Check Electric System message

Zoe’s error messages to the driver are not always crystal clear. This one usually points to a failure in the 12 volt system.

There are basically two reasons why the 12 volt system can be compromised (barring real faults somewhere in the electrical system):

  1. failure of the 12 volt lead acid battery
  2. unexpected drain of the 12 volt battery (leading very very quickly to 1.)

Let me start by saying the 12 volt system feeds anything and everything that is not traction or the air conditioning compressor. For the non-Nordic version, it also feeds a few rheostats for fast wind shield defrosting. It’s all pretty beefy but still it can drain fast. Remember that all 16 computers are powered from the 12 volt system. If this bus runs bad, literally nothing will work as expected, if at all really.

Renault has the lead-acid battery replacement in their schedule set for after 3 years. This does seem pretty short indeed, but given the above, I wouldn’t dismiss the dealers suggestion for replacement flat out. If you are in doubt, at least have it tested. Lead acid batteries are loosing a notoriously amount of capacity when it gets cold, and you don’t want to get stranded with a full traction battery, but a dead 12 volt system. And if it’s dead, the computers are dead, and there will be no way to bootstrap charging it without hooking it up to an external 12 volt battery charger. Been there, read on.

Unexpected drain is pretty hard to do. The auxiliary power shuts off when the car goes in sleep mode, so even leaving on some sort of accessory through the lighter plug should shut down.

There is one scenario however, which I am pretty sure happened to me. The charger plug was not seated properly, or at least the car thought so. You can actually detect this when the motor lock retries every 2-3 seconds. This retrying continues forever and while this is going on, the car is fully awake, all computers are on, the lock motor is being fired continuously and of course no charging is happening while there is a serious load on the 12 volt system. Now one could think the 12 volt system is being replenished by the traction battery, but it isn’t. The lead acid battery was drained down to 5 volt in a few hours at which point the car went completely dead. 5 volt is devastating to a lead acid battery if not quickly charged. Luckily, I found out and diagnosed this within a few hours of it happening.

I couldn’t bootstrap the car “in situ”, because as soon as I connected my small 12 volt car charger to the battery, the car woke up, started to initialize all it’s systems and while doing so overwhelmed the charger. I removed the mass cable from the battery and charged it for an hour. After that, the battery had enough juice to pull the car through it’s initialisation. I then was able to remove the charger cable, hooked it up again and charged the car normally. The error went away after one cycle.

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8 comments on “Check Electric System message
  1. Borut says:

    How big of a drain it is, while initializing,would a 3s RC Lipo do the job, lets say 2200mAh,30C ?
    A small weight to save your self in a situation like that.

    • Jeroen Meijer says:

      I don’t really know. In rest (i.e. while charging) the 12 volt system draws roughly 2.5 amps, but coming from no 12 volt at all, I noticed it started clicking relays, opening the (stuck) charger plug, doing lots of startup stuff. It is a totally wild guess, but I would not be surprised is was 10-20 amps. It would also prime the brake servo pump. My wild guess is a 30C peak discharge Lipo would surely do the job, assuming the DCDC converter can take over pretty fast. Also, I would be slighly scared, because that DCDC converter can put out a lot of current, about 100 amps. If it decides to start charging with the Lipo still connected…….

  2. Borut says:

    I’m thinking on replacing the leadacid with Lifepo4 4s.
    The charging voltage in my car is 14.3 and that is a little under max charging voltage for lifepo4.
    That would work fine.
    But further I’m thinking to reduce the running voltage of a dc/dc converter to something like 12.0V.That would fully discharge the lifepo4 between charges,that way I would gain additional range.
    What do you think? Do you think it is possible to modify or “correct” dc/dc converter running voltage with Clip diagnostic tool?

    • Jeroen Meijer says:

      The documentation I have seen contains very little writable items. I have a clone CLIP system on order which I hope will arrive in a few weeks, so I can have a peek, but I am not hopeful. BTW, what I wrote earlier about capacity reflected on the startup sequence of the car. In operation there can be massive loads on the 12 volt bus. Read windshield heater is fused on 40A. Same on the fan for the battery.

  3. Borut says:

    I’m looking at this battery
    http://eauto.si/metron-shop/?product=lifepo4-cell-module
    It is reasonably priced, can be rearrange so it will fit and it will outlast the car.
    I’m not sure how often the car charges the battery at 14.3, it should on every charge cycle for this to work.
    I could easy get out of the battery more then 1 kwh on a cycle where a lot of 12 V power is needed if it is possible to set the running voltage of dc/dc to a lower state . Not to low so a small charge will stay in the battery for sleep power.

  4. Tobias says:

    Think there is a third reason for a failing 12 volt system:
    If the DC/DC converter fails recharging the 12 battery from the traction battery during driving.
    With a broken DC/DC converter even a healthy 12 volt battery will loose its capacity quite fast during normal operation, especially in cold conditions.

  5. Borut says:

    Hi
    Can you make 12 volt consumption graph with total consumed energy on 12 V bus.
    The phone should be connected all the time for logging.

    • Jeroen Meijer says:

      Please log as request on the bug tracker. Indicate if the field you would like to see is the same as 12 volt system current in the charging tech screen

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