I'm converting a 2002 Chevy S-10 Shortbed. Key components are an ADC 9-inch motor and a DCP Raptor 1200 controller.
Weight of the truck after removal of engine, exhaust, fuel system, etc.: 2600 lbs. Have considered using 13 Optima D31A YellowTops, but I'm mindful of the battery weight rule-of-thumb; namely, that batteries should account for one-third of the vehicle's finished weight. I haven't added anything back to the truck yet, but let's say that cables, battery boxes, and all the other stuff add back 500 lbs, which would put the truck back up to 3100 lbs. That would suggest a battery load of roughly 1530 lbs., if I were to observe the one-third rule. So you can understand why I'm concerned about the YellowTops. I'll need 13 of them to get 156 volts, but -- at 60 lbs. each -- they only add up to 780 lbs. That is only 1/4 the finished weight; not 1/3. Here are my questions: -- Will I sacrifice handling and drivability with an "underweight" battery load? -- Would I still need to put at least one or two of these YTs under the hood, or could I safely put all of them in the bed? Before you answer, I'll just give these additional details: -- The truck will be a daily driver. Total distance from home to work and back: 32 miles. -- Fortunately, I WILL be able to charge at work. -- Need to keep up with freeway traffic. Occasional peppy accelerations, with a top sustained speed of 60 mph. -- Planning to protect the YTs with BattEQ balancers. I've also considered flooded lead, but I'm concerned about the adverse effects of heavy current draw. Thanks in advance for any guidance you might have. Cheers, Steve Kobb _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
How about doubling the yellow tops and running them in parallel buddy
pairs? -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Steve Kobb Sent: Tuesday, August 14, 2007 9:56 To: [hidden email] Subject: [EVDL] YellowTops and the one-third weight rule I'm converting a 2002 Chevy S-10 Shortbed. Key components are an ADC 9-inch motor and a DCP Raptor 1200 controller. Weight of the truck after removal of engine, exhaust, fuel system, etc.: 2600 lbs. Have considered using 13 Optima D31A YellowTops, but I'm mindful of the battery weight rule-of-thumb; namely, that batteries should account for one-third of the vehicle's finished weight. I haven't added anything back to the truck yet, but let's say that cables, battery boxes, and all the other stuff add back 500 lbs, which would put the truck back up to 3100 lbs. That would suggest a battery load of roughly 1530 lbs., if I were to observe the one-third rule. So you can understand why I'm concerned about the YellowTops. I'll need 13 of them to get 156 volts, but -- at 60 lbs. each -- they only add up to 780 lbs. That is only 1/4 the finished weight; not 1/3. Here are my questions: -- Will I sacrifice handling and drivability with an "underweight" battery load? -- Would I still need to put at least one or two of these YTs under the hood, or could I safely put all of them in the bed? Before you answer, I'll just give these additional details: -- The truck will be a daily driver. Total distance from home to work and back: 32 miles. -- Fortunately, I WILL be able to charge at work. -- Need to keep up with freeway traffic. Occasional peppy accelerations, with a top sustained speed of 60 mph. -- Planning to protect the YTs with BattEQ balancers. I've also considered flooded lead, but I'm concerned about the adverse effects of heavy current draw. Thanks in advance for any guidance you might have. Cheers, Steve Kobb _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
I'd agree on doubling the number of batteries, although might consider
keeping two separate strings of 13 each and parallel the strings (if you can afford twice the BattEQ balancers). The merits of buddy pairs vs buddy strings have been debated in the past... Handling with just 13 batteries should be fine, but you will have very limited range. You may make your 16 highway miles each time, but be shortening the battery life expectancy with deep discharges each time. I'd agree that AGMs and a Raptor 1200 will be a good match to your peppy/highway speed requirements, having driven a 1990's S-10 w/ Raptor 1200 and 168 volts of floodeds. 26 batteries may fit in; if not perhaps 24 batteries, still in 2 strings for 144 volts, or 22 batteries for 132 volts if really tight on space. Dewey, Jody R ATC COMNAVAIRLANT, N422G5G wrote: > How about doubling the yellow tops and running them in parallel buddy > pairs? > >-----Original Message, On Behalf Of Steve Kobb > > I'm converting a 2002 Chevy S-10 Shortbed ... > Have considered using 13 Optima D31A YellowTops ... -- Jim Coate 1970's Elec-Trak's 1997 Solectria Force 1998 Chevy S-10 NiMH BEV 1997 Chevy S-10 NGV Bi-Fuel http://www.eeevee.com http://www.electrictractorstore.com _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Dewey, Jody R ATC COMNAVAIRLANT, N422G5G
