Hybrid Car – More Fun with Less Gas

using a 120v inverter - Page 4

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Posted by Was Istoben on December 31, 2008, 4:35 pm

Try this:  With jumper cables, a second car nearby, and knowing where the
jump start point is (under the hood inside the fuse box) leave your dome
light on overnight.  You will find out the 12V battery will run down.  After
you jump the car you will also note that many system settings have been
lost, especially if you have a navigation system.

I suspect it's cheaper to purchase a small generator than modify the Prius
to yield the same KWH rating.

Posted by Peter Granzeau on December 31, 2008, 8:14 pm
On Wed, 31 Dec 2008 06:35:34 -0800 (PST), ransley

No, I said it can run down, not will run down.  It is possible to turn
the car off, and leave (for instance) a dome light on.  Leave it like
that long enough, and the 12V battery can be drained.  The 12V battery
is recharged by the traction battery only when the car is in READY

Posted by Al Sherman on December 31, 2008, 12:11 am
 This has been discussed extensively in the Yahoo group

You can join this group and find a lot of answers to your questions.

One of the members has posted his experience in building a Prius "UPS" on
this web page:


Posted by Bob & Holly Wilson on January 3, 2009, 5:26 am

Any questions?

Bob Wilson

Posted by Ike on January 3, 2009, 3:31 pm
 Bob & Holly Wilson wrote:

This seems to be a highly optimized solution - thank you.

My inverter (true sine wave) has an inrush thermistor, but I'll add your
suggested RF toroids.

When drawing more than a kW I don't see the voltage drop that you
reported. It could be internal resistance because conversion to 18650
Li-ion cells affects both energy-density and energy-flow. Thoughts? (my
car is an '04)

My inverter is heat-sunk onto a thick (0.5") Al plate, battered into a
shape such that it attaches to the car's sheet metal at several points
and becomes a heat pipe. It stays pretty cool for short-term use, but I
added a 12V computer fan to keep air moving over the outer finned case.
It vents into the car with no problems, but I've been thinking of
running the air to the outside. If I make the system more automated like
yours, heat may become an issue. What do you think?

Also, as I understand your diagram, the traction battery charges the 12V
circuit when the 'ignition' is ON, and you've added an automatic switch
to the 'ignition' circuit. Can you provide details of that circuit?

We just bought a 2.5kW gas generator for backup purposes, so the Prius
solution is less important. I may restore the original battery, freeing
up the Li-ion pack for other uses.



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