HV battery SOC wrong after flat 12v battery

[white-prius]

Can anyone explain the following?

I left the Prius in IG-ON for a few hours so I could use the radio while I was in the garage. (I was thinking the 12v battery would charge from the HV battery, but I now know I was wrong! The car needed to be in READY for this to happen.)

I walked away and when I came back the interior light was dim and the main display was blank. The scary thing was that it seemed the car was still in IG-ON - I could hear a quite hum which I assume was the HV battery fan. But there was not enough power to turn the car off! Lucily I had a batter charger, so I was able to charge the 12v battery from that allowing me to turn off the car...

Now the strage part: before the 12v went flat, the Hybrid battery SOC showed three bars. After recharging the 12v battery this had jumped up to 6 bars. Obviously the HV battery had not been recharged in this time since the engine won't run in IG-ON (if anything it would have gone down further) so this must be wrong.

I am assuming that the computer lost its memory and forgot how much charge was in the HV battery, and 6 bars is its default?

My question is - is this normal? Will the computer "recalibrate" or could it continue to overstate the charge level in the battery? Is there any risk it could allow the battery to run down lower than it should?

Is there any manual procedure required?

I asked my local Toyota dealer but the best I could get out of them was "it is normal for the hybrid battery to vary between 3 and 6 bars"!

Any information woud be greatly appreciated.

[Hupipoka]

Hi there,


Just arrived from the car dealer because my 12v battery went flat during the weekend. The explanation from the Garage was all but clear, according to them I have to many gadgets connected to my car.
Ok, I have a bluetooth car kit, a GPS a safety camera a DVD player and a reversing camera. This could be a little bit over the top, but a normal car can cope with this without the battery run flat in two months.


The True is that both pioneers in the Hybrid technologie Honda and Toyota can't perform miracles. If the car is running from electrics there is nothing going into the 12v battery and some of the “normal” electric components like lights, heating (not air cond) radio etc. running from it, will dry out the battery faster then the usual. There is no practical solution for this according to the manufacturers as the aim is to keep the engine working as less as possible.


The solution for this will be to top up your battery with a charger regularly. This will prevent the battery to go flat. As alternative, you can do as I have and order a solar charger. This requires some DIY work as you will have to connect the panel directly in to the battery (the option for the cigarrete lighter is not practical if you want a permanent solution). These panels use a recent technology and have reasonable sizes (394X127X20mm) and most of all can be fitted very easily.


Here is a link to one of the newest of these panels that cost around £30/$45. As they are protected there is no danger to discharge the battery during the night or to overcharge the battery. As long your car can have some daylight it should work.
Due to the relative high power of these panels 2.5w (older models would struggle to supply 0.25w), a exposure of 3 to 4 hours in a cloudy day would allow to recover your battery even if is half charged.


selectsolar. co. uk/pics/2.5W%20Sunsei.php
(add 3w's and remove spaces in the link)

Signs to look if you think your battery is becoming discharged:
The head lights are softer and are not giving the normal ilumination.
The engine does not goes of as it should. (on Honda cars)


Hope this helps,


Hupipoka

[efusco]

There really is no need for a solar charger for the 12v battery unless it is left unused for weeks at a time.

Regarding the OP's actual question...I don't know if there's a default and that's why you're now seeing 6 bars or if there's some other hysteresis causing the variation you're seeing.

But yea, I think it'll recalibrate quite quickly.

[Flying White Dutchman]

when you unplug the 12volt to the prius ( for more then 5 sec ) the OEM batt. ECU will deault back to 60% SOC