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12 V Battery Beware

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Posted by Steve Giannoni on April 13, 2008, 3:31 pm
This sucker started going dead on my 2001 if I didn't use the car for
more than a day or so. It just apparently lost capacity over 7 years
and couldn't keep up with the theft deterrent and other "off use"
electronics. So I had to pay $35.37 to Toyota for a replacement. Nice
Hugh! The new is different from the original (hope it's upgraded
capacity!) and required special new mounting hardware which they
didn't stock (natch!). Three days and all that dough just to change a
12V battery (sheesh!). Any one with similar experience?

Posted by Chas Gill on April 13, 2008, 3:39 pm

Any lead-acid battery that manages 6 years has done well.  Having said that,
this seems like an awful lot of money for what is, essentially, a low
capacity, small battery.  Maybe it's because it's relatively rare?  Living
in the UK - and being used to dollar/pound parity - i.e. anything that costs
a dollar in the States is usually around a pound in the UK ;-(  - gives me
cause for concern about what it will cost me in 3 years time.........


Posted by Mike Rosenberg on April 13, 2008, 3:48 pm

A quick Google search for "Prius 12 volt battery" turned up several hits
at $33.95, which is still ridiculously expensive but a far cry cheaper
than the OP paid.

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Posted by Bob & Holly Wilson on April 13, 2008, 4:09 pm

That is a shame but last year over in "Prius Technical Stuff" we looked
at servicing the 12 V battery. I took mine out; removed the "Do Not
Remove" seal; took out the little plugs; and added distilled water; and
put it back together.

Eventually my 12 V battery will fail and when it does, if water
rehydration doesn't work, I'll buy a $5-35 lawn tractor battery and
copper piping from Lowe's. I'll fabricate two adapters and use the
cheaper battery.

There is an adapter that allows you to use a Miata battery in your
Prius. This brings the price to about $0 the last time I checked. But
for my purposes, a sealed, lawn tractor battery with vent tube will work
good enough.

Bob Wilson

Posted by e on April 13, 2008, 4:30 pm
 Bob -

On my '04 (now ~4.5 years old), I notice that the
windows run UP/DOWN more slowly - probably a function of
internal resistance of the 12V battery.

I'd like to service that battery and clean/protect all
high-current connections. Presumably you must clip any
12V source in parallel while yanking it to avoid losing
system memory. Any other advice?

Can you recommend a suitable replacement battery? How
difficult is it to handle the venting?


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