auxiliary 12 volt battery

Just starting a project to add more 12 volt battery power to my Prius.

Wondering if others have done it and what they did?

So the first decision is replace the Toyota battery, or add and fit in a second
12 volt battery. I want around 90 AH available for accessories.

Assuming I can make something fit looks like an Optima Yellow top will be
my battery choice, as it is readily available and is AGM.

I think I read a post once where someone swapped the Toyota battery for
an Optima but can't seem to find the message now.

 

My old car was a diesel with 90 amp alternator and 90 amp hour battery. It was perfect for my needs but just got too old to keep on the road. I just gave it away. 17 years old and 260,000 miles. Can't replace it in MA so I have to make my new hybrid match it's capabilities:

1 Back up house power for when the grid is down. (been down as long as 2 weeks where I live in the middle of winter) I have a several KW inverter. It could run my freezer and refrigerator during the outages, or
my sump pump and furnace. Prius will do it better because the engine won't have to go all the time! The motor starting surges are more than I want to subject the little Prius battery to however. Steady state load may be around 700 watts

2 I keep a little car refrigerator/freezer going 24/7 at times by running on battery during the day and grid power at night. It is an Engel which is quite efficient but still needs 2-3 amps at 12 volts. Has built in ac line
power too; dual power cords.

3 Someone mentioned audio, and I do have a subwoofer and amp to move over from the old car! I think the amp is 100 watts or so. Be nice to listen to music parked once in a while and we aren't supposed to just idle our engines anymore.

4 There are times where I've wanted to leave my car with parking lights
or flashers going. Wouldn't dare to in the Prius with it's tiny battery.

 

I don't expect whole house power at once. Just the necessities. I've done it with 90 amps so the 100 in the Prius should be easy.

I generally run the fridge and freezer, and then switch to furnace and sump pump instead as needed. Load stays around 700 watts
except for motor start, and for that reason the inverter is rated
closer to 2 kw.

 

I may not get this done till summer, but I will try to keep everyone up to
date with my current ideas case they are doing mods too for this.

So far I have run into two problems.

1 normal battery isolators can not be used that use diodes and have a
0.7 volt voltage drop. The drop is bad anyway, but the problem is the
single power rail for power front to back of the car.

My solution is to try the isolators from http://www.hellroaring.com/bic75150.htm

If you look at the RV section especially they have several suggested
circuits to use depending on what you want to do! You can make some
adjustments since there is no big starter load in a Prius!

Can't say much about them yet but I ordered one to look at.

2 The more serious problem is space and battery sizes. I would like to use something fairly available, but might not if I found the perfect fit.

This may take me the rest of the winter to decide but here are the options
I can see:

A Smaller battery than I want mounted on side beside the regular one.
Cut and re-shape the bin to give it space.

B Put battery in the tire well and move tire up to the top somewhere. Then cut bin and mount battery box cover in it to allow the extra 2 inches or so needed. All standard batteries seem to come in one size only: "too high"

C Remove the left side bin and put battery in box there, allowing for a 2-3 inch hump there. Discard the little cover, and cut the main cover as
needed.

That about covers the possibilities though there are permutations of these.

There seems to be room for a slightly wider battery from Toyota, but this
would make installing it harder, and would not even then be close to the sizes I could use. Might help some people to look into. Looks like room
for about a 1 inch wider battery in place of the stock one, but duct would have to move for installing or removing. Might let someone go away for
a week longer without disconnecting stuff.

 

http://www.toyota-industries.com/product/e...ogy_center.html

Just some specs on the converter. 1120 watts total max.

 

Well it was Google, but I was searching for more Prius battery info, not
converter info and it just showed up!