>From what I've heard about the 1/3 weight rule, I believe it only
applies to flooded batteries. I think the reason the rule exists is too assure people that 1,000+ pounds of flooded batteries is really what's required for an EV. As for the handling, isn't lighter weight better for handling? On 8/14/07, Dewey, Jody R ATC COMNAVAIRLANT, N422G5G <[hidden email]> wrote: > How about doubling the yellow tops and running them in parallel buddy > pairs? > > -----Original Message----- > From: [hidden email] [mailto:[hidden email]] On > Behalf Of Steve Kobb > Sent: Tuesday, August 14, 2007 9:56 > To: [hidden email] > Subject: [EVDL] YellowTops and the one-third weight rule > > I'm converting a 2002 Chevy S-10 Shortbed. Key components are an ADC > 9-inch motor and a DCP Raptor 1200 controller. > Weight of the truck after removal of engine, exhaust, fuel system, etc.: > 2600 lbs. > > Have considered using 13 Optima D31A YellowTops, but I'm mindful of the > battery weight rule-of-thumb; namely, that batteries should account for > one-third of the vehicle's finished weight. > > I haven't added anything back to the truck yet, but let's say that > cables, battery boxes, and all the other stuff add back 500 lbs, which > would put the truck back up to 3100 lbs. > > That would suggest a battery load of roughly 1530 lbs., if I were to > observe the one-third rule. > > So you can understand why I'm concerned about the YellowTops. I'll need > 13 of them to get 156 volts, but -- at 60 lbs. each -- they only add up > to 780 lbs. That is only 1/4 the finished weight; not 1/3. > > Here are my questions: > -- Will I sacrifice handling and drivability with an "underweight" > battery load? > -- Would I still need to put at least one or two of these YTs under the > hood, or could I safely put all of them in the bed? > > Before you answer, I'll just give these additional details: > -- The truck will be a daily driver. Total distance from home to work > and back: 32 miles. > -- Fortunately, I WILL be able to charge at work. > -- Need to keep up with freeway traffic. Occasional peppy accelerations, > with a top sustained speed of 60 mph. > -- Planning to protect the YTs with BattEQ balancers. > > I've also considered flooded lead, but I'm concerned about the adverse > effects of heavy current draw. > > Thanks in advance for any guidance you might have. > > Cheers, > Steve Kobb > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Jim Coate
I totally agree on the keeping them separate. That is what I was
implying when I said buddy strings. In my 240SX ev I have a contactor for each string of 10 batteries (120V). When I turn the key on, both energize putting them in parallel. When the car is off, I have two separate strings that I can charge separately. The only problem I can forsee with doubling the batteries is cost. I think a yellow top battery costs $160 each. That's $4200 for 26 batteries not counting any discounts or shipping. -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Jim Coate Sent: Tuesday, August 14, 2007 11:37 To: Electric Vehicle Discussion List Cc: [hidden email] Subject: Re: [EVDL] YellowTops and the one-third weight rule I'd agree on doubling the number of batteries, although might consider keeping two separate strings of 13 each and parallel the strings (if you can afford twice the BattEQ balancers). The merits of buddy pairs vs buddy strings have been debated in the past... Handling with just 13 batteries should be fine, but you will have very limited range. You may make your 16 highway miles each time, but be shortening the battery life expectancy with deep discharges each time. I'd agree that AGMs and a Raptor 1200 will be a good match to your peppy/highway speed requirements, having driven a 1990's S-10 w/ Raptor 1200 and 168 volts of floodeds. 26 batteries may fit in; if not perhaps 24 batteries, still in 2 strings for 144 volts, or 22 batteries for 132 volts if really tight on space. Dewey, Jody R ATC COMNAVAIRLANT, N422G5G wrote: > How about doubling the yellow tops and running them in parallel buddy > pairs? > >-----Original Message, On Behalf Of Steve Kobb > > I'm converting a 2002 Chevy S-10 Shortbed ... > Have considered using 13 Optima D31A YellowTops ... -- Jim Coate 1970's Elec-Trak's 1997 Solectria Force 1998 Chevy S-10 NiMH BEV 1997 Chevy S-10 NGV Bi-Fuel http://www.eeevee.com http://www.electrictractorstore.com _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Steve Kobb
Thanks, Guys.
