12 volt battery charge rate on vehicle

[Hibird]

Does anybody have a chart/graph or even self measured data that shows the actual charging amps that the system puts into the 12v Battery plotted against Battery state of charge.

I have looked far and wide for such information and have drawn a blank I guess toyota would not publish such details but I am sure someone somewhere has recorded it.

The reason I am interested is that while doing a 30 min in Ready mode thing today I got distracted and it turned into a 2 hour marathon and the Battery now has more volts than I could dream of 12.75 volts 2 hours after shutdown .... amazing.

So I am intrested to get to the bottom of how long it really takes to keep it fully charged.

I of course realize there are many factors involved but the vehicle is used daily and I have never seen such a high voltage. I monitor that voltage with a bluetooth voltage logger so am very familiar with how that voltage behaves.

Look forward to your thoughts.

 

[flash22]

It depends on many factors, the DC to DC convertor is intelligent, Its an AGM Battery so has deep cycle characteristics, it charges at low current, slowly,  and typically .4 - 1v higher than a lead acid

I don't have any info on the MK4 charging system i can see what i have for the mk3

[Hibird]

Thanks for your input, I have never seen the AGM on my Yaris charge at anything close to 14.7 volts it always around the 14.1 - 14.2 volt mark even after sitting unused or a couple of days. I do wonder if the Battery is ever fully charge by the vehicle system but that may be the design intent.

If charged by an external Battery charger I can get around the same voltages that I achieved after that 2 hour Ready mode run.

The Battery charger used terminated the Bulk phase at 14.5v quite a bit higher than the 14.2v volt from the vehicle sytem and more in line of what an AGM battery needs to achieve a full charge.

All food for thouight

[flash22]

Voltages are taken at the Battery terminal under test conditions, so you will get some variation in voltage due to cable length, termination and loading, as the current rises you get a slight voltage drop if tested in car

it also depends on the test equipment used and how they are calibrated

Bulk phase can spike at up to 16v depending on the level of charge in the Battery

[Hibird]

I am happy with my measurements being good. I have checked the bluetooth logger against a calibrated fluke 189 meter at the point of measurement and Battery terminals and it all ties up.

I have never seen nothing approaching 16 volt even from a more than partially depleted Battery. I am still hoping that someone has a rate of charge V's Battery voltage (SOC). As I still feel the vehicle could do better in keeping the battery in shape but maybe thats the way it is or perhaps it's just my vehicle. 

I will only have the vehicle for another couple of weeks but am still interested to fully understand the system.