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2021 FORD F150 SCREW...HELP!! Battery only getting to 12.6 volts


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Hi all!

 

 

I went and installed all of this car audio gear into my 2021 ford f150 SCREW and notice on the bass knob that I am only getting 12 volts pretty much all the time.  I replaced the front battery with a XS power d4800 and combined it in parrallel with a Titan 8 lithium batt in the back.  The ford BMS system is limiting the voltage to aroun 12.4 to 12.6 volts pretty much all the time.  I am not sure what to do honestly.  

 

I have runs of 2/0 sky high going from front batt to back batt and the BMS is limiting my voltage sometimes as low as 12 even.  

 

Anyone have any ideas on how to side step the BMS or fix this issue?

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2 things:

1. Have you measured the voltage at your alternator with a multi meter?

2. Hard to tell, but in the second pic, is that a  ground clamp on the negative terminal? I'm looking at the thing with the plug. If it is, you'll want to route your ground wire through that. Else, you could try unplugging it and see if the vehicle defaults to some other voltage, without the smart charge. That charge algorithm won't work with the LTO batteries anyway

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22 hours ago, SnowDrifter said:

2 things:

1. Have you measured the voltage at your alternator with a multi meter?

2. Hard to tell, but in the second pic, is that a  ground clamp on the negative terminal? I'm looking at the thing with the plug. If it is, you'll want to route your ground wire through that. Else, you could try unplugging it and see if the vehicle defaults to some other voltage, without the smart charge. That charge algorithm won't work with the LTO batteries anyway

That is a ground clamp that Fords BMS system uses.  I wasnt sure how to make the transition from 2/0 wire to this small wire.

 

I did unplug this and it does jump to 13.3 or so but i get the idiot light (which i cant stand :))

 

I am aware that the LTO isnt great for this but with size requirements not sure i have any other options.

 

Thank you for the knowledge.  I do apprecaite it.  Looking forward to more.

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On 7/28/2023 at 9:20 AM, MikeyD said:

That is a ground clamp that Fords BMS system uses.  I wasnt sure how to make the transition from 2/0 wire to this small wire.

 

I did unplug this and it does jump to 13.3 or so but i get the idiot light (which i cant stand :))

 

I am aware that the LTO isnt great for this but with size requirements not sure i have any other options.

 

Thank you for the knowledge.  I do apprecaite it.  Looking forward to more.

LTO is great for this

The charge profile, however, is not

LTO charges CC/CV - alternator holds a voltage and keeps it there. No hot/cold.

You might have luck turning on the headlights too. On some vehicles, it'll boost/lock charge voltage to 14-14.4 or so.

Barring that, you'd want to get an aftermarket alt from mechman or something, but ask for an external regulator and use the dial to set voltage. If you do this, throw the wiring kit out and use 8 gauge to connect the thing.

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  • 5 weeks later...
On 8/1/2023 at 11:02 AM, SnowDrifter said:

LTO is great for this

The charge profile, however, is not

LTO charges CC/CV - alternator holds a voltage and keeps it there. No hot/cold.

You might have luck turning on the headlights too. On some vehicles, it'll boost/lock charge voltage to 14-14.4 or so.

Barring that, you'd want to get an aftermarket alt from mechman or something, but ask for an external regulator and use the dial to set voltage. If you do this, throw the wiring kit out and use 8 gauge to connect the thing.

I am at my end with this and Fords BMS system lol.  I cannot get the voltage to anything above 12.6 no matter what i do.  I have tried to turn on headlights and everything.  It wont go up at all.  

 

I have looked at mechman alts and they do not offer an alternator for my truck.  I dont know what to do honestly.  I cant be the only one with a 2021 or up FORD f150 with this problem.  Do i have to void my warranty to get this running properly?  Do i need to scrap my current setup of amps and go with the sundown line S.A.L.T ?  Would this even help?  Very frustrated.

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21 hours ago, MikeyD said:

I am at my end with this and Fords BMS system lol.  I cannot get the voltage to anything above 12.6 no matter what i do.  I have tried to turn on headlights and everything.  It wont go up at all.  

 

I have looked at mechman alts and they do not offer an alternator for my truck.  I dont know what to do honestly.  I cant be the only one with a 2021 or up FORD f150 with this problem.  Do i have to void my warranty to get this running properly?  Do i need to scrap my current setup of amps and go with the sundown line S.A.L.T ?  Would this even help?  Very frustrated.

DC power makes one for the 3.5 ecoboost

Not sure which engine you have. But that might be a lead

Shoot them an email. You'll want to do 3 things
1. See if this fits, or if they have something that would. If not, could possibly be a tester to validate
2. Ask if you can get it externally regulated
3. Ask if there's any sort of bypass for what would be a charge warning / CEL


If you're feeling spicy..... It looks like these alternators are indeed externally regulated from the factory, controlled via PCM.

I found an unconfirmed wiring diagram from another forum. Could be a start point for investigating some custom wiring. Looks like GENCMD is a PWM control for field strength. What I'm unclear on is how GENMON works. If it's acting as a 'ground' for the rotor, or if the alt has any sort of internal communication. Again, need to do  some investigation on it.

https://f01.justanswer.com/nmwagschal/d3965968-12f0-4239-8ac6-1a9c81501c76_2012_6.7__charging_testing_.pdf

image.jpeg

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15 minutes ago, SnowDrifter said:

DC power makes one for the 3.5 ecoboost

Not sure which engine you have. But that might be a lead

Shoot them an email. You'll want to do 3 things
1. See if this fits, or if they have something that would. If not, could possibly be a tester to validate
2. Ask if you can get it externally regulated
3. Ask if there's any sort of bypass for what would be a charge warning / CEL


If you're feeling spicy..... It looks like these alternators are indeed externally regulated from the factory, controlled via PCM.

I found an unconfirmed wiring diagram from another forum. Could be a start point for investigating some custom wiring. Looks like GENCMD is a PWM control for field strength. What I'm unclear on is how GENMON works. If it's acting as a 'ground' for the rotor, or if the alt has any sort of internal communication. Again, need to do  some investigation on it.

https://f01.justanswer.com/nmwagschal/d3965968-12f0-4239-8ac6-1a9c81501c76_2012_6.7__charging_testing_.pdf

image.jpeg

WOW!

 

YOU FREAKING ROCK!

 

I will check them out!  Thank you so much!

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  • 3 months later...
  • 1 month later...
On 7/26/2023 at 4:07 PM, MikeyD said:

I have a very similar setup as you with a titan 8 4800 in the back but stock batt up front. I’m about to build a 64ah bank in the back and move the titan 8 up front. I disabled the BMS in Forscan (still get the annoying warning) but it now charges past what I was previously regulated at (12.6 idle) and I can hold 14v with a Crescendo 4k, Crescendo S2, and a JP23. I’d recommend Brand X for the alt, I’ve got a 370a not yet installed on my 2.7. I’ll be running a 2/0 ground from the alt to the rear bank, and the titan 8 up front as I’ve heard it’s the best way with these trucks.IMG_2690.thumb.jpeg.ae49f7f7857c8e4e8bb9474bc51a2b69.jpegPhotoRoom_20230414_213015.thumb.jpeg.d81259882a0850877b5ac8663bef46c5.jpeg. I’m going to a Salt 6 soon

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