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

Does that battery has its own heater to allow it to charge below freezing? Charging a frozen Lithium battery will damage it.

 

Pretty sure this has been done multiple times, search google with Prius chat

 

Oh, right. The engine in the standard Prius is used quite often. I guess that could be different in a Prime.

 

You may want to investigate the charging requirements for each of the batteries. The charging algorithms for a lithium battery are significantly different than those of a lead acid battery. A starting point might be The Battery University (yep, it actually exists). Or, you could just rely on the opinions of folks who don’t even know there are significant differences between the two (like PC egineers (misspelling intentional)

 

That question has been answered. Do a google search.

In short due to a difference in the resistance between a standard 12v car battery and a lithium-ferric 12 v battery, you will burn the alternator; seriously burn it..

 

Good thing the Prius doesn't have an alternator then

 

My understanding is the Prius 12V battery is charged via a DC-DC converter from the hybrid battery and there is no 12V alternator in a Prius.

 

Your understanding is correct.

 

What about a AGM (absorbent glass mat) battery? Would that be okay?

 

Not in a 2020 (contrary to what some will tell you here). One, the charging algorithms were set up for lead-acid (meaning you will shorten the life of the AGM); Two, you won’t REALLY gain anything; Three, you will waste your money; Four, there is a slight (emphasis on “slight”) chance of damaging the ECU system (it’s assuming you are smart enough to read the owner’s manual and not to replace the battery with the wrong type).

 

My AGM question is because my sister, who has a non-plugin Prius, had her 12v battery die during Covid lockdown and had to get a jump start and then drive around while braking to charge the 12v. Is my plugin different? Will plugging in the HV battery charge or help the 12v battery? I'm new to hybrid technology and am not sure of how the charging systems work.

 

Yes, your plugin will charge the 12V battery at a voltage of 12.8V while charging. It will also charge the 12V battery at a voltage of 13.5V when plugged in, not charging and the heater elements are actively heating the battery pack because it got below 2°C.

 

Are both those voltages consistent for the span of times for both charging and battery heater warming the pack?
And if you ever use pre-conditioning and monitor the 12 volt batteries voltage, do you also see a similar charge rate during that 10 minute session?

I'm sure you've noticed all the complaints about how the Gen 4 and 5 plug-ins don't charge the 12 volt battery at all while plugged in and only charge that 12 volt battery while in Ready Mode. and that rumor spreads pretty fast. Possibly due to the cars may not always charging the 12 volt battery when some owners take a look at their 12 volt battery voltage one time and think they've discovered a big problem. Than start looking for the parasitic draw which keeps the 12 volt battery at their observed SOC.

My 12 volts SOC is typically around 12.2 volts, until I post that stat here and than next time I look the voltage is around 12.5 ... lol

 

SOC is a power rating in percent of the battery watt-hour rating. It is not the voltage of the battery.
Watt-hour=VoltXAmp-hour
A 12 volt 100 amp-hour battery is a 1200 watt-hour battery (12Vx100Amp-Hour battery rating = 1200Watt-hour battery capacity)

 

What are you trying to say?

Is your post supposed to have something to do with the question I asked @sylvaing about his 12 volt battery readings?