Regular Battery Charging

I'm pretty sure the "regular" battery is charged by the "traction" battery when the engine isn't running (Even when the car isn't being charged by AC).

 

toyota are genius!

 

I don't believe this is correct. MG1 is a high voltage motor/generator and thus will charge the traction battery, not the 12V battery. The only way to charge the 12V battery is by using the power supply that runs off the traction battery, exactly as xray22 said.

I haven't been able to find the rating of this power supply for the Prime, but it was rated at 100A on my 2004 Prius.

I commonly charge my R/C airplane batteries off the 12V battery. If I charge a lot of them, I'll put the car in Ready mode for 10-20 minutes to let the 12V battery charge up. This definitely charges the 12V battery since it's voltage changes from something like 11.8V to something like 14.1V but it doesn't start the engine. In fact, if I shut off the A/C and headlights, you'd never know the car was on.

 

WeberAuto Prof John Kelly says in the battery removal video (around min 22) that the charger has built-in DC to DC converter and output 14 V to charge the 12 V battery while charging. He also showed low voltage connector in the front part of the high voltage battery.

Posted via the PriusChat mobile app.

 

12V battery is charged by traction large battery. So no worries.

 

A minor worry. I understand that the 12V is charged by the traction battery. Looks like it is only while the traction battery is being charged. So if I park my car for a month or two, looks like the 12V will lose its charge unless I connect a battery tender to it. I recently did park it for 60 days and left the traction battery discharged; then hooked it to the charger the first day I got back. I am guessing that I didn't need the battery tender because the 12V would have been also recharged at that time. Is that correct?

 

Or the car is in ready mode.

 

Yeah you could disconnect the 12V battery for more than a month.

 

I am afraid that some of the settings that I or the dealer have done (like removing back up beeps) might be lost if I did that.

 

I don’t think that would change but all your presets on the radio would be lost.

 

I heard the same thing from Kelly. However when I check my 12 volt battery during charging of the traction battery in my Prius Prime, it does not show that the 12 volt battery is charging. When the Prime is in READY the 12 volt battery always is being charged.

 

it's funny that this isn't well known yet, after two years on the market

 

In my Prius Plugin 2015 the 12 volt battery is charged during the time the traction battery is being charged. Wonder why Toyota changed this for the Prime.

 

this came up in another thread.

my theory; they either didn't want to spend the money on the wiring to get to the 12v now under the hood, or they saw it as an unnecessary feature that didn't help sell cars, and a good place to cut costs.

it's nice to have, but the lift back does okay without it, and toyota is the king of decontenting