Battery Protection

High Voltage Charging Cut-off

After some good basic Electrical Engineering 101, Jane now has a charging cut-off circuit that monitors each cell individually. This involved designing and wiring a circuit (schematic will be posted soon), that takes the alarm output from the CellLog monitor and uses to turn off a high-current contactor between the charger and the batteries.  As part of this enhancement, a couple of relays have been added to only turn on the CellLog monitor board when either 220V (charger) is connected or when the key is turned on.  This should solve the slow drift that the CellLogs were causing on some of the cells, since they don't draw evenly across the sub-banks.  Also, put on push-button switch to provide a quick check option for the batteries.  Pushing the button, powers up the CellLogs.

The relay controlling the charging contactor require two special considerations:

• Latching - Wired it so that it would latch ON once the alarm triggered.  This way, even if the alarm condition clears, there is no way to resume charging without disconnecting the 220V supply.
• Delayed-On - Added a cap (4700 µF) across the coil and a resistor (50 ohm) in series with the coil to require the alarm to sound for about 2 seconds before the relay will activate.  This filters short alarms and any temporary issues that may occur at power-up.

The CellLog Monitor has a buzzer attached to alarm if a cell is out of range.  A quick connection to the original Alternator indicator on the dashboard now provides the driver a red warning light (replaced with LED bulb for extra brightness) if an alarm condition is in effect. The buzzer is audible inside the cabin but if the windows are down or music is up, it may be missed.

Also, added a heavy-duty marine-quality manual cut-off switch on the positive side of the battery pack.  This provides a quick, secure cut-off of the high-voltage pack, making it safer to work on the systems.

http://www.discountmarinesupplies.com/Blue_Seas_Battery_Switches_E_Series.html

The CellLogs are set to the following:

Voltage Range: 2.5V - 3.6V

Delta P (maximum cell variation): 100mV

Alarm Type: Normally Closed  (this provides a safety if a unit become disconnected or is not functioning, since the alarm will open up, triggering a alarm condition)

Pack Voltage:  

• 6 Cell sub-pack = 17.5V - 21.0V
• 7 Cell sub-pack = 20V - 25.2V

2 CellLogs have 6 cells connected to them, 2 have 7 cells to cover 26 total cells.

Completed one charge cycle and the system performed well.  One cell was slightly higher than the rest and hit 3.6V, shutting off the charge current.  Next is to test it while driving.  All of the cells are within 25mV of each other. 

Heat

A little warmth is a good thing...

Well since winter has arrived in full force (18" of snow this week), having a heater in Jane became a priority.  Originally the gas engine provided hot water to the heater coil but that is not possible now, so this project required a bit more invention.  The final implementation ended up being:

1. A ceramic heating coil from a 110V space heater: Warmwave 1500-Watt Ceramic Electric Portable Heater
2. A high current contactor to control the heater: Cole Hersee (24059-BP) 12V Insulated SPST Continuous Duty Solenoid  - First attempted to use a 30A 12V automotive relay but it melted with the high voltage.  The heating coil should only be pulling ~10A.
3. High-temperature cut-off Protection: Amico 5 x KSD301 250V 10A 70 Celsius Temperature Control Switch Thermostat N.C
4. Lighted toggle switch for the dashboard.  This was placed where the old heater mechanical control was located.  The old controlled connected to a valve which regulated the water flowing to the heater coil.  The lighted version will help the driver remember to turn this off when not in use since it will use the same power source as the drive motor, impacting overall range.

Connecting it all together....

Electrical

The blower's original switch controls the ground to the blower, so that was connected to one side of the contactor.  The new lighted toggle switch was wired to the 12V side of blower motor which is switch by the ignition switch.  This way the ignition must be on and the blower switch on before the contactor will activate.  The contractor was wired through a 20A fuse to the 84V battery main battery (after the main contactor, which is also activated by the ignition switch).

Heater Contactor mounted on the firewall

The High temp cut-off device was wired in series to the heating coil and mounted inside the blower housing near the coil.
The coil is rated at 1500W at 120VAC, so at 84VDC, I am not sure just how much heat will be available.

Mechanical

The ceramic coil was much smaller than the original Mini water coil so a adapter plate was cut from sheet metal and fit within the blower housing with the power wires being fed through on of the water inlet holes in the housing.

Cooling the motor -  A bit of irony

Cooling the Motenergy ME0913 has continued to be a problem.  Since the motor is running in reverse, the built-in centrifugal fan does not move any air. The hall sensor magnets are connected to the fan, so it cannot be removed or modified easily.  After attempting to utilize two 1" hoses to pull air through the motor using a 200CFM blower, the motor continued to overheat (100C) under only a slightly elevated load (driving the hills around home).  

Next idea...  

1. Cut a 4"x1" rectangular hole in the motor fan cover (black area on the right in the photo below).
2. Deform a 3" to 4" round duct adapter (shiny sheet metal with the bar-code in the picture) to act as a funnel from the 3" flexible hose from the blower to the round cover with the rectangular hole.  The adapter was screwed to the cover and sealed fairly well.  It would have been better to mount this on the end of the motor, but there is no room since the motor is right up against the inner-fender.  To avoid the cover screw shown in the photo there was very little room for the funnel.
3. Currently, the blower is set to pull air through the motor since that is direction that the built-in fan would move the air if it was functional.

ME0913 Traction Motor with cooling adapter.  The new right front coil spring is visible through the hole
in the sub-frame.

Next ideas - Can the motor heat be directed into the cabin to supplement the electric heat?