parasitic draw testing

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.

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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.

 

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.

 

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.

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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.