I just finished looking into the Puekert constant for LiFePO4 cells. I happened to be working with GBS cells at the time.
The shape of the Puekert curve (current vs real amp-hours) for lead acid batteries does not apply to LiFePO4 cells. The shape of the curve for liFePO4 cannot be replicated by the Puekert equation for any value of the Puekert number. It would be interesting to develop a proper formula, but that would take quite a bit of time. I have an equation I would like to propose (it is only valid from 1C to 3C): Amp-hrs = -0.44 x Amps + 1.12 x rated Amp-hrs. This came from one set of discharge curves for a GBS 100AH battery, so it is really a stretch to expect this behavior from other cells. It would be interesting to see what people actually measure for all kinds and sizes of LiFePO4 cells. I suspect that the -0.44 constant will vary between manufacturers and also depending on the geometry of the cell. I hypothesize that this value for a cube shaped cell would be quite different than for a large area, thin cell. The 1.12 will definitely vary from manufacturer to manufacturer due to differences in how they test and specify the capacity of their cells. A company who is more conservative in their specifications will end up with a higher value. OK, have at me! Wadda ya think? Wistar Rhoads KTA Services > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of [email protected] > Sent: Wednesday, May 15, 2013 1:04 PM > To: [email protected] > Subject: EV Digest, Vol 7, Issue 20 > > Send EV mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of EV digest..." > > > Also, please be careful not to append the entire digest to your reply. > Many mail systems do this by default. Trim or delete the digest text > from the bottom of your message, and quote only the parts to which > you're replying. > > > > Today's Topics: > > 1. Uneven brush wear (Mark Hanson) > 2. Re: Uneven brush wear (Jeff Major) > 3. Re: Brush uneven wearing, premature failure - fix (M. G.) > 4. Re: Brush uneven wearing, premature failure - fix (Marc Blum) > 5. Puekert Effect (Pestka, Dennis J) > 6. Dissimilar brush wear - data point (Mark Hanson) > 7. EVLN: Fun EV Ads You?ll Want To Watch (videos) (brucedp5) > 8. EVLN: Ret TX dealer McCall supports Tesla (brucedp5) > 9. Re: Dissimilar brush wear - data point (Roland Wiench) > 10. Re: Dissimilar brush wear - data point (Lee Hart) > 11. Re: Dissimilar brush wear - data point (Marcus Reddish) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 14 May 2013 16:27:32 -0400 > From: Mark Hanson <[email protected]> > To: "[email protected]" <[email protected]> > Subject: [EVDL] Uneven brush wear > Message-ID: <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > Hi Jeff etc, > > Maybe my milli-ohm meter that measured .2 milli-ohms was off but all 4 > rear brushes are wearing down fast and the front one's no wear at all - > so that's the only explanation I can come up with is non-symetrical > brush bars. The ADC motor brush rigging are symetrical . I guess it's > no biggee, I can change brushes fairly quickly now, just let the rears > wear down in 3k, then the fronts will start conducting for another 3k > miles. I'm just used to taking motors for granted, never bothered with > brush replacement till about 100k miles in the past. > > The brushes that seat first start shunting away the current from the > others and then it's a positive feedback loop, the shorter they get the > more current they pull. > > best Regards, > mark > > Hi Mark, > > I think you're barking up the wrong tree.? My calculations for added > resistance of the extra buss bar length to the inside brush connection > at 20 degrees C is 0.01 milliOhms.? That only carries one fourth of the > armature current so represents 1.25 millivolt drop at a 500A load on > the motor.? The typical voltage drop per brush at that current would be > on the order of several volts.? So the voltage divider method would > indicate a possible current imbalance of a tenth of a percent due to > the extra copper bus bar length.? > > Another thing to consider is the fact that the rear brushes sit on the > comm further away from the armature so the current flowing through them > has a longer path through the commutator segments to reach the armature > circuit.? This kind of counteracts the shorter path from the A > terminals to the rear brush. > > In both cases you're talking about a