As a result of the "reality therapy" that you gave me, I'm starting to think harder about flooded lead. In particular, I was helped by a recent post from Lee Hart, where he offered these guidelines for floodies and gels: *********** 1. Keep the *average* current below the 20-hour amphour capacity. For example: - 220 amps for a 6v 220 amphour golf cart battery - 175 amps for an 8v 175 amphour golf cart battery - 100 amps for a 12v 100ah deep-cycle battery 2. Keep the *peak* current times the seconds you draw it below 5 times the battery's 20-hour amphour capacity. For example: - for an 8v 175ah golf cart battery: 175 amps for 5 seconds 350 amps for 2.5 seconds 700 amps for 1.25 seconds *********** My real challenge is having to cross 3 lanes of traffic to get onto I-10 in the morning. That's really the only time that I need to accelerate hard... IF I need to accelerate, that is. On many days, I can just ease into a west-bound lane without having to speed up in a hurry. So what about those days when I DO have to fight my way in? Well, if I had Trojan T-875s, I could pick up speed with a 350 amp pull for less than 3 seconds. Once I'm in the correct lane, I'm hoping that an avg of 175 amps would keep me at or above 55 mph. Does that sound realistic in what would be a 4300+ lb. truck? Steve Kobb |
Steve,
What I am considering doing is putting in two chains: 4/5 cap flooded, 1/5 cap AGM, separate contactors, independently fused and in parallel. The AGMs will give up current faster than the floodeds (the AGMs voltage won't drop as much as the floodies under heavier load so the AGM pack will be supplying the power mostly), for those quick acceleration needs, but over the long haul the parallel circuit will balance that back out with the floodies sized properly to handle your highway speed load. It's more complex, probably uses two chargers, and I believe you will need to make sure your floodies are at a slightly higher (or identical) voltage than your AGMs after recharge, and during normal operation... that will likely take some finesse. But, you can get the acceleration you need without worrying about AH ratings too much. Now 375 A * 144V = 54kW = 72HP And, to accelerate 4300lbs from 0 - 60 in say, 20 seconds (assuming no friction or air resistance) requires 60 mph = 26.8 m/s, 4300 lbs = 1950 kg and to get to 26.8 m/s in 20 seconds is 1.34m/s^2 So... F = (1950) (1.34) = ~2615 n/m = ~ 178 ft/lbs of torque Though its not entirely right, we can just double the Torque scale for equivalent amperage, since the PDF put out at EVParts shows 75V curves, and we can see that 375A, 72HP is going to land us just about on top of 178 ft/lbs.. maybe a bit over. But that's assuming no friction, rolling resistance or wind resistance. So it will probably take longer. That's pretty anemic acceleration. I'd think to get reasonable acceleration in a 4300 lbs vehicle you'd need a bit more pep. This is why I am contemplating a Warp 11" motor for my conversion, and why I am agonizing over battery pack configurations :) --T . PS: By the way, all of that math is just straight from my Physics background.. please let me know if I've missed anything important, or misinterpreted anything! _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
Since you asked for it ;)
> Now 375 A * 144V = 54kW = 72HP Ignoring the I*R drop, yes, however the I*R drop makes for quite a difference. > > And, to accelerate 4300lbs from 0 - 60 in say, 20 seconds (assuming no > friction or air resistance) requires > > 60 mph = 26.8 m/s, 4300 lbs = 1950 kg and to get to 26.8 m/s in 20 > seconds is 1.34m/s^2 Correct so far. > So... F = (1950) (1.34) = ~2615 n/m The result of this should be in Newtons not nano per meter. This is the force you need to apply to the vehicle to achieve your desired acceleration. > = ~ 178 ft/lbs of torque Torque is measured in ft*lbs. However you seem to have skipped explaining how you went from force to torque. > > Though its not entirely right, we can just double the Torque scale for > equivalent amperage, since the PDF put out at EVParts shows 75V > curves, and we can see that 375A, 72HP is going to land us just about > on top of 178 ft/lbs.. maybe a bit over. > > But that's assuming no friction, rolling resistance or wind > resistance. So it will probably take longer. That's pretty anemic > acceleration. I'd think to get reasonable acceleration in a 4300 lbs > vehicle you'd need a bit more pep. > > This is why I am contemplating a Warp 11" motor for my conversion, and > why I am agonizing over battery pack configurations :) > > --T > . > PS: By the way, all of that math is just straight from my Physics > background.. please let me know if I've missed anything important, or > misinterpreted anything! > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > -- www.electric-lemon.com _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Steve Kobb
