Backing way up in this thread, I believe one of the things that prompted everything was that the 12V battery went "dead" while using a tire inflator. Is that correct? Was your Prius in ready mode while you were using the inflator, or just "ignition on"? (power button x2 without the brake). When in ready mode, the HV battery supplies power to the DC-DC converter, which provides about 14.0V at up to 100amps to run all the low voltage systems and charge the 12V battery. The HV battery will eventually get down to 1 bar on the MFD, and the ICE will run just enough to charge it a bar or so via MG1. In ignition on mode, the 12V battery supplies all power for everything (such as inflators). The 12V in a Gen2 is pretty tiny (some had only a 35Ahr unit) and will discharge fairly quickly in such use - even if it is fully charged. Posted via the PriusChat mobile app.
correct, that was the first time it died. this happened several months ago, so not sure which mode i was in.
it just came to my attention that this is a AGM battery. i had no idea what an AGM battery was, and charged it will my 10 amp noco genius charger in normal 12v mode. after some reading, i see this "could" be a problem. my understanding, you can charge a AGM battery safely with standard charging, but it's not advised, or guaranteed to not cause problems. whether you have problems or not depends on how much voltage the charger pumps in to the battery, and if the charger has multiple charging phases. the most important being a slow charge for the final 20% of the battery. i know this charger does have multiple charging phases, and better than your average sensors to prevent over heating and over charging. so, maybe, after a few years of not driving very often, the battery slowly lost charge and was barely hanging on. when i hooked up the tire inflator, that was the nail in the coffin. then i charged it improperly, and didn't have the cables tight, and all of the above reduced it's ability to hold a charge, and it died again a few months later. maybe. can i test this? even though autozone tested this battery and it passed, maybe it passed because it was freshly charged but it won't hold that charge for very long? maybe i can test it myself with the multi meter over days or weeks to see how quickly the voltage is dropping to guesstimate the health of the battery?
What specific model do you have? For a one-off, I wouldn't worry and I doubt you would have damaged it by doing that. You are more likely to have long-term damage if there was a long period of time between when you drained it with the tire pump and when you charged the battery back up. Actually, the voltage is not as much of a thing as it is the current. The thing to remember is that even though it might say that it is capable of charging at 10 A, that is a maximum and the charger will vary both the voltage (usually between 14.4 V and 13.2 V) and the current depending on the stage that is it charging. The owner manual should have a description of how your charger works. As above, the programming of the charger will protect the battery from being damaged. Without a doubt. Charge the battery up fully then let it sit. Take readings at the battery with your multimeter set to Volts (20 V DC setting) and record the voltage over several days. You would hope to see the battery drop by 0.xx V over the first few days, then hopefully it will plateau out and barely drop any voltage over several days. This all relies on you not using the car at all. For good measure, you should ideally disconnect the negative clamp for the entire time you're monitoring the battery voltage.
GENIUS10. not a one off at this point. it's been charged twice like this from completely dead. the first time it was a few days before it was charged. the second time is undetermined as i just got in the car and it was dead. it could have been dead a few days, or 2 weeks before i noticed. i see this is the manual - 14.5V | 10A. i'm not sure if this is what you want though so i attached the manual. i read 15v is the point where you should worry with AGM.
It's another one of those time will tell situations. Yes, but those are maximums and I'm sure the charger is not charging all the time at either that voltage or amperage. Thanks for attaching the user manual for your Noco Genius10. It didn't detail what it does at the different stages it goes through like I was expecting, so, oh well. An interesting thing though is the 12 V Supply function; Converts the charger to a DC power supply for powering any 12VDC device, like a tire inflator, oil changer, or as a memory retainer when replacing a battery. When selected, a red LED will illuminate. 13.6V @ 25°C | 10A | Max 12A
It seems some fundamental electrical and multimeter training is in order before risking burns due to incorrect use of an unfused meter connection on a high amp agm battery. From the manual of that meter:
Yes, it won't do any harm and then you're starting from a known reference base. No, you need to move the red lead to the red V/Ω/Hz plug as per PTS's table (second line) in post #68.
Wow! Sometimes it pays to take it to a pro. Repeated non use for three weeks or the equivalent is bad for the battery. Often the cheap electronic load testers are inaccurate Smoking gun. Was this fixed? How long was this going on using your current battery? Answer to latest question previously answered. Dangerous multimeter user. Need to get a better car and a girlfriend. Results influenced by this? He does not know what he doesn’t know.
Hmm, that's down a bit, but not totally awful. If you can do a couple more day's worth of voltage readings and then post them here. It will be interesting to see how it holds up.
Meaningless after charging. Let it sit for three days without charging and read. My bet is the 12v battery is weak and incapable of the normal three weeks of low 20 ma draw.
did a bit of reading, even at 12.35 it's still holding 70% charge. to be expected with a 4-5 year old battery. probably fine for normal drivers, but maybe not for me. i called 2 places to find out what battery i need, both of them told me we can't help you. did some google searching, i mostly hear about 2, the AC delco and optima yellow top. i hear mixed things about the yellow top, it's a good battery, and it's over priced and won't last any longer than most other batteries. i have the AC delco, apparently people consider this a cheap battery. surprising, since it's lasted 4-5 years with my usage. i will keep calling around, but figured i will also ask you guys. what battery do you guys recommend?
I have had good experiences with replacement 12V from Toyota, or made by East Penn manufacturing - sold by Deka, Napa (AGM), Duracell (AGM) and others. Posted via the PriusChat mobile app.
The general model is S46B24R and most aftermarket replacements use all or most of that in their compatible batteries.
The voltage readings you’re getting, directly after charging, are very low, indicative of a battery on the way out. Attached is a reading taken of our near eight year old 12 volt, the morning after a good drive, no external charging though. We’re driving around 3k kms yearly (very little), and the car spends the majority of its downtime connected to a CTEK 4.3 charger.
