Ford Focus ST Forum banner
1 - 20 of 21 Posts

·
Registered
Joined
·
91 Posts
Discussion Starter · #1 ·
Howdy folks, so those of you who flash/reflash their FoST ECUs, do we need a battery charger connected during the process? The folks at Cobb tuning certainly recommend that we do so. Problem is, some of us do not have access to power points (e.g., in apartment complexes). Maybe go out for a 20-minute drive and make sure the battery is fully charged, and then turn off lights and all other accessories before the flash?
 

·
Super Moderator
2014 ST3. Garrett GTX2860R Gen 2. FBO
Joined
·
5,795 Posts
These cars do eat batteries though. A lot of guys report replacing them every 2 to 3 years when weird stuff starts to happen.

Point being, if you dont know the battery history, put a new one in and perform the BMS reset before tuning. A battery is a couple hundred bucks. A new PCM and a tow will run you around 1,300 plus waiting time. It's cheap insurance.
 

·
Registered
2013 Ford Focus ST
Joined
·
812 Posts
  • Like
Reactions: Duece McCracken

·
Registered
Joined
·
1,651 Posts
If I recall correctly, Cobb recommends a 10A charger be connected during the procedure. I have one, and a garage- so it was simple and convenient to do, but I can imagine it being a challenge if you do not. I agree with the above sentiment that you would be wise to either make sure you have a new battery that is fully charged, or buy a charger and find a place to plug it in as directed.

I offer you my garage and charger to perform the flash if you are in the NJ area.
 

·
Registered
Joined
·
327 Posts
I have never used one. Does it take that much juice to reflash the ECU in 2 minutes?

I mean I am not opposed to use a charger.
 

·
Super Moderator
2014 ST3. Garrett GTX2860R Gen 2. FBO
Joined
·
5,795 Posts
I have never used one. Does it take that much juice to reflash the ECU in 2 minutes?

I mean I am not opposed to use a charger.
No, but if a battery has very little reserve capacity left, it certainly can drop low enough to fry a computer.
 

·
Registered
Joined
·
1,651 Posts
If your battery has been working well, I think chances are pretty good that you'll be fine just going for it without taking any other precautions. The consequences of a disruption in power during the flash are too dire, in my opinion, and I'd rather be safe than sorry. I guess it all depends on your risk tolerance.
 

·
Registered
Joined
·
327 Posts
If your battery has been working well, I think chances are pretty good that you'll be fine just going for it without taking any other precautions. The consequences of a disruption in power during the flash are too dire, in my opinion, and I'd rather be safe than sorry. I guess it all depends on your risk tolerance.

Low risk tolerance here, well for some things. I still have the original battery that is almost 4 years old. Charger will be used during flashes from now on. I do not like dire consequences. 2 minutes of my time to potentially save a crap ton of $$$...easy choice.
 

·
Registered
2013 Ford Focus ST
Joined
·
812 Posts
I think of it as updating the bios on a computer, if it looses power during, it is bricked and that sucks.
 
  • Like
Reactions: TurboGT

·
Registered
Joined
·
1 Posts
I installed my AP yesterday for the first time after a 30 minutes run with my '17 ST original battery and no issue whatsoever without the charger. Took somewhere between 5-10 min and enough battery to start 2 time after that without issue.
 

·
Registered
Joined
·
91 Posts
Discussion Starter · #11 ·
Thanks to everyone for their responses. I do have a battery jump starter. Would that work in place of a charger? I'm not sure that is the case.

I have a relatively new battery, replaced a few months ago after the original battery died, with a very generous dose of corrosion on the negative terminal. Boo! Lesson learned - regular battery inspections from now on.
 

·
Super Moderator
2014 ST3. Garrett GTX2860R Gen 2. FBO
Joined
·
5,795 Posts
Your new battery should be fine. Did you perform BMS reset? If not you need to do that now. Have a search, theres a topic on how to do it manually
 

·
Registered
Joined
·
91 Posts
Discussion Starter · #13 ·
Your new battery should be fine. Did you perform BMS reset? If not you need to do that now. Have a search, theres a topic on how to do it manually
I actually did not perform a BMS reset. I can go ahead and do that - found the instructions to do so on the relevant thread. What are the pros/cons of performing/not performing the reset?
 

·
Super Moderator
2014 ST3. Garrett GTX2860R Gen 2. FBO
Joined
·
5,795 Posts
I actually did not perform a BMS reset. I can go ahead and do that - found the instructions to do so on the relevant thread. What are the pros/cons of performing/not performing the reset?
If you dont perform it, the alternator strategy still thinks its charging an aging battery and will only charge yours to 80% SOC. Which will cause an early demise for your battery.
 

·
Registered
Joined
·
91 Posts
Discussion Starter · #15 ·
If you dont perform it, the alternator strategy still thinks its charging an aging battery and will only charge yours to 80% SOC. Which will cause an early demise for your battery.
Oh, I did not realize that. I'll go ahead and perform the reset today. Thanks for the insight. You guys are a goldmine of info!
 

·
Registered
2013 Ford Focus ST
Joined
·
812 Posts
Bestowed upon us from of our admins awhile back…

Battery Monitor Reset:
Steps 2, 3 & 4 must be done in 10 seconds or less...
1) turn on headlights
2) ignition button on foot off of clutch, don't start the engine
3) flash brights 5 times
4) step on brake 3 times
5) engine light flashes 3 times
6) battery light flashes 2 times...done
 

·
Registered
Joined
·
91 Posts
Discussion Starter · #17 ·
Bestowed upon us from of our admins awhile back…

Battery Monitor Reset:
Steps 2, 3 & 4 must be done in 10 seconds or less...
1) turn on headlights
2) ignition button on foot off of clutch, don't start the engine
3) flash brights 5 times
4) step on brake 3 times
5) engine light flashes 3 times
6) battery light flashes 2 times...done
Thank you!
 

·
Registered
Joined
·
530 Posts
I charge the battery to 100%, disconnect charger and then flash. Most chargers will not stay at max charge amps and tapers down, your not supped to have fluctuations.
 
  • Like
Reactions: MacawMania

·
Registered
Joined
·
522 Posts
If you change battery chemistry or CCA I think you should go into the BCM with ForScan and make the appropriate changes. If not you can over or under charge. Same for same battery specs BMR only.
 
  • Like
Reactions: MacawMania
1 - 20 of 21 Posts
Top