The body is removed and now the battery packs can be disconnected. Every pack has two wires attached which connect all 4 packs in series.in total there are 100 cells (3,7V) which results in a voltage of 375V. .
DC voltage of battery packs
After the wires and the fiber cables where removed I lifted the packs with a forklift. the motor is mounted on to the original Lotus (Toyota) gearbox. The motor is on the right side under the black round cover.
Battery packs removed
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.
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.
The Lotus Elise ECE EV conversion is based on the AC-150 Gen 2 from AC Propulsion. Unfortunately the AC-150 Gen 2 is developed before any charging standard was published. Charging is managed by de PEU (Power Electronics Unit) and is limited to 20KW (240V/83A one phase). 83A on one phase is way more than a standard household wall outlet in Europe provides. Home charging on a standard 240V wall outlet is limited to 16A. Public charging using the Mennekes connector is also limited to 16A (one phase). In Holland most modern houses have a 3x25A powerline which can often be upgraded to 3x35A without replacing de powerlines to the power company . 35A is better than 16A but it isn’t real fast charging.
An alternative would be public DC fast charging, But which standard should be used in a DIY install. ChaDeMo is getting popular in Holland. Currently (begin 2016) there are over 100 ChadeMo fast charge stations. So ChaDeMO would be the wiser choise. Currently there are a few suppliers of ChaDeMo interface which work on any EV. EVWest developed the jld-505 and Lithium Balance sells the LiBal Fast Charge interface for €1000,- or more.
For both interfaces the challenge would be how to integrate them into my EV. I think it might be easier to develop a custom interface based on the ChaDeMO standard and the information available on internet.
I was able to find 8 out of the 11 converted Lotus Elise.
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 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.