The long holiday weekend was perfect for finishing up the battery installation. When I last posted the batteries had been bundled and physically installed in the battery box. The next step was wiring everything up.
There are 48 individual batteries making up the pack. Each battery needs to be connected to the next battery. Batteries are connected in either blocks of 4 or 8. The blocks are then connected to make the whole pack.
Because the lithium batteries require a little more monitoring than lead acid batteries I decided to install a battery management system(BMS) with the batteries. The BMS serves several important functions. The most important function is to prevent the batteries from being overcharged and over stressed.
In order to accomplish this the batteries are monitored by a multiple circuit boards. These are pictures of the mounting boards prior to installation. The top board is for 4 cells and the bottom one for 8 cells.
These copper bars connect the cells together and are attached to the bottom of the mounting boards.
The mounting decks and copper bars installed on the cells.
A closer view showing the circuit boards on top of the mounting deck. The circuit boards are connected to each other in order to communicate with the charger.
Here the packs of 4 and 8 cells have been connected to each other to form one big pack.
A fuse in the middle of the pack. In case of a short the fuse should protect the cells in the pack.
Close up of the fuse.
With the pack wired up the car is now drivable again!
Next step is charging up. Also need to do some slight modification of the software settings since the pack voltage has changed. Final part will be to get a top for the battery box.
2 comments:
Great blog! Glad I found this (not that I will be doing a conversion but I am obsessed with it at the moment as a mental exercise.)
I was wondering about the new battery allocation. (Maybe you have already addressed my question but I haven't gotten there yet.) You said you removed the batteries from the front and now all are in the rear. Does this affect handling as all the weight is in the rear now? If you have put some of the batteries back in the front wouldn't you have been able to regain 25%-30% of the space in the rear...enough to put the back seat back in?
Keep up the great work on the car and the blog!
Dexter,
Glad you found the material interesting and hopefully helpful.
I haven't noticed any change in the handling, other than quicker acceleration due to less weight. The weight lost in the front from battery removal (~400lbs) is roughly equal to the weight lost in the back.
As for the space issue, yes I could have moved some of the new cells into the front and regained the space for the back seat. Couple reasons I didn't.
I usually am the only person in the car and rarely carry a passenger, other than the dog. So given that I don't have a need for the extra passenger capacity not having the rear seat lightens the vehicle by about 100 lbs.
Having all of the batteries in one space was a lot easier to wire and build an enclosure. If I put any cells in the front I would have to build a second enclosure. It would have to be completely watertight so as not to damage the BMS boards.
Good luck on your mental exercise. Hopefully it will turn into a real endeavor.
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