Replacing the 12 Volt Battery in a 2013 Ford Fusion Energi

Searched the web and there was just a sorta-helpful YouTube video on this but nothing really all that instructive. I had to do this today, so here goes. If you are having issues getting locked-out of your 2013 Energi and having your car send emails on low battery warnings for the 12 volt, yeah, you have to to get that battery replaced. WARNING: If you are uncomfortable doing this, go to the Ford Dealer for service. Don’t risk damaging your car or yourself trying to do this. 

1. The 12 volt is in the Energi alongside the massive PHEV battery. It lives in the trunk area of the car on the driver’s side. Make sure things are unplugged and get a big flathead screwdriver, 10 mm socket and wrench, long nose pliers and decent lighting. 

2. Open the trunk, twist the dials on the little door to see the 12 volt battery.

3. I tried to do all of this via that small cutout window. This was a mistake. You can’t get that battery out of the space and I really really tried because I didn’t want to take out all the interior panels in there. 

4. Immediately and carefully remove the fastener bolts on the main PHEV battery assembly, the driver side panel, and the lower panel. You don’t need to remove the Styrofoam stuff holding the tire tool and 120v charging cable if you are not using it. They are a totally pain to remove carefully. Long nose pliers and a large flathead screwdriver help, but you probably could easily destroy them. There are 4 on the PHEV battery, a couple on the side panel, and a couple on the back plastic you need to remove along with the plastic bolt and a cap or two to get these all loose. 


5. Once you have things open, you can operate. I did most of this with the panel up, you shouldn’t. Once you get things open, you can use the 10mm wrench to loosen the positive and negatives of the battery. Do that and ease the connectors off the battery. Immediately electrical tape over the positive side so you won’t spark anything or you won’t get electrocuted. 

6. You’ll also have to remove the side restraint on the base of the battery that holds the battery firm to the sled and the bolt on the fabric straps that go over the top of the battery as an additional restraint. 

7. There is also a connection to the side of the battery for any liquid drain. You need to disconnect that prior to extraction as well. 

9. With the battery out, get the replacement and bring it back to install. There was an option to get a more powerful battery, so I did. 

10. The replacement 12 volt battery fits perfectly and lock it in via the side restraint and the fabric strap. Then CAREFULLY add the positive connection after the ground side. All and all, you should get to something like this prior to putting the panels back up. 

11. Make sure you get good vibes from the car on hookup – you can open the doors, play the radio, etc. You want to know if something is bad no because the panel installs are not fun. 

12. All good power-wise, then put in the side panel covering the battery, then the panel over the PHEV battery, then the lower shelf above the Styrofoam stuff. If you have the patience, it should look nice again after you are done. 

Then, you are essentially done. You’ll have to go back and set the clock again on the car along with checking other Sync settings, but you should be good. 

Hope this helps!


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  • I stumbled across this looking to replace the 12v battery in a 2014 hybrid. Thank you for the info but I did want to point out one safety item. You always remove the battery ground cable first and reinstall it last. Any time it is hooked up the positive side can short to virtually anything in the car, where as when the positive is hooked up the only thing the negative could short to is the positive itself or an unprotected power cable which there should not be any of around.

  • Thank you for the details. How did you end up opening the trunk with a dead battery. I am unable to even jump start the car as it says the battery is damaged.

  • This article along with two videos on YouTube showing this really helped. I was do the whole process fairly quickly. However, I noticed my positive terminal didn’t have a cover, and grew concerned. Now I see yours doesn’t either. Is it necessary since our batteries are in the trunk?

  • Can I assume that the procedure will be the same for my “non-energi” hybrid? Nothing has to be reset except the clock and stuff like that?

    • Dan, you know I am not sure. I do know the 2013 with battery is basically the same as the non-energi in physical design. I just have that massive battery that basically kills off most of that trunk space. So, I’m assuming the 12v is back there for the regular hybrid too. If you take a look, please post and confirm if possible. Thanks for commenting.