Eco Mode, new battery, new Alternator, Battery drained.

Our newly bought used C3 1,4l -05 seemed to be in good shape but the "econ mode" was haunting us, it was flashing now and then and ultimately drained the whole battery. The first cheap auto shop look at the car 2 days and decided to change the alternator. Three days later the battery was empty again and could not start, Econ mode was flashing again. This time we booked repair at Citroen authorized workshop. After some days they replaced the battery with a new one because it was keeping only 60% after all deep drains. In addition the alternator was changed a second time as the first one was claimed to be a "pirate" with only part effect. Again battery was drained and Econ Mode flashing some days later. We started to be desperate. BAck to the Citroen work shop, this time visit took 10 days, electrical engineer used 9 hours to trouble shoot. The real problem was a defective Earth (- pole) wire and also defective +pole at battery. Now it works but Econ Mode still flashes now and then. The shop said that by updating the BSI unit SW the flashing, which is now only cosmetic, could go away. We can liev with the Econ Mode flashes as the battery and charging system now finally works. All credit to Citroen Work shop they did not bill us the 9 hours as they regarded this their fault as we already paid for the fix one time. Journey continues.
This is our first French car, only 126tkm on ODO and really good chassis, hopefully only routine troubles ahead. Electrical problems are difficult to find I learned.

Hello

Do you have an aftermarket stereo in the car?

The C3 goes into "Eco Mode" for two reasons;
1) If your car has an automatic transmission (auto and sensodrive) the car will go into eco mode to protect the transmission from damage, if there is some form of problem with the transmission.
2) If the ignition switch is set to the 'accessory' or 'on' for more than 30 minutes.
Under any circumstance the car will not come out of eco mode until the engine is started. In the case of the auto transmissions this can become a catch 22. The engine wont start until it's out of eco mode but it wont come out of eco mode until the engine starts!! But I digress.
Having a manual transmission your car will not go into eco mode unless the ignition is left on. So "eco mode" is a normal function and is not part of the battery going flat.
Judging by the photos you posted, some one has replaced the battery terminals. They are not the same as the stock terminals. I assume the dealer did that.
If that was the fault, the battery was not being fully charged.

I have a post on how to check your charging circuit with a multi meter and it doesn't take 9 hours to perform.