short distance though a relatively > large cross section of low resistivity conductor which results in > negligible voltage drop compare to the rest of the circuit. > > You mention 100K miles on your Prestolite and it had a similar brush > connector bus bars (coming from the opposite way).? Did those show > uneven wear?? I think your current problem is not associated with that > small distance difference in the brush connectors. > > Jeff M > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130514/6325964a/attachment.htm> > > > ------------------------------ > > Message: 2 > Date: Tue, 14 May 2013 13:37:17 -0700 (PDT) > From: Jeff Major <[email protected]> > To: Electric Vehicle Discussion List <[email protected]> > Subject: Re: [EVDL] Uneven brush wear > Message-ID: > <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > Mark, > > My first reply from May 8th: > > "Hi Mark, > > My first thought is damage or a discontinuity to the commutator > surface.? This can be checked with a dial indicator.? If found, lathe > turning may be needed.? Also check for high mica.? The other things to > check are all electrical connects and spring pressures.? > Make sure all brushes slide smoothly in the respective holders. > > Jeff M." > > You are marking invalid assumptions.? Noticeable rapid and uneven brush > wear rate is an indication of a problem which you are not addressing. > > Jeff M > > > > > ________________________________ > From: Mark Hanson <[email protected]> > To: "[email protected]" <[email protected]> > Sent: Tuesday, May 14, 2013 4:27 PM > Subject: [EVDL] Uneven brush wear > > > Hi Jeff etc, > > Maybe my milli-ohm meter that measured .2 milli-ohms was off but all 4 > rear brushes are wearing down fast and the front one's no wear at all - > so that's the only explanation I can come up with is non-symetrical > brush bars.? The ADC motor brush rigging are symetrical .? I guess it's > no biggee, I can change brushes fairly quickly now, just let the rears > wear down in 3k, then the fronts will start conducting for another 3k > miles.? I'm just used to taking motors for granted, never bothered with > brush replacement till about 100k miles in the past. > > The brushes that seat first start shunting away the current from the > others and then it's a positive feedback loop, the shorter they get the > more current they pull. > > best Regards, > mark > > Hi Mark, > > I think you're barking up the wrong tree.? My calculations for added > resistance of the extra buss bar length to the inside brush connection > at 20 degrees C is 0.01 milliOhms.? That only carries one fourth of the > armature current so represents 1.25 millivolt drop at a 500A load on > the motor.? The typical voltage drop per brush at that current would be > on the order of several volts.? So the voltage divider method would > indicate a possible current imbalance of a tenth of a percent due to > the extra copper bus bar length.? > > Another thing to consider is the fact that the rear brushes sit on the > comm further away from the armature so the current flowing through them > has a longer path through the commutator segments to reach the armature > circuit.? This kind of counteracts the shorter path from the A > terminals to the rear brush. > > In both cases you're talking about a short distance though a relatively > large cross section of low resistivity conductor which results in > negligible voltage drop compare to the rest of the circuit. > > You mention 100K miles on your Prestolite and it had a similar brush > connector bus bars (coming from the opposite way).? Did those show > uneven wear?? I think your current problem is not associated with that > small distance difference in the brush connectors. > > Jeff M > ??? ??? ??? ? ??? ??? ? > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130514/6325964a/attachment.htm> > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA > (http://groups.yahoo.com/group/NEDRA) > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130514/f680edc3/attachment.htm> > > > ------------------------------ > > Message: 3 > Date: Tue, 14 May 2013 20:25:46 -0700 (PDT) > From: "M. G." <[email protected]> > To: "[email protected]" <[email protected]> > Subject: Re: [EVDL] Brush uneven wearing, premature failure - fix > Message-ID: > <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > I remember forklift motors having this same issue years