Gen 4 Aux Battery in Short Supply

Oh yeah, also, the correct size appears to be 140R, though ALL the on-line databases show no aftermarket battery available for the Gen-4 Prius. The 140R is an exact dimensional match to the battery that came in my Gen-4, it even has those cutout recesses on the top where the two terminals sit. Electrically, the numbers for the few 140R examples are very close to those on the battery that came in my car. No clue why the 140R doesn't "link" to the Gen-4 in the parts databases.

 

Humm, another Gen4 (or PRIME) 12v battery short life span thread. I really should watch out for my 12v. If it fails outside of the warrenty, I will definitely go with aftermarket one. There seems to be problem with OEM batteries in all Gen4 and PRIME.

 

i hope it's the batteries, and not the charging system

 

If the charging system is a culprit, then aftermarket battery will also experience early demise. I wonder if there has been any report of dead aftermarket battery with Gen4/PRIME?

 

Not necessarily -- there's hope if it's the charging system. The Odyssey batteries and the Optima (Yellow and Blue Top models only) are specifically designed as "deep cycle" batteries, intended to withstand being heavily discharged, over and over again. Normal lead-acid standard car batteries are designed to provide a burst of cranking power, but are notoriously intolerant of even a few deep discharges -- which usually kill them in short order. The deep cycling type can deeply discharge again and again. The trade-off, usually, is less cold cranking "burst" power, but that's irrelevant for our cars -- and the Odyssey I've been looking provides about 100 more CCA than the same-size wet cells. Go figure.

 

12v battery is my only concern about the car at this point. Mainly because when I went to go test drive it, the 12v was too low to power up the car and emitted a buzzer sound. That was the only time, in my ownership, the 12v had to be boosted with a power pack so that the car can start. I'll use a multi-meter sometime later today, after running errands, to see what the battery voltage is at.

 

mine did...

 

I have a 2016 number 2 and replaced the battery after 3 years. It was 300.00 at the dealer. I tried to have my local mechanic change it. He was not able to get the battery.


Posted via the PriusChat mobile app.

 

I would suspect the SG of being reasonably accurate, though with the caveat that it should probably be calibrated with a proper VOM. What can introduce error into the reading, is other devices on the same circuit as the OBD port. That being said, activating the SG while the Prius is off (and with dome lights off), one should get a reasonably close reading. (The voltage is read by the SG even if no connection to the computer can be made on the OBD port, the SG can be activated at any time with the Prius off by pressing the red-circled button)

 

As to the mentions of the charging system, I will note my observations of the charging system. I run a ScanGauge, and on startup the voltage usually goes to 14.0-14.4V, (typical charging voltage for 12V systems, for those unfamiliar), but after extended driving I will notice that sometimes the voltage will be in the 12.5V range, and I'm not sure if this is an issue with the inverter, or if it's by design for longevity purposes.

As for myself, I've not had a problem with my battery, in spite of occasionally leaving my CB radio on overnight, (seems to draw about 7w idle, by my testing) though I do drive quite a few miles on a daily basis.

If I had to switch the battery out, though, I'd probably replace it with one of the lithium units made for motorcycles. Far too much discussion going on here about getting the "correct" or very close battery, and not nearly enough discussion about the pros and cons of using velcro to secure a smaller battery. The Prius 12V battery doesn't need to crank the motor over, it only needs to trip a few relays and start a computer or 30. Try not to overthink things too much.

 

i’ve noticed after few minutes of driving, the alternator voltage goes from about 13.8v to 12.1v about. indicating that the car stops charging the 12v battery. but when P or N is engaged instead of D, the battery voltage goes back to 13.8v

 

It's doing a lot more than that - yes, it doesn't crank, but there is the power steering, all the lights, wipers, blower motor, electric A/C compressor, door locks and windows, defoggers and ignition as well.

Have you watched this - he gives an idea of the loadings in the 2nd ½ of the video.

Personally, I'd be dubious of a Lithium. The battery as well as charging characteristics are quite different from a Wet Lead Acid which the system is designed for. How TOYOTA's battery sensors (temperature sensor, internal resistance and current sensors etc) will cope with a Lithium battery, I don't know. Those 7 sensors send results to the Hybrid ECU - which could well throw up her "hands" in horror.