If you want acceleration comparable to the original ICE, then you will
probably need AGMs (YTs, Orbitals, etc.) If you can accept somewhat lower acceleration, then 6V GC will work. Do NOT use 8V (T875, etc) in your vehicle. You will regret it. I have a much lighter pickup that uses 15 of the T875 batteries. Acceleration is lethargic at best. 0-60mph in about 80 seconds (no that is NOT a missprint). A more powerful controller might get a bit better acceleration, but then I'd be replacing my batteries every year, or less. As a ball park figure, to go 32 miles on a daily basis in your truck you will need approx 10 kwh or useable battery capacity. If you are comfortable with replacing the batteries every 1-2 years, then you want a pack with a 1hr rated capacity of at least 12.5-13 kwh. You need the extra to make sure you can still make the trip after the battery capacitiy drops a bit, which will start happening after about the 50th cycle. If you want to get 3-4 years from the pack, then you want an initial 1hr capacity of 15-20kwh. Each of the smaller YTs (45lbs?) is good for about 330wh at the 1C rate, so you'd need about 40 or them. I'd guess that the larger group 31s are good for about 450wh, so that means about 28 of them. A cheaper option would be 144V worth of 6V GC batteries. The T-105s can't be beat for price per mile. 24 of them will weight about 1500 lbs and should last about 3-4 years. Acceleration (with a suitable controller, 600-1000 amps) will be better than my truck, but less than the original. > > Thanks, Guys. > > As a result of the "reality therapy" that you gave me, I'm starting to > think > harder about flooded lead. In particular, I was helped by a recent post > from > Lee Hart, where he offered these guidelines for floodies and gels: > > *********** > 1. Keep the *average* current below the 20-hour amphour capacity. > For example: > - 220 amps for a 6v 220 amphour golf cart battery > - 175 amps for an 8v 175 amphour golf cart battery > - 100 amps for a 12v 100ah deep-cycle battery > > 2. Keep the *peak* current times the seconds you draw it below > 5 times the battery's 20-hour amphour capacity. For example: > - for an 8v 175ah golf cart battery: > 175 amps for 5 seconds > 350 amps for 2.5 seconds > 700 amps for 1.25 seconds > *********** > > My real challenge is having to cross 3 lanes of traffic to get onto I-10 > in > the morning. That's really the only time that I need to accelerate hard... > IF I need to accelerate, that is. On many days, I can just ease into a > west-bound lane without having to speed up in a hurry. > > So what about those days when I DO have to fight my way in? Well, if I had > Trojan T-875s, I could pick up speed with a 350 amp pull for less than 3 > seconds. > > Once I'm in the correct lane, I'm hoping that an avg of 175 amps would > keep > me at or above 55 mph. > > Does that sound realistic in what would be a 4300+ lb. truck? > > Steve Kobb > -- > View this message in context: > http://www.nabble.com/YellowTops-and-the-one-third-weight-rule-tf4267497s25542.html#a12153368 > Sent from the Electric Vehicle Discussion List mailing list archive at > Nabble.com. > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > -- If you send email to me, or the EVDL, that has > 4 lines of legalistic junk at the end; then you are specifically authorizing me to do whatever I wish with the message. By posting the message you agree that your long legalistic signature is void. _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Timothy Balcer
I pondered the curves quite a bit, and came to some conclusions that are
counter intuitive for old hot rodders like me. When geared correctly, and big enough, motor size has little to do with acceleration. The batteries are the power producer, the motor is just another piece of the drivetrain between the batteries and the tires. Motor diameter has to do with two things, steady state power capability without overheating, significant for high speed cruise or climbing hills, and gearing. Bigger motors generally like lower RPM. As the RPM comes up in a bigger motor, they generate more back EMF, which makes the current draw drop off at a lower RPM than a smaller motor at the same RPM unless your pack voltage is higher. That means your pack would have to be configured for more voltage to maintain current and torque as the RPM rises. For a given pack weight, more voltage means less current capability. So you've got two choices, configure the pack for more voltage but less current (which reduces torque production) or use less gear reduction to keep the RPM down (which reduces torque multiplication). Either way, the total torque supplied