It keeps getting better

Covering some real ground

With the full battery pack and a instrumentation package up and running, we are now going for longer drives.  Yesterday, we covered over 10 miles on a single charge.

The charging system is working great.  Two charges, both tied to the 220V input.  One is the 1500W 91V Lithium Ion charger for the drive battery and the other a 120W 12V charger for the system battery.  Since both are automatic, they shutoff independently when charging is complete.  I have the 220V outlet on a timer just to be safe.

Instrumentation Pack

Here is a the roughed-out instrumentation pack.  This will be mounted behind the dashboard once it is installed.

1) On the left are 4 CellLog8M battery monitors.  These are set to alarm if any of the individual cells go out of range.  Currently I have them set tightly at [3.0V - 3.6V].  Charging is set to 91V which should be 3.5V/cell on average, so any major drift will be detected.  The cells have sagged below 3.0V on a recent hill climb, but recovered to 3.2 very quickly once the road leveled off.  

2) The top-right rectangular LCD is one Arduino Uno which is connected via the CAN Bus to the Kelly Controller.  It monitors: 

• Top Row: RPM, Battery Pack Voltage, Controller Temperature
• Bottom Row: Drive/Reverse, Calculated Speed (Assuming 2nd Gear for now), Motor Amps, Motor Temperature

3)  The lower LCD is another Arduino which is measures battery current through a 600A/75mV shunt.  It is power separately from the drive battery pack via a 12V adapter.  This keeps the battery system isolated from the rest of the car's 12V electrical system.  This Arduino is always on and maintains a running count of the amp-hours consumed.   The shunt is installed at the battery negative terminal to eliminate noise from the motor and to allow for monitoring charge going into the battery from either the charger or from the motor's regeneration braking.

In a quick experiment, after a 5 mile drive, I then connected the charger.  The Amp-Hour counter returned to within 3% of full.  Please note, I have not calibrated the system yet, so this is very promising.  The system is using an Analog Devices AD8210 Shunt monitor to measure the voltage drop across the shunt.  It is wired with a split-supply configuration, so 0 Amps = 2.5V going into the A/D on the Arduino.  This setup should yield about 1A precision on counting amp-hours.  Given the 20% DoD (depth of discharge) limit, this should provide plenty of margin.

Controller settings

Now that there is decent current monitoring, we tweaked the Kelly KHB72701 controller settings a bit to see if there is a bit more power available.  During the drives yesterday, The battery current never exceeded 200A and the motor current peaked at about 300A.  The spec on the motor is a max of 420A for 1 minute and the batteries should be capable of 400A-600A for short bursts since they are 60AH packs and there are several reports of people safely pulling 8C-10C.  Batteries are rated in terms of multiples of the AH measurement, so a 8C battery can deliver 8x60AH for a short burst. 

With motor blower providing plenty of cooling, he motor's temp peaked about 55C.

New Settings:  

• Throttle Range 5%-80% (this is a mapping to the mechanical throttle position).
• Max Motor Current 90% (this is of the controller max of 700A --> 455A)
• Max Battery Current 100% (700A)
• Undervoltage (Controller will start to cut back power draw at 110% of this value): 68V (cut-back at 74.8V, or 2.87V)
• Overvoltage (Controller will limit regeneration if voltage exceeds this): 90V
• Throttle Ramp: 4 (How fast it will ramp up acceleration)
• Regeneration: Off 

Off for another test drive to the grocery store....

Starting to see some encouraging signs

First Extended Drive

Today, we headed out on a extended drive.  Not knowing the real efficiency of the car (miles/charge), it is going to take some testing to become comfortable with the nominal range.  The Amp-Hour meter that is currently connected does not retain its values after a power cycle, so it is not a great fuel gauge.  More on that later.....

It was a sunny day here, about 65 degrees, so a perfect day for test drives.  Earlier in the week, I did a 4 mile run around the flat part of the neighborhood and the batteries only required about 30 minutes to recharge fully.  Today, we drove for 8 miles with some hills.  The batteries still read about 85V but since the drop off near the end of the charge is fast, I am hesitant to let them get too low.  Well after a 7.5 mile drive, they took about an hour with the 16A charger to return to 91V (the current target charge level).  This was the previous charge level so it should represent a reasonable replacement energy measurement.

Based on these estimates, the car averaged about 180 Watt-Hours/mile.  Right in the expected range of 150-200.  With a conservative 80% usable capacity, this should equate to 22 miles of range per charge.  A GPS was used to track distance, but a more accurate charge timer is needed to estimate the actual Amp-Hours that are being put into the batteries, or taken out with the a better amp-hour meter.

Here is the boot with the batteries in position.  Not a lot of extra room  The brown and blue wires are the battery monitors which make sure that none of the cells deviate too much.  The next step will be to route these up to the dashboard so the driver can monitor the battery condition.  The large blue connector is the charger connection.  The charger will be mounted to the left of the pack.  The large (red) 12 battery is powering all of the electronics in the car (lights, radio, controller, fans)

Cooling

The motor coil temps, as reported over the CAN bus from the Kelly controller is running between 80C-90C after a couple of miles.  This is well below the limit of 145C but still on the high side.  The internal fan on the motor has two issues:

1. It does move a lot of air - @2,000 RPM, I could barely feel any air leaving the motor.
2. It does not cool when the motor is not spinning. 

A supplemental fan is needed and I found a 12V marine exhaust fan that moves a lot of air.  The challenge is how to duct the fan into the motor in the tiny Mini engine compartment.  I tried a Rube-Goldberg solution today using 4" flexible ducts but there is just not enough room at the end of the motor (where the internal fan draws air) to route the ducts.

The Plan:  Bring in 1" hoses (probably two) into the fan housing on the motor, from the top to push more air through the motor.    The challenge: How to plumb the 4" fan down to a couple of 1" hoses through a manifold.  The air is moved from one end of the motor to the other, horizontally.  There are large vents in the housing on the shaft end, so if enough air can be pushed into the fan end, it should push on through, providing much better cooling.

First test of the Full Battery Pack

We headed out around the block with the new 84V 60AH battery pack.  Starting out in 2nd gear to keep things gentle, Jane climbed our hill with little hesitation.  Next we headed for the short flat stretch of street around the corner and in third gear, she got right up to speed.  Here is a video of us returning home.   You will see the pack mounted in the boot along with the battery monitor leads.

Even under the full hill climb, the pack only sagged to 80V, still close to 3.1V per cell.

Next - Clean up.  Lots of cables and mountings to sort through.   However, it is a great motivator to be able to see it all coming together.  Also, a quick run down the to the non-hilly part of the neighborhood for a real speed test.