Copyright Malcolm Faed. Images and text may only be copied with the permission of the author. This blog includes personal things of interest including electric vehicle conversion. I have documented the conversion of a petrol (gas) powered vehicle to Electric. http://www.austinev.org/evalbum/1149. The blog now documents the conversion of a BMW E30 to electric.
Monday, 23 June 2008
Controls and centre console
I have fitted a forward, neutral, reverse switch and the display/keypad for the motor controller. I am VERY pleased how these worked out.
Throttle Pot Installation
I fabricated what was needed from scrap aluminium. All in all I am happy with how it turned out. Placement in the engine bay is a little awkward due to the limited length and the stiffness of the cable.
The rubber dust boot should be pushed back over the cable shroud.
Thursday, 19 June 2008
ICE Removed & Weight loss
Electric motor and ICE side by side
The curb mass including Driver and a 1/4 tank of fuel was 1340kg
780kg on the front Axel and 560kg on the rear. (58%F 42%R)
There was a total of ICE components 285kg removed
This leaves a vehicle mass of 1340 - 75(me) -285 = 980kg before installing electric components.
Wednesday, 11 June 2008
Danfoss VLT 6042 for sale.
It is a Danfoss VLT6042 30kW 380-500v unit. It is in an IP54 case.
It has the DC bus option so it can be powered directly from a ~600v battery pack. According to Danfoss it can be lighted by (~20kg) removing the AC input filter components.
The Danfoss tech may also have a PCB to upgrade it to a VLT5032.(lower number, higher spec)
See here for images
Here is a link to the Specifications and Manual. (look for the VLT 6000 HVAC)
It is suitable for a conversion where you will retain the gearbox in a larger vehicle or a small vehicle with direct drive.
Please drop me a line if interested. (m.faed at ieee.org)
12 Volt Power Requirements
|Accessory||Current Draw||Include in Max total|
|Dome Light||0||Needs Bulb|
|Total Draw Amps ||46.2|
12 volt charger mods.
As a consequence 2 modifications were required.
1. The feedback circuit needed changing to increase the adjustable output to 13.8V. This was done by tracing the voltage divider circuit and adding the required resistor in parallel with an existing resistor.
2. The 20 ohm bleed resistor needed removing in order for it not to discharge the battery while the vehicle is not being driven.
The image below shows the modifications. (zoom in for detail)
The completed power supplies have been installed into the Variable Speed Drive where some of the AC filter components have been removed. The device between the power supplies is a 50A circuit breaker that will be used for the 12V protection. The Power supplies will be wired in parallel.
Battery Balancing the cheap way
There are 2 x 6.8V diodes and a 5 ohm resistor across each battery.
(Thanks again for the info from Tuarn)
The Lead Acid batteries at rest are about 13.3V at new and fully charged so no power is lost when the batteries are not in use.
The Zener voltage must be greater than the battery full charge voltage
The idea is that the more voltage there is across a battery, the more current is bypassed that chargers lower batteries.
This worked surprisingly effectively.
The batteries before installing the balancer were from 12.5 to 14 volts at 'full' charge.
After balancing they were all within a few millivolts of each other, even after some discharge.
I was concerned that the bypass current may effect the automatic charger cutoff point as the batteries became fully charged however the charger still functions properly.
Given Zener voltage = 13.6
Maximum charger voltage = 15.2
Bypass resistor = 5 Ohms
The maximum current through the resistor is (15.2-13.6)/5 =.32A
The maximum resistor power dissipation is .32 * (15.2-13.6)=.5W
My ceramic 5W resistors are overkill. I will use 1W resistors in the vehicle system.
Maximum zener power dissipation will be 6.8V * .32A = 2.2W
The long awaited 20Ah Greensaver Test Results
Microprocessor controlled battery discharger and charger.
4 x 1 Ohm 200 watt resistors. Hard wire configurable.
Relay to switch between 2 discharge currents
Microprocessor calculates V, I, Temp, Ah, Wh and Peukert Factor.
After discharge, the battery is automatically charged.
The discharge cutoff voltage is programmable.
The negative figures in the LCD indicate that the battery is being charged.
I know, it looks like a weapon of mass destruction :)
To determine the Peukert effect of the 20Ah and 27Ah Greensaver battery.
The reason for perform the test is because the specifications state a low Peukert factor fro these batteries and I wanted to verify this before purchasing a pack of 50 batteries.
Discharge curves. (note glitch in V5 between seconds 3 and 12. As this is only a 9 second occurrence, it does not affect the overall result.
The average Peukert factor of 1.105 is low compared to other batteries that are usually greater than 1.13 for batteries of similar capacity. The calculated Peukert factor from the 20Ah specification sheet is 1.07. My tester is probably not that accurate but is sufficient to confirm that the battery performs close to specification.
Given this result, if Lead acid batteries are used, they should have superior performance under load and give a long service life.
Original discharge data is available in an Excel sheet upon request.
I also have a 27Ah battery that will be tested next.
The high current wiring will be upgraded to allow testing at 40A
The discharger will also be reprogrammed to continuously charge and discharge a battery to determine de rating over time.
The charge curve for the 20Ah battery is below.