ago. The fix > was to have two different brushes. A harder compound for the end brush. > I seem to remember the explanation having something to do with the > magnetic fields created with high current. > > > Sent from Yahoo! Mail on Android > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130514/f6235ba0/attachment.htm> > > > ------------------------------ > > Message: 4 > Date: Tue, 14 May 2013 22:32:49 -0500 > From: Marc Blum <[email protected]> > To: Electric Vehicle Discussion List <[email protected]> > Subject: Re: [EVDL] Brush uneven wearing, premature failure - fix > Message-ID: > <CANNt8JjKrobb8G65f5_LNO+M8sNuiXK_Pj- > [email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > I raced RC Cars and would use a small dynomonater (SIP) and found that > to > be true with the one harder compound on with the high current. Much > higher > wear than on these big motors. we also run a large diode across the > brushes > but that was to reduce arcing. > > > On Tue, May 14, 2013 at 10:25 PM, M. G. <[email protected]> wrote: > > > I remember forklift motors having this same issue years ago. The fix > was > > to have two different brushes. A harder compound for the end brush. > > I seem to remember the explanation having something to do with the > > magnetic fields created with high current. > > > > > > Sent from Yahoo! Mail on Android > > > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > > http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130514/f6235ba0/attachment.htm > > > > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > For EV drag racing discussion, please use NEDRA ( > > http://groups.yahoo.com/group/NEDRA) > > > > > > > -- > Most Sincerely, > Marc Blum > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130514/60b7b2cc/attachment.htm> > > > ------------------------------ > > Message: 5 > Date: Wed, 15 May 2013 11:15:02 +0000 > From: "Pestka, Dennis J" <[email protected]> > To: "Electric Vehicle Discussion List ([email protected])" > <[email protected]> > Subject: [EVDL] Puekert Effect > Message-ID: > <[email protected]> > Content-Type: text/plain; charset="us-ascii" > > I saved this old e-mail from Peter, because it really honed in on what > the Peukert Effect does to the range of your EV. > See Below. > > Hit it right on the money for my 65 Datsun and its 156V pack of 65Ah > Odyssey AGM's. > I'm thinking of replacing them with (50) CA180FI, 180ah CALB LiFePo4 > Cells. > > Question I have is the Peukert Effect on these Lithium Cells. > I've heard they're much better that Lead Acid, or AGM's, but does > anyone know the approx. adjustment % > > Thanks; > Dennis > > > 950 lbs. of what kind of lead? AGMs don't like to go below 50% > Floodies can tolerate 80% as can Gels. > > 12V, 8V, or 6V batts? How many? How many AH are they rated for (20 > Hr > value)? > > > Here's a calculation method I've found that seems to match well to what > I get for range (can't remember > where I found it): > > (Total pack voltage X AH rating of each battery) = watt-hours (whr) > stored > > whr stored X 0.57 (adjustment for Peukert effect) X 0.80 (useable DOD > for floodies or Gels) = usable whr > > useable whr divided by watt-hours per mile used (conservative value = > 300-350; not sure how > aerodynamic the Nash is) = range in miles > > > Peter Flipsen Jr > > > > Thanks; > Dennis > Elsberry, MO > http://www.evalbum.com/1366 > http://www.evalbum.com/3715<http://www.evalbum.com/1366> > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130515/db06612c/attachment.htm> > > > ------------------------------ > > Message: 6 > Date: Wed, 15 May 2013 07:25:49 -0400 > From: Mark Hanson <[email protected]> > To: "[email protected]" <[email protected]> > Subject: [EVDL] Dissimilar brush wear - data point > Message-ID: <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > Hi Folk's, > > > > Since swapping the brush locations (front rear), the rear brushes that > were shorter are still wearing faster than the other 4 just now in the > front location so it appears that the first one's to seat, suck most of > the current (on the 9" "Impulse"). I ordered a milli-ohm meter (to > compare to the one I borrowed) to verify the .2 milli-ohm between the > bar that feeds the front brushes. George at Netgain has been very nice > sending 3 sets of brushes over the last 10k miles since the motor is > over a year old and I'm sure out of warranty. I'm just