Can a 12V LiFePO4 Battery Replace the Lead Acid Battery in a Car?

Can a 12V LiFePO4 battery replace the lead acid battery in most cars and trucks? I've been asked this question many times on the LiFePO4 review videos that I've published. Here are my thoughts...

*WARNING:* Lithium batteries are dangerous and can result in fire! This video is NOT intended to be instructional or a "how-to" lesson. I am not a professional. Do not attempt anything you see here without first contacting a certified and/or licensed professional.

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[rlordonio]

I directly replaced my car battery with a 46AH Lifepo4 battery in June 2018 out of curiosity. It only lasted for 3 years (until July 2021) when I expected it to last for 10 years! It was still able to start my car until the end but what I noticed was the engine stalls while we were on neutral in the middle of traffic. When I replaced my battery with SLA, my car went back to normal.

[StanleyPhua]

Just want to share my experience. To cut story short. Recently caught a hit and run case while parking, therefore decided to build a 125A lifepo4 battery with a BMS can handle 200A discharge to replace my Lead starter battery, so I can run my 3 car cams 24/7 for week without worries.  

I am using for two months now, so far very satisfied with the battery performance. Tips and my finding. 

1. I add a super capacitor (360F x 6 nos, 16.2V60F) in parallel to the battery with 60A fuse. Reason is to help to jump start the engine (although I know my 200A lifepo4 battery is strong enough to handle the 2.0 Camry starter that will draw around 180A+-), second to buffer the voltage from alternator, also sudden cut-off from BMS ( Do it based on instinct). 

2. I also add a TVS diode at the alternator to protect the alternator from the back emf if the battery turn-off by the BMS while running. (Based on research, and hope my research is correct)

3. I set the single cell over voltage at 3.65v and low voltage protection at 3v to prevent frequent on-off of BMS. Nevertheless I set my pack over voltage at 13.9v and turn-on charging voltage at 13v. Reason been the alternator voltage is always fluctuating, so when BMS sense 13.9 volt, the BMS turn-off the charging, the lifepo4 battery will has a voltage reading around 13.3v or 13.4v volt which is around 80% to 90% SOC. When the battery fall below 13v (around 40% SOC) the BMS will turn-on and start charging again. The main reason I doing so is because I want the battery to always fall between 90% or 80% to 40% SOC so I can enjoy max charging cycles of 4000 or more.  

4. I stay in Singapore, base on my observation, my Lifepo4 +ve terminal, Battery and BMS temperature is around 50+- degree celsius, the battery will get hotter to around 56 or 57 degree celsius when parking. Therefore I have a build in Thermostat switch (activate at 55 degree celsius) to activate a 12v mini fan to cold the battery down. So far I only experience it turn-on one time while I am parking.

[geraldkoth]

Very good explanation of the differences in LiFePO4 and Lead Acid. I build my own LiFePO4 batteries and do not use a BMS. I use them to power all sorts of things, even to start the outboard motor on my boat. I have specific chargers for LiFePO4, I use QNBBM balancers to keep cells in balance during charging and discharge. I monitor voltage of the batteries during use and storage. I have been following battery technology for five decades. Do not just go putting this that or the other thing batteries into use unless you understand all the factors necessary. Any battery with sufficient energy to start a large engine can also quickly start a large fire.

[wy]

Thank you for taking the time to explain this so clearly. I have always wondered why I cannot use a LiFePo4 battery for my car or boat as a starter battery. The manufacturers always recommend to use it only for a trolling motor of a boat.
Thanks again, I was still planning to try using a LiFePo4 battery as my starter battery. Now I understand what can happen, so I definately won't do it.

[fernandoesteban]

I just built a Lifepo4 12.8v battery pack and use it without a BMS and put an active capacitive balancer to keep the cells balanced. It's installed on my 2005 Ford Ranger with the WL diesel engine. It works just fine and has done so for a couple months. I'm in South East Asia.

[BenMitro]

Excellent overview of using a LiFePO4 as a starting battery - fets, under bonnet heat, low temperature performance and charging - kudos to your thorough and accurate knowledge and simple, well delivered explanations. Your honesty in outlining the limits of your knowledge is commendable too. There is a reason why I rush to see your videos, this probably has a lot to do with it.

[javierferrer]

You should test antigravity car batteries lifepo4 chemistry. BMW and other car manufacturers have been using lifepo4 with success for years. Many autocross racers and track cars use antigravity batteries since there more reliable and weight is less than lead. Hope you buy one to tear it down to see how they make them for car use.

[lasersbee]

I've been using a LifeP04 8AH battery to start my 54" Zero turn 27HP Lawnmower. I also use a LifePO4 8AH battery to start my 15HP Hydraulic Power Pack. So far I've had no problems. This summer I'll be testing the same 8AH LifePO4 Battery on my Harley. Of course all my uses are only during the warm seasons

[lloydthegreat]

You're 100% correct about not disconnecting a battery while the engine running. The battery just in its inherent design absorbs those spikes that you know we see on the electrical system.

[GordLamb]

Holy market opportunity. It's utterly *trivial* to design a lifepo4 battery for automotive use. For below-zero (and >14.6V) charging, shunt excess current into a warming circuit. Use a contactor instead of mosfets for disconnect. Monitor the terminal voltage for reengagement.

Outstanding and accurate video as always. :) I'm just amazed how *bad* lifepo4 battery manufacturers are at producing reliable products, generally speaking.

