Replacing 12VDC auxiliary battery - NHW11
 

Hi,

When the temperature finally dropped to freezing, I began to have intermittent starting problems from the original, 2003 battery. So I decided to replace the OEM battery with an Odyssey PC925PL:

http://hiwaay.net/%7Ebzwilson/prius/pri_12V_010.jpg
I knew the Toyota OEM battery had metric, not SAE terminals traditionally found in North America. Also, the Toyota replacement is pretty expensive, $165+, and only lasts another 5 years. The Odyssey battery, $175, is rated to last 8-10 years but would take a little work.

http://hiwaay.net/%7Ebzwilson/prius/pri_12V_020.jpg
The PC925 battery has the same depth but the width and height are less. It also uses screw terminals, which made the adapters much easier than expected.

http://hiwaay.net/%7Ebzwilson/prius/pri_12V_030.jpg

As shown below, I used heavy duty ring lugs and #6 wire bought at the local hardware store. I only needs 2-3 inch lengths of wire and a hammer to 'crimp' the lugs:
http://hiwaay.net/%7Ebzwilson/prius/pri_12V_040.jpg

It turns out the original terminal clamps have a nut and bolt that exactly fit the ring lug. Once the shortie jumpers are made, just use the original terminal clamp bolts to connect to the battery:
http://hiwaay.net/%7Ebzwilson/prius/pri_12V_050.jpg

Sad to say but the autofocus doesn't work well in the dark but you'll notice some wood shims on the hold-down clamp and another block to handle the narrower PC925 battery:
http://hiwaay.net/%7Ebzwilson/prius/pri_12V_060.jpg
Otherwise, everything just bolts together and you are done. Unexpected, there is more space between the battery terminal bolts and the body. There is no risk of a short. Note, I've temporarily disconnected my inverter in this photo.

Bob Wilson

Re: Replacing 12VDC auxiliary battery - NHW11
 

I think I would have looked at inexpensive off the (lowe's) shelf garden variety garden tractor battery first.

Re: Replacing 12VDC auxiliary battery - NHW11
 

I looked at several options:

• lowest purchase price - the garden tractor batteries are attractive for purchase price but when I looked at their warranty, many were for 2-3 years. They looked to be more of a 'disposable' plus there is the problem of 'venting.' A garden tractor battery is often on an open frame. Rain or a hose washes it down. I had visions of making a special battery holder and spending every other year replacing it.
• commodity battery - the SAE terminal batteries won't work with our metric clamps. So I'm faced with getting one of these adapter kits and trying to find a Miata battery. Although less expensive than the Toyota replacement, I would still be stuck with another 5-6 year battery.
• top of the line - the Odyssey battery has a very good reputation built upon using exceptionally pure lead electrodes tightly packed. They have high energy density and a rugged case that requires no vent. Best of all, they have an 8-10 year expected life. This means once installed and working to my specifications, I can 'forget about it.' Best of all, the screw terminals worked much better than expected.

I don't fault anyone for taking a different choice and encourage it. I can see with a garden tractor battery with screw posts using the short jumpers could work OK. If you got a marine battery case to hold it so no electrolyte could ever escape, it could be a very nice solution.

You also have a 2003 Prius. Are you still on the original battery?

Bob Wilson

Re: Replacing 12VDC auxiliary battery - NHW11
 

Electrolyte "escaping" is a pretty rare event, usually resulting only from "boiling" due to SERIOUS overcharging. Electrolyte "out-gassing", on the other hand, due to a FAST charge rate, is a VERY common event.

Our company's lead hardware design engineer was given the keys to the Prius from the get-go, I've driven maybe a total of 50 miles. I'll check to see if he has had any battery problems/issues.

Re: Replacing 12VDC auxiliary battery - NHW11
 

Thanks,

I've done some 12VDC system testing as part of my inverter modification:

http://hiwaay.net/~bzwilson/prius/priups.html

Within the limits of my uncalibrated test instruments, it looks like the Prius maintains 13.94 VDC maximum to the lead acid battery. My understanding this is well within the safe range for these types of batteries.

Bob Wilson

Re: Replacing 12VDC auxiliary battery - NHW11
 

What did you do about the vent hose? I just got a replacement OEM battery, and the new battery doesn't have the thing on the side of the battery that the vent hose connects to. The pictures you posted suggests that the Oddysey battery also doesn't have this piece sticking out of the side of the battery. What did you do? Or better yet, what can I do since my new battery doesn't have anything to connect the vent hose to? I tried getting that connector piece out of the old battery, but it won't budge and I don't want to break it. Any help would be greatly appreciated!!!

Thanks,

Tim

Re: Replacing 12VDC auxiliary battery - NHW11
 

Owch! I just took it to the battery shop for recycling.

My Odyssey battery is sealed and has no vent. They claim it doesn't need one.

Bob Wilson

Re: Replacing 12VDC auxiliary battery - NHW11
 

Since my new GS battery didn't come with a hose connector attached to the side, do you suppose that means it doesn't need to be vented, either (like your Oddysey)?

Re: Replacing 12VDC auxiliary battery - NHW11
 

Never mind. I was able to get the connector out of the old battery without damaging it, and I put it in the side of the new battery. Installed the new battery, and the car started up like a champ! Wish I had found this Odyssey thread before I bought the 5-year battery, though. :confused:

Thanks.

Re: Replacing 12VDC auxiliary battery - NHW11
 

Actually, I had to put the Odyssey battery in before leaving to see the 3d generation Prius. . . . . Guess I'll have to wait 8-10 years before getting my next Prius. <GRINS>

I'm glad things worked out. Did you take any pictures?

Bob Wilson