A couple of months back I nearly posted as Start Stop was taking 45 minutes some days to stop displaying "Power Consumption too high" as its reason for not stopping.

 

I took it into the dealer, and they first looked at replacing the ignition switch.  I asked if that was the bit that the key went in, as opposed to something deeper in the engine, and they confirmed this.  After I got the car back, it still was acting up.

 

They took another look and decided the Alternator was fine, the battery health was fine,  but was just flat, so bench charged it and returned the car.

It then was fine for a month or so.

 

On Saturday, on one of my few short runs that the car ever takes I did notice the "Power consumption too high" message while at a level crossing, but didn't panic, as it was just a short run, and monday would be back to normal with my normal 30-40 minute drives each way to and from work

 

However, when I went to turn the car on to de-ice it (it got down to about -3 last night)  it wheezed and spluttered and started saying "Very Low battery, turn engine off"

 

I left it off and unlocked, called skoda assist / AA, and they were pleasantly quick at getting out to take a look.

 

It started first time with their booster pack, and the alternator was giving about 14v (I didn't see what current it said it was putting in).  Once some charge had built, he shut the car down and locked it while measuring the current draw to check everything was off.  I think at the point the battery test was run, the residual draw was something like 0.48 amps, and the battery tester said battery is flat, but healthy. They recommended I left it running for 40+ mins before turning it off.

 

I'm trying to get the dealer to look at it asap, as I don't fancy being stranded at home or at work

 

Any suggestions what might be the cause?  My dash cam is only on when the ignition is on.  I had left a 12v phone charger plugged in to the always on sockets, but that would hardly utterly drain the battery over 2 days.

 

The car is a 150 PS 2.0L diesel

The initial deep discharge probably screwed the battery. 

 

A 12V charger - especially if it's a cheap one - could be eating 0.2A or so, which might be enough to kill a battery on its last legs.

 

I would first remove *all* the potential users of power, including the dashcam and phone charger, for testing purposes. If that doesn't help, you'll need an auto electrician to confirm what the cause of that really quite high residual current is. Pulling fuses is the other way to do it, but that will take time and still needs you to be able to measure residual currents while you're doing it. Is there an aftermarket radio in?

 

 - Bret

What date was your car built?
There were a few owners of early models that had the battery manuagement module replaced because of a similar issue.

What date was your car built?

There were a few owners of early models that had the battery manuagement module replaced because of a similar issue.

I got it in Feb 2014, I can't remember which side of the new year was its allocated build week

 

The initial deep discharge probably screwed the battery. 

 

A 12V charger - especially if it's a cheap one - could be eating 0.2A or so, which might be enough to kill a battery on its last legs.

 

I would first remove *all* the potential users of power, including the dashcam and phone charger, for testing purposes. If that doesn't help, you'll need an auto electrician to confirm what the cause of that really quite high residual current is. Pulling fuses is the other way to do it, but that will take time and still needs you to be able to measure residual currents while you're doing it. Is there an aftermarket radio in?

 

 - Bret

I've left the 12v charger unplugged now. The dashcam should have no way of drawing power. When I fitted it just after I got the car in 2014, I used a multi-meter to select a fuse to piggy back from that is off when the ignition isn't on.

The AA Tech seemed happy that the remaining 0.48 amps was from having only just turned the car off and locked it.  He suggested that some systems in the car can take several hours before they shut down and stop drawing power.  Locking it did very quickly reduce it from 3-4 amps to 0.4

The radio is an original one, so that shouldn't be doing anything unusual.

 

 

It's about a 35 minute drive to the dealer, and for the first 10 minutes I made sure start stop was disabled. I did try re-enabling it, and the 40+ mins I left it idling, and the 10 minutes driving seemed to have filled it up enough to allow it to work again.  But I have left it with them to investigate, as it would be very different being stuck near work rather than at home.

I'll report back any progress reports I get from them, but I don't think they can start looking at it till tomorrow.

AGM2 batteries do not like it if they suffer deep discharge. The only module that doesn't go into deep sleep after a few minutes is the alarm system, and that only draws about 20 milliamps IIRC.

 

For charging AGM2 batteries you need a special charger, even an AGM V1 charger wont do the job. The charger needs to be able to take the battery all the way up to 14.6 volts at no more than 2 amp charge rate if the car battery is left connected. The charger must also ALWAYS be connected with negative to the bulkhead connection, and positive to the battery + terminal. Incorrect charging can damage the battery control module.

 

The situation is made worse by the fuel saving alternator clutch, as the battery is only charged in over run or when braking.

 

Nothing should be left plugged into the 12V socket which is always live. The car will sense the extra current draw, and wake up modules to see if there is a problem, so then you have several amps been drawn and soon the battery is flat.

Thanks for the suggestions.  I will be careful to leave the phone charger unplugged in the future, just in case it was causing some nastiness.
 

I've heard back from the dealer.  They did do some tests on the battery and it was saying it was good.  They charged it and tried to find sources of current draw, but didn't find anything noticeable.  However, after a 2nd night in their workshop and looking at it again, they have now found something wrong with the battery, and will get a new one fitted later today.
 

I don't have a battery charger at the moment, I was thinking something like this Ring Automotive RSC605 should do the trick, or at least be something useful to have in the garage. It is surprising how many "universal" chargers are not suitable for the modern battery tech used by cars with start stop!

http://www.briskoda.net/forums/topic/414398-battery-charger-for-kessy-stop-start-cars-aaskoda-breakdown-service/

 

http://www.halfords.com/workshop-tools/garage-equipment/battery-chargers-jump-starters/ring-12a-smart-charger-charge-and-diagnose

 

https://www.tantronics.co.uk/ring-rsc612-12v-12a-smart-charge-car-battery-charger.html

Edited 7 December, 20169 yr by BATVANVRS