Introduction: LiFePO4 Battery for Gasoline Engine Starting.
How to install a shorai lfx18a1-bs12 LiFePO4 starter battery in a car.
Lifepo4 offers 2000 cycles of 100% depth of discharge versus approximately 400 cycles of 80% depth of discharge for lead acid. Do the math and understand the increased lifespan for Lifepo4!
The Lifepo4 cranks my engine much faster than an lead acid ever did. It's been nearly 20 months it has been in service and it continues to impress me.
Also, the lightweight and faster recharge time of the Lifepo4 allows for some noticeable fuel savings.
I posted a YouTube video on this same installation.
Step 1: Run Extension Wiring
I used 4 core, 10mmsq cable to extend the positive and negative terminals from the engine bay into the glove box. Two cores per battery terminal. Heat destroys Lifepo4 batteries so this is critical to ensure a long lasting reliable solution.
Step 2: Connect Lugs Within the Engine Bay.
Use compression lugs on the ends of the cable within the engine bay. The right most pic is the negative connection to the chassis of the car. I soldered mines to guarantee a solid connection. Two wires per lug. Tighten properly to ensure a low resistance path for the starting current.
Step 3: Route the Cable Into the Glove Box.
Using an existing or spare cable transit through the firewall, get the cable into the glove box. Mines was routed up against the back of the glove box.
Step 4: Connect the Battery and Completion!
Using compression lugs on the cable ends, connect to the battery's terminals paying attention to polarity! I made sure to solder the wires in the lugs for guaranteed low resistance. For ease of changeout, I used XT60 connectors (I love a plug and play battery!).
The shorai battery is small enough to fit in most glove boxes. Now you can have a Lifepo4 battery for your car. Benefits include improved fuel economy, affords longer service life to the alternator, no danger of explosion, no toxicity to the environment and up to 3x lifetime compared to lead acid.
Please note that due to the low amp hour rating of the battery, do not have any electrical loads on for long when the engine is off! The shorai battery I have is actually a 6Ah battery so you can imagine how long that battery will last if you left your lights on by mistake. I installed a relay to cut power to the ALL lighting circuits once the engine is off. The shorai battery will not survive being discharged below 13.0volts (as per the manufacturer's instructions).
If you want an additional peace of mind that the battery wont be accidentally drain too fast, you can go full leds lighting inside and outside of the car, including LED headlight bulbs. Take a look at my instructable on cooling my LED H4 headlights.
Update: May 2016
The battery still cranks the engine as it always has. Very admirable performance!
Update: July 2016
Both batteries actually went dead (as in less than 4volts each) while plugged into the car. I did my checks and the parasitic drain was the same as for the past decade. I recharged and balanced both and to my utter surprise, they are working like nothing happened! The LiFePO4 chemistry is totally amazing in my experience. Awesome!