The 12v batteries on the E Tense are notorious for depleting.
I’ve had both the main 12v (under bonnet) and back up 12v (under the armrest) changed TWICE under warranty in the last 7 months.
Even the slightest drop in voltage can cause certain features to not function, such as the keyless entry, auto welcome lights, data downloads.
When you charge the hybrid battery a small amount of charge will feed through to both of your 12v batteries but not a great deal.
The main 12v battery gets its charge from the alternator, the current is then fed from the main 12v to the smaller 12v battery under the armrest, it’s a one way flow of current , so the current doesnt come back from the smaller one to the bigger one.
This is important to know because if you ever want to remove the batteries you must remove the terminals in a specific order.
If I recall it’s, negative off the smaller battery first, then the positive off the main, then positive off the smaller and the negative off the main last.
DOUBLE CHECK I MIGHT HAVE THE SEQUENCE WRONG ?
It shows this in the manual, and the Master Tech at my dealer tried to explain why but it was a bit over my head.
Apparently removing them the wrong way around interferes with the cars BMS (Battery Management System) and can lead to problems.
Technician also told me that DS are big on recycling, down to using recycled 12v batteries, in in their brand new cars, which mine is.
So having two sets of 12v batteries in 7 months might be the reason why ??
I’ve had issues with the batteries , both the 12v and the hybrid.
Heres some tips :
Drive your car on the motorway for a good 50 miles.
You should start to see your hybrid starting to work.
But if you do low mileage town type driving you might start to see less 100% full hybrid electric.
The car likes to have a bit of mileage done to access full hybrid electric.
You may also notice that the car will drop the revs to around 1400rpm and the blue hybrid bar becomes active, it then drops to 800rpm but still has an active blue hybrid bar.
So basically the car is using the hybrid battery but keeping the engine ticking over.
this is NORMAL.
Theres a number of reasons for this.
Engine is cold.
Car wants more mileage for lubrication, and internal checks, it wants to stop fuel waxing up on the fuel system.
You have features on like A/C or heaters.
Your speed is above a certain point so its easier for the cars engine to kick back in when it needs to.
Even though you might be querying the hybrid battery, it could very well be one or both of your 12v batteries thats throwing up issues, like no full hybrid electric.
My E tense has been back and fore the dealership at least 6 times for similar issues.
They have changed both 12v batteries twice but I still find that the car doesnt always give full electric when it should.
However, it is far better if I put a bit of milage on it.
Have you tried manually charging your 12v batteries ?
If you read the manual it does mention that certain features may shut down if the car does low mileage.
My advice would be to charge the hybrid, charge the 12v main battery (this will trickle into the smaller 12v) and take the car for a nice long trip, hopefully you’ll see a difference in how the hybrid starts to behave.
If this doesnt work get your 12v batteries checked out, if one of them needs changing remember to check the terminal removal sequence before removing.
Remember though, as mentioned above, that even with a full hybrid charge, the car will still want you to run the engine for a certain amount of mileage , it needs this done to run its own checks and get the engine lubricated ect.
