Auxiliary Battery Problems; Sometimes Dead sometimes auto restart

Is the ground wire from the battery to the car body loose?

 

batteries fail for all kinds of reasons, vibration, heat, ect... have the battery tested where you got it and if its bad they will prorate a replacement.. 11.6 volts is considered bad in a prius

 

could be the battery had a low charge when you installed it.

 

It should have recharged over 8-10 months of use. If there were a poor ground connection that could affect voltage readings, charging, & vehicle behavior.

 

depends on how it's driven.

 

get an oem at the dealer, check the voltage before installing. should be 13+.

how many miles a year do you drive? maybe you need a trickle charger.

 

all batteries have different warranties. i think the oem is 8 years, 2 full then prorated.
there's nothing wrong with optima if you get a good one. that's the key, to test it before installing, and buy from a place that will honor the warranty.
you can try different auto parts stores, and batteries plus bulbs.

'just not that far' is a big problem.

 

These voltages are not too terrible, the drop from 12.2 V to 11.4 V is reasonable, but, really, all they show is your battery is low and needs to be charged up. It is not so much the voltage itself, but whether the voltage holds steady at whatever load it is under, particularly the last one. Was it holding the voltage steady at 11.4, or was it dropping over time? If it was the former, try using a modern automatic battery charger with an AGM setting to charge it up. If it was the latter, then your battery is not in good shape and needs to be replaced.

This shows the DC/DC converter is working properly to charge the 12 V battery,

Your usage points to not enough driving to keep the 12 V battery fully charged, particularly the short daily drives. Investing in a good Schumacher, CTEK or Harbor Freight battery charger capable of a 4 Amp charge will be a good investment then charge your battery on a regular basis (fortnightly or monthly) to keep it in top shape.

Having said that, I do not believe that your 12 V battery is the reason for the symptoms you detailed in your OP. You may have a combination meter on the verge of failure. For some reason removing the 12 V from the system, as you would do changing the battery, seems to send them over the edge. Normally this happens closer to the time you change the battery, so YMMV.

I don't want to see you waste money on needless parts, or get distracted by a red herring that will not solve your original symptoms.

 

try brining it back to a local store that sells the same brand, in my area its Advanced Auto Parts.. the manager might work with you on any warranty left .. they did with me when mine died, it was in the car when I bought it and was only a year old..

 

Apart from this mention, you haven't stated any information about what lights are on, whether they stay on or, go on and off. So can you tell us about that? If you have lights on, you have trouble codes set. You need to scan the computer(s) and tell us what codes are set.

Unplugging those connectors removes 12 V power from the system. Doing this clears codes from some of the computers. Unfortunately for you, one code that behaves in the way you describing in your OP is one for a HV isolation fault, which can be a fault in either the HV battery, transaxle or A/C compressor. Getting the codes will confirm what is actually your problem.

 

if everything has power, it's not a fuse. more likely low voltage.

to clarify, prius does a pretty good job of painting the 12v, but it must be driven very couple days for an hour or so. but that's not scientific, just a guess.

it may be that you drive enough, but you need to start with a fully charged battery. prius does a poor job of charging up the 12v, and needs to be driven a lot for that to happen. before losing out the battery, get an inexpensive charger, then monitor it.
even if you buy a new battery, someone needs to check the voltage before installation.

 

No, it is not. It is a bit low, but a bad battery will quickly drop below 11 volts heading to 10 before long with the headlights on.

No; the HV battery has an 8 year flat warranty. The 12v battery is an expected replacement item with no warranty. Dealerships often charge way too much money for them and the factory ones don't last for squat. Mine died after 2 years and so did the factory replacement I got from the dealer. Got the optima one and it's been fine for 6 years, which is far longer than I've ever had a 12v battery last in the Florida heat.

The fact that it is intermittent suggests a bad connection. Try cleaning the connections with some sandpaper. Also the low voltage indicates you may not be driving it long enough to fully recharge it. Leave the car on for half an hour to charge it, then shut it down and check the voltage again and see if it is higher.

 

11.6 is extremely low for a 12 volt battery. Basicly dead. So low that it's probably throwing the big red exclamation point upon boot up. It only flashes once but it's not part of the bulb check routine so it's noticeable.
That's the only warning the car gives you. I saw it on mine when the oem battery died after 7 years.

It's really the only car that will never show you a resting charge level above 12.6.
Most cars and I Have owned a lot with a full size battery will have a resting voltage of 13.3 or around there. You will never see that in a Prius.
For whatever reason. Probably because it's so small. So with that issue if you add just Mostly small trips the battery will never see a good charge.
And it will eat battery's.

Dead 12 volt complaints is what made this site. There are thousands and thousands of posts about it.

Just replace it....it's bad. The oem is a superior battery to an optima as I have owned both bought new. It's more expensive.
My optima lasted 3 years and they gave me a new one. One day it just went 11.4 volts I saw the red exclamation point went oh no and out it came.
That was after many months if maintence charging.

Wish I had bought the factory stock battery.

 

i have been accused of puling the 12v card way too often.

 

No, no, no. A 12v battery is not considered fully discharged until 10-10.5 volts. When my two factory batteries died, the computer did not start complaining until 10.5 volts. It would still start up and the lights would only be on for a few seconds as long as it was over 10.0 volts.

A bad battery that needs replaced will quickly drop below 11 volts with the load of the headlights on. If it holds above 11, it just needs recharged. And virtually everyone on the forums agrees that the optima battery is far better than the factory one.