curious to what > is causing the disimilar brush wear and the pattern seams consistent. > It's always the rear brushes that seat and then wear first shunting the > current away from the front. But when I swap the positions the shorter > brushes - now on the front continue wearing fast (wear down in 3K > miles). I'm treating the others like a spare tire, giving another 3k > miles for 6k total but most of the current is really gooing through a > sing > le brush instead of two, thus overcurrenting it and resulting in > faster wear. > > > > Best Regards, > > Mark > > www.REEVA.info community service RE & EV's > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130515/d6c258b2/attachment.htm> > > > ------------------------------ > > Message: 7 > Date: Wed, 15 May 2013 04:33:05 -0700 (PDT) > From: brucedp5 <[email protected]> > To: [email protected] > Subject: [EVDL] EVLN: Fun EV Ads You?ll Want To Watch (videos) > Message-ID: <[email protected]> > Content-Type: text/plain; charset=UTF-8 > > > http://www.plugincars.com/five-funny-ev-ads-you-want-watch-127189.html > [image] Five Funny Electric Car Ads You?ll Want To Watch > By Nikki Gordon-Bloomfield May 10 2013 > > [videos > http://youtube.com/watch?v=davBx9n62M4 > Gangsta (EV) Grannies > > http://youtube.com/watch?v=nnPXE3knSG4 > Electriphobia Research Institute Silent Treatment > > http://youtube.com/watch?v=KDnCpc-isXk&list=PL031C93E14D2121D5 > Reva Electric Car: Small Car Big Soul > > http://youtube.com/watch?v=RvMbHa8S1Lk > Fiat 500e Electric Sexy > > http://youtube.com/watch?v=LiFa0E89LSs > Nissan LEAF Gas Station Prank > ] > > With electric cars so squarely in the sights of everyone from > misinformed, > bitter journalists to right-wing politicians hell-bent on destroying > the EV > industry, it?s easy to forget to have a little bit of ev-related fun > once in > a while. > > So, we thought we?d share with you five different videos that remind us > that > promoting electric cars doesn?t have to be devoid of humor. > > Gangsta (EV) Grannies > > Take Belgian car sharing website e-cambio, add a Mitsubishi i, some rap > music and a trio of seniors for this fantastic promotional video for > all-electric car sharing. > > Who said electric cars weren?t hip? (Thanks to @jcstp for the tip!) > > > Electriphobia Research Institute Silent Treatment > > You?ve got to hand it to the folks at Mitsubishi Canada. As well as > figuring > out a way to dispel some common EV myths, those clever Canucks figured > out a > way to have a little fun in the process. > > Meet the Electriphobia Research Institute. Completely fictitious, it > tackles > six of the most common EV myths (or fears) in six fun video shorts. > Silent > Treatment, a video about getting folks used to the fact that EVs don?t > make > much noise, is must-watch material. > > > Reva Electric Car: Small Car Big Soul > > Long before Mitsubishi Canada?s Electriphobia Research Institute, the > Emerald Isle was putting a comedy spin on electric cars. Behold this > YouTube sensation, from Irish electric car distributor Greenaer. > > Promoting the tiny Indian-made REVAi electric car, this video is one of > a > few fun ads made to promote electric cars, and of course the REVAi?s > Irish > importer.While the tiny car (NEV) is no-longer made, the video lives on > in > digital infamy. Enjoy. > > > Fiat 500e Electric Sexy > > Fiat C.E.O. Sergio Marchionne may have said numerous times that the > all-electric Fiat 500e was made under duress. But that hasn?t stopped > the > automaker from having a little fun promoting the car. > > Playing on stereotypical Italian passion, the video starts with a > supposed > range and acceleration test, but then takes an unexpected turn. > > > Nissan LEAF Gas Station Prank > > What happens when you take an electric car to a gas station and ask the > attendant to ?fill ?er up?? Nissan decided to find out in Rio De > Janeiro > last year, playing what we think is a rather scripted prank on various > gas > station attendants. > > While the premise is funny, we?ve heard of funnier anecdotes from > drivers in > New Jersey and Oregon. Nissan?s cheesy music makes this particular > video > seem a little...overly staged. It?s not officially an ad, but hey, it > made > us groan the first time. > [?2013 PluginCars.com] > > > > > For all EVLN posts use: > http://electric-vehicle-discussion- > list.413529.n4.nabble.com/template/NamlServlet.jtp?macro=search_page&no > de=413529&query=evln&sort=date > > Here are today's archive-only EV posts: > > EVLN: Ohio, A Potential Hub For Plugin Jobs > EVLN: Testing out Leaf EVs on Luton?s E-Car green car scheme (video) > EVLN: Purdue-U Technique Sees Li-ion Electrode Defects Before Assembly > EVLN: Tesla, unlike-Apple|like-Google, makes your lizard brain go Wow! > + > EVLN: Ret TX dealer McCall supports Tesla > > > {brucedp.150m.com} > > > > -- > View this message in context: http://electric-vehicle-discussion- > list.413529.n4.nabble.com/EVLN-Fun-EV-Ads-You-ll-Want-To-Watch-videos- > tp4663022.html > Sent from the Electric Vehicle Discussion List mailing list archive at > Nabble.com. > > > ------------------------------ > > Message: 8 > Date: Wed, 15 May 2013 04:34:25 -0700 (PDT) > From: brucedp5 <[email protected]> > To: [email protected] > Subject: [EVDL] EVLN: Ret TX dealer McCall supports Tesla > Message-ID: <[email protected]> > Content-Type: text/plain; charset=UTF-8 > > > TX state franchise law is being unfair to Tesla > > http://www.autonews.com/apps/pbcs.dll/article?AID=/20130513/RETAIL07/30 > 5139961/retired-texas-dealer-mccall-supports-tesla#axzz2TGE5GGFO > [image] Retired Texas dealer McCall supports Tesla > by Amy Wilson May 13 2013 > > [image > http://www.autonews.com/apps/pbcsi.dll/storyimage/CA/20130513/RETAIL07/ > 305139961/AR/0/AR-305139961.jpg&MaxW=622 > Sterling McCall, right, with his Tesla Model S and Roadster, and Tesla > representative Armen Dekmezian, who demonstrated the features of the > Model S > after its delivery > ] > > Group 1 co-founder testifies that state franchise law is unfair to EV > maker > > Retired Texas auto dealer Sterling McCall surprised fellow dealers in > April > when he testified in favor of Tesla Motors Inc.'s bid to carve out an > exemption to state franchise law. > > But after buying two Teslas himself -- and taking delivery of his Model > S in > a high school parking lot -- McCall became convinced that the current > Texas > law is unfair to the electric vehicle maker. > > "When you have a case like Tesla, which doesn't have dealers, it just > isn't > right to tell them they can't sell their cars to a willing buyer in > Texas > without having to go through a local owner of a dealership," said > McCall, a > former longtime Houston Toyota and Lexus dealer who co-founded Group 1 > Automotive Inc. "I just think it's wrong." > > Tesla is seeking approval of legislation that would exempt it from > current > Texas law prohibiting manufacturer-owned dealerships. The Texas > Automobile > Dealers Association opposes the bills. > > In addition to testifying at a legislative hearing on April 9, McCall > wrote > an op-ed piece supporting the Tesla bills that ran in the Houston > Chronicle > on April 29. > > Though Tesla has two gallery locations in Houston and Austin, they are > prohibited from sales activity. Customers must contact out-of-state > Tesla > representatives to complete a sale and make shipping arrangements. > > For McCall, 78, who retired from Group 1 in 2006, that meant sending > his > money to Tesla's California operations and having his Model S titled in > California. He picked up the car in the parking lot of Austin High > School. > > That approach won't work long term, McCall said. "I've been delivering > cars > for a long time, and this is not the way to deliver a car." > > McCall should know. After working as a lawyer, he became a dealer in > 1970, > opening Houston's first single-line Toyota store. A former president of > the > Houston Automobile Dealers Association and former director of the state > dealers association, he built large Toyota and Lexus stores before > co-founding Group 1. > > His name is still on eight Group 1 stores in the Houston market, > according > to Group 1's Web site. But McCall's old company disagrees with him. > > "Let there be no doubt: We are totally, completely and firmly opposed > to > this," said Marvin Marcell, director of public affairs for Group 1. The > franchise system is "a fundamental building block of our industry." > > McCall bought his Tesla Roadster in 2010. He participates in the Tesla > owners club of Austin, where he now lives. The Model S is his daily > driver, > and he says he sometimes feels a twinge of guilt about leaving his > Lexus GS > 450h in the garage. > > McCall says he wasn't asked by Tesla to testify and