@TerFar A bigger battery will still go flat if short journeys are the norm...

 

It will just take longer to go flat (but that is only if we are talking fully charged in the first place, and longer to fully charge)

 

If it doesn't get charged enough, you will just have a bigger battery capacity but with a similar amount of charge that the lower capacity one had.

This last statement may not be technically correct, but you will still be at risk of a flat battery imo.

In terms of 'normal use' I don't think 2000 miles a year over 3 years is a very normal pattern at all.  ( as in 6k over 3 years).

Most modern car's batteries will discharge at a rate or 1-3% a day due to a mix of it's internal resistance and the always on parts of the car. Then throw in lots of short journeys and you battery is toast if it gets discharged too deeply.





 

12 minutes ago, abaxas said:

In terms of 'normal use' I don't think 2000 miles a year over 3 years is a very normal pattern at all.  ( as in 6k over 3 years).

Most modern car's batteries will discharge at a rate or 1-3% a day due to a mix of it's internal resistance and the always on parts of the car. Then throw in lots of short journeys and you battery is toast if it gets discharged too deeply.

 

Totally agree about the mileage. The car was in storage for a long period (whilst an awkward probate was progressed), and the battery was on a trickle charger for much of that period. Our normal mileage is around 5-6,000 a year, so although not in anyway huge, it was perfectly adequate for our previous cars (diesel Yeti and Octavia DSGs). So it should be adequate for Fabia.

Over the course of investigating the low battery warnings problem, the battery was charged using a smart charger that initially spent around 1 hour discharging, then 6+ hours in desulphate mode and almost 40 hours trickle charging to full. So possibly the long desulphation period was a legacy of the long storage. But the problem recurred until the start/stop was disabled (both by disconnecting the connection to the negative terminal and in software). 

I'm happy not having start/stop: I find it a real pain when negotiating busy roundabouts or junctions when you need to jump away smartly. 




 

 

On 16/04/2019 at 10:32, TerFar said:

I have thoroughly tested the battery and it is definitely good and holds a full charge fine. It definitely isn't charged sufficiently in normal short distance driving. The Yeti did: the Fabia MC doesn't. I've disabled the start/stop, we make sure everything is turned off when parked and I'm going to use the trickle charger once a week. That seems to be OK for now. When the battery dies, I'll make sure to replace it with a higher capacity AGM battery. Until then, I'll make do with the standard EFB fitted.

 

You don`t need an agm battery otherwise it would have been fitted by the manufacturer, stop/start just drains the battery, the smart charging system is the problem as it won`t allow the alternator to charge the battery level beyond 75% when the car is under engine power, the other 25% capacity is for regeneration only, short journeys= little or no regeneration which = a near to flat battery as you have discovered. Disconnect the sensor on the negative post of starter battery, buy an Ebay voltage tester as pic and plug it into the cig lighter socket, run the car on your usual short journeys for about a week then test the battery with a multimeter after the car has rested overnight, if the battery is good it will be fully charged 12.6/7 volts. When driving the car the test meter in the cig socket should show continuous charging of between 14.3 and 13.8 volts.

 

Nothing will be damaged, disconnecting the sensor is same as sensor failing there is not even a EML shown on dash, if that sensor fails the EMU reverts to a continuous standard charging regime 14.3 to 13.8 volts, as previously stated I have been running my 2012 Merc with this sensor disconnected for the last 6.5 months.

Disconnect sensor, small black connector as pic of Merc sensor, yours should be similar.

Edited 18 April, 20197 yr by Bobclive2

Terfar,

 

As said If you have disconnected that sensor both stop/start and the smart charging system would have been disabled, this should have solved your low battery problem as the alternator will now charge continuously under the engines power, the battery on my Merc is stamped 23/11 on the negative post which means it was produced on the 23 week of 2011, it is still going strong, before disconnecting the sensor I always manually switched stop/start to off.

Thanks for all the expert replies. A cheap cigarette socket volt meter confirms exactly what you suggest. 

 

With the S/S connected and enabled (with a full battery), the meter reads 12.4v with the engine off and 12.5v with the engine running. 

 

Once I disable and disconnect the S/S, the voltage reads 12.4v with engine off and 14.1v with the engine running. Allowing for tolerance of the cheap meter, those readings seem to be close to what should be expected. 

 

I've no real gripes against S/S, especially as there is a dashboard button to temporarily disable it, but the 25% - 75% regenerative charging is totally bonkers. Does Skoda really believe it will eek out any extra mpg! 

After reading this topic I am going to check the Neg terminal on my Fab for the regeneration block and also get a voltage reader for the cigarette lighter to monitor battery V's - Is start stop really not that beneficial on the fabia then?

 

Also @TerFar What colour mk3 monte do you have? I am also from Chi. I will give you a wave if I see you! (Blue Colour Edition Fab CP17) 

Red, black panoramic roof and black alloys.