|Location||Austin, Texas US map|
|Vehicle||1999 Porsche Boxster|
|Motor||Netgain Warp 11 Series Wound DC|
The first motor fan was destroyed at less than 5000 rpm requiring a tear down of the motor to repair. We damaged the replacement fan sent under warranty, and had to order another one on our dime. I recommend sending the motor back to the factory for any repairs. Recently we think the balancing putty came off the motor and found fragments that fell out. The motor is mildly vibrating with intermittent scraping noises... Contacting Netgain for a solution.
|Drivetrain||5 speed manual, lightweight flywheel, high performance clutch|
|Controller||Cafe Electric Z2K-HV|
|Batteries||1920 Peak K2 26650 EV 3.2Ah (now <2 Ah on many cells af, 3.30 Volt, Lithium Iron Phosphate|
Pack is arranged with 10 cells in a parallel column, then 4 columns in series constituting a blade. A string is made of 16 blades in series at ~205V. 3 strings are arranged in parallel. Per K2 spec the pack should have 96Ahrs or 19.66 Kwh capacity. However, cell capacities on install were less than 2400mAh per average cell based on 3rd party tests. Cells were 2 years in garage storage before installation. Since then, the cells continue to diminish in capacity. We only have about a third remaining capacity which gives about 18 miles range driven conservatively.
We removed the Revolt BMS boards off two of the strings and bottom balanced. The batteries cool faster with better airflow without the BMS boards on top. Unfortunately with cold weather and reduced capacity, there is no good way to monitor overdischarge and this may have contributed to more damage particularly to the front pack. The front pack had taken some over-discharge damage previously from a BMS malfunction. K2 and BMS has been a mess.
|System Voltage||205 Volts|
|Charger||Manzanita Micro PFC-40 Liquid Cooled|
PFC-40 is plugged into a 50A 240V outlet. We had trouble initially obtaining rated 40A output, and sent it back to Manzanita. The temperature regulators were adjusted followed by adding fans to the liquid cooling system. Now without a BMS, we set the charge amps to limit at 214V and set the timer to shut off completely after about 2.5 hours. A couple of cells reach about 3.8-4.0V for up to an hour which seems to be tolerated.
|Heater||Ceramic 1500W, not adequate for very cold weather. Heat ducting may not be correct. Masterflux A/C works surprisingly well.|
|DC/DC Converter||Iota 55A 220V|
|Instrumentation||eVision 2: Shunt amp measurements are working better but still not consistently accurate. Problems we have are might be related to interference, and have improved somewhat after rearranging high voltage wiring nearby.|
|Top Speed||100 MPH (160 KPH)|
Theoretical 132 mph based on a max rpm of 5500 with the Warp 11 on stock transmission gear ratios. So far 95mph was no problem at around 3500rpm.
|Acceleration||0-60 was roughly less than 7 seconds, but gradually losing performance with loss of battery capacity. Maximum battery pack output was about 1000A for short bursts with a full pack, and about 600-850A for average accelerations. K2 battery pack is not cold temperature tolerant, and loses more than half the power and capacity in subfreezing temperatures. Now I don't even try to push it hard for fear of damaging batteries faster. 0-60 is probably 10-12sec now.|
|Range||15 Miles (24 Kilometers)|
1.6 Ah/mile when driven conservatively with about 185V avg sag when cruising at 70mph. K2 cells degrading with time and front pack sustained overdischarge damage from a BMS failure. Best range early on was 47 miles.
|Watt Hours/Mile||315 Wh/Mile |
Improved since installing Michelin Green X tires.
|Seating Capacity||2 adults|
|Conversion Time||Started project in August 2008. Purchased car late 2008 and delivered to Revolt Custom Electric (Chris, Aaron and Mark)for conversion in Feb 2009.|
|Conversion Cost||Over $60K: BMS $3450, Netgain Warp 11 |
plus Masterflux AC $3816, Cafe Electric $4782, K2 Batteries $16351, Manzanita $3020, Ultrarev Flywheel/sport clutch
$1396, KTA $429, MetricMind $1210, Custom battery boxes $3850. Total parts plus the car = $49804 not including labor and maintenance costs.
|There has been a lot going on over the last year with the Boxster which I have been driving as my main commuter car. It has been a challenging 4 year hobby, and I don't regret it. Pretty soon it will be down for 3-6 months when we upgrade the batteries to CALB CA100s and fix the balancing putty. The new pack should give us 2-3 times more power and far more range! I am emotionally attached to my Boxster, but I might be willing to sell for the right price if someone wants to adopt it as their project. I should have my Model S by end of March, and the Boxster may become less useful to me as a commuter car.|
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