2009 6j - Upgrade battery from Lead acid to AGM / EFB ?

[vtxracer]

Hello !

I own a 2009 Ibiza Fr Tsi Dsg. I was thinking about upgrading the battery.
Right now I use a Varta silver (63Ah, 610A). It still starts the car fine after 3,5 years but the volatge gets too low. Before that I had a Bosch s5005 (Same battery as the Varta). It lasted 3 years.
The problem with this generation of 6Js without BMS and start stop is the charging voltage. It charges at 14v for only a few minutes after a cold start. As the temperature under the bonnet rises, the charging voltage drops to around 13v.

My question is, If I replace my current battery with an AGM, will it be charged sufficiently ? Will I have any issues ? If I chose an AGM maybe I should go for lower Ah capacity ? Will the heat under the bonnet affect an AGM ?

Thanks

 

[vw.man]

Would have thought your problem is with the charging system, rather than the battery. If it's putting out only 13v then something is wrong; I don't think that replacing or upgrading the battery will change that.

I used to have a 2009 1.4 Ibiza (85bhp) and sold it last year. It was on only its second battery (a Bosch). From memory, the voltage was around 13.8v with the engine idling when warm.

Have you scanned the car for fault codes? Does a new battery need to be coded in with your car (I don't think it does, but thought it worth mentioning)? Have you checked the cabling between the battery and the alternator?

 

[vtxracer]

Would have thought your problem is with the charging system, rather than the battery. If it's putting out only 13v then something is wrong; I don't think that replacing or upgrading the battery will change that.

I used to have a 2009 1.4 Ibiza (85bhp) and sold it last year. It was on only its second battery (a Bosch). From memory, the voltage was around 13.8v with the engine idling when warm.

Have you scanned the car for fault codes? Does a new battery need to be coded in with your car (I don't think it does, but thought it worth mentioning)? Have you checked the cabling between the battery and the alternator?

Hello,
Thank your for your reply.
The charging system actually works as intented. I have compared it to many other similar cars (Polo 6R, Ibiza 6J), same year, same engine and gearbox configuration (CAV* engines and Dsg). Its just how this car is designed. Thats the rated output of this specific OEM voltage regulator used on these cars.
I have already rebuilt the alternator just in case and replaced the voltage regulator. It made no difference.
My question is if this charging voltage is enough for an AGM battery. The initial voltage after a cold start is enough to charge it. (especcially in winter where it can get up to 14.5v). Is the float charge of 13v enough for this type of battery ?
Thanks

 

[dm222]

Mine does the same starts with 14v cold and then goes to around 13.6.

 

[vtxracer]

It will drop usually to mid 13s as you both mention.
(Note that 1.4 CAV + Dsg combo do not have the same alternator and voltage regulator conpared to NA 1.2, 1.4 and 1.6 engines, or the newer 1.2 tsi)
If the weather is very hot and all electrical consumers are on (lights, air con) the voltage will drop to 13.0 - 13.2.
Other newer cars I usually drive with modern electronics, start-stop and factory fitted AGM batteries with usually start at 14.7-14.9 and then drop to about 14.2.

So, is a constant voltage of over 14v necessary to charge an AGM or can I manage with just an initial voltage of 14 and then a float charge at mid 13s ?