12 V battery replacement

[old man's hybrid]

I have a 2019 Fusion Hybrid, when should I expect to replace the original 12V battery,?  I have already replaced the factory tires at 35K miles. I will appreciate any input...

 

[mwr]

My 2015 FFH will be eight years old this October, has 95K miles, and still has the original 12V battery.

[2014FordFusionSE]

19 hours ago, mwr said:

My 2015 FFH will be eight years old this October, has 95K miles, and still has the original 12V battery.

That's really good. I would replace it preemptively if I were you.

That way, you won't have any surprises and you're good for another 8 years.

[mwr]

36 minutes ago, 2014FordFusionSE said:

That's really good. I would replace it preemptively if I were you.

That way, you won't have any surprises and you're good for another 8 years.

I'm sure you're right, but it's become sort of a challenge to see how long it will last ?

[MeeLee]

On 8/14/2022 at 3:31 PM, mwr said:

I'm sure you're right, but it's become sort of a challenge to see how long it will last ?

So far mine is at 105k miles (granted it's only 3 years old).

The good thing is battery checks are free with ford until the end of the year (though our ford dealer has a few day wait time before the first appointment is available).

 

The high voltage battery in my case will go bad before the 12v battery. It currently has about 50% range left.

[Sky14FFH]

On 8/13/2022 at 6:40 PM, old man's hybrid said:

I have a 2019 Fusion Hybrid, when should I expect to replace the original 12V battery,?  I have already replaced the factory tires at 35K miles. I will appreciate any input...

 

The NOCO 5 battery charger on Black Friday sale will save you a LOT OF MONEY and hassle.  $50.  It restored two of my batteries. One is an 11 year old Optima AGM and the other the 8 year old OEM in the FHF. I've been trying to get an original 22 year old lead acid to recharge with it too but I'm going to have to do some chemistry experiments to clean it out and add new battery acid. 
https://www.amazon.com/NOCO-GENIUS5-Fully-Automatic-Temperature-Compensation/dp/B07W8KJH44/ref=sr_1_5?crid=2JG3C8KN9FKMV&keywords=noco+genius+5&qid=1669445147&sprefix=noco+%2Caps%2C449&sr=8-5

[MeeLee]

On 11/26/2022 at 1:48 AM, Sky14FFH said:

The NOCO 5 battery charger on Black Friday sale will save you a LOT OF MONEY and hassle.  $50.  It restored two of my batteries. One is an 11 year old Optima AGM and the other the 8 year old OEM in the FHF. I've been trying to get an original 22 year old lead acid to recharge with it too but I'm going to have to do some chemistry experiments to clean it out and add new battery acid. 
https://www.amazon.com/NOCO-GENIUS5-Fully-Automatic-Temperature-Compensation/dp/B07W8KJH44/ref=sr_1_5?crid=2JG3C8KN9FKMV&keywords=noco+genius+5&qid=1669445147&sprefix=noco+%2Caps%2C449&sr=8-5

I've replaced the lead acid with a 12v lithium.

Since then, my mpg went up from 42 to 45mpg.

Did a 300 mile ride yesterday, with an average of 53mpg (not accounting for the 4% taller tires, which make the actual numbers closer to 55.5mpg).

 

Did a recent smaller trip, no highway, and got 60mpg average readout. Used all the tricks in the book (accelerate in normal mode until 10-15mph over the limit, then coast on electric using only 1 bar (10hp) to slowly decrease speed to 45mph, and also coast in neutral for stoplights far away)...

 

The 12v lithium isn't charged up by the car, becasue the bms cuts off when the charge voltage increases above 14.7V.

 

Instead I've bought this $25 10A charger:

https://www.amazon.com/dp/B09DCK7XG1

 

I did the math, charging the lithium from empty costs me around $25-33ct. The gains in mpg are 3+ MPG(and still rising).

 

I only have to charge it about every other week. Since I do uber part time, that means I save roughly 100 miles on gas out of 1500 miles, or ~$20 every 2 weeks.

[Sky14FFH]

On 12/30/2022 at 1:18 AM, MeeLee said:

I've replaced the lead acid with a 12v lithium.

Since then, my mpg went up from 42 to 45mpg.

I just replaced my 12v with a Motorcraft AGM BAGM-H4 from Rockauto (beware they don't reimburse for core).  I have to confirm, my fuel economy went up from an already good tank from 50mpg to 56mpg averaging out the fillup at 52mpg.  Since I also changed my oil using Mobil 1 5w-20 hybrid at the same time the fuel economy on Trip 2 where I keep my oil change miles is over 54mpg.

Got both batteries tested at a ford dealer and one of the cells conked out in the OEM.  Not bad for 11 1/2 years though.  AGM tested at 650 CCA even though it is rated at 540.

 

If anyone knows where to get reimbursed for the full amount of the core $18, I'd like to know.  I really hate being scammed.

Edited October 8, 2025 by Sky14FFH

[2014FordFusionSE]

On 10/7/2025 at 6:13 PM, Sky14FFH said:

I just replaced my 12v with a Motorcraft AGM BAGM-H4 from Rockauto (beware they don't reimburse for core).  I have to confirm, my fuel economy went up from an already good tank from 50mpg to 56mpg averaging out the fillup at 52mpg.  Since I also changed my oil using Mobil 1 5w-20 hybrid at the same time the fuel economy on Trip 2 where I keep my oil change miles is over 54mpg.

Got both batteries tested at a ford dealer and one of the cells conked out in the OEM.  Not bad for 11 1/2 years though.  AGM tested at 650 CCA even though it is rated at 540.

 

If anyone knows where to get reimbursed for the full amount of the core $18, I'd like to know.  I really hate being scammed.

