David, I can corroborate your numbers on pack sizing. You pretty much summed up my conversion. I have 45 cells of ThunderSky 100Ah cells in a Honda del Sol for a nominal 144V pack and 13 kWh. In that car, I have a 50 mile range (barely). When new, I drove it 46 miles without issues, but I wouldn't try that on a regular basis.
The car weighs 2550 pounds after electric conversion. I need a little more than 250 wh/mile with LRR tires and fairly conservative driving. >From my experience, I would say your estimates for a hybrid conversion are >quite close. My pack takes up about 1/2 the trunk (20 cells in 2 rows of 10) and two places under the hood (10 cells in front of the grill and 15 cells in front of the firewall along with the charger). See www.evalbum.com/2778 for more details and pictures. Mike On July 21, 2014 11:21:14 PM MDT, EVDL Administrator via EV <ev@lists.evdl.org> wrote: >On 21 Jul 2014 at 14:12, Ben Goren via EV wrote: > >> I'm really only looking for a battery pack big enough for local >trips; >> a couple dozen miles would be plenty. I suspect that the smallest >pack >> that puts out the necessary voltage is going to be just about the >> right size ... > >Hmm. Maybe. Let's do some math. > >A typical subcompact conversion uses around 250 Wh/mi. (Some have done >as >well as 150-160 Wh/mi, carefully driven.) You're not going to match >that >with a heavier, less aerodynamic car that wasn't designed with fuel >efficiency in mind, however. > >What can you do? Well, in the EV Photo Album I found a '66 Mustang >conversion that does 375 Wh/mi. > >http://www.evalbum.com/733 > >Here's a '65 ragtop that does 330 Wh/mi. That sounds a little better. > >http://www.evalbum.com/2056 > >One other similar Mustang entry estimated his energy use as "at most >500 >Wh/mi," but we'll take that with a grain of salt that since he doesn't >seem >to have measured it accurately yet. > >Now, these are BEV conversions. You're leaving in all the ICE bits for >a >car that will probably weigh in the 2800-3000lb range before >conversion, >maybe 3500 or more after. You'll might also pass up the skinny LRR >tires >for sticky high performance ones. So let's be conservative (and assume >you >probably won't drive like I do ;-) and allow 400 Wh/mi. > >You want about 25 miles of range. So you need 10 kWh, but you don't >want to >size your battery to that. You probably want to not exceed 80% DOD for >good >life, but let's say you're OK with giving up a little battery life, and >go >to 90%. So you actually need a battery capacity of about 11.1kWh. > >Doing that with lead in the space you have is going to be a >non-starter, so >I guess we'll go right to lithium. A LiFePO4 cell has a nominal >voltage of >3.2v. Let's say you're going to use a 144v drive system, so you'll >need 45 >cells. (In a more reasonable world, you'd determine how much energy >and >power you need, and size the battery from that. THEN you'd decide what > >motor and controlller would work with that battery. However, we'll >assume >for now that you've already chosen a motor and controller, because it >makes >the calculations easier.) > >We'll start with, as you suggest, "the smallest pack that puts out the >necessary voltage." The laptop-size cells are obvously too small >unless >you go to massive paralleling a la Tesla, so let's jump to something >like >Headway 38140 cells. I'm no lithium expert, but I'd guess that these >are >about the smallest lithium cells practical for an EV (and a pretty >light one >at that). > >The 38140s are 12ah cells, 38mm in diameter and 152mm long. Because >they're >cylindrical, packaging isn't optimum, but (allowing a little wiggle >room) a >5x9 matrix would be 152mm (6") high, 200mm (7.9") wide, and 360mm >(14.2") >long. Your battery box will need to be at least 25-50mm (1-2") larger >in >all dimensions than this, to allow for wiring, ventilation, and (in the > >winter) insulation. So you're looking at maybe 8"h x 10"w x 16"l. I >don't >know how that compares to a banker's box, not being familiar with such >a >critter. > >Each cell is good for about 38.4 Wh, so 45 of them would be ... >1.73kWh. >Hmm. That would get you about 4.3 miles of range. We're going to need >something larger. > >How about CALB? The smallest one EVSource sells (that's not an >endorsement, >it's just one place I found offering them online) is 40ah. > >Each cell is 181mm x 115mm x 46mm. Again allowing a couple mm per cell >for >breathing room between (the lithium experts here can give you more info >on >whether this is necessary), your battery is now 181mm (7.1") high x >585mm >(23") long x 432mm (17") wide. Again add at least 25-50mm (1-2") to >each >dimension to allow for battery box sizing, to get to around 9"h x 25"l >by >19"w, maybe even a little higher to allow for installing a BMS. > >Now with 45 cells we're talking 5.8kWh and a practical range of 13 >miles >with new cells, declining to perhaps 9.8 miles after a few years of >use. >Still only about half what you want. (But can you live with it?) > >Let's see what we can do to get closer to your target range. The >Winston WB- >LYP90AHA is a 90ah cell. This will give you nearly 13kWh for a >practical >range of 29 miles, perhaps 22 miles as they age. Now we're talking. > >Each cell is 218mm high x 143mm long x 61mm wide. Sticking with our 5 >x 9 >configuration, we now have 218mm (8.6") x 1100mm (43") x 567mm (22.3") >for a >battery box about 11"h x 45"w x 24"d. This is a significant distance >from >"the smallest pack that puts out the necessary voltage," unfortunately, >but >still smaller than a lead pack would be. > >The specs in Wikipedia say the Mustang Mk I is about 68" wide. Would >there >be enough room for this battery in the forward part of the trunk, >between >the wheel wells and above the rear axle? I'm thinking that otherwise >you'd >lose a fair bit of trunk space. Or maybe you could fit a half-size gas > >tank, and use some of the freed-up space for part of the battery. > >David Roden - Akron, Ohio, USA >EVDL Administrator > >= = = = = = = = = = = = = = = = = = = = = = = = = = = = = >EVDL Information: http://www.evdl.org/help/ >= = = = = = = = = = = = = = = = = = = = = = = = = = = = = >Note: mail sent to "evpost" and "etpost" addresses will not >reach me. To send a private message, please obtain my >email address from the webpage http://www.evdl.org/help/ . >= = = = = = = = = = = = = = = = = = = = = = = = = = = = = > > >_______________________________________________ >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)
