Has anyone tried replacing the 12 volt battery with a LiFePO4 12.8 V battery?

What I am trying to say is that "12.2 volts" is not a battery SOC. It is a bettery voltage.

 

So basically your nit pickin my use of SOC. You wanna be the first to take a set of Amp reading while 12 volt charging is happening by the Gen 4 and or 5 Prii, so we all can hone in the real 12 volt battery SOC, and I'll promise to never use SOC in a description of only the voltage reading again. Great job.

 

The 13.5 volt is pretty consistent, yes. As can be seen here when the battery was warming up


And when preheating (or A/C) was turned on (that 13.5V before the drive was 10 minutes long)


But when charging, the voltage does fluctuate, as can be seen below. It fluctuates around 12.8V.

 

It's probably like the Prime. The 100% of the traction battery for EV is actually from 15% to 85% of the traction battery. At 8.8kWh, that's 6.1kWh. Below 15% is reserved for the hybrid mode. Above 85% isn't used to, like you said, prevent battery degradation.

 

The voltage is important. LiFePo4 battries won't hit 100% charge and will begin to suffer sulfation unless they hit something like 14.8v during charging.

The guy who mentioned charging system voltage dropped great information. That means that adding any kind of lithium, even with a battery isolator, isn't going to work.

I almost installed that solution with a standard isolator. I see now that I'm going to need a different solution such as a DC to DC charger added between the regular supply of current, and the isolated lithium battery pack (I'm going to be powering an inverter) however this all definitely answers the question of if you can put a lithium batter into your prius as a starting battery.

Nope, you can't use a lithium starting battery. You'll mess it up and waste your investment.

You also definitely can't do it with LiFePo4, because those will take damage during every start since they're made for slow cycling, not fast discharge like lead acid.

AGM is ok in a Prius. Every time I buy a new 12v starter, that's exactly what comes up in retail matching systems like at Autozone. AGM isn't a true deep cycle battery, it's more or less a non-spillable improved version of lead acid that handles deep cycling better, but not as well as an actual deep cycle battery made for deep cycle applications like solar, running inverters, etc.

 

Where will the sulfur come from?

 

Damn diabolical question))

 

I can confirm this!

https://youtube.com/shorts/iI9Zvs1xlYU

 

A 12V voltage monitor would tell you that too lol. However, of all the time the 12V is topped off, while charging is the slowest at merely 12.75V. The highest is when in Ready mode/preconditioning at 14.5V and the other time is when the battery heater elements are on at 13.5V.

See this post I made last winter

Using battery maintainer | PriusChat

 

well... ill say this, whoever said Lithium won't work... might need to go check their fact Rolodex.

https://black.jmyntrn.com/2024/03/12/bye-bye-overpriced-batteries-my-journey-to-creating-the-perfect-prius-12v-battery/?utm_source=PriusChat&utm_medium=weblinkt&utm_campaign=commentlinkAugust



and also...

https://black.jmyntrn.com/2024/08/16/who-do-you-trust-nowadays/?utm_source=PriusChat&utm_medium=weblinkt&utm_campaign=commentlinkAugust

 

How does it handle below freezing charging? Lithium batteries hate it when they are charged below freezing temperatures.

 

I have realized, the main reason advances in the new and exciting have been limited in the Prius platform, its because most are so worried about the what-ifs. Personally, living in Southern California, I don't have any concerns about below-freezing charging and if I did a battery warmer would be used. Simple. |

Can't wait to show you all what I've done... just know that 87% of the things people say is the truth about the Prius, like Lithium wont work... or my favorite, when they tell me I didn't observe a significant rise in the rate in which the EV battery charges in my PHEV after installing upgraded aftermarket brake parts.... is wrong! next they will tell me the max bore size on the 1.8L which I found out through having a fresh block analyzed cant be used with the stock ECU... hahahahaha

 

Well it's not so simple as the battery has to be warmed up before the charge can happen, so the BMS must account for that. It's possible, but needs to be taken into consideration.

 

That's the thing. For me, it's simple. I already planned for that and added code to the .ino file I wrote for an ESP32 device, which would trigger the relay to turn on the heating pad and monitor the temps independently of the rest of the system. Those lil boards can be run on 3.7-7V of power easily.

Thats why I guess I don't understand the thought in the worry about cold temps... Id just make something to overcome that obstacle and its over. These Silicone rubber heating pads are pretty cool if you ask me!

 

It was not meant to be a worry, but to plan for it.

 

There are so many errors in the facts presented in this post that I choose to not even address the grossly incorrect statements made here. If you do not see at least one untruth, you know nothing about LiFePO4 batteries.

 

I'll say this... after going through 3-5 isolators, they are not what will work in a Prius that's for sure!

https://black.jmyntrn.com/2023/06/03/upgraded-my-prius-12v-battery-system-with-a-second-12v-battery-from-a-smart-battery-isolator-to-a-victron-cyrix-ct-12-24v-120a-to-use-with-my-battery-monitor-smart-shunt/?utm_source=PriusChat&utm_medium=weblinkt&utm_campaign=commentlinkAugust













It baffles me how often people post online as if their words are the absolute, undeniable truth. More often than not, I've seen these "facts" stray far from reality, making me wonder how they manage to convince themselves—and others—that they’re right. It's bonkers how easily misinformation spreads when people speak with such unwarranted authority. If you’re curious about where I’m coming from, check out my thoughts in more detail here: Who Do You Trust Nowadays?.











Lately, I’ve been tapping into the power of AI to review comments on certain PriusOverlanding.com threads, especially those mega discussions that try to paint things in a negative light. Let me tell you, it’s bonkers just how intelligent AI is! The insights it provides are not only eye-opening but also incredibly accurate, cutting through the noise to reveal the truth. If you're curious about what AI found, check out the details here: I Used AI to Analyze Reddit Threads—Here’s What It Found

 

No sulfur, yes, but there could be lithium plating and electrolyte, structure and other issues with prolonged low SOC.

I agree that an LFP 12-V battery, which has a higher charging and discharging voltage (even higher than an AGM lead–acid battery) will probably not work well in a Prius with a 12-V-battery-management system, which is the case for Gen 4 and Gen 5. The Gen 4/Gen 5 Prius BMS (an identical system found in both generations) likes to keep the voltage at 12.89 V at most times and only raises it to 14.1 or higher according to the present and historical voltage and current data. It works with flooded-cell and AGM lead–acid batteries (I have an AGM battery), but with an LFP 12-V battery with a built-in BMS, it will likely get confused, resulting in unexpected behavior. Those LFP batteries are meant to be for cars without a BMS that charge constantly at around 14.3 V.