[Josh-pyin]

I would really like to see you open and look at the Antigravity lithium car battery. They're very expensive and seem to get a lot of positive feedback. They have some pretty great claims too.

[uhjyuff]

I have not tried this, but if you connect a lifepo4 battery in parallel, there is small risk of losing 12v supply and your lead acid battery will last forever because it will basically be in float stage and never discharge even when the starter is used. It would be cool because you could turn the car off and still have a large battery system without the added weight of heavy AGM deep cycle batteries in the trunk!

[DLMR]

Thanks for answering the million dollar question. My 22 Tesla Model Y has 12v lithium battery and I been asking myself this question for a while

[unionseen]

I've used very small LIFEPo4 batteries as the sole automotive battery. Above freezing it's simple. I've put a lot of thought into doing it below freezing, but it adds a lot of complexity. Smart management, insulated battery box with electric heater...and possibly running warm coolant into that box as well....

[JeremyAkersInAustin]

While it's correct that most LFP batteries on the market today aren't suitable for starting engines, there are plenty of LFP battery options that are perfectly capable of doing so which still have under temp charging protection and good CCA outputs.

I have several vehicles with LFP starting batteries:

1.) A Farmall Super H tractor using an EarthX battery (Which are actually designed and approved to crank aircraft engines where they see very cold temperatures). This battery has been in service since 2018 with no issues and has started the tractor in zero degree weather.
2.) I have a diesel motorhome with a 6.6L diesel engine. I replaced the two lead acid batteries with two Banshee Lithium Starting batteries. These have been in service since 2019 with no issues, and have started the engine in zero degree weather many times.
3.) I have a diesel Jeep Liberty where I replaced the lead acid starting battery with a Banshee Lithium battery. In service since early 2020.
4.) My parents have a diesel motorhome where they replaced the two lead acid starting batteries with two Dakota Lithium engine starting batteries (Just installed this year so no real use on them yet)
5.) The 8kW diesel generator in my motorhome is cranked by two BattleBorn batteries, in service since 2017 and has started the generator in below zero degree weather many times over the years without any issue.
6.) I also have several smaller engine equipment like garden tillers, portable generators. All have been switched to LFP starting batteries because they last longer.

None of the above applications required making any modifications whatsoever aside from swapping the batteries. The notion that LFP can't crank an engine is ludicrous. Any decent LFP battery, especially one designed for engine cranking, will have a BMS that protects against charging in cold weather and no that won't cause a "voltage spike" if the BMS shuts off charging. I don't understand where notion came from. Don't just repeat things you've "heard". If you think there's a voltage spike, prove it. Show us where the spike occurs. These FETs usually have large resistors across them so when they shut off they can still dissipate any "spikes" that might occur from the alternator. And you can absolutely disconnect the battery from a running car and nothing of any significance happens. I have done it many times when testing batteries and alternators.

As long as the battery has a properly designed BMS then an LFP battery will crank a car motor just fine. My diesel powered vehicles need a lot more cranking amps than the average gas car, so if these batteries can crank a diesel motorhome in zero degree weather then I think they'll start your Corolla just fine. I have been using LFP batteries to start engines for several years now and I have not had any issues.

[christiano.]

Good video! For everyone asking this question, it's important to understand that there are different types of LiFePo batteries. There are different types of cells and different BMS'. In general, LFP batteries can be used in your car. I think it was Porsche who even started fitting LFP batteries to some of their production cars many years ago. But most of the batteries reviewed here cannot be used for all the mentioned reasons. You need the right cells, there are LFP cells with a charging temperature of down to -20°C and end of charge voltages of 4V, and the right BMS or just no BMS at all. A BMS is usually there to protect the battery from situations which are considered normal workload in a car, so most BMS' will just interfere with the normal operation and might stop you from using your car. So, if you desperately want to do it, get the right parts needed for the job. But, don't forget that your car battery is subject to excessive wear in normal operation and will be consumed over time. Switching from LA to LFP will not change this.

[scotwilliamson]

I have a super cap under hood and small LifePo4 under back seat. When truck is off, they are in parallel. When truck is on and above 13v they are separated and charged independently. Also have temp sensor on the lifepo4 that switches between charging/heating. Going almost 3 yrs now. Expensive but I'll never have to buy a battery again.
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Love the supercap. Sat in parking lot after work one day watching someone try to jump off a truck that had left his lights on. After 15min of just hearing them getting nothing but clicks, clicks. I drove over, said hold my beer. Hooked cables to my truck, it started instantly. They both just stared in shock at how awesome Toyota trucks must be to be able to do that. I didn't tell them about my secret 10, 000 amps. lol
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Must careful with what you "jump"/"power" though, A non resistive or non amps limited load will let the smoke out before you had intended.

[stubbshomestead]

Wonderful topic I've been wondering the same thing, Thank you! I've personally used the battery tender one on my motorcycle and I had no issues with it for the 2 years I had it. I just bought a lithium starter battery for my lawnmower so I'll see how that goes.

[MrTespro]

This is the best explanation I've seen yet as to the many inherent problems in this goal. I wish he would experiment with the addition of super-capacitors to see if the combination works - and, if not, why. Ruining your car's electronics is a REAL issue!!!!

[pawelallable]

I have a lifepo4 battery in my motorcycle, and it's been a great improvement over lead acid. It feels a little weak when cold, but running the headlight for 30 seconds first seems to warm it up and get it going hard and starts great.