Prime 2023 12V battery integrity on EV

I suspect it is the same for pretty much every EV / hybrid out there - they do not have alternator, they use traction battery to charge 12V battery.

 

On the Prius, the ICE does not charge the 12-V battery, as there is no alternator. The 12-V battery is charged by the high-voltage battery. Note that the car needs to be in the READY mode for the 12-V battery to be charged.

Likewise, the 12-V battery does not start the ICE, as there is no starter.

 

Plug ins, and some hybrids, use a DC to DC converter to step the high voltage coming out of the traction battery down to 12 volts power all the those accessories in the car. This will also charge the starter battery. Of course, the car needs to be in Ready mode or fully on for the traction battery to supply energy to the converter. So an EV chargers up the starter battery while it is driven, just like an ICE car.

The PP will also charge the 12 volt battery while the car is actively charging. Not sure if it is at just a maintenance rate or while increase its state of charge though.

 

They still haven't gotten rid of the 12v battery? What a PITA! On my Gen3 it was a small battery in the trunk. It lasted 8 years and was old $40 to replace. In my Gen4 it is a $200 battery under the hood that lasted just 4 years. Where is the 12v battery in the Gen5 and how expensive is it to replace?

 

It's back in the hatch (right corner near the door). I don't know the replacement cost

 

where did you get a battery for $40.? i paid $200, in 2018, and most here have paid similar

 

Yep. I think I paid around $175-$185 in late 2021. Or maybe I'm misremembering and it was over $200(I was in a hurry at the time). It's currently $239 MSRP at Toyota dealerships for a gen3.

Doing a quick search, I'm seeing a low of around $240 for a few brands of battery and almost $300 for an Optima.

 

There is a vast number of reliable, well tested parts that use 12 volts. Did you really want to pay for "hybrid" bulbs instead of 12 volt bulbs?

Also the 12 volt battery does POST safety checks before allowing high voltage in your car. This seems wise.

 

Was wondering this myself, as my 12 volt battery just failed in my 6mo old Prius Prime. I asked my Toyota service rep if the car charges the 12v battery in EV mode, since I drive most days in EV. He shrugged his shoulders. They replaced the battery under warrantee but I do hope this isn't an issue with the car if I keep driving in EV mode. Oddly, the battery ALSO failed on my old 2013 Gen 3 this morning - I had asked my son to pick me up from the dealer! It's charging now but taking a long time to charge - it's only a year and a half old, so it might be bad, too! Crazy. But also under warrantee.

 

A battery monitor makes it easy to tell what the battery level is, and when it’s charging. I found taking off an old aftermarket cruise control on my 96 Toyota solved the parasitic drain loss. The monitor tells the voltage while driving and when turned off in real time. I have seen no drain issues from the monitors themselves.
Two battery monitors using the same app could show the soc and voltage of both car batteries on your phone on the same screen. Have to be within 10 feet or so to start the bluetooth connection.

 

The 12V battery can be charged from the high-voltage system whenever the system is in READY mode, same as any Prius since 1997. The Prius has always had a lot of measures taken to cope with the engine not running, and this was there on day one. Many of the plug-in or EV problems like that were solved some time ago - the Prius was a testbed for such stuff.

In the Prime, the 12V battery can also charge when the on-board charger is active and drawing power from the charging port - so either charging the battery, heating it, or being in "My Room" mode.

 

He must've dropped in a small cheap Home Depot lawn mower/tractor battery.

 

OK, I realize I am a relatively new Prime owner, but I've not heard anything about "heating" the battery or "My Room" mode. Is this in the 2023, or the previous model?

 

As long as the car sees regular long trips—regardless of the EV mode—and you don't sit in the car unless the car is in the READY mode and you don't leave the AC charger plugged in for longer than overnight, you shouldn't have 12-V-battery issues.

Possible replacement alternatives:

Walmart EverStart Maxx 140R or EverStart Maxx H4
ACDelco AGM EN1
Toyota TrueStart H4

I know for sure that the Walmart EverStart Maxx 140R comes with the required drain holes on either side and a drain plug for the unused drain hole; so, it is a solid choice for a trunk-installed battery with a drain hose attached.

 

Heating's in both - when you're plugged in and the charging schedule permits, it will draw power into heater elements to keep the battery above about 5°C/40°F to improve performance when you start. That has a 3-day timeout. It's an option somewhere in the menus, and on by default - you'd only turn it off if you were worried about the electricity billing. (It would be pretty minor if purely on kWh).

"My room" mode is prompted if you go into ACCESSORY or POWER ON mode when plugged into the charger - it will draw power to run the car's accessories, including ventilation. That's new in 2023, I think.

Both are in the manual. Don't have US page numbers, but probably section 2.2 - Charging > Charging methods > Charging-linked functions.

 

In the Prime is doesn't matter if in EV or HV or HV Auto mode, the 12 volt gets changed the same way. It also gets charged when plugged in, while charging the traction pack and sometimes when plugged in and using accessories like pre-conditioning and or the traction pack heaters.
And trickle charging at 14.5 - 15 volts,. is really all that ever seems to happen, which is why (I think) the 12 volt never gets much above 12.6 volts, ever, and more likely hovers around 12.2 volts static, unless it is manually re-charged.

 

I have monitored the 12 volt and it doesn’t charge during traction battery charging. It does charge to 100% when in ready mode, but can be sort of slow and sometimes, often, it stops charging well below 100%. Most of the time voltage fluctuates very often with every change going on to the car. The monitor has a graph reading in essentially real time, every tiny or large dip and rise in voltage is displayed.
After car is turned off the graph shows the battery voltage, and wherever it goes to the second. The rate of change is also seen by the slope of the voltage readings.
This is for a 20 Prime, not a 2023.

 

Thanks!