to the rear wheels after considering gearing isn't that much better than it is with a smaller motor, if at all. With the price of 11 inch motors being what it is, twin 8 or 9 inch motors start looking like a much better solution. They can produce twice the torque off the line as a single motor, and then switch to parallel to make best use of a relatively low voltage, high current pack, so you don't have the gearing and/or high voltage requirements of a bigger motor. The conclusion I came to was that with a single motor, geared appropriately for it's size, and the battery pack configured appropriately, acceleration is determined by battery capability and the weight of the vehicle, not motor diameter. Changing the motor size just alters gearing requirements. It looks like if you want more acceleration, you've got to limit range, put money into exotic batteries, or multiple motors. I'm really interested in the capabilities of parallel strings of 12V AGM's and floodies. The AGM's would supply the acceleration current, then the floodies would top them off again to keep DOD up. It certainly would require a complex charger setup, but could they just be paralleled while driving? They are all lead acid afterall (probably showing my ignorance here, but that never stopped me from throwing out ideas). Marty ----- Original Message ----- From: "Timothy Balcer" <[hidden email]> To: "Electric Vehicle Discussion List" <[hidden email]> Sent: Tuesday, August 14, 2007 10:59 PM Subject: Re: [EVDL] YellowTops and the one-third weight rule > Steve, > > What I am considering doing is putting in two chains: 4/5 cap flooded, > 1/5 cap AGM, separate contactors, independently fused and in parallel. > The AGMs will give up current faster than the floodeds (the AGMs > voltage won't drop as much as the floodies under heavier load so the > AGM pack will be supplying the power mostly), for those quick > acceleration needs, but over the long haul the parallel circuit will > balance that back out with the floodies sized properly to handle your > highway speed load. > > It's more complex, probably uses two chargers, and I believe you will > need to make sure your floodies are at a slightly higher (or > identical) voltage than your AGMs after recharge, and during normal > operation... that will likely take some finesse. But, you can get the > acceleration you need without worrying about AH ratings too much. > > Now 375 A * 144V = 54kW = 72HP > > And, to accelerate 4300lbs from 0 - 60 in say, 20 seconds (assuming no > friction or air resistance) requires > > 60 mph = 26.8 m/s, 4300 lbs = 1950 kg and to get to 26.8 m/s in 20 > seconds is 1.34m/s^2 > > So... F = (1950) (1.34) = ~2615 n/m > > = ~ 178 ft/lbs of torque > > Though its not entirely right, we can just double the Torque scale for > equivalent amperage, since the PDF put out at EVParts shows 75V > curves, and we can see that 375A, 72HP is going to land us just about > on top of 178 ft/lbs.. maybe a bit over. > > But that's assuming no friction, rolling resistance or wind > resistance. So it will probably take longer. That's pretty anemic > acceleration. I'd think to get reasonable acceleration in a 4300 lbs > vehicle you'd need a bit more pep. > > This is why I am contemplating a Warp 11" motor for my conversion, and > why I am agonizing over battery pack configurations :) > > --T > . > PS: By the way, all of that math is just straight from my Physics > background.. please let me know if I've missed anything important, or > misinterpreted anything! > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Steve Kobb
Steve Kobb wrote:
> My real challenge is having to cross 3 lanes of traffic to get onto > I-10 in the morning. That's really the only time that I need to > accelerate hard... IF I need to accelerate, that is. On many days, I > can just ease into a west-bound lane without having to speed up in a > hurry. > > So what about those days when I DO have to fight my way in? Well, if > I had Trojan T-875s, I could pick up speed with a 350 amp pull for > less than 3 seconds. The limits I posted are conservative -- use them if you want to maximize your battery life. The harder you "push" beyond them, the shorter your pack life. But like I said, it's a gradual thing. Do it once in a while, and it has little effect. Do it many times a day, and the damage adds up fast, like a 3-pack-a-day smoking habit. > Once I'm in the correct lane, I'm hoping that an avg of 175 amps > would keep me at or above 55 mph. Does that sound realistic in what > would be a 4300+ lb. truck? Yes, you should be able to average well under 175 amps if you pay attention to details (tire pressure, wheel alignment, no dragging brakes, etc.). -- Ring the bells that still can ring Forget the perfect offering There is a crack in everything That's how the light gets in -- Leonard Cohen -- Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
