LFP (LiFePO4) 12V install

[Isaac Zachary]

So I put a 100AH LFP (aka: LiFePO4) battery in the Avalon. It's from Li Time. It has battery protection including cold temp shut off and automated warming. We'll see how it goes.

My main reason wasn't for fuel mileage though. The Avalon has no alternator, so there's no way to stop the car from charging it without disconnecting the battery. But it does have a theoretical 10X the amount of usable energy than the tiny lead acid battery it replaced. This will make running my amateur and GMRS radio equipment for extended periods of time a bit easier.

So far the battery seems quite a bit more "thirsty" than the lead acid. It took several hours of driving around for it to finally reach 14.4V. The lead acid would easily go up to 14.4V after a short time, even after an extended period draining it (and the LA battery fairly new too). At least now, at normal temperatures, the voltage drop is a lot less with a load on the LFP. And since the LFP battery sits at 13V, more or less, the drop is still above 12V with that load, whereas with the LA it would easily get down to less than 11V.

We'll see how it does in winter. I'll keep the lead acid on hand and charged just in case.

[Ecky]

To be clear, this has replaced your lead acid battery?

At 14.4v, it ought to be at 96% state of charge, with 14.6v being the maximum operating voltage. Aside from it being better to hold it at a slightly lower state of charge, a hybrid is pretty much in ideal use-case for one, assuming Toyota doesn't have any DC-DC behavior to improve the health of lead-acid batteries.

My experience has been that LiFePO4 will survive extreme winter conditions, especially if not being used for starting purposes. If charged below freezing, dendrites begin puncturing and destroying the insides of the battery, but LiFePO4 appears (anecdotally) to be able to survive a bit of this. In my Insight, I still chose to swap out for a lead acid during the months where the average temperature would be below freezing.

Out of curiosity, how much did it cost? Have any specs?

[Isaac Zachary]

I've had a volt meter on the car since I bought it. It never goes above 14.4V and often will sit around 13.6 for a while before trying 14.4V. And even when the inverter goes to 14.4V, another measurement at the battery will be lower, sometimes nearly a volt lower, if it's drawing a lot of current. So apparently there's a good deal of resistance on the wires that go clear from the front of the car back to the trunk where the 12V battery compartment is.

Here are the specs. It was around $315 USD, which is incidentally about the same price as the only 12V LA battery I can find for the car in an original size since the only place that carries them is Toyota. No one else sells a 12V for this car.

https://www.litime.com/products/12v-...ithium-battery

PS. This battery is physically bigger than the original, but feels lighter. It barely fits in the battery compartment, but I can get the door closed, so I say it's a good fit.

[Ecky]

Self-heating too. Looks great.

I found the Insight has the same behavior, where the DC-DC varies its voltage. One can change the DC-DC's target voltage from 14.4 to 13.8v by cutting one wire, and disable the voltage variation by cutting another (so it will stay at 13.8). If one wanted to get more clever, a 5v PWM signal allows complete control over the DC-DC output from 13.8 to 15v.