LiFePO4 Battery for Gasoline Engine Starting.


Introduction: LiFePO4 Battery for Gasoline Engine Starting.

About: Update 12 September 2017: A very special thanks to Sam Elder, a manager here at Instructables, who tracked down the cause of my lost publications and fixed the issue. Take a bow Sam!

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!



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    10 Discussions

    I have been restoring a 1965 MGB, and I think in place of the two six volt lead acid batteries, I may have to install one of these. The batteries on the car are mounted behind and below the seats, so heat should not be an issue. Since I am not driving the car everyday, I may have to add a battery maintainer just to keep things up to par. Thanks for the great idea.

    1 reply

    No problem. I recommend using a dc clamp ammeter to measure the starting current to ensure you purchase the right size Lifepo4. The bigger is always better however it's all about cost. Also never let any lights or radio on without the engine running. I installed 2 relays to prevent any of those loads to be on once my key is out of the ignition.

    If I wired 2 of these together it would double the cca right, cuz my car needs 720cca

    3 replies

    yes nothing wrong with that but you should measure the starting current using a peak function DC clamp ammeter. Vehicle starters actually dont use that much amps for mid nineties and newer engines. My car uses only 68Amps peak to successfully crank the engine. The CCA rating is the max amps at a given temperature for starting batteries.

    i highly doubt you need much amps to crank your engine but you do need to take a measurement first to be sure.

    Is this replacing or adding to your existing battery.

    Also, while heat is an issue for LIPO. How well does this unit handle cold?

    3 replies

    The Lifepo4 is the only battery in my car. How cold are you referring? If it's about 5 Celsius then it should work but may require trying a few times to allow the Lifepo4 to warm up.
    I have been thoroughly impressed with this battery so far. I live in a tropical island BTW.


    Temperature wise I was suggesting much colder.
    I'm here in mid Michigan and it got down to -3c last night.

    Hmm at sub zero temperatures.. It will be tricky. I've read reviews of folks in cold countries that would simply try starting a second or third time and boom. Engine runs. If you wish to try the battery in a gasoline car, wait for a warmer period to prove the battery works and see how it goes for winter.