Electric motors and controllers
Topic: Ultracap addition idea to AC controller
Replies: 49
Views: 8430

Ultracap addition idea to AC controller

I like the simple diode circuit. One of these beauties should do the trick, on a suitable insulated heatsink. AU$40. Stud Cathode http://au.farnell.com/semikron/skr240-04/diode-standard-320a-400v-stud/dp/9564551 Stud anode http://au.farnell.com/semikron/skn240-04/diode-standard-320a-400v-stud/dp/956...
by weber
Fri, 24 Apr 2009, 04:00
Forum: EV Motoring
Topic: EVme $70K
Replies: 48
Views: 14068

EVme $70K

Here's what I estimate the contributions of air drag and rolling resistance (RR) to be for the Mazda MX-5. http://forums.aeva.asn.au/uploads/690/MX-5_power_vs_speed.gif This is power, so if you want range in km you have to take the energy available from your batteries in kWh, multiply by the efficie...
by weber
Wed, 22 Apr 2009, 23:51
Forum: EV Motoring
Topic: EVme $70K
Replies: 48
Views: 14068

EVme $70K

doubling your speed doubles the energy needed per km to push the air out of the way. It also increases 4 fold the power needed to hold present speed. Doubling your speed quadruples the energy per km needed to overcome air drag, and increases the power requirement 8-fold. http://en.wikipedia.org/wik...
by weber
Wed, 22 Apr 2009, 17:04
Forum: Members Machines
Topic: Hemonster's ACIM conversion
Replies: 189
Views: 33805

Hemonster's ACIM conversion

The store of energy and the cutting force. Makes sense ! http://forums.aeva.asn.au/smileys/smiley36.gif Very clever. Actually the relationship between coulomb and weber is fairly symmetrical. http://forums.aeva.asn.au/smileys/smiley1.gif For a capacitor, voltage is force-like (called electro-motive...
by weber
Wed, 22 Apr 2009, 03:24
Forum: Members Machines
Topic: Hemonster's ACIM conversion
Replies: 189
Views: 33805

Hemonster's ACIM conversion

Hemonster wrote:What is a VDR?

Voltage Dependent Resistor, more often known as a MOV or Metal Oxide Varistor.
by weber
Tue, 21 Apr 2009, 16:33
Forum: Members Machines
Topic: Hemonster's ACIM conversion
Replies: 189
Views: 33805

Hemonster's ACIM conversion

Weber has covered most of the points http://forums.aeva.asn.au/smileys/smiley20.gif Hi acmotor, I'm afraid you're confusing me with my electrostatic analog. It was probably the flux capacitor that did it. http://forums.aeva.asn.au/smileys/smiley2.gif Just so we're clear: A coulomb (charge) is an am...
by weber
Mon, 20 Apr 2009, 04:33
Forum: The Lounge
Topic: Divorce your Car! Interesting reading
Replies: 3
Views: 1114

Divorce your Car! Interesting reading

Divorce my car? No chance. I'm just converting my love to electric. http://forums.aeva.asn.au/smileys/smiley2.gif Here's a video clip of the original Queen song: http://www.youtube.com/watch?v=gdDNFJpil50&NR=1 Now we perform an electric conversion on the song, by replacing the infernal combustion pa...
by weber
Sun, 19 Apr 2009, 03:39
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 399518

Weber and Coulomb's MX-5

That's 4.3 or 3.6, only a relative change of 1.18 or 0.85 depending which way you look at it, but still worthwhile for maintaining near original top speed and near original gear-change points in km/h. Which raises the dilemma of whether to make the tacho (and possible audio feedback device) lie abou...
by weber
Sun, 19 Apr 2009, 00:07
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 399518

Weber and Coulomb's MX-5

Some weeks back I was talking to our MX-5 parts recycler (Richard Larsen of MX-5 Plus) about the electric conversion and I mentioned that, compared to the original ICE, we expected to have a lot more torque from our electric motor but max rpm would be a lot less. He said, "So you need a taller diff,...