My car battery was getting old and needed replacement. Thinking I would try something new I got hands on some Lithium Iron Phosphate cells previously used for Go Cart racing. These cells has a somewhat lower capacity than the lead-acid equivalent but features a much lower internal resistance (good for starting).
Me and a friend First I got the specs for battery terminals and then made some from aluminium.
We then build a wooden box that fitted 8 cells and had the same form factor as the original battery:
Bus bars were made from two layers of 1 mm. sheet aluminium. The cells are in a 3P4S configuration which happen to exactly match the voltage of lead-acid batteries.
Having used the battery for at couple of month I am very impressed with the performance. The only downside is that the terminal voltage does not drop much when the car is turned off. I have a circuit that detect this voltage drop and turn off all the extra electrical stuff I have in the car like phone charger amateur radio and GPS. This circuit will have to be adjusted for the new voltage drop.