 

As I always say, call around and ask. O'Reilley's, AutoZone, Walmart

IIRC, O'Reilley's will give you a gift card in exchange for the core.

[fastFusion]

That's impressive longevity on the original 12V - I've heard that hybrids can be easier on the battery since the engine cycles less, so getting over a decade isn't unheard of but definitely on the high end of what you'd expect.

[Sky14FFH]

On 11/19/2025 at 3:18 PM, fastFusion said:

That's impressive longevity on the original 12V - I've heard that hybrids can be easier on the battery since the engine cycles less, so getting over a decade isn't unheard of but definitely on the high end of what you'd expect.

I think it helped that I got a Noco Genius 5amp battery charger during pandemic.  I'm still really annoyed that the guy who was repairing my car after a rear ender left it out in the heat for weeks ultimately killing the battery.  I guess it was time to get a new one but I am just not a buy-and-throw-away-buy-and-throw-away person and do not understand why so many Americans are.  I'm also really annoyed that what was once $50 for batteries are now $200 but I hope it is worth it for an AGM.

[Davewn]

How important is it to reset the BMS after changing the 12v battery?  I just preemptively replaced my 2017 FFH's OE Motorcraft T5/90 580 CCA with an off the shelf T5/90 640 CCA battery from Costco last week.  I have not been able to reset the battery monitoring system manually with the sequence of 5 high beam flashes and 3 brake pedal pumps in accessory mode (cited on multiple websites) despite numerous attempts.  

Edited January 21 by Davewn

[Sky14FFH]

On 1/20/2026 at 6:41 PM, Davewn said:

How important is it to reset the BMS after changing the 12v battery? 

I dunno. I never heard of this.  Mine seemed to work right away.  Let us know what you find out.  Isn't the BMS for the hybrid battery?

[Davewn]

28 minutes ago, Sky14FFH said:

I dunno. I never heard of this.  Mine seemed to work right away.  Let us know what you find out.  Isn't the BMS for the hybrid battery?

The BMS is for the 12V and is present in all newer Ford vehicles.  All the videos I saw with the manual high beam/brake pedal reset seemed to be in non-hybrid vehicles come to think of it. The main reason I saw people resetting the BMS in videos was because they were tripping codes and/or losing some functions like auto start-stop and proximity key due to low voltage in their old batteries.  I've driven my car about a week now and am finding it drives exactly the same way it did before.  All I had to do was reset the clock and radio presets, just like any regular car...  

Edited January 23 by Davewn

[Sky14FFH]

On 1/20/2026 at 6:41 PM, Davewn said:

 I just preemptively replaced my 2017 FFH's OE Motorcraft T5/90 580 CCA with an off the shelf T5/90 640 CCA battery from Costco last week.

Curiously, why did you "preemptively" replace your OEM 12v battery?  My goal was to nurse mine along as long as possible with a NOCO Genius charger helping out which I obtained during the pandemic when my car was sitting for longer times than normal. I got to 11.5 years before someone else killed it letting it sit out in the heat with no operation for 6 weeks. 

I ended up putting something in that will hopefully last longer, a Ford AGM battery.  Never had to reset anything.  When I swapped the battery I connected the car to my other car's battery with jumper cables so no memory would be lost. I try to do everything carefully like that.  

Edited January 25 by Sky14FFH

[Davewn]

I replaced the battery because it was 9 years old and we are in the teeth of winter here in the upper midwest.  I'm as frugal as the next guy but it's the car we inevitibly take on road trips, so for $125 I consider it cheap insurance against having a problem on a subzero day hundreds of miles from home.  I got my money's worth out of the old one...From what I could ascertain, Ford switched to the current BMS for the '16 model year.

[2014FordFusionSE]

On 1/20/2026 at 3:41 PM, Davewn said:

How important is it to reset the BMS after changing the 12v battery?  I just preemptively replaced my 2017 FFH's OE Motorcraft T5/90 580 CCA with an off the shelf T5/90 640 CCA battery from Costco last week.  I have not been able to reset the battery monitoring system manually with the sequence of 5 high beam flashes and 3 brake pedal pumps in accessory mode (cited on multiple websites) despite numerous attempts.  

I didn't do any of this when I replaced the 12v. No issues so far.

[Sky14FFH]

19 hours ago, Davewn said:

so for $125 I consider it cheap insurance against having a problem on a subzero day hundreds of miles from home.

Ah that is comparatively cheap even though 12v lead acid batteries used to be half that.  I hope I didn't get ripped off on a sketch battery from Rockauto.  I've since been taught by a mechanic that rockauto sells blemished parts.  I paid about $180 including $18 core deposit rockauto would not reimburse. I used to recommend them.  Not so much anymore. Someone has pocketed that $18. I got the battery tested at a dealer and they said it was good but I am still concerned.  And I got the motorcraft AGM hoping to avoid headaches. (ok thinking out loud)  Where did you get the $125 one?

[Davewn]

I bought my battery from Costco.  It's an Interstate, a regular lead acid T5/90 battery like the OEM Motorcraft one it replaced.  The cases were identical with the exception of  a handle on the Interstate so everything was plug and play.   I did splurge on an $8 set of nylon trim tools from Harbor Freight so I wouldn't break or mangle the button clips for the trunk trim in my cold garage.  The reason for my initial question is I read that not resetting the BMS can lead to premature failure of the replacement battery as the car recharges the new one based on parameters of the old, potentially under or overcharging it.  This is all a grey area for me,, however, as nothing I read or saw online about the BMS was 2016 or later FFH specific.  My ownner's manual was basically worthless in this regard with the typical high dollar solution of "bring it to your Ford dealer," hence my internet rabbit hole.