Blinking battery light

[juanse_2691]

Hello everyone. 

 

Recently, my 2007 Mk1 Fabia 1.4 16v has developed an habit of showing a blinking battery light after the first cold start of the day. No beeping or any other symptoms whatsoever. The light works as intended otherwise, and electrical accessories work fine. The light goes off on its own after a couple of minutes.

 

Alternator, regulator, earth and positive leads have been recently serviced. Battery is 18 months old at most, though I suspect it's going weak already.

 

Don't mind the engine revving in cold in the video. Only did it to test if the light flickering was affected by engine speed, which it apparently is.

 

The voltmeter video (sits at 14 ish volts) is the reading at the battery posts with the engine running at idle and air conditioning on.

 

As always, I appreciate your input.

 

Thanks.

 

Edited 3 August, 2021 by juanse_2691

[juanse_2691]

Battery sits at 12.8 volts with engine turned off, with no appreciable discharge.

[Breezy_Pete]

Can you borrow another battery from a friend briefly, to see whether that changes things?

 

Try measuring the alternator output voltage right at the alternator, to see if you are losing some in the cabling.

Negative meter probe on a scraped clean bit of alternator casing, positive on the output connection (careful not to short that probe  to any nearby metal).

 

14.0 seems a little low, but the alternator setpoint is temperature dependent, what's the ambient temperature in your area at the moment?

 

 

 

 

 

 

 

[juanse_2691]

Checked voltage across the alt casing as suggested and found no relevant difference in voltages, or resistance for that matter. It always has been the case that the car runs between 13.8 to 14.4 volts. Took the car to a garage so they could make some tests, and the charging system did well. The battery, while not completely hopeless, is weaker than it should, and they advised me to get a new one.

 

Temperatures year round are in the high 30°C, sometimes even 40. I wonder if heat could degrade a battery so much that it would make it go weak after a year and a half, as my battery box has no insulation whatsoever and I don't know where to get the factory blanket. The radiator fan blows hot air directly to it.

 

Since my daily usage consists of many starts scattered throughout the day, continuous use of air conditioning and headlights, lots of idling and short trips, is it possible that the battery has no chances of recovering from every start, and therefore degrades faster than say, a car that's only used to go to and from work twice a day? Because if that's the case, I suppose an AGM battery meant for modern Start-Stop cars would fare better, and despite costing easily double or triple the price of a conventional lead acid one, it would last longer I reckon, offsetting the cost of initial purchase. 

 

The weird thing is the occasional blinking of the battery light, of which I find no mention on the owners manual. 

Edited 7 August, 2021 by juanse_2691

[Breezy_Pete]

I'd be quite wary of fitting an AGM battery without modifying the charging system. Cars with those batteries tend to have charging management systems that deliberately keep them at a state of charge about 20% below maximum.  Many people on here will tell you that this is to leave capacity space for 'micro-hybrid' boost charging on cars with variable voltage alternators, but I suspect it's at least equally because of possible problems with overcharging.

 

See BU-201a: Absorbent Glass Mat (AGM) - Battery UniversityBU-201a: Absorbent Glass Mat (AGM) - Battery University

Also they are not keen on getting warm. Here's a quote from that page:

 

As with all gelled and sealed units, AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive. (See BU-403: Charging Lead Acid.)

AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F). Table 1 spells out the advantages and limitations of AGM.

[juanse_2691]

That's been very informative, thank you. I'll shop around looking for more suitable alternatives, and I'll have to get some sort of insulation around the battery. Getting all the heat from the rad fan is no good.