2001 Prius dead 12v battery

Things wear out due to use and age, including batteries.
Charging it overnight might get you by for a week before you get a new one.......but it might not too.
10 V is really bad.

 

Any old small 12v battery will work--the standard is a deep cycle, but a lawn tractor battery will work and they're c heap. If you keep using a worn out battery, it'll go bad at the most inconvenient times.

I'm using a computer UPS (uninterrupted power supply) battery in my 03. Seems to work fine. If it needed to crank a starter, I'd have a bigger battery, but basically the 12v battery is used to wake up the computers and click some relays.

 

Measure the old one, go to Walmart, O'reilly's, Autozone, etc. and find one that will fit into those measurements.

Probably if you use User CP for my username and look at my old posts, you can get the size and source for a UPS battery. Or find a local Batteries Plus. and give them the dimensions you're looking for. Might be a scooter battery or it might be a UPS.

No, a 12v battery won't damage anything. Probably a 12 or 14 amp motorcycle battery would provide enough power, even. The 12V does NOT power a starter motor.

 

Pay attention to the battery post locations, take a picture and take it with you.

 

AND has the same kind of posts as the old one.

IF you go cheap, it will probably be a "wet cell" battery with caps that you need to check the water in occasionally.

If it is smaller than the original, the charging system might "overcharge" it and cause more rapid water loss.........and the creation of more acid fumes, so be sure the vent tube is in place if your model has one. Problem there is: Many wet cell batteries vent through the caps and has no external vent tube.

Then.......be careful with the polarity of the posts. With different size or style of battery, they can be reversed.

I really think that a person who has to ask this many questions should get an "exact replacement" from a dealer or auto parts store.
Trying to save a few pennies might end up costing MANY dollars.

 

AGM motorcycle batteries and UPS/Scooter batteries don't vent at all. The only problem is that they use a different kind of connection post. Which can be worked around. When I started with Classic Pri's, batteries were critically supposed to be deep cycle, certain amounts of amps. Bottom line was an overpriced battery from the dealer or an online source.

The Prius uses a voltage regulator (like everything else) that lowers the amps/charge when the battery hits full charge. Might be able to "overcharge" a battery, but something else that was wrong would have to be present.

How would it end up costing "MANY" dollars?

 

If you aren't paying close enough attention and get the connections crossed during installation.
Or you short the + side to "ground".

 

Whoops, just noticed this a Gen 1

 

I have replaced the 12v battery with a small lawn mower battery (there are only 2 due to one config is pos on left...other is pos on right) Cost $30 incl core dep and will last anywhere from 9 months to a couple years depending on when you buy battery at Walmart...Spring is best because stock is fresh...fall /winter is bad as stock is old. Works like a charm...never smell any hydrogen in trunk area. second battery for me in 26 months, just now getting a bit weak. (PS will studder and PS alert may be thrown is voltage starts sagging)

 

Hydrogen has NO odor.

 

Most AGM batteries don't vent. A properly sized AGM motorcycle battery would be sufficient. The only problem is that the spec. for
Prius batteries is a deep cycle. The Optima is one such battery. At EricBecky's suggestion I'm using a UPS Computer battery and after about a year, it's still working just fine.

 

If your 12v battery fails, the replacement is type 51R - that's the closest mechanical size (a bit too tall), correct terminal location, but requires new terminals. "Modern" batteries have larger diameter terminals than the original Toyota battery. Preferred is an AGM design (like the original Toyota battery). Be prepared to replace the ground wire and the +12v connection. That's an extra $10 in parts. Yes, lawn tractor batteries will let you limp around for a while, but you really want to get a proper fit replacement for capacity.

 

Tried a lower cost option in our 2001. Harbor Freight has a deep cycle battery for solar applications, 35Ah, smaller than the original in all directions, less than $75 (before 20% discount), but with flag connectors instead of round posts and with the positive and negative reversed (12 Volt, 35 Amp Hour Sealed Lead Acid Battery). For less than $10, NAPA has flag to post adapters (https://www.napaonline.com/en/p/NW_728219?cid=paidsearch_shopping_dcoe_google&gclid=Cj0KCQjw3s_4BRDPARIsAJsyoLPZHeycTPkiZnZySA47HlNJbXTk7LkkZ9hboHQof7T0nBaZiQ_fFtAaArOwEALw_wcB) which only needed slight trimming to convert the HF battery to standard posts. We put the battery in backwards (posts to the outside of the vehicle) and both the positive and negative connections were long enough to reach with no issues.We used the styrofoam block from the packaging to fill the space between the factory hold down and the battery top. We will see how this works. Definitely better than the old battery which worked only if we drove the car at least daily. We plan to replace the styrofoam with a more permanent spacer, probably something built out of ABS plumbing pieces.

 

This set-up should work fine. However, those terminal adapters from NAPA are severely overpriced. I bought a pair from Tractor Supply awhile back for well under $10. Let us know how that battery holds up. From the description, it looks real good---sealed, AGM, and enough capacity to boot the hybrid system, which is all this battery does in a Prius.