prius engine keep running

Hi ,this is my first time posting on this forum ,I have found this forum very helpful for Prius owners.
I have Prius 2gen 2007 UK model 1.5L ,High mileage 200000 . My Prius petrol engine keeps running on very low revs, when I stopped by traffic lights or when I parked , on display it doesn't show that engine charging battery or indicates that is running , I have few months old 12v Toyota original battery ,I have measured reading from 12v battery all readings as recommended, so I eliminate possibility of 12v battery failure.
Can it be Failing hybrid battery back, not providing enough electricity to support to engine?
Or ,can it be something wrong with the engine? I have notice oil consumption is high and I need to top up between changes more frequent ,I'm changing oil around 6000 miles.
For reference, My air condition unit is off , I have temperature on lowest setting, I have only fresh air intake set to M or off .I know how the hybrid system supposed to be running, as this is my third hybrid and I'm driving hybrid cars for more than 10 years. I have tried to use techstream , not really sure on how to use it.
Please, anyone have any ideas?
Thanks in advance.

 

Thanks for your answers.

It's a bit strange why, when engine working, it doesn't show up on the display, that it charging hybrid battery.

I'm planning to keep this car at least for the another year or so. Should, I invest in the new hybrid battery pack?
lots of prius has high mileage with original parts.
Any other ideas what can be wrong with the car?
Average mileage on display is over 50mpg I can feel loss of power car a bit slower when starting accelerate, and engine kicks in too soon after you accelerate, some times car won't allow me to switch on electric mode only (ev mode) with nearly full battery on display.
Thanks in advance .

 

Thanks for your help guy's, I'm really appreciate that.

 

I'll probably drive as it is and see, I have plans to buy new prius anyway, sooner or later.
I will try to join 299999 mile club
Thanks.

 

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I'm completely agree with both of you, that's why I have started this conversation,
One side of me still wants to change hybrid battery, other side saying hold on and wait ‍♂️
I have find out that my 12v battery failed, it's only a few months old, Toyota original batery, it doesn't hold the charge,, so I was wrong in first post that my 12v is good.
I have dropped battery to dealer so they can test and if it's bad they should replace.
If Anyone interested how much changing hybrid batteries in uk, I have taken some prices from dealer in Berkshire :
Change hybrid battery at dealer £1400
Service hybrid fan only,, one at the back, £69
Hybrid battery alone, if you changing yourself £1140 +£500 deposit refundable if you bring your old hybrid battery back within 1 week..
12v battery £124.
I hope it helps for folks here in UK.
Thanks.

 

Yesterday I switch the car on without brakes, and try to close windows, by the time windows close completely 12v battery went down to 8v, red triangle appeared some noise, then I have started car and it jumped up to 14v,, I went to garage to test the battery today and they confirmed that battery is no good.

I have installed my old duracell 12v batery and try to close windows again few times up and down and battery maintain between 11.8 to 11.9 volts never dropet bellow..
Dealer told me that battery needs to be charged and it's nothing wrong with battery. They said that I have drained the battery when closing windows.I'm a bit stumped now, I'm silly or them.
You can drain the battery just for closing windows. Well I'll charge the battery and I see.

 

Tomorrow I will pick up battery from dealer and hang on charger for 24 hours.
Instal back in the car and will do some tests to see if it's drops voltage, if it's same I will take to independent garage to do testing on the battery get some proof and then hang on toyota.
I have noticed , with old 12v duracell car works much smooter.
I drive for about 40 min. Before uninstaling toyota 12v battery from the car and give to dealer.

 

I'm a bit suspicious about how they test, in such a short time. I think they just trying to fool me into something, I ask them if they will charge battery before giving back to me they ask me to pay for this, and again try to accuse me that by opening window I have discharged battery, hold on how about driving for about 40 min. Before removing battery and leaving for dealer to test.

 

Yes ,its Toyota dealer .Back here most drivers doesn't know how to open bonnet , everybody goes to mechanics or dealers. There is not much good auto car parts stores , most of stores online anyway, auto mechanics or pseudo mechanics doesn't give a dam about cars they just charging ridiculous money for small jobs , or even worst ,if they fix something they will find or do something to get you back.