Adding secondary battery for 12v outlets

But, it seems you don't understand how IGBT inverter circuit works.
The diode with the IGBT does not work as rectifier. It works as freewheeling diode (inverse diode).
Patrick already explained about it.

For more clear explanation, please refer to "C. Switching Behavior" section on page-2 of following article.
http://library.abb.com/global/scot/scot256.nsf/veritydisplay/961e5ee4fcb30221c12575e600295446/$File/An98sb_web.pdf
"Obviously the load current of the inductive load commutates from the freewheeling diode (inverse diode) to the turning on IGBT. Therefore the IGBT has to take over the reverse recovery current of the inverse diode during the turn on transient in addition to the load current."

Ken@Japan

 

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The Gen3 DC-DC converter supplies up to 120A anytime in ready mode, not limited to MG2 regeneration.
It supplies enough current to charge two batteries, I think.
I believe you'll be required a battery isolator to connect two 12V's suggested by #2 post of this thread.

Ken@Japan

 

Which means you should know better than to make the overstated claim that the car battery will supply those loads for well over a year.

The vehicle will not always keep the Aux battery charged. The Aux battery is only charged when the Prius is in Ready or Ig-on. The threads on this forum will show many examples of dead and dieing Aux batteries, even without the additional burden of extra loads.

If you drive often and long enough the charging circuit will keep the Aux battery topped off. However, it's important to know that it is easy to kill the Aux battery in a Prius. The battery is small, the charging circuit is not very aggressive, and there is a fair amount of drain even when the car is powered off.

I understand your point: the loads are small and shouldn't cause any trouble under normal operating conditions. If you had simply stated it like that there wouldn't be any misunderstanding.

I've done exactly what you did, which is to make a valid general point using specific information, only to get called on the specific information. Human nature, especially for an engineer, is to defend the information even when it is wrong. In this situation you are much better off saying something like "I stand corrected. My general point is correct, but I didn't do the arithmetic. Thanks for pointing out the real numbers." If you do that, no one will think less of you, and the issue goes away in one post.

Tom

 

This was his response.

This was my response.

Ok, I stand corrected on the math. It will take 30 days to drain the battery if I never started the car.

His post makes it sound like the car never chargers the battery ever. Most people buy a Prius to drive, not to sit in around looking good.