@unofixthis is prob a repeated question so apologies I've got no experience with car mechanics or electronics plus I'm disabled so can't lift anything above a full kettle 😩

Why stick with an EFB battery like the suggested YBX7096 over an AGM one? 

18 minutes ago, TheKesselRun said:

Why stick with an EFB battery like the suggested YBX7096 over an AGM one? 

Your Focus Mk4.5 does not have the charging algorithm to use an AGM battery. Fitting one would give you no advantage, and potentially you could end up in a worse predicament. Vehicles that use AGM batteries have very specific charging requirements, generally higher than those used to charge an EFB battery.

The best solution that myself and others have come up with is to use the largest capacity EFB battery that will fit the car. In this case the YBX7096 as used by the Focus 2.0 EcoBlue. Then use FORScan to change SOC from the factory default of 80% and increase it to 95%. This of course does not fix the problem that the Focus Mk4 and Mk4.5 have an extremely poorly designed charging system, but it does mean that the time between needing to 'top up' the battery with a Smart charger is somewhat increased.

36 minutes ago, unofix said:

Your Focus Mk4.5 does not have the charging algorithm to use an AGM battery. Fitting one would give you no advantage, and potentially you could end up in a worse predicament. Vehicles that use AGM batteries have very specific charging requirements, generally higher than those used to charge an EFB battery.

The best solution that myself and others have come up with is to use the largest capacity EFB battery that will fit the car. In this case the YBX7096 as used by the Focus 2.0 EcoBlue. Then use FORScan to change SOC from the factory default of 80% and increase it to 95%. This of course does not fix the problem that the Focus Mk4 and Mk4.5 have an extremely poorly designed charging system, but it does mean that the time between needing to 'top up' the battery with a Smart charger is somewhat increased.

Makes sense, think I just saw users advising to use AGM and switch the charger type in Forscan, beyond my knowledge anyway. 

1 minute ago, TheKesselRun said:

think I just saw users advising to use AGM and switch the charger type in Forscan

That was a couple of years ago, and suggested by a few people. The problem was that FORScan used to have a 'drop down' list of batteries to choose from which included some AGM batteries. It then transpired that the battery menu was wrong and FORScan have now removed many of the batteries that were once listed.