HELP - 12v battery on backorder

I've read someplace that there's a mechanical valve in the filler neck. Your low voltage battery my be preventing it from opening all the way; resulting in slow fill ups. I believe it's part of the emissions control system. Once you get the battery issue sorted; the problem will probably go away.

 

12.3 volts, directly after charging, is very low. A healthy battery would read around 12.8, or higher.

 

I noticed that if I charged the battery connected to the car, voltage was low. When I charged it not hooked up to the car, the end voltage was 13+. I would not base a decision on the health of a battery solely on charging the battery while in the car. Remove the negative battery terminal and then fully charge the battery.

 

It's actually almost 12.7 *directly* after charging. It takes 30-60 minutes before it settles around 12.35 volts. When I use the car, once I'm done the battery is around 11.95 volts when I shut it off but it recovers somewhat to over 12.3 within a few minutes.

Still not a "good" battery by any stretch, but not totally dead. I'm going to install the new one this weekend anyway.

 

That is commonly called "surface charge" and is indicative of NOTHING useful.

 

Yes, but my point is you can't fully charge the battery while it is connected to the car because of parasitic drains. You can charge it enough to start the car though.

 

And your "point" is absolutely wrong.

IF you have a charger that won't fully charge with a "normal" parasitic drain, then you need a different charger.
Or you need to find out why you have an EXCESSIVE amount of drain.

 

BS. Even Toyota says to disconnect the neg. lead. I charged the battery in my Prius and Tacoma while in the vehicle, and the batteries were not fully charged. I doubt a CTEK MUS 4.3 is a not a good battery charger either.

You got any proof to back up your statement?

 

I think that's mostly covering their butt, just in case. I too doubt there's any difference, charging while the battery's in the car and connected, or not.

Due to our low usage, I've got a CTEK 4.3 pretty much permanently connected, with the quick-connect wiring installed, for convenience. Never bother to check voltage directly after charging, but I recall seeing high 12's, directly after charging.

 

I almost always charge the 12v battery in a vehicle without disconnecting. I had no problem charging my PP (2020 model) newish (less than a year old) 12v battery fully to above 13v fresh off the charger. After the charger is disconnected, the battery stays ~12.8v for a week or so and slowly discharge if not driven frequently enough. Eventually, it will discharge down to 12.4v, but never below 12.0v if the car is driven at least ~1hr every 2 weeks.

You should read this long thread on the drain of the 12v battery on PP.

12v Battery Is Discharging, Re-Charge Now ! | PriusChat

It is true that there is some amount of parasitic drain on PP by just parking the car for a long time, but if the car is driven regularly, then the new battery should hold the charge above 12.4v at least for a few weeks without doing anything. It becomes a problem for the older (I think more than 3 years old) that has not been maintained or have been parked for a long time (longer than two weeks) or drained due to use of accessories or leaving lights on or by having the charging cord plugged in while parked for a long time.

Here is a 12v battery voltage reading before, during, and after charging. As you can see, almost 24 hours after charging, the resting voltage remains high at ~2.8v.

 

If your battery drops the charge down to 12.3v that quickly, then it is getting old. My thinking is that it will still last a few more years since you really don't need much above 12.0v to start the car, but the new (less than a year old) battery does hold the charging bit higher and a bit longer as I have shown on the graph above for my 2020 PP when it was less than 6 months old but mostly sitting on our driveway not driven.

 

What charger are you using?

I just measured 12.56v on my new battery with my Solar battery tester about 10 minutes after taking it for a drive. How is your battery staying at 12.8v? What are you measuring voltage with and are you sure it's accurate?

 

I use a 12V/5A Victron charger now, but before upgrading to it, I was using a cheap no-name 12V/6V battery 4A Chinese brand charger called Suaoki. It is currently not available at Amazon. I am not surprised if the company no longer exists now. I paid ~$35 which is less than half the price of Victron charger. Did not have a problem with it, but I wanted something better. I especially like having BlueTooth connectivity of Victron so that I can check the charge in progress on my phone app without going outside. But both chargers worked exactly the same.

 

Well, yeah, it's almost 3.5 years old and original equipment. These shipped with notoriously weak batteries anyway. I just finished swapping batteries. The new one is solid at almost 12.7 volts. The old one was holding 12.38 when I pulled it out. I may try some reconditioning experiments on it before returning it as "core" to get my $25 back. Just to learn some things (safely, of course). Now that it's out of the car I'm running "repair mode" on it just to see what happens. Once an engineer, always -- gotta tinker....

I'm pretty sure I could have gotten more out of the old one, but these batteries are hard to find now, especially around here, so I grabbed the last one I could find. And I don't feel like taking a chance on it. Its resting voltage isn't dangerously low but it runs down quickly.

 

This hasn't been my experience with 2 PPs now. Both batteries show around ~12.0V after surface charge is bled off. In my 2018 I drove it 80+ miles every single weekday and the battery was often under 12V even within a month of buying it. My 2021 has nearly identical battery behavior. I am reluctant to chalk it up to coincidence, especially given that my 2012 PiP still has the original 12V battery with no signs of trouble 9 years later.

 

When you turn it in for the core charge, see if they can test it. Check the voltage on the new one after it's been in the car for a week, just for grins. I doubt it will still be at 12.7v. In my experience, the PP undercharges the battery.

 

Perhaps. I can easily test that myself, though. It's feeling like it may be important to make a point to maintenance charge it at least every few weeks.

 

Have you checked it with different multimeters? I have used at least 5 different multimeter/voltmeter/battery testers and found they can be off by 0.2v or more easily. My multimers were all very cheap ones, and I could not trust which one is giving me the correct voltage. The most expensive was the $20 Craftsman 82141 multimeter. I actually bought a 5.0000v voltage standard with +/- 0.01% accuracy and calibrated it.

But in the end, I bought a well-used but recently calibrated Fluke 87 multimeter with +/- 0.05% accuracy on eBay. If new, it has a $395 price tag, but I got it for a little over $100. I did not check the 12v battery on my 2017 PP. Never had any issue for the duration of my short ownership of 2.5 years. I checked my 2020 PP 12v battery from new to 10 months old on a daily basis. Although it got driven only once a week for ~1 hour, the 12v battery never got below 12.3v. I did maintain it by charging it once in a while, but I don't know if it was really necessary. I did not keep the car long enough to see what effect it had. I have not checked my current 2021 PP 12v battery. Maybe tomorrow morning, I will check it. It gets driven ~twice a week for about 1 hour each time. I will let you know what resting voltage it shows 6 months after the purchase.

 

What are the Ah and CCA ratings of your new battery? (Should be labeled on the battery).

 

I think CCA was 470, something like that. It's the Toyota TrueStart battery. But in reality, for a hybrid the CCA isn't really all that important. I don't see the AH on it.

I have my old battery on "repair mode" with my charger (Noco Genius 5). I'm going to take it off soon and let it rest overnight and see where we are with it, just for fun.