Prius Aux battery dead?

the battery is just a different size, you can use it, but would have to adapt the holder if permanent.
easiest is to put 12v to the jump point under the hood and pop the hatch.
otherwise, crawl in back and use the emergency release.

 

Do you own a voltmeter? If so, check the voltage at the jump point, or better yet, right on the battery. We are all assuming the battery is toast and that you would see 11V or something bad like that, but it could be something else entirely, like a bad short somewhere.

 

i haven't tried it. probably not hard, depending on skill level.
you could fabricate something, or buy the tray and hold down bracket for the smaller battery. but be aware that sks will drain it more quickly than the jarger battery. that's why sks gets the big one.

 

I can't imagine you would need to adapt anything to swap the smaller (S34B20R) battery in for the larger (S46B24R) one.

It is the same height (202 mm) and width (128 mm), just a little shorter across the length (197 mm vs 238 mm), IIRC.

 

There should be a date code on it. If the car sat for a long period of time without the battery being detached then the 25 mA or so the car draws when off could easily have run it down far enough to damage it.

 

If you have another battery just put it in and see if the car starts. Just please make sure the "-" terminal on the battery goes to ground, the wire that is bolted to the body. Cold weather and age kill these but because all they do is power the computer they last a long time.

 

the oem has a date code on the top. did it have a brand name?

 

An AGM battery with the same form factor as the OEM can be had at Walmart. The parts stores sell them too, but for more than the Walmart one.

EverStart Platinum AGM Automotive Battery, Group Size S46B24R 12 Volt, 410 CCA - Walmart.com

 

i can't remember what brand my 04 and 08 had. Yuasa, i think.

 

Keep an eye on the voltage on the new battery. If it falls more than around .04 volts per day when not in use there might be a parasitic draw. It is best to do a test like that by leaving the hood unlatched and testing at the jump point. If any door is opened it will drag down the voltage for a while and make a mess of the test. This test assumes sane temperatures, like say 50F and fairly constant. If the temperature fluctuates wildly where you are so will the resting voltage. Another test which has been mentioned here is to see what the voltage is at the outlet in the cabin (the one under the glove box) once the car has been on for at least 30 seconds. The 12V battery in our 2007 has pretty low capacity and it starts at like 14.50 and falls quickly to 14.10. A new battery should read 13.something. (Not sure what "something" is, never tried this on a new battery.) I keep a voltmeter/USB adapter plugged in all the time now, so it will be easy to tell when this battery gets even worse. These won't tell the resting voltage though, since the outlet is only live when the car is on. For an example device, go to Amazon and enter B01N00I4TM. The advantage of one of these devices over a voltmeter is that there is no chance of shorting the two leads when making the measurement. (Assuming the device itself doesn't short internally.)

 

Understood.

You should still keep an eye on the 12V voltage for a while. Since the car is new to you you wouldn't know yet if it has a large parasitic draw, and those will kill a Prius 12V in no time. Silly way to lose a brand new 12V.

If you had a DC clamp ammeter this could be ruled out pretty quickly. Just open the hatch, stick a carabiner into the latch slot to make the car think it is closed (or the car will draw 500 mA from the 12V), wait 15 minutes or so for all the computers to shut off, then measure the current on the ground wire at the battery. It should be 25mA or so. Press the button on the hatch to release the carabiner.

With a regular DC ammeter it is slightly more complicated. Unhook the ground from the battery. Use something like a jumper cable to connect the battery post to that ground cable, or to bare metal on the chassis. In parallel, place a DC ammeter between the negative post and the ground wire. After the 15 minute wait detach the jumper. Then the ammeter will see the 25 mA or however much is present. The current spikes can be pretty high in the period after the car "turns off", and those may be enough to burn out an in line ammeter, so instead the current is shunted around it with the extra cable. If the ammeter has ranges start it at the largest one (likely 2A) and then shift down until an accurate measurement can be made.

DO NOT CLOSE THE HATCH WITH THE CARABINER IN THE SLOT!!!!!!