Battery level drops randomly whilst driving.

[Mattgr]

Hello everyone,

 

I have a 2015 avensis business icon edition T270 tourer. 

So what has happened is the Battery level reading drops from 13.4/14 to 12.   The engine cut out while on the motorway one time.  

But what I noticed bizarrely is if it drops to 12 volts the engine is a little slower.   But if I turn on the headlights or ac.  The Battery level recovers.

 

It's really strange.

 

Anyone experienced this?

I have a digital hud plugged into my obd which gives me the Battery voltage constantly. 

 

Thanks 

 

Matthew 

[Mattgr]

Now I just saw the level spiking to 14.6 after slowing down to leave the motorway.  

Then it dropped to 12 volts. But reliably it recovers if I turn on the headlights weird 

[Gerg]

I think at least part of this pattern is explained by the car probably having an 'intelligent charging' alternator.

That type of alternator is designed so that it produces charge on the overrun and when braking, but not at some other times when you would expect it to, so enabling the car manufacturer to claim the car has 'regenerative braking', 'energy recuperation' or similar.  And probably marginally enhancing the car's performance with regard to the government's CO2 emission test results etc.

If you are used to knowing how alternators previously worked, then this type of alternator throws a big spanner (figuratively) in all of that.  The 12 volt Battery will be designed to operate with this type of charging. 

Of course, that doesn't explain your car cutting out etc.