 

Those aren't all going to hit at once, nor are all of them even run from the 12V. The power steering I will admit ignorance to, but I would suspect needs more than could reasonably be provided on 12V, so I suspect it's on the HV circuit, the lights, 20A would be a stretch as most are LED, the wipers might be still activated if one forgets to turn them off, so let's guess 20A for those, blower motor is delayed, so it won't start before the inverter energizes, the A/C compressor is for sure run off the HV as it definitely draws way too much for the 12V circuit, the door locks and windows don't really need to be running in the 2-3 second startup procedure, the defogger I would expect to be delayed, and I'm not sure what the ignition is? All of that a traditional battery needs to contend with, PLUS drive several hundred amps into a starter motor, in a traditional car.

It seems like you meant to link something, but forgot to do so, or the forum may have ate the link.

Also, I would tend to doubt that the car has that many (or any, aside from simple voltage) sensors for the 12V. The traction battery, yes, it has a gang of sensors, but the 12V, not so much. As for the 12V lithium batteries, they are generally designed with their own BMS's to mimic the behavior of a LA/SLA 12V battery, so as to be drop in compatible for charging systems designed for traditional batteries. I was initially dubious of lithium batteries in a constantly-charging/rarely discharging application as well, but reading the reports of early adopters on motorcycle forums, I've been disabused of that concern. It seems like they sorted out the BMS properly.

That being said, I'm willing to be proved wrong, either through personal experience or vicarious. I do wish I had my motorcycle around still, so I could just pop that battery in. Maybe I'll dig the (even smaller) battery out of my UPS...

 

You're right - the A/C compressor itself is at Hybrid battery voltage, just the blower fan etc.

Lots of sensors though:

 

At 70K miles i haven't had to replace mine but i like to keep a bookmark of commonly replaced items for my cars for when they do die or need replacing. The AutoCraft below claims an "Exact Fit" for the 2016 Prius. Anyone tried this one?

https://shop.advanceautoparts.com/p/autocraft-gold-battery-group-size-h4-480-cca-h4/11348065-P

 

Yeah, H4 is the same as 140R, or really close. I would go with the Napa though.

 

I guess the next time someones dies they can try one of these and get us a solid answer on whether it works. On another note, it looks like the Napa only has an 18 month warranty compared to 36 on the AutoCraft, and with coupon the Autocraft is like 110 bucks. Thanks for the other option, ive bookmarked both.

 

I posted the following in another thread a couple of days ago:

I've been monitoring my 12v aux battery since my 2016 was new, purchased on 5/31/16. I've noticed that unlike cars with conventional alternator charging, my 12v battery only reads in the range of 12.4 vdc—12.8 vdc when checked immediately after driving. I understand that the 12v battery is charged/maintained via a converter, which I assume is a step-down transformer supplied by the drive battery. My Prius has less than 7000 miles since new, the car is always garaged in southern CA with very moderate weather extremes and since the car is not driven regularly I've had a battery maintainer on it since new. It appears that the specific gravity of the electrolyte is a mite low under the circumstances. Also, my maintainer keeps the battery float voltage at 13.2 vdc and when I put a conventional ferroresonant automotive battery charger on it the voltage almost immediately goes to over 15 vdc with less than 1 amp of output current. I've had a wide range of experience with battery systems of all manner, both personally and professionally and this behavior is something that I've rarely ran into.....
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Since that post I've done some additional testing. After a full charge at 14.4 volts for several hours, I let the battery sit overnight. The voltage dropped down to 12.8 volts, which would be normal for any 12 volt battery in good condition. When I turn on the headlights with the ignition off the voltage drops within a minute to 11.8 volts, which I would say indicates that the battery is indeed bad. I'm convinced that the problem with premature failure lies with the battery and not the charging system. This conclusion is based on my close monitoring of the battery since new and keeping it properly maintained. That coupled with the amount of use the battery has had with less than 7000 miles and the number of failures being reported, I'd say that Toyota had a bad batch of batteries they had manufactured and used in the 4th Gen's. Since I'm still under warranty, I will have the dealer replace the battery rather than possibly upgrading to a different more reliable battery. BTW, all of the dealers in the San Diego county area say that the battery is back-ordered. This fact alone tells me that there is an inherent problem with these batteries.

In another thread, I read that there are some hoops to jump through after removing 12 vdc from the system. Anyone have any experience with this? If this is indeed the case and if I were replacing the battery myself, I believe I'd go to the trouble of keeping 12 volt supplied to the car while swapping out the battery.

 

Just have to reinitialize a few systems:

- roll windows up and down
- open and close gas flap
- drive in a straight line for a short amount of time

Nothing too daunting.

 

Thanks for that info, any problem with the odometer readings resetting (trip A, trip B & overall)? I've noticed on 2 random occasions that my overall mpg reading (since new) has spontaneously reset and started over. This first happened when the car was about 18 months old and had around 4500 miles and then again recently @ 33 months with 6800 total miles.