Why DC - DC converter runs continuously when car is off ?

[Volxu]

I have a 2012 Nissan Leaf, that suffers from blue blink, when the car is off.
- during car parking, i am loosing about 01 to 02 kwh.
-When i turn off the car, the DC DC starts after few seconds.
-When i unplug AC-supply, the DC DC starts after few seconds.
Workaround:
-If i start the car, without pushing the brake, and then stop it, the DC DC converter does not start after i stop the car.

Any one knows why this happens and how can I solve it ?

Thank you

 

[ReptonAU]

I believe that the DC-DC is working when ON, so does simply not switch OFF (HV relay stays open
The DC-DC is also working when AC is connected; so again does not switch OFF

The reason your workaround works is that it is not suppose to activate the HV (DC-DC), but is still making sure that it switches OFF at the end

Hopefully it is just a software glitch and a reset would fix the problem. Disconnect the 12V for a while. I would do that after the workaround, as I believe that it is not wise to work under the bonnet when the HV is live!

Actually has to be after the workaround, because there is no reset when there is still the second power source (DC-DC) active.

Your 12V battery seems to be fine at12.6 volts.

A second brain fart I had is that the DC-DC has 2 active states either charging (14+ volts) or merely maintain (13+ volts). The software switches when the current from DC-DC to 12V drops as the12V battery gets fully charged. Your car could be in charging mode (14+), but because the 12V is already fully charged there is never a drop anymore to initiate the switch. So when you switch the car ON and you get 14V, I believe that it could be possible by playing with high beam and heater to generate fluctuations in the current. This could potentially trigger the switching from 14V to 13V and the problem is fixed. Similarly get the car in 12.6 mode and switch high beam on until 12V gets to low 11 volts Switch the car OFF and when the 12V is about to be finished recharging the drop in current will switch the DC-DC off (blue led dims)

 

[knightmb]

I have a 2012 Nissan Leaf, that suffers from blue blink, when the car is off.
- during car parking, i am loosing about 01 to 02 kwh.
-When i turn off the car, the DC DC starts after few seconds.
-When i unplug AC-supply, the DC DC starts after few seconds.
Workaround:
-If i start the car, without pushing the brake, and then stop it, the DC DC converter does not start after i stop the car.

Any one knows why this happens and how can I solve it ?

Thank you

I would suspect a 12V battery issue. The blue blinking light usually comes on like that when the 12V battery is too low and it is trying to charge it back up.

 

[LeftieBiker]

I agree. At least eliminate the 12 volt battery as a suspect by having it tested. If it's 4 or more years old, replace it anyway, and fully charge the new battery or have the auto parts store do so. Explain that the car has no high output alternator.

 

[Volxu]

Dear all,
First of all, thanks for your valuable feedback / advise.
Please, be informed that the 12v battery is new and after doing further measurements , I found that around 4.5 amp are running out from the 12v battery continuously when the car is switched off and this is the reason behind keeping the HV battery charging the 12v battery via DC - DC converter.

My initial finding , I removed the triple 40A fusible links (H, G & I) which feeds (body computer system, M/C relay & Ignition relay) then the current stopped

Now, I have to continue my investigation and find out which sub-system under those three circuits draws this current during the car is off !?

What is your opinion ?

 

[ReptonAU]

Hi Vokxu very exciting that we have passed the 'it's a faulty 12V battery' stage. No opinion about the specific problem, but disappointed the 12V disconnect afrer 'OFF from no break' did not fix the problem. I still wonder if you are right in assuming this (4.5A current) is the reason . . . (chicken and egg issue) Would you mind considering that not switching OFF properly would keep the DC-DC active, resulting in the 4.5A current I have my suspicions about the switching OFF; the problem occurs only when you switch OFF and stop charging, but not if you switch OFF from the No Break ON state. You also say that 4.5A are running out from the 12V; the DC-DC is active so current is coming from the DC-DC not the 12V as the voltage on the DC-DC is higher then the internal voltage of the 12V. The circuit is providing the 4.5A and the circuit is supplied by the DC-DC(HV). So I am curious as to your voltages on the 21volt circuit and the terminals of the 12V in the various states:
values on my 2019 healthy Leaf
OFF 12.x
ON 13+ (initially 14+ until 12V is full, DC-DC lowers to 13+)
Charging 13+ (initially 14+ until 12V is full, DC-DC lowers to 13+)
ON without break 12.x
OFF from No break 12.x

There are 3 levels of voltage provided by the DC-DC
0 (HV closed)
14+ to recharge the 12V
13+ to meralely supply the circuit and maintain the 12V

I hope with your measurements we can establish that the DC-DC is stuck in 14+ mode. When driving the car the voltage would never drop to 13+. and after switching OFF the HV is opened to start charging the 12V