Progress has been very slow lately, it’s been cold, I hurt my shoulder, (insert 20 other excuses here). Now the shoulder is basically better, and to add some outside motivation there is The Future of Transportation Symposium and Car Show coming up next weekend.
For anyone in the Edmonton area, I encourage you to attend! I will have the car there in running condition, but not “complete”. It should be a great show, and there should be a lot of great cars and great people.
In preparation for the show I have to get the car to a level of completeness that is both safe and informative to the show attendees. First step was sorting out the battery and charging system to ensure that I can charge the car. The 2nd was to mount and wire the dc/dc converter, it turns out I was able to reuse the mounting holes for an aftermarket CD changer that was installed in the side cubby, this serves to plug the existing holes and mount the converter all in one shot.
A short video of the beginning of the first charge is below. The pack started off at the bottom balanced 255v and quickly increased to around 280 as you can see below, it continued to increase quite quickly to around 300v from there it increased very slowly.
The first thing you’ll notice is the very high “runtime” count, this is what happens when you need to charge a 300V pack off of a 120v 15A ciruit, to maintain a safety margin on the circuit (the garage lighting is also on this circuit) I’d like to keep it below 13-14A, but I also never intend to run the pack this low ever again. This reinforces the need for a high current 240v circuit in the garage. A 240v 50A circuit would allow me to make use of the full 10kw and charge the car in less than 2 hours from completely empty (vs 15 hours for the charge I just completed). In the future I will likely build a new version of the EMW charger, they are in the 15kw range now and water cooled, this would allow me to mount it in the side panel opposite the dc/dc converter which would allow me to install 8-11 more cells.
During testing I measured my smallest cell at 61.08Ah so as the charge was coming to completion I watched that cell along with a few of the other “small” cells. Sure enough, at 61.2Ah my smallest cell was coming up on 3.65v and the charger terminated shortly after as the cell got close to 3.7v. I think this is the perfect charge level to fill the cells, however I may visit undercharging a bit more as that would extend the life of the cells with a small decrease in maximum range. The front pack of A123’s is significantly undercharged as the smallest cell groups are around 76Ah, but only charged to 61, they also won’t be discharged too deeply which uses them in the middle section and should make them last for a very very long time.
I have a lot of small things to do before next weekend, including installing the wiring harnesses that I showed in previous blog posts. Make new brackets to install the fan/radiator and pump for Soliton cooling. Since I will be towing the car up to the show, it just needs to make it on and off the car dolly and to and from the parking spot at the show.