My completely uninformed opinion here.... I know of a few pickup
conversions using around 156 volt packs and 9" ADC motors and 5 speed transmissions, which have very peppy acceleration. Quicker off the line than any of my ICE vehicles, and I could not keep up with one of them in my old turbodiesel truck on the highway. I think that it may depend more on upgrading your controller and battery choice than going to a larger motor, unless you are looking for drag racing ability.... :) I'm not sure what they were running for controllers, but I know they only had 8 volt batteries --- and rapidly killed them. On 8/15/07, Lee Hart <[hidden email]> wrote: > Steve Kobb wrote: > > My real challenge is having to cross 3 lanes of traffic to get onto > > I-10 in the morning. That's really the only time that I need to > > accelerate hard... IF I need to accelerate, that is. On many days, I > > can just ease into a west-bound lane without having to speed up in a > > hurry. > > > > So what about those days when I DO have to fight my way in? Well, if > > I had Trojan T-875s, I could pick up speed with a 350 amp pull for > > less than 3 seconds. > > The limits I posted are conservative -- use them if you want to maximize > your battery life. The harder you "push" beyond them, the shorter your > pack life. But like I said, it's a gradual thing. Do it once in a while, > and it has little effect. Do it many times a day, and the damage adds up > fast, like a 3-pack-a-day smoking habit. > > > Once I'm in the correct lane, I'm hoping that an avg of 175 amps > > would keep me at or above 55 mph. Does that sound realistic in what > > would be a 4300+ lb. truck? > > Yes, you should be able to average well under 175 amps if you pay > attention to details (tire pressure, wheel alignment, no dragging > brakes, etc.). > > -- > Ring the bells that still can ring > Forget the perfect offering > There is a crack in everything > That's how the light gets in -- Leonard Cohen > -- > Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Lee Hart
OK math wizards, is there something here, or am I off base. This looks like
calculus, at which I am impaired, too ADHD. What happens if you couple a smaller motor to the back of a bigger motor and parallel them (electrically). I'm thinking the big motor might suck up most the current and produce tremendous torque at low RPM, then when the big motor's back EMF is taking it down as RPM rises, the little motor is getting into it's power band? Might this combination make for a broader power band and reduce the need for a transmission or series parallel switching? Another advantage might be that the output shaft size of the small motor may be the same size as the small shaft end of the big motor, and couplers may survive better as the big end of the big motor isn't being asked to handle twice the torque it was designed to. I'm thinking ADC 11 and ADC 8 for example. Comments? _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Peter Gabrielsson
> > Now 375 A * 144V = 54kW = 72HP
> > Ignoring the I*R drop, yes, however the I*R drop makes for quite a difference. Well sure.. I was ignoring it. 375A was the proposed current draw by the motor. > > > > > > And, to accelerate 4300lbs from 0 - 60 in say, 20 seconds (assuming no > > friction or air resistance) requires > > > > 60 mph = 26.8 m/s, 4300 lbs = 1950 kg and to get to 26.8 m/s in 20 > > seconds is 1.34m/s^2 > > Correct so far. > > > > So... F = (1950) (1.34) = ~2615 n/m > The result of this should be in Newtons not nano per meter. This is > the force you need to apply to the vehicle to achieve your desired > acceleration. No idea why I put n/m.. I meant to put Newtons. :) > > > > = ~ 178 ft/lbs of torque > Torque is measured in ft*lbs. However you seem to have skipped > explaining how you went from force to torque. And here is where I lost my caffeine and fell off the bridge :) Apologies there. I took this as a lesson and am reading up again. Been longer than I thought since I looked at mechanical physics stuff!! --T _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Marty Hewes
The problem I can think of right away is that once the 8" motor gets up into its "power band" as you put it you could be well past the redline of the bigger motor. It would probably be best for both motors that they share load equally at all power and RPM levels. If you want the torque of an 8" and 11" in combination why not go with two 9" motors. In my rough figuring two 6.7"s equal a 9", two 8"s equal an 11" and two 9"s equal a13" for torque. The benefit for the two smaller motors is the higher RPM limits and the ability to affect a series/parallel shift point.
My two motors worth, Mike Anchorage, Ak. ----- Original Message ----- From: Marty Hewes <[hidden email]> Date: Wednesday, August 15, 2007 7:46 am Subject: [EVDL] twin, different motors? To: Electric Vehicle Discussion List <[hidden email]> > OK math wizards, is there something here, or am I off base. This > looks like > calculus, at which I am impaired, too ADHD. > > What happens if you couple a smaller motor to the back of a bigger > motor and > parallel them (electrically). > > I'm thinking the big motor might suck up most the current and > produce > tremendous torque at low RPM, then when the big motor's back EMF is > taking > it down as RPM rises, the little motor is getting into it's power > band? > Might this combination make for a broader power band and reduce the > need for > a transmission or series parallel switching? Another advantage > might be that > the output shaft size of the small motor may be the same size as > the small > shaft end of the big motor, and couplers may survive better as the > big end > of the big motor isn't being asked to handle twice the torque it > was > designed to. > > I'm thinking ADC 11 and ADC 8 for example. > > Comments? > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
My thought was to better emulate the wide power band of an AC motor. A
large DC motor pulls well at low RPM, but has too much back EMF at higher RPM to draw much current and generate HP unless a high voltage pack is used. The smaller motor isn't as torquey at low RPM, but comes on stronger at high RPM due to less back EMF. I'm thinking a 6.7" coupled to a 9" might produce the same power as twin 8's, but with a broader power band and less stress on the small shaft end of the bigger motor. Might be cheaper also, I seem to remember 8" and 9" being similar in price, but the 6.7" is significantly cheaper. I also wonder about the red line on the bigger motor though. Guess I'll have to get out the curves and graph paper. Marty ----- Original Message ----- From: "MIKE WILLMON" <[hidden email]> To: "Electric Vehicle Discussion List" <[hidden email]> Sent: Wednesday, August 15, 2007 12:28 PM Subject: Re: [EVDL] twin, different motors? > The problem I can think of right away is that once the 8" motor gets up > into its "power band" as you put it you could be well past the redline of > the bigger motor. It would probably be best for both motors that they > share load equally at all power and RPM levels. If you want the torque of > an 8" and 11" in combination why not go with two 9" motors. In my rough > figuring two 6.7"s equal a 9", two 8"s equal an 11" and two 9"s equal > a13" for torque. The benefit for the two smaller motors is the higher RPM > limits and the ability to affect a series/parallel shift point. > > My two motors worth, > > Mike > Anchorage, Ak. > > ----- Original Message ----- > From: Marty Hewes <[hidden email]> > Date: Wednesday, August 15, 2007 7:46 am > Subject: [EVDL] twin, different motors? > To: Electric Vehicle Discussion List <[hidden email]> > >> OK math wizards, is there something here, or am I off base. This >> looks like >> calculus, at which I am impaired, too ADHD. >> >> What happens if you couple a smaller motor to the back of a bigger >> motor and >> parallel them (electrically). >> >> I'm thinking the big motor might suck up most the current and >> produce >> tremendous torque at low RPM, then when the big motor's back EMF is >> taking >> it down as RPM rises, the little motor is getting into it's power >> band? >> Might this combination make for a broader power band and reduce the >> need for >> a transmission or series parallel switching? Another advantage >> might be that >> the output shaft size of the small motor may be the same size as >> the small >> shaft end of the big motor, and couplers may survive better as the >> big end >> of the big motor isn't being asked to handle twice the torque it >> was >> designed to. >> >> I'm thinking ADC 11 and ADC 8 for example. >> >> Comments? >> >> _______________________________________________ >> For subscription options, see >> http://lists.sjsu.edu/mailman/listinfo/ev >> > > _______________________________________________ > For subscription options, see > http://lists.sjsu.edu/mailman/listinfo/ev > > _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
--- Marty Hewes <[hidden email]> wrote:
> My thought was to better emulate the wide power band > of an AC motor. A > large DC motor pulls well at low RPM, but has too > much back EMF at higher > RPM to draw much current and generate HP unless a > high voltage pack is used. > The smaller motor isn't as torquey at low RPM, but > comes on stronger at high > RPM due to less back EMF. I'm thinking a 6.7" > coupled to a 9" might produce > the same power as twin 8's, but with a broader power > band and less stress on > the small shaft end of the bigger motor. Hey Marty I'd advise against it. If you try to run both motors at the same time they will probably fight each other. On Waylands 8" motors I paid careful attention to getting the RPM's and voltage as close as possible so they pulled equal. Even on dual forklift motor drives I always hate when they send just one. That one gets back up to par and then the one they didn't have done isn't running as well and it puts the new motor under a harder strain. As Mike stated you're now limited by the larger motors RPM limits (whether it's commutating or not) which kind of defeats the purpose. In short, unless I was dealing with some free / cheap motors I'd stay with "like piars" and stay on a more tried and true set up. I sure wouldn't go out and buy a new FB1 and L91 for example where in reality twin 8's would cost pretty close to the same and be a reliabe system. In as much as this might get you your desired power outputs it says nothing as to whether the motors will be happy about it. Just something to chew on. I missed the first parts of this I believe like car weight, voltage, and controller Anyway, hope this helps. Jim Husted Hi-Torque Electric ____________________________________________________________________________________ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545433 _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Timothy Balcer
[Very Cool Formula!]
Ok I've re-edumicated myself over lunchies.. man it was like being in a mechanics class again :) Now that I've remembered impulse, momentum, and unit conversions, I wont subject all of you to it ! Rather than go through the whole thing again, I'll post the extremely cool Kludge that I found, which was posted up on a forum by some automotive engineer types. I've checked it and it does seem to get you 'in the ball park'. They posted some examples as well that showed them being off by no more than 0.2 seconds in 6 cases. Have fun! :) ------------------------------------ - But can you calculate 0-60 times based on horsepower and weight Well, having decided that in theory it's not possible we're reminded of the engineer's adage - In theory, practice and theory are the same thing, but in practice they're not. We analysed the manufacturer's 0-60 times for a range of popular sports cars and found that in practice the quoted 0-60 times are easily and quickly calculated to the nearest second by dividing the weight of the car in Kg (Kilogrammes) by the cars' maximum brake horse power. Further analysis revealed that the more precise formula for most cars is:- 0-60 time = weight of car in kilogrammes / (maximum bhp of car * 0.9) OK, it's not a precise science, but it does work (most of the time), _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Hi-Torque Electric
What Jim said :)
Well, except that if you weren't worried about money, you could setup a dual differential of some kind that was connected to the controller via a shaft RPM sensor at both motors. That way neither motor could be on at the same time, but wouldn't drag each other much...the big one would start you off and the little one would take over at X rpm. Heehee. Who wants to do the boring thing with a transmission when you can make slipping, electronically controlled differentials!! *ahem* --T _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
In reply to this post by Timothy Balcer
On Wed, 15 Aug 2007 15:31:21 -0400, you wrote:
>[Very Cool Formula!] > >- But can you calculate 0-60 times based on horsepower and weight >Well, having decided that in theory it's not possible we're reminded >of the engineer's adage - In theory, practice and theory are the same >thing, but in practice they're not. > >We analysed the manufacturer's 0-60 times for a range of popular >sports cars and found that in practice the quoted 0-60 times are >easily and quickly calculated to the nearest second by dividing the >weight of the car in Kg (Kilogrammes) by the cars' maximum brake horse >power. Further analysis revealed that the more precise formula for >most cars is:- > > >0-60 time = weight of car in kilogrammes / (maximum bhp of car * 0.9) I like this. It says that I will have a 0-60 time of 10.2 seconds! : ) 0.45359237 * 3000 / 120 * 0.9 = 10.205828325 Of course that assumes that I jack the Zilla all the way up and really do a hard one on the batteries. My plan is to put the car on a dynamometer when I can afford it. R. M. Milliron 1981 Jet Electrica http://www.austinev.org/evalbum/702 This machine has been garaged for 17 years. I am upgrading it and getting it running. Tabitha, my daughter, named it, "Pikachu". It's yellow and black, electric and contains Japanese parts, so I went with it. _______________________________________________ For subscription options, see http://lists.sjsu.edu/mailman/listinfo/ev |
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