To replace te bad isolation the body shell and two battery packs need to be removed from the car.

Body shell removal

Recently the car wouldn’t start charging and Error Code 5 started showing up. It started intermittently and could be solved by unplugging and plugging the charge cable. Last week it wouldn’t charge at all. The cause of the problem is known, a kind of Pertinax (phenol formaldehyde) is used as isolator between the rotor and the flywheel, when Pertinax ages or gets damaged it gets hygroscopic. To replace te bad isolation the body shell and two battery packs need to be removed from the car.

chgresult_MOTOR_ISOLATION

AC-Propulsion offers a LOM (Lithium Optical Monitor) diagnostic interface. This interface enables you to diagnose one or more LOM modules. I used this interface, which I borrowed, when I replaced a bad cell from the battery pack (see my other post).

Original AC-Propulsion LOM interface

The original interface is based on a CP2102 USB to serial chip, one Single Bilateral Analog Switch and a few transistors and resistors. The blue and black plastic connectors are from Industrial Fiber Optics (IF-E96E and IF-D91). I draw the schematic based on the original Interface and replaced the SMD components with normal sized components. I couldn’t find the DIL version of the SMD bidirectional binary switch (SN74LVC1G66DBVR) so I used the 4066 a Quad Bilateral Analog Switch. To prevent problems with the CP2102 chip I ordered a standard Micro USB to UART TTL Module 6Pin Serial Converter.

LOM interface v1.0

I wanted the Yakazi X1DT0027 CHL-02 ChaDeMo charge inlet but a stagering 650,- USD was a bit to much. I don’t know if I can get the thing running, so I tried to find a cheaper source. I got a charge inlet from a totalled Mitsubishi Outlander PHEV for only 250 Euro.

Mitsubishi Outlander PHEV inlet

The high voltage wires used in the Mitsubishi Quick charge inlet are relatively thin. This is because the charge current of the PHEV is limited to 50A. But for my project it is just fine. If I get the ChaDeMO interface working I can always upgrade the wires to support the max current of 125A.

I was able to find 8 out of the 11 converted Lotus Elise.

http://evblog.wanjon.nl/?page_id=2

The ECE Lotus has 4 battery packs with in total 100 cells. Based on the fiber optical cable which runs from the VMS thru all 4 packs I guessed that cell #65 would be in pack #3. Pack #1 has 24 cells and is behind the driver seat. Pack #2 is above the gearbox and Pack #3 is next to it, both have 24 cells. Pack #4 is behind the passengers seat an has 28 cells

Lifting battery pack #3

Pack #3 removed, Pack #2 above the gearbox and Pack#4 slightly vissible

After Pack #3 was removed it was placed up-side down and opened up.

Battery pack (Up side down) showing wires to LOM modules

The top cell of the lower 8 cells was defect.

Removing the bad cell from the pack

The replacements cell was at it’s nominal voltage of 3.7V it need precharging to match the other cells at 4.10V. The picture shows two cells in serie.

Precharging the replacement cel

After charging the pack was assembled and bench tested. Each set of two cells is monitored by LOMs (Lithium Optical Monitoring system by AC Propulsion). Each LOM is connected to the next cell with a fiber cable.

Bench test of new assembled pack of 8 cells.

Lom module

LOM module

LOM Utility test software screendump.

New cel 65 in pack

After some testing the 8 cells where placed back in Pack #3 and the car was put together. I’m getting better at it 🙂

The VMS showing nice voltage levels (first line). The second line shows the temp of the cells. Pack #3 is a few degrees warmer since 8 of the cells where in doors for a day or two.

Yesterday I visited the ECE Factory and talked to the engineer who converted my Lotus into an EV back in 2008. Learned a lot about the car. During my visit they where working on the Enexis Demo car.

Enexis Lotus at ECE

One of the 100 cells, cell #65 is dying. This is noticeable under hard acceleration and the top speed has dropped to 141 Km/h.

VMS display showing cell #65 dropping in voltage

It will be quite an operation to get to the defect cell. First te body needs to be removed and than I need to open the black box.

Battery pack, rear clam removed.

After working on the Lotus Elise the airbag light stayed on. A thread on lotustalk.com told me that the airbags in the Elise are the same as the ones used in the Opel Speedster/Vauxhall VX220 and that the diagnose interface also works on the Elise. So I purchased a Opcom interface (OP-Com V1.45) on dealextreme for €20,- . It did the job. Cleared the fault codes and noticed that it is possible to disable the airbags and seatbelt tensioners. This might be handy if you want to carry a child in passenger seat or visit the track.

Op-Com interface

Lotus airbag opcom

Airbag measurement blocks

In one of my previous posts I installed a Webasto HTM T100 remote to control the MES-DEA RM4 heater. The remote works perfect, it shows the actual temparture in the car and has a great range.

Unfortunately the MES-DEA heater isn’t connected to the PEU and in the situation that the PEU isn’t charging the battery, the heater drains the battery which affects the range. To prevent the heater to “drain” the battery the PEU charge mode needs to be enabled.

By feeding 12v into pin 8 of connector J1 (see Interface Document for the AC-150 Gen 2 Electric Propulsion System) the APS (auxiliary power supply) turns on and when connected to the grid it will start charging.

Wiring schematic Webasto HTM T100