View Full Version : Lithium Hawk

14 March 2012, 0810
In their "How 2.0" section, starting on page 71, the April issue of Popular Science has an article titled (I don't know why) "Road Hawk". The article is about Nap Pepin, a fellow from Alberta, Canada, who has built a reverse-trike powered by 1,975 Li-ion cells, which he calls the "Lithium Hawk". The trike weighs around 1000 pounds and uses a Honda Goldwing rear drive, with a home-built chassis. The article says that he found the $3,500 shaft-drive on eBay for only $106 being sold by someone who had converted a Goldwing to a standard trike using a kit. Mr. Pepin has been tinkering with battery-powered 3-wheelers since 2005.

That article says that the batteries presented the biggest challenge to his build (I guess that is no surprise to anyone here) and he bought and tested a number of battery cells for months before deciding upon the ones that he wanted to use (the article doesn't say which brand or cell size he is using). He spent over 100 hours precisely welding copper plates to the cells only to find that the copper welds didn't hold. He then had to start over with strips of nickel, which he spot-welded together with the cells at 23,712 different points.

The article doesn't mention what drive motor he is using. The only failure discussed was a "manufacturing flaw" in his (unnamed) controller, which he now has corrected.

In the sidebar on page 73, it mentions that he was concerned that the DMV regulators would call his trike a car if he used a steering wheel and so he is steering it with motorcycle handlebars, which results in heavy steering. He later found out that the DMV regulators that inspected the Hawk would have approved a steering wheel. Most of his braking is accomplished by regenerative braking and the system he uses is the same as the throttle-control that Vectrix used (uses?). Mr. Pepin has driven his trike over 2000 miles and he says that it out-accelerates practically every other vehicle on the road. He can jump from 45 mph to 70 mph in just two seconds. The trike is currently unclothed, but he plans to cover it with a more aerodynamic fairing in the future, which he says should extend its range.

On the last page of the magazine is a little blast from Pop Sci's past (from their June 1975 issue), titled "The Proto-Electric". This paragraph mentions the small crop of odd, tiny electric cars that resulted from the 1970's gas crisis. The car mentioned is the Sebring-Vangard CtiCar. It was a two-seater and featured a thermoplastic body, unopenable windows and 524 pounds of lead-acid batteries. Between 1974 and 1975, Sebring-Vanguard built 800 CityCars, which sold for $2,690 each. I wonder where they all are now? :confused:

14 March 2012, 0847
He's got a webpage for the Lithium Hawk: http://www.nappepin.com/LithiumHawk.htm

14 March 2012, 0914
Whoa. That thing is awesome.

Sent from my ADR6350 using Tapatalk

14 March 2012, 1351
I found his comments about Thundersky batteries interesting. I think sucking 3C out of my Hi Power batteries (which are a step down the battery rung from the Thundersky brand) surely helped them along their path to an early end.

14 March 2012, 1657
On the 2nd page he lists the Hawk motor as the AC-31from HPEVS.


15 March 2012, 0133
He has some specs on his site with his own comments. Looks like he started with the Thunder-sags, and then got struck with the under-whelming punch they deliver, and swapped to a nano-phosphate chemistry. Folks that make EV packs from hundreds or thousands of tiny round cells are either nuts or really determined to have decent performance without using a pouch cell. More power to the guy for making it happen.


Old- AC 9, 38HP, 85 ft-lbs

New- AC 31, 50HP, 115 ft-lbs

Likely similar power to weight ratio since the Lithium BugE was tuned down but this much larger motor will remain cooler.


Old -Curtis 2265, 102 Volts, 300 Amps

New- 130 Volts, 550 Amps

More powerful and higher system voltage


Old- Prismatic Thunder Sky TS-90LFP, 24 cells X 90AH, total energy 6.9 to 7.2kwh

New- Cylindrical K2 Energy LFP22650P,
1980 cells X 2.6AH

Far superior cells handling 8 to 10 C continuous compared to 0.8 to 1 C for Thunder Sky cells. Total energy will be >15kwh. There should be much more usable energy as a result of far less internal losses.

Gross Weight

Old- Est. 400lbs

New- Est. 900lbs

At more than twice the weight, the Lithium Hawk will consume more energy to start off or to accelerate but the added vehicle mass will add tremendous stability and improve handling