Hey Guys- My first venture into the FOC world. Having owned virtually all marks of Fiesta, had to buy one of the run-out cars.

Purchased a neat Vignale 125, MHEV, two year old from TrustFord with 9500 miles recorded.

Within 3 months had first battery issue with total drain down, leaving car virtually immobilised. No power sources left on !

Battery was fully charged by a nice AA man. Comments made to the high 12v battery demands by the 48v Hybrid battery

and Stop/ Start system !  After further battery drain down issues, complained to Ford supplier, advised new battery required.

Original fit 12v battery was an inferior SL type unit, not a superior EFB unit required for most small engine Stop/ Start car systems.

Let alone the additional 48v hybrid battery demands. I deem the OEM Ford fit SL type battery not fit for purpose.

Anyone else had these issues ? I’m guessing yes. If so, check your main battery type, and advise further.

Hi Steven, welcome. 

You should really post this in the Fiesta forum since your point is on that model.

I take it you haven't had chance to have a thorough look around the site yet? Battery issues as you describe are the most common topic along with wet belts!

MHEV's don't 'need' an EFB battery because stop/start is done using the 48v MHEV battery on those.

50 minutes ago, Eric Bloodaxe said:

Hi Steven, welcome. 

You should really post this in the Fiesta forum since your point is on that model.

I take it you haven't had chance to have a thorough look around the site yet? Battery issues as you describe are the most common topic along with wet belts!

Hey Eric-

Loving your surname ! Ford fit the MHEV 1.0 engine to multiple models.

I wanted to reach as many Ford users as possible, who may have similar issues with an OEM fit SL battery.

44 minutes ago, TomsFocus said:

MHEV's don't 'need' an EFB battery because stop/start is done using the 48v MHEV battery on those.

Duly noted Tom, thanks. My original concern was electrical demand from the 48v battery and the cars stop/ start capabilities on an SL type 12v battery. I don’t believe too many cars with stop/ start systems use SL batteries. Indeed, Ford OEM finis No. for my car now only lists an EFB unit not an SL. I think Ford fitted SL batteries to earlier MHEV 1.0 engined cars to cut financial corners.

48 minutes ago, Steven Gray said:

Duly noted Tom, thanks. My original concern was electrical demand from the 48v battery and the cars stop/ start capabilities on an SL type 12v battery. I don’t believe too many cars with stop/ start systems use SL batteries. Indeed, Ford OEM finis No. for my car now only lists an EFB unit not an SL. I think Ford fitted SL batteries to earlier MHEV 1.0 engined cars to cut financial corners.

I don't understand where you think the extra demand is?

The 48v generator charges the 48v battery.  The 48v battery restarts the engine after stop start.

The only demand on the 12v battery is the first engine start of the day and running the alarm overnight.  Standard batteries managed that for years.

I'm not disputing that Ford are clearly rubbish at mapping a charging system, and fitting batteries of a capacity too small for the car, but I don't believe the lack of EFB is the issue here.  Most of the battery faults we see are on cars with EFB batteries.  Both MHEV & non-MHEV.

54 minutes ago, Steven Gray said:

Ford fit the MHEV 1.0 engine to multiple models.

Indeed they do, but problems with 12V batteries pre-date the introduction of MHEV. There was a big upsurge in such issues with the introduction of the Mk 8 Fiesta and Mk 4 Focus as you'll see with a good look around. Just one (of many) threads:

https://www.fordownersclub.com/forums/topic/115331-car-battery-mk8/

 

4 hours ago, Steven Gray said:

high 12v battery demands by the 48v Hybrid battery

Just to clear this up, on an MHEV vehicle the belt-integrated starter-generator (BISG) charges the 48v battery when the engine is running, especially when you slow down. A DC-DC converter provides power to the 12v battery to charge it from the 48v battery.