Wanted to see what those more knowledgeable in battery technology have to say about this battery from Dakota Lithium:

Dakota Lithium 12v 60Ah Dual Purpose 1000CCA Starter Battery Plus Deep Cycle LiFePO4 Performance

It’s being marketed as a starter/deep cycle:
-1000CCA
-Optimal Operating Temp: -20 to 150F
-BMS prevents charging below 32F, High temp cutoff at 167F
-100A-Continuous | 750A-2sec | 650A-5sec
-Charging: 60A optimal, 80A Max
-24F size (same as stock battery)
-16 lbs

I’m very far from “smart” on battery technology, but I do understand some of the limitations of LiFePO4. That’s why some of these specs seem a little bit suspect to me.

From my perspective:
Things I like:
-25 lb lighter than stock, same size/terminal config
-High CCA/discharge rates for winching purposes
-High cycle life, with greater DoD capability

Potential issues:
1. Engine bay temps. I couldn’t find any definitive data on 4Runner engine bay temps. Seems like it would get hotter than 167F in there, especially on a hot day at low speed/stop. Maybe not as hot up front at the stock battery location? Would a temp shield battery blanket help? On the flip side, it seems like you’d rarely have to worry about the low-temp charging cutoff while the engine is running.
2. Obviously, the charging profile. I believe our stock alternator outputs much greater than 80A (~130 IIRC). Also wouldn’t provide the needed voltages to properly charge it, so you’d have to figure out a way to properly charge it from the alternator. Anyone know of any products out there than can do this? I’ve seen some “alternator regulators” from Sterling Power but I’m not sure how this would have to be wired between the battery, alternator, and vehicle loads.

Thanks for any thoughts and feedback! I think it’d be really advantageous to run this battery, but it seems like the effort required to make it work might not be worth it.

Not sure I'd trust this not to leave me stranded in the middle of nowhere for <0.5% weight savings.

At 1k CCA it's I think 25% more capacity than my sla batt. Def not double. 4x life? Under what test conditions? If they set the parameters they can make it any result they want. I haven't read up on battery chemistry tech for a few years, but last I knew lithium loses a significant amount of life if stored at temps over 70* and dramatically more over 100*, certainly not ideal for under a hood whether the engine's running or just baking in the sun. Po4 is newer tech but doubt they were able to alter that shortcoming too substantially. And as they allude to, you don't want to charge up to 100% as that also dramatically decreases life span. So does it have circuitry built in to cut off at 80% charge, or what? Even for the same price it's be a toss up for me without a bunch more research, at 4x the price it's a hell no.

From what I have read, under hood temperatures are just too high to place a lithium battery under the hood. I wanted to use a lithium as my auxiliary battery but almost everyone recommends against it. Some have used them successfully, but since I live in the Mojave Desert, I decided against it.

1000cca may just strip the gears right off your starter on the first try. My 840cca is already ridiculous. lol

My understanding is that LiFePO4 batteries are best used as an auxiliary battery for powering 12V refrigerators, lights, etc., which require continuous but relatively low amp draws, instead of as a starter battery. Most LiFePO4 battery makers do not market them as starter batteries.

You would need a battery charger connected to your alternator, e.g. the RedArc BCDC1240D, which could be mounted behind one of the headlights.

Charging a LiFePO4 battery below 32 degrees F will quickly kill it. The engine bay and the starter battery will start off below 32 on a cold day, so you'd need a way to turn off the battery charger if it's that cold outside, and turn the charger on only when the battery warms up to say a few degrees above freezing. In the meantime, that starter battery is powering all of the vehicle's electrical loads without benefit of alternator charging.

There are a few LiFePO4 batteries with internal heaters, but you could also rig a 12V heating pad to keep the battery warm. But if left on overnight, you would have to calculate how much power the heating pad draws from the battery, to make sure the battery could start the truck the next day.

High heat in the engine bay: one LiFePO4 battery maker claims 5,000 charge cycles at 80% depth of discharge each cycle, before losing 30% of the battery's maximum amp hours at full charge. Installing the battery in the engine bay at 140 degrees F all the time might reduce the battery lifespan to maybe 4,000 charge cycles. If at 160 degrees F, maybe only 3,000 charge cycles. If at 175 degrees F all the time, the lifespan might be reduced to only 1,000 charge cycles. Best to ask the manufacturer if they have a data sheet that shows the number of charge cycles if the battery is stored at various high temperatures.

You might be able to bolt a CHT thermocouple with a 10mm ring terminal to the battery terminal to measure the battery temperature.

A heat shield between the stock battery location and the rest of the engine bay would help deflect heat from the battery, but would not completely prevent the battery from heating up, especially on a hot day.

May want to check out this study, results and feedback. Thanks to @WanderlostOverland Is It Safe To Put A Lithium Battery Under The Hood

Thanks for all the input folks! The video is especially helpful, I hadn’t seen exact numbers for under-hood temperatures. I agree that with the current limitations of LiFePO4 it’s not a good idea. The excessive price, and additional expense of a proper charge controller/alternator regulator make it hard to justify as a replacement for all the excellent AGM options out there, unless weight is somehow that critical. I do think it’s interesting that the max operating temp of this battery is substantially higher than the 120F I’ve seen recommended on other lithium iron phosphate. According to their specs (which I agree can definitely be deceiving based on how the manufacturer tests their battery) it could still operate within limits under the hood of a 4Runner. I think it’s cool that we are starting to see lithium technology pushed to new limits/applications. I’m excited to see if the shortcomings of these batteries will get worked out, I would love to run 200ah of lithium under my hood!

When I think of lithium batteries and heat, I think of e-cigarettes. Wouldn’t want that under my hood.

I lived in Ridgecrest 10 years (‘92-‘02). Worked in Trona ‘87-‘04.

As everyone has pointed out, temperature extremes are limiting factors for lithium batteries. Just not suited for under hood where subjected to both low and high extremes. Great batteries for 2nd aux battery installed in cabin where temp extremes are much less duration. New technology and it will develop in time. Or another and better battery tech will be discovered as a result of EV’s. I am convinced the next major milestone for the automobile will be battery tech and whoever comes up with the best battery tech with least amount of limitations will make bank.

Here's what works really well. No need to worry about extreme heat or cold, can keep it in your 4runner all year round. I have a regular lead acid battery as a starter battery and my other battery for my fridge is using an AGM stored in the back. It's charged by my DC-DC charge.

Yeah that isn't how that works. The starter pulls the power it needs from the battery, which can provide up to a certain maximum amount of cranking amps in a given environment.

Same reason your phone's battery doesn't just slam the phone with everything it has all at once and blow it up when you turn it on - unless you had one of those Samsungs from a few years back :P

Please post video when it catches fire.

you do know that lithium iron phosphate batteries aren't the same as lithium ion, right? LiFePO4 batteries don't catch fire, even when punctured.

Well I hope you do know now that I don’t care.