2016 GT Battery issue

[justa16yote]

I have a 2016 GT, was recently dealing with my battery dying after sitting for longer than a day, has anyone had issues with the BMS and the current sensors? I jump started the car and disconnected the negative current sensor and my dash voltage is reading 14.2 V while my tuner reads 14.5-14.7 V

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[Farkel]

More info would be helpful. The 14+ volts shows that the alternator is trying to do its job. Not sure why you disconnected the BMS; what was the voltage before you disconnected it? Have you added any components that could cause the battery to drain? Have you had the battery [load] tested?

 

[justa16yote]

More info would be helpful. The 14+ volts shows that the alternator is trying to do its job. Not sure why you disconnected the BMS; what was the voltage before you disconnected it? Have you added any components that could cause the battery to drain? Have you had the battery [load] tested?

I had disconnected it before I jump started it, with it connected it would show 12.8-13.5V, and having it sit longer than a day would cause it to not have enough power to start, the only thing I have added is a amp for my sub, and I have gotten the battery tested, the battery is good and the alternator is good also

 

[KeyLime]

Original battery? If so, it's way past its drop dead date.

Drive the car so the battery charges. Disconnect the negative terminal and let it sit overnight. Check the voltage. If it's low then the problem is the battery or the charging system, not a parasitic load. Given that you are seeing a voltage of 14.2-14.5 while the engine is running my assumption is that the alternator is okay and your battery is kaput.

You can go to some auto stores and they will check your battery under load and also the alternator for little or no $. Cheap way to diagnose.

And forget about any advice about BMS. It's there to optimize charging to extend battery life and maybe eek out an extra fraction of an mpg. Not resetting BMS will not result in a dead battery or no charging. It just means your new battery will die in 46 months instead of 48.

 

[Farkel]

I'm no expert, and I won't pretend to be one on the interweb. Unless you're good with tracing parasitic draw, my only guess would be to see what happens if you disconnect the amp, fully charge the battery, and see what happens when it sits for more than a day.

 

[justa16yote]

Original battery? If so, it's way past its drop dead date.

Drive the car so the battery charges. Disconnect the negative terminal and let it sit overnight. Check the voltage. If it's low then the problem is the battery or the charging system, not a parasitic load. Given that you are seeing a voltage of 14.2-14.5 while the engine is running my assumption is that the alternator is okay and your battery is kaput.

You can go to some auto stores and they will check your battery under load and also the alternator for little or no $. Cheap way to diagnose.

And forget about any advice about BMS. It's there to optimize charging to extend battery life and maybe eek out an extra fraction of an mpg. Not resetting BMS will not result in a dead battery or no charging. It just means your new battery will die in 46 months instead of 48.

It’s a brand new battery, I got it about 2 weeks ago, checked the voltage at 14.5V, repeatedly turned off and started it about 5-6 times, and then drove it around for 30 minutes with no issues. Already got the battery/alternator tested and both are good

 

[KeyLime]

It’s a brand new battery, I got it about 2 weeks ago, checked the voltage at 14.5V, repeatedly turned off and started it about 5-6 times, and then drove it around for 30 minutes with no issues. Already got the battery/alternator tested and both are good

Wow, I'm stumped. Maybe the new amp is a parasitic load?

 

[Sparky1337]

Try a BMS reset:

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

 

[justa16yote]

Wow, I'm stumped. Maybe the new amp is a parasitic load?

I doubt it but idk, this is currently my 3rd amp, 2 were 600W amps and this one is a 1200W, they never really drained the battery before

Try a BMS reset:

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

I tried that before, and it didn’t work, I let the car sit a day and a half after that, and it didn’t have enough power to start

 

[Sparky1337]

Dang, figured it was worth a shot.

These cars definitely like to suck power when they aren’t fully “asleep”. Even leaving it unlocked vs locked in the garage will have mine dead within a few days.

Alternatively, you could rule out the amp by just disconnecting it. Maybe this one doesn’t play well with the Ford system.

 

[justa16yote]

Dang, figured it was worth a shot.

These cars definitely like to suck power when they aren’t fully “asleep”. Even leaving it unlocked vs locked in the garage will have mine dead within a few days.

Alternatively, you could rule out the amp by just disconnecting it. Maybe this one doesn’t play well with the Ford system.

I could try it out and see

 

[Rwwilli09]

AMP clamp on the positive battery cable will show you if you have a draw. Willing to bet the new AMP is drawing the battery down. I'm old, saw it a lot in my teenage years when we all had "systems".

 

[Optimum Performance]

Make sure you are not under the brake light switch recall. I destroyed a perfectly good AGM battery before we knew about it. The little rubber bumper falls a part and gets worse overtime, keeps your tail lights on and your system running, draining your battery. Our's has the parking lot zip-tie fix. No more problems.

 

[compucarnut]

Do not jump start these cars without following the correct procedure. These arent fox bodies. I did and it was a very expensive mistake

 

[Postal Bob]

New battery, how long have you driven it continuously for any one time? And do you have it on a battery tender?
Reason I ask, is that the first time I replaced the battery, it took a 4 hour drive before the voltage reading on the dash dropped from 14.5V, down to 12.6V. And this time when I replaced the battery, keeping it on the battery tender, it took days before the tender showed the battery charged. In other words, these batteries take a long time when new, to get completely charged.

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