Alternator charging issue 2017 Focus 1.5 ecoboost, 10k miles.

[Paul49]

Fitted a new battery due to not being used in lockdown the oe battery died. New one is correct spec Yuasa efb, no problem there, been fine for 2 months. I have charged by accumate trickle charger in situ every 2-3 weeks so this doesn't go the same way. Checked with multimeter, battery 12.5v after 2 weeks off charge, good. Started engine 14.5v dropped over 1-2mins to 12.2v? this would normally be 15v & hold steady, checked 2 weeks ago. Switch off & try again, same thing 14v dropped to 12.2v. Switched everything on inc aircon & it reads 13.5v? Switch aircon off drops back to 12.2v. Seems like the alternator is charging at high demand, but not low. Fitted a voltmeter in cig socket & went for a run to check, every so often it would go up to 13-14v then drop back to 12.2v.

Anybody had similar, got any clues to the problem? TIA for answers.

Paul

[pcaouolte]

Did you reset the battery monitoring system after fitting the new battery? The smart charge system will be trying to maintain the battery at about 80% charge, if it's already at 100% charge the system doesn't want to waste fuel keeping it at 100% it will reduce the charge input until the battery falls to 80%.

[Paul49]

58 minutes ago, pcaouolte said:

Did you reset the battery monitoring system after fitting the new battery? The smart charge system will be trying to maintain the battery at about 80% charge, if it's already at 100% charge the system doesn't want to waste fuel keeping it at 100% it will reduce the charge input until the battery falls to 80%.

Yes, done that now. I wasn't aware of how this charging system works. Our older Focus is more suited to us old folks. Thanks for your help. Sorted.