The CALB battery pack went together very smoothly and easily, in a bottom balanced fashion in series with the remaining A123 pack. The final pack is 92S with the smallest cell being 61.08Ah giving me total pack size of about 18.26kWh (using 3.25v as the average voltage during discharge). This gives me a 97-117km range at 100% discharge, which is not something I would do every day but represents the drop dead range of the car. The safe range is 78-94km at 80% discharge which gives me a very usable car. My commute to work is only about 16km each way giving me plenty of range for errands, going for lunch or being able to absorb a cycle or two of not being able to charge either at home or at work. I have one CALB cell which has internal discharge, when it arrived I flagged it as having a lower open circuit voltage (OCV) than the rest of the cells, after cycling and bottom balancing the pack I revisited the OCV before I set up the charger. This same cell is the only cell in the pack that now has a lower OCV than what I bottom balanced to. I’ll have to contact Don and Keegan and see if there is anything they can do, I believe the cell will need to be replaced. It’s other specs are quite good, it has low IR and high capacity, I would say it easily falls in the top half of the cells for performance. The decreasing SOC with no load just doesn’t work though, I will be able to use the cell for awhile as long as I don’t discharge 100% and I keep an eye on it’s state of charge relative to the rest of the pack. This won’t work long term and takes me back to the issues I had with the A123 cells (constant monitoring required).
With the decrease in available battery current with the replacement of A123’s with CALB’s I needed a new smaller fuse, I went with a 500V 400A Ferraz Shawmut semiconductor fuse that is mounted with the service disconnect in the rear of the car splitting the two halves of the CALB pack. The service disconnect is the same one that Jack R. has started to use in his vehicles it’s made by Blue Sea Systems it has very solid 1/2″ terminals and is rated for 600A continuous, 900A for 5 minutes and 2700A for 10 seconds which is well above what the battery or motor can do. The down side is it’s rated for 48v, so it’s not a switch that could be reliably used as a safety disconnect, one instance of breaking 300V @ high current would likely destroy the switch. This switch will be used to break the circuit only when there is no current flowing, IE for storage or servicing. You can buy it from EVTV or find it at some marine supply stores.
The EMW Dashboard is a bit finicky and although it is very attractive and provides a great deal of information (when it works) just isn’t at a state of hook it up and go. I’m not going to give up on the system, however I am going to supplement it with what is already known to work. The JLD404 from Lightobject.com or EVTV isn’t the most attractive meter out there, but it runs off a shunt, displays voltage/current/Ah and has been shown to be very repeatable and reasonably accurate. I will be mounting this meter in the glove box to make it accessible but hidden.
Since I will be using the JLD404 as a backup system I’d rather not have to think about it, which includes resetting the meter to Zero the display after charging. It’s likely the meter will be very close to zero due to the efficiency of charging LiFePO4 cells however I don’t want to have to open the glove box, hold the down arrow just to reset the meter after a full charge. The first step in automating the reset is to bring out the terminals to the down arrow switch. On my version of the JLD there are some unused terminals on the back, 11, 12, 13 and 14 aren’t connected to anything.
The first step is opening the meter, which is simply two tabs at the front and the rear cover slides off. Next remove the front face by sliding it off the latches on the PCB’s. De-solder the daughter board with the small transformer on it to gain access to the 2nd terminal on the down arrow switch from the inside. (If you are uncomfortable de-soldering and re-soldering the daughter board, you could solder the wire to the front of the board directly to the switch, this may make it difficult to re-install the front or rear cover) Once the meter is stripped down to this state simply solder in two wires as shown below:
Then re-attach the front panel, this photo shows the relationship between the new wire and the location of the down arrow switch.
Attach the rear cover and put some kind of marking on terminals 11 and 12 to represent the newly wired switch.
This simply allows you to put a momentary switch or relay in parallel with the existing switch to activate the Ah reset function on the meter. I will be looking at interfacing this with the “charge complete” signal from the EMW 10kW charger so when the pack is charged it automatically resets the meter. I’m sure there are other chargers that have some sort of charge complete indication and this could be used to reset the meter. If the pack is only partially charged the meter will continue it’s count uninterrupted. Doing this for many cycles will accumulate an error over time that will not give you a true representation of SOC. Allowing the charger to fully charge the car and reset the meter will counter this.
Terminals 13 and 14 also remain unused so if I don’t need to break out any other signals to make the auto reset work I may use them for the other switches, which would make it much easier to cycle through the Volts, Amps, Ah, Time display. All of the switches share one common terminal so it would only require 4 terminals to break out 3 switches. Using the Set, Right arrow, and down arrow would provide full functionality for the meter since all menus continue in a loop making the up arrow optional.