his decision to do > so > startled even himself. He still counts himself a strong supporter of > the > franchise system and said so during his remarks to legislators. > > "Looking back, I'm amazed I put on my dark blue suit and went down to > the > Capitol, but I did," he said. "That's not something I would normally > do. But > then I felt so strongly about it, I thought: 'Doggone it, I'm going to > go do > that.'" > > McCall hasn't heard directly from many dealer friends on his testimony. > But > he learned through the grapevine that his testimony sparked much > conversation -- "Dealers gossip worse than a lady's bridge club," he > said. > > If Tesla's legislation doesn't pass, McCall said, he hopes the company > could > still negotiate a compromise with dealers. But he also believes most > dealers > aren't worried about Tesla. > > "I haven't had anybody call me out and say you're a real jerk for doing > this," McCall said. "It's of no concern to the average dealer. It > really > isn't." > > > Sterling McCall > The retired Texas dealer is backing Tesla's effort to sell cars > directly. > Age: 78 > Dealer from: 1970 through 2006 > Dealerships: Sterling McCall Toyota and Sterling McCall Lexus, Houston > Co-founder: Group 1 Automotive, nation's 4th-largest retailer > In his garage: Tesla Model S, Tesla Roadster, Lexus GS 450h > Spends his time: Running family foundation financed by Group 1 stock > holdings and sale of a classic car collection ... > [? Crain Communications] > > > > > For all EVLN posts use: > http://electric-vehicle-discussion- > list.413529.n4.nabble.com/template/NamlServlet.jtp?macro=search_page&no > de=413529&query=evln&sort=date > > Here are today's archive-only EV posts: > > EVLN: Ohio, A Potential Hub For Plugin Jobs > EVLN: Testing out Leaf EVs on Luton?s E-Car green car scheme (video) > EVLN: Purdue-U Technique Sees Li-ion Electrode Defects Before Assembly > EVLN: Tesla, unlike-Apple|like-Google, makes your lizard brain go Wow! > + > EVLN: Fun EV Ads You?ll Want To Watch (videos) > > > {brucedp.150m.com} > > > > -- > View this message in context: http://electric-vehicle-discussion- > list.413529.n4.nabble.com/EVLN-Ret-TX-dealer-McCall-supports-Tesla- > tp4663023.html > Sent from the Electric Vehicle Discussion List mailing list archive at > Nabble.com. > > > ------------------------------ > > Message: 9 > Date: Wed, 15 May 2013 09:25:35 -0600 > From: "Roland Wiench" <[email protected]> > To: "Electric Vehicle Discussion List" <[email protected]> > Subject: Re: [EVDL] Dissimilar brush wear - data point > Message-ID: <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > Hello Mark, > > As I said before, the rear brushes are shunting the front brushes. The > rear > brushes are closer to the armature circuit connections to the > communtator > bars, thus a more resistance path to the front brushes. > > This is normal in the three motors that I am using in my EV. I run > three > types of motors in my EV. One is a WarP-9, a WarP-11 and a GE-11 which > the > WarP-11 motor frame is the same frame as a GE-11. > > I have run the GE motor for 10 years where the rear brushes worn down > 1/4 of > the original length of 2 inches. The front brushes only worn down > about 1/8 > inch. Every 10 years as per GE maintenance, pull the motor, check > spring > tension, resistance tests and check the communtator surface. > > I had my motor shop verify if the communtator needed any work. They > said, > do not touch it. It still had a very smooth surface. > > It is noted that there were twice as many of communtator bars segments > than > the WarP-11 motor. The brush angle is set very steep to where the > brush > face contacts five communtator bars where the it makes with the next > bar, > while the last bar is still in contact. This results in no arcing. > > Also note the motor is design only for clock wise rotation looking at > the > pilot shaft of the motor. If you run this type of motor in the reverse > direction, you will chip the sharp edges of the brushes. > > The communtator bars are very hard and the brushes hardness are set one > point lower in hardness than the bar hardness. The brushes are very > smooth > looking like tool steel. They are a silver-graphite compound. > > The WarP-9 and WarP-11 motor brushes are much softer and will wear > faster. > You can get a option silver-graphite in the correct hardness for these > motors. > > Every 10 years, I switch the rear brushes with the front brushes. I am > still running the brushes in the GE-11 for 24 years where both are now > at > the same length. > > Roland > > > > > > > ----- Original Message ----- > From: "Mark Hanson" <[email protected]> > To: <[email protected]> > Sent: Wednesday, May 15, 2013 5:25 AM > Subject: [EVDL] Dissimilar brush wear - data point > > > > Hi Folk's, > > > > > > > > Since swapping the brush locations (front rear), the rear brushes > that > > were shorter are still wearing faster than the other 4 just now in > the > > front location so it appears that the first one's to seat, suck most > of > > the current (on the 9" "Impulse"). I ordered a milli-ohm meter (to > > compare to the one I borrowed) to verify the .2 milli-ohm between the > bar > > that feeds the front brushes. George at Netgain has been very nice > > sending 3 sets of brushes over the last 10k miles since the motor is > over > > a year old and I'm sure out of warranty. I'm just curious to what is > > causing the disimilar brush wear and the pattern seams consistent. > It's > > always the rear brushes that seat and then wear first shunting the > current > > away from the front. But when I swap the positions the shorter > brushes - > > now on the front continue wearing fast (wear down in 3K miles). I'm > > treating the others like a spare tire, giving another 3k miles for 6k > > total but most of the current is really gooing through a sing > > le brush instead of two, thus overcurrenting it and resulting in > faster > > wear. > > > > > > > > Best Regards, > > > > Mark > > > > www.REEVA.info community service RE & EV's > > > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: > > <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130515/d6c258b2/attachment.htm> > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > For EV drag racing discussion, please use NEDRA > > (http://groups.yahoo.com/group/NEDRA) > > > > > > > ------------------------------ > > Message: 10 > Date: Wed, 15 May 2013 14:46:43 -0500 > From: Lee Hart <[email protected]> > To: Electric Vehicle Discussion List <[email protected]> > Subject: Re: [EVDL] Dissimilar brush wear - data point > Message-ID: <[email protected]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > On 5/15/2013 6:25 AM, Mark Hanson wrote: > > I'm just curious to what is causing the disimilar brush > > wear and the pattern seams consistent. > > Since we have well over 100 years experience with commutators, I have > to > believe this is an problem that has been well researched and well > understood. However, this information seems to be a "lost" technology. > > Maybe it would be worth studying some old books on motors. I had a > great > written in the 1920's. However, it got stolen (with a bunch of other > stuff). It was from Lindsay Publishing, and they sadly now out of > business. > > I would think that the voltage drop of the brush-commutator interface > is > much larger than the drop in the commutator bar, brush bulk resistance, > pigtail leads, and pigtail connection strip. Getting equal current in > each brush then seems like a matter of making both brushes seat the > same > and have the same spring pressure. > > -- > ICEs have the same problem as lightbulbs. Why innovate and make better > ones when the current ones burn out often enough to keep you in > business? -- Hunter Cressall > -- > Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm > > > ------------------------------ > > Message: 11 > Date: Wed, 15 May 2013 13:49:03 -0600 > From: Marcus Reddish <[email protected]> > To: Electric Vehicle Discussion List <[email protected]> > Subject: Re: [EVDL] Dissimilar brush wear - data point > Message-ID: > <CAEN-gvkRrsW5ARQV8aFk8f_XXdVRhVHFxiFOP+oDiEp- > [email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > That GE-11 sounds like a really good motor. I love old industrial-duty > stuff. <l:] > > > On Wed, May 15, 2013 at 9:25 AM, Roland Wiench <[email protected]> wrote: > > > Hello Mark, > > > > As I said before, the rear brushes are shunting the front brushes. > The > > rear > > brushes are closer to the armature circuit connections to the > communtator > > bars, thus a more resistance path to the front brushes. > > > > This is normal in the three motors that I am using in my EV. I run > three > > types of motors in my EV. One is a WarP-9, a WarP-11 and a GE-11 > which the > > WarP-11 motor frame is the same frame as a GE-11. > > > > I have run the GE motor for 10 years where the rear brushes worn down > 1/4 > > of > > the original length of 2 inches. The front brushes only worn down > about > > 1/8 > > inch. Every 10 years as per GE maintenance, pull the motor, check > spring > > tension, resistance tests and check the communtator surface. > > > > I had my motor shop verify if the communtator needed any work. They > said, > > do not touch it. It still had a very smooth surface. > > > > It is noted that there were twice as many of communtator bars > segments than > > the WarP-11 motor. The brush angle is set very steep to where the > brush > > face contacts five communtator bars where the it makes with the next > bar, > > while the last bar is still in contact. This results in no arcing. > > > > Also note the motor is design only for clock wise rotation looking at > the > > pilot shaft of the motor. If you run this type of motor in the > reverse > > direction, you will chip the sharp edges of the brushes. > > > > The communtator bars are very hard and the brushes hardness are set > one > > point lower in hardness than the bar hardness. The brushes are very > smooth > > looking like tool steel. They are a silver-graphite compound. > > > > The WarP-9 and WarP-11 motor brushes are much softer and will wear > faster. > > You can get a option silver-graphite in the correct hardness for > these > > motors. > > > > Every 10 years, I switch the rear brushes with the front brushes. I > am > > still running the brushes in the GE-11 for 24 years where both are > now at > > the same length. > > > > Roland > > > > > > > > > > > > > > ----- Original Message ----- > > From: "Mark Hanson" <[email protected]> > > To: <[email protected]> > > Sent: Wednesday, May 15, 2013 5:25 AM > > Subject: [EVDL] Dissimilar brush wear - data point > > > > > > > Hi Folk's, > > > > > > > > > > > > Since swapping the brush locations (front rear), the rear brushes > that > > > were shorter are still wearing faster than the other 4 just now in > the > > > front location so it appears that the first one's to seat, suck > most of > > > the current (on the 9" "Impulse"). I ordered a milli-ohm meter (to > > > compare to the one I borrowed) to verify the .2 milli-ohm between > the bar > > > that feeds the front brushes. George at Netgain has been very nice > > > sending 3 sets of brushes over the last 10k miles since the motor > is over > > > a year old and I'm sure out of warranty. I'm just curious to what > is > > > causing the disimilar brush wear and the pattern seams consistent. > It's > > > always the rear brushes that seat and then wear first shunting the > > current > > > away from the front. But when I swap the positions the shorter > brushes - > > > now on the front continue wearing fast (wear down in 3K miles). > I'm > > > treating the others like a spare tire, giving another 3k miles for > 6k > > > total but most of the current is really gooing through a sing > > > le brush instead of two, thus overcurrenting it and resulting in > faster > > > wear. > > > > > > > > > > > > Best Regards, > > > > > > Mark > > > > > > www.REEVA.info community service RE & EV's > > > > > > -------------- next part -------------- > > > An HTML attachment was scrubbed... > > > URL: > > > < > > http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130515/d6c258b2/attachment.htm > > > > > > _______________________________________________ > > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > > For EV drag racing discussion, please use NEDRA > > > (http://groups.yahoo.com/group/NEDRA) > > > > > > > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > For EV drag racing discussion, please use NEDRA ( > > http://groups.yahoo.com/group/NEDRA) > > > > > > > -- > Marcus Reddish > > *North Valley Systems LLC* > Stevensville, Montana > 406-360-8628 > northvalleyev.com > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://lists.evdl.org/private.cgi/ev- > evdl.org/attachments/20130515/08071bd2/attachment.htm> > > > ------------------------------ > > _______________________________________________ > [email protected] > For general EVDL support, see http://evdl.org/help/ > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > > End of EV Digest, Vol 7, Issue 20 > ********************************* _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
