Electrical Problems?

welcome!
start with the 12v, it's cheap and easy. if that proves good, look at the multi info display threads here, you may need a replacement.
all the best!

 

11.8 is bad, but if you'd rather move on, call auto be yours for a repaired mid. there's a you tube video on replacing it.

 

Combo meter is bad. Very common. Use SEARCH FORUMS button on top of page and put in the phrase Combo Meter as your search and search the G2 forum and you’ll get hundreds of hits.
A few posters offer repair services to repair it,

 

Good advice to start with the 12 V. You need a good and reliable 12 V supply. Agree also, it is easy. However, disagree it is cheap.

That photo does not have enough information to judge whether the battery is bad. At best it is flat and needs to be charged up fully. Best is to use a fully automatic multi-stage auto battery charger with an AGM setting. Max Charge current should be 4 Amps.

Ironically, it seems that a good, strong, 12 V power supply somehow exacerbates the failed MFD, in some situations. Seen a lot of posts here, where the poster comments that the issue with the MFD only started when they replaced the 12 V battery. Whether that is a true co-relation, or just that the poster noticed it then, is not clear.

While I think AutoBeYours is a good choice, Matt @Texas Hybrid Batteries also offers a good swap service where he supplies a repaired combination meter in exchange for your old failed meter plus some cash, about $110, I believe.

 

yeah, relatively cheap compared to some other prius repairs, but expensive compared to most car batteries.
i just have a hard time with the '12v is fine, what else could it be' responses we get sometimes, and then the following silence when more info is requested.

 

Yes Bisco and the constant "it needs to be put on a charger " as if that's going to fix it. Its been in the car the car is charging it if that's not enough to keep it at least in the 12.5 range an auxiliary outboard charge will not fix it. It may prop it up enough to get down the road a little but next morning its dead again.

Why is it so perplexing that the battery cannot hold a proper charge?

 

11.8v on the display could actually mean the battery is at 12.3v without the load. I would not think the 12v is an issue at this time. Charge it up to get it full but it shouldn't be causing any problems

 

It depends on how the car is driven for one thing. The Prius charging system seems to be nothing more than a trickle charger, and if the battery gets low, it may never get properly charged, if the car is only driven short distances interspersed with sitting for a couple of days or three. We just don't know. Further, putting it on the charger is not a fix, merely the first step in diagnosing whether the battery can hold a charge. Trouble is, not many come back with the results to go on to the next step.

When we do get feedback, most of the time that is not the case. Sometimes charging might be a good bandaid to get someone by until the battery is replaced. Not everyone has immediate cash to drop 300 on a battery.

The problem is, you do not know that it cannot hold a charge until you try a few things.

Sure, for crystal ball gazers, it is easy, for the rest of us, not so much.

 

So far, the only post I've seen by someone actually measuring charging current was back in August 2014 by AHetaFan, who reported some pretty substantial 60 to 70 amp trickling going on there (early in the charge, of a well-discharged battery). It's one report; I don't know of anyone else posting a similar exploration.

-Chap

 

The test was on a Gen 3 which is why I had not seen that, but maybe a useful benchmark.

Looks like I could replicate that for a Gen 2. My comment about the being a trickle charger is from personal observation of voltages as I drive. This has been over a 3+ year period. Of course the tells me nothing about the current, but am surprised that they might be as high as 60 to 70 Amps. Curiosity has been piqued.

 

Prius 12V battery charging is designed for sealed battery. The idea is to charge the battery with lowest possible current (and voltage) to still keep it full or even just almost full. That way the 12V battery should have longer life especially in hot climates. So to test the charging system output you need almost empty battery or better would be to use a something like carbon pile load tester.

Unfortunately these smart charging systems on almost all makes and models (regular non-hybrid cars) seem to have problems of just not charging the battery enough in some conditions.

 

The Prius maintains the 12V bus at around 13.8V, the battery will take whatever current it wants given that voltage. I could understand charging current of 60A if the battery has a shorted cell and is therefore dead anyway.

If the battery is in decent shape I would say that the car is acting mostly as a trickle charger. A discharged battery could easily take 12 hours or more to become fully-charged given a charging voltage of 13.8V.

The OP driving 1 mile round trip to work, and a total of 40 miles a week is really not enough usage to keep the 12V battery fully charged. Note the Prius is charging the battery whenever the vehicle is READY, so it is not necessary to actually drive the car, but it needs to be READY for an extended period (like overnight). I suggest the OP get a battery charger if he does not want to leave the car READY sitting on his driveway for such a long period of time unattended.

Cruise control: it could be that the switch has failed or the clockspring cable in the steering wheel hub needs to be replaced.

Combination meter display (the speedometer, fuel gauge, gear selector, and warning lights display): it is a known issue that the meter will fail due to electrolytic capacitors drying out. The combination meter can be repaired or else you can buy a used unit, however the odometer reading will be whatever the used unit has in its memory. If you disconnect 12V battery power, then reconnect, the combination meter may resume operation for a while.

 

Battery charging voltage does go up to 14.2V sometimes. But it would be better if it got even higher in cold temperatures (or even stayed at that 14.2V) as that would charge the battery faster. Now the system tends to keep the battery partially discharged in the winter as the cold battery just doesn’t accept charge with those low charging voltages.

 

My Gen 1 seemed to regulate to a steady 13.8. My Gen 3 seems to choose among more than one voltage, sometimes above 14. (Gen 3 also has a temperature sensor on the bracket above the battery, which Gen 1 did not. OTOH, Gen 3 has done away with the remote voltage sense return to the converter. Or rather, the converter still has that input, but in Gen 3 it is just tied right to the bus in the engine room junction block about six inches from the converter, so, not very "remote" any more.)

Honestly, the post by AHetaFan is the first one I've seen reporting actual current measurements in any generation. I don't think it would be bad to have more. I wouldn't be too surprised if even 13.8 could drive a fair bit of current into a battery, briefly, even one that's not shorted but merely well discharged. I, however, am not an ammeter.

Gen 4 is the first to actually have a current sensor located at the battery.

-Chap

 

Time for a new 12 V battery, methinks. Not that complicated. Haha.