[djt5278]

That video is exactly what my car is doing, makes sense how I made the two hour trip back home after advanced auto said my alternator is dead.
My only concern now is why all the sudden is it doing this? My car used to sit at 14.3 volts all the time only rarely dropping to 13.8 at the lowest. Could it be ford sent out an Ota update?

And thanks! I hope to help out a lot in the stereo area, have had mine all pulled apart and modified.

 

[djt5278]

You indicate concerns based on 'measuring' alternator output ..... What 'symptoms' are you seeing in terms of battery health (dead battery, inability to start .... ?)

Some WAGs ...

1. The battery monitor system (BMS) may not 'like' the characteristics of your larger AGM battery, causing inappropriate charging characteristics

2. Failure to reset the BMS when you installed the new battery may not be giving it a chance to work right; among other things it 'thinks' it is looking at an older battery; see http://www.fordescape.org/forum/diy-garage/52369-diy-battery-monitor-system-reset.html

If you truly drive your 'rated' 3600W system at full-power (300 amps in theory) you probably are indeed overloading things. But it is most likely that you are not really approaching that load. Have you measured your actual main stereo feed (connected at the battery + terminal with a nearby main system fuse, right?) amp load at typical listening conditions?

Curious to know ... what do you use as the 'turn-on trigger' for your added amps? IF you use a signal-sensing device on one of the OEM speaker outputs then your system amps should 'shut-down' when the OEM stereo shuts-down as part of the battery-saver technology (e.g. when listening with the key-off after a few minutes). If you use any other turn-on trigger you will not get that 'battery saver system' benefit.

1. (and 2) I am purchasing a OBD to USB too and will try the battery reset.
3. It is a true 3600w amp(DD Audio) but I am not pulling the full 300 amps. Pulling maybe 200A in bursts, have it turned down a lot.

For a turn on lead I put a wire under the fuse for the heated seats which is in the rear fuse panel, they go on and off with the ignition.

Will report after I try the BMS reset. But an update on how the voltage is going: starts at 14.9, sometimes 15, volts. Tapers off down to around 13.8 then trickles down to 12.0. Using any factory electronics such as AC or headlights the voltage is taken up to 13.4-14. However, using the stereo kills the voltage. Before I was able to run the full ~200amps from the stereo and would never drop below 14 unless I pounded it for a while. Really no issues other than when using the stereo.

Hoping I can get this cleared up before my next competition in June!

 

[djt5278]

Used the scan tool to reset battery and bms. Had an error code for losing communication with bms module, but that was likely from when I removed the battery. Unfortunately there is no change in the charging voltage.

 

[djt5278]

I reset the dtc, and the bms system. Using the forscan application. I reset it and let it sit overnight, nothing left on.

Absolutely no change from before. Left from erie to Buffalo, 2 hour drive. Got to Buffalo with no voltage problems, did what I had to do there then started the car and noticed the battery was sitting at 12v. Measured using the voltage meter for my amp. Checked accuracy with a fluke meter on the battery.

I am going directly to the negative post with my amps ground. That is something to think about, because I am bypassing the bms doing that. But how else could I increase the size of the ground wire?

The issue is while driving and idling, engine speed seems to have no effect. Turning on the hvac, or anything else has no effect either.

The competitions do not allow anything to charge the car, except the car itself.

No apology necessary, I appreciate the help!
I think I replied to all your steps.

Phazewolf, using fluke meters on the battery, clamp on stereo positive runs, and clamp on alternator positive lead. And rpm doeant effect anything.

 

[djt5278]

Figured I would update this, but I have fixed the issue. I disconnected the small red wire from the positive terminal on the battery. This must feed the BMS, as the forscan reads as lost communication with BMS. Now the alternator regulates the voltