82 Miles In the Zombie @ 77% DOD

Responding to another thread on the SEVA list, Steve Lough brought this up:

By the way of HIGH PERSONAL CURIOSITY, how is the Insight project coming ?? Keep thinking for my self a 60 or 80 mile per charge All Electric Insight.. say… round the $22,000. price tag.

The Silver Streak Insight project is behind schedule but is still very much alive. We had a glitch with the CNC guy we had been using and have been waiting for clamp/conductor parts for more than a month. A new shop is now being looked into. The clamp/conductors we’ve designed for these larger 75 ah cells (the Zombie uses 30 ah cells) are totally different than what we use in the race car’s modules, and have to be made ‘just so’. Once I have the hundreds of clamp/conductors in hand, the dress rehearsal Meanie project’s 20 kWh, 266V pack can be assembled and road-tested. Then, the Insight goes under the knife.

I am very happy with both the track performance and the street performance of the Zombie’s large format 30 ah Dow Kokam ‘ultra high power’ cells, and am looking forward to seeing what these even larger format 75 ah ‘high power’ cells will do. As the model type name suggests, though physically larger than what we are using in the Zombie, the 75 ah cells are not as crazy-powerful, so instead of 1200 amps @ 10 seconds (40C), these guys are rated at just 750 amps (10C) @ 10 seconds. Their continuous rating is 6C, or 450 amps. Both the Meanie and Silver Streak need less peak power than 750 amps (the Insight’s max. current should be 380 amps or so and Blue Meanie should be about 600 amps), and both will merely sip juice on the open highway at around 40 amps for the Meanie and 25-30 amps for Silver Streak. The stronger suit of these 75 ah cells, is their energy density. One 75 ah cells weighs 3.81 lbs, nearly the same of what a paralleled pair of the 30 ah cells weigh (1.8lbs. X 2 = 3.6 lbs.), so that’s 75 ah for 3.81 lbs. vs 60 ah for 3.6 lbs.

Minus its 147 lb. 9 inch DC motor, flywheel, clutch, transmission, 700 lbs. of 12V batteries and all the brackets, enclosures and heavy cabling for them, and with just 275 lbs. of cells in one light container and a smaller and lighter AC drive, I am predicting that the Meanie will drop about 500 lbs. in weight from its former 2460 lbs. and will be at around 1950 lbs. curb weight. Using a 93% efficient AC motor and a 20 kWh LiPol pack, I am predicting 100 miles range. Given this info and with regard to Steven’s electrification of his Insight, I think a 20 kWh pack of less costly cells in the similarly light but much more areo car, and using an affordable small (light) DC motor and using the stock tranny, 80-90 miles range is very likely for about $22,000.

Speaking of range…

I had previously written:

The Zombie is fully street legal and is driven often on the streets with its 100+ miles range per charge. Last weekend it delivered 60 miles in aggressive driving that included a 3 mile 6.5% grade pull at 65 mph (punched it once and shot way past the speed limit briefly going uphill just for fun), freeway cruising, and in-town side streets as well. Returning to the EV Juice bar the lithium pack had about 55% capacity remaining!

 

The Zombie on display in late April at Rosedale Elementary School’s ’Green Festival’ in  Hillsboro, Oregon, after traveling 30 miles west of Portland.

Completing a 60 mile round trip to Hillsboro and back, without a recharge the car sat for a week. The following weekend I took it back out for some around-town runs to see how close to my prediction of range per charge the car could come. As before, I used a GPS unit to keep track of the exact miles driven. This weekend, I am ‘finally’ getting a proper sensor wheel built and installed on the Siamese 9 motor so all the cool functions of the EVision system can be utilized. I am also ‘properly’ installing the Bruce Sherry SOC gauge as well. The two systems will really give me accurate data on the next range tests. I again, did not baby the car and drove in a spirited fashion. Another welcome change is the new Superior Gear brand ring and pinion set, at the same 3:50 ratio used to get the 10.2 runs…only these are heavy duty street cut gears, not race cut as were the previous set that were ear-splitting LOUD! The new gears are super quiet, though you can still hear the whir of the meshing teeth. The Zombie is now very quiet and smooth on the road at speed sup to about 45 mph. After that, the age-old drive line rumble comes into play – we’re working on a solution for this as well.

I know many think my estimates of my EVs’ performance capabilities are too optimistic at times (many doubted the Zombie could run high 10s, let alone nearly cracking the 9s), so I love to prove them wrong ;-) I am happy to report it is the same with my range predictions for the Zombie. I have been saying that even with the car’s high drag Ford 9 inch rear end (they are known to be bullet proof tough while at the same time inefficient) and it’s fat 225 rear tires on 8 inch rims, that due to efforts to reduce drag in all other areas (145/65 LRR tires on 4 inch rims up front) and with the Datsun 1200′s small frontal area and the Zombie’s low curb weight (2352 lbs.) that the car would achieve somewhere in the neighborhood of 195 Wh per mile when driven conservatively. Based on all this, plus my general seat-of-pants feelings I’ve been predicting that with a 100% discharge (the cells can do this 1440 times and still retain 81.1% capacity) 90 miles urban driving and 110-120 miles highway.

Drum roll please…with the front LRR tires at 45 psi and the drag radials pumped-up to 43 psi (they are rated to 44 psi) the Zombie logged 82 miles total with 23% charge still remaining. I would have kept going with the tests, but had to get the car to a show (May 2nd ‘Taste of the Nation’ charity event) I had made a commitment for. This last portion of the range test included several hard near-full-throttle street launches, too…as I said, I did not baby the car, traveled at speeds in excess of 70 mph at times, and fully expected the Wh per mile to be higher than for more moderate 55 mph cruising. The pack’s resting voltage is only a few volts higher than the indicated voltage while driving under light cruise conditions, and was down to 325V after 82 miles for 3.38V per cell. I consider the safe discharge range to be from 4.0V down to 3.0V, even though they are rated from 4.2 – 2.7V. The cells are 30 ah rated @ C1, but are 32 ah at C3, so the paralleled cell pairs are 64 ah (X 355V gives the 22.7 kWh rating). It took exactly 49 recharge ahs to put all the cells into low current regulation at 4.17V per cell. 49 ah X 355V = 17.4 kWh used for 82 miles driven, giving 212 Wh per mile…22.7 kW divided by 212 Wh per mile gives 107 miles range – this with aggressive style driving.

It’s clear the Zombie can easily hit my predicted 90 miles city driving range, even when driving with a heavy foot. In a more conservative style and at a steady 55 mph the Wh per mile should be quite close to my estimate of 195-200 Wh per mile. I don’t think there are too many EVs are there that can rip 0-60 in 1.8 seconds, run a 10.2 @ 123 mph 1/4 mile ‘and’ do this kind of range :-) With exception to the EV1s I used to drive and the Teslas I’ve had the pleasure to drive, the only other EV I’ve had that gave this type of range was Red Beastie – Dick Finley’s Toyota truck stuffed to the gills with just shy of 2500 lbs. of lead acid batteries. Though I ran that truck 120 miles on one charge, it was a 100% discharge that left the 6V batteries with their tongues hanging out and ‘not happy’ about it. Staying within the reasonable 80% DOD for lead acid, the 5300 lb. truck could do about 95 miles per charge. Of course, its 0-60 was a bit slower than the Zombie’s! It took 2500 lbs. of lead acid to get 100 non-pack damaging miles per charge – the Zombie has this same range with just 345 lbs. of LiPol cells contained in the trunk, 11 of the 12 modules recessed down low in the floor. Were it not for the required 6 point roll bar system the Zombie would still have its back seat.

Though the Zombie’s Dow Kokams have seen many high current discharges at the drag track, this range test was the first deep cycling of the 355V pack. After the recharge the already stiff cells seemed even stiffer. Typically, after taking the pack to full charge at 400V on the nose, right off charge the pack sits at 395-397V ‘surface charge’. Keying-on and moving the car out the driveway dissipates that surface charge quickly though, and the pack settles in at 383-385V…3.99-4.0V per cell. Moderate driving at 45 mph sags the pack to somewhere around 379-380V, but after the 82 mile/49 ah run and subsequent recharge, driving on the freeway at 60 mph the pack was hanging at 381V!

The Dow Kokam cells have been fantastic and have surpassed my expectations. Though they were delivered in un-opened boxes in the Fall of 2009, they were already nearly 3 calendar years old. They are now 4 years old, have seen 1500+ amp discharges per cell, and are easily hitting their rated ah capacity. I realize I am fortunate to have Dow Kokam as a sponsor and wish these large format ‘ultra high power’ type LiPol cells would be mass produced at a reasonable price that everyone could afford. The new even larger 75 ah ‘high power’ type cells that are going into both Blue Meanie and Silver Streak will be fun to wring out to see what they can do.

See Ya…John Wayland

 

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