i30 N Battery replacement

[NaXter24R]

I have to replace the OEM battery as it's now over 4 years old and winter is coming. I'd rather do it sooner to avoid any potential issue.
I'm in Italy, for reference, which battery brand would you suggest? I know is a standard 70A L3 AGM battery but there are many brands out there. The OEM one is a Varta but I never had much trust in that brand in the past. They cost a lot and usually they don't deliver. Mainly I was looking into Alto Adige, FIAMM (Alto Adige is made by FIAMM), Bosch, Yuasa and I've heard mixed opinions ab out Exide. Any suggestion?
Lastly, can I just undo the old one and put in the new one or do I have to follow some different procedure? With modern cars I'm never so sure.

 

[Bu11eT]

Its super important that the new one also has exactly 70Ah.
Just install the new one and leave the car locked overnight. This triggers a relearn-cycle for the new battery.

 

[tacthecat]

Why "exactly" 70 ah? Is the "install & overnight relearn" a Euro thing?

 

[Bu11eT]

Why "exactly" 70 ah? Is the "install & overnight relearn" a Euro thing?

70ah, because there is no way to tell the car that you've changed the battery capacity. It cannot properly adapt it's charging logic to a battery with a different size. For AGM type batteries this is negligible, but lithium for example it should be a hard fact. The car starts acting really weird after some time with another battery size. So even with AGM it is recommended to not change the capacity of the battery.

The learning procedure is in the manual of the car. Usually, on other euro cars, the battery needs coding to the car, but with the i30Ns its just an overnight battery-relearning-cycle.