12V battery charging

MFD always reads a good fraction of a volt lower than at the battery, or even at the DLC3 port. It's a measurement made internally at the MFD, reflecting voltage drops in the circuit feeding it and internally. The 0.44 volt difference you're seeing is actually a bit smaller than the .6 or .7 I'm used to seeing. Depends in part on what other stuff is on in the car. Doesn't indicate any problem.

 

A battery that's persistently around that level, probably just replace. How old is it; I forget if you mentioned?

The best diagnosis would be an electronic load tester, testing CCA and making an assessment. In lieu of that, persistent low voltage, and getting on in years (say over 3~4 years), just replace.

 

Yeah, research chargers, smart charger around 3.5 amp rating max. And better avoid ACC.

 

The CCA sounds good.

 

Check again in a day or two, to avoid falsely high reading due to surface charge (due to charging). Preferably with digital multimeter, with car off, not car display.

All that said, that reading fresh after charging seems very low.

 

After charging you can run the high beams for 30 secs. This is another way to get rid of surface charge. Then measure voltage at the terminals with a V/multimeter.

moto g(7) power ?

 

Not wrong but totally unnecessary to disconnect anything.

I don't see a "done" light on your charger. 50 minutes might not be nearly long enough.......and 13.1 is not a high enough "float" voltage. It should be at least 13.4.

And your conclusion that the battery did not charge fully might not be right.
And old, weak, worn out battery will often "self discharge" at a rapid rate.

Your reading of 12.4 after charging and sitting overnight with no load.......indicates that your battery is right on the verge of total failure, if it really was charged as much as possible to start with.

 

If the OPs conventional lead acid battery has a 'resting voltage' of 12.4, that wouldn't indicated it being on the verge of total failure.

The battery is between 50%-75%, depending on temperature and the voltage meter being used, and assuming a 'resting' state.

 

IF you have an AGM (sealed) battery, then 12.4 is more like 55%.
Either way, it is low.

 

With automotive size batteries, "lead acid" and "sealed" usually mean two DIFFERENT types.
If it really is sealed, then it likely is AGM, which uses similar chemical technology but in an entirely different way.

 

I KNOW about batteries.

Ones marked "Maintenance free" are usually not really sealed completely.
They are mostly conventional lead acid with a slightly different chemistry.

What it "means to you" isn't necessarily the truth.

I'm pretty sure that the "old" hybrids all had AGM batteries but someone could have replaced it with a "maintenance free" conventional.

You are clouding the issue.......which IS that 12.4 is low, regardless of what type it is.