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Thanks for the information.
I understand that one of the possible sources of discharge of the 12 volt battery is a search/lock mode between the vehicle and the smartkey. To eliminate this possible cause of discharge of the 12 v battery, and to increase security, I routinely disable the smart key as suggested by Toyota Tech Tip TIP5042, copy attached.
I'm having a hard time seeing that this would cause the car battery to discharge. Cars that use smartkeys are constantly polling to see if the smartkey is near. From reading this article, the battery savings referenced are for the fob's battery. Not the car. The load on the car from polling for the smartkey is just not that great. But... I could be wrong. It doesn't kill the battery of my CRV and its battery is not nearly as robust as the battery on a hybrid.
 

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As previously mentioned, the Prime does in fact charge the 12v Aux battery when the Prime is plugged in AND charging. As seen in the graphic in this screen shot I just took. The voltage was only 12.2v and goes up to 13.42 when I initiated the charge cycle.
View attachment 176646

But, even after 20 minutes, the charging voltage is still only at 13.42v
View attachment 176647

For those charging on L2 @ 6.6KWh, this will not be long enough to fully charge the 12v Aux battery. It barely maintains it. This problem is worsened in winter, because if you use mostly HV mode because of the cold, the battery does not discharge as much and requires less charging time and compounds the energy deficit for the 12v Aux battery that the cold already imposes.

I personally think a small smart charger/maintainer is an easy fix to alleviate possible issues. Every few week during the coldest months should be enough.

I also carry a small booster pack (Noco GB40) in my trunk just in case.

dp
Doesn't the 12V battery get a charge when running the ICE? I know there is no alternator, but doesn't one of the MG's help maintain the 12V? Otherwise, on a long trip in HV only mode you would lose the 12V battery all the time.
 

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No. There is a DC-DC inverter that steps down the high voltage traction battery to low voltage 13-14V DC in order to maintain the battery. This is active when the vehicle is in a READY state, a charging state, and maybe another state I'm forgetting at the moment.
Then it should be maintained when running in HV mode. Correct? In other words, I should be able to run entirely in HV mode without ever plugging in and still maintain the 12V battery.
 

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I don't quite understand the great concern on the battery voltage. After three days with no activity on the car, my battery is at 11.5V. I am not concerned. A full battery is 12.6v. When I see 10v, I will be concerned. When I start (ready) the machine, the battery voltage will go to 14.3v or.4. Parasitic draw is there, and that is a fact. I believe that as long as it is not an external draw the car will function just fine. My rav is 11 months old and has sat for up to a week with no external connection and starts just fine. FWI
I agree. They use AGM batteries in the Prime, which is more of a deep-cycle battery. It should be able to handle the standard parasitic load, unless there is a firmware issue. There was one, but it should have been fixed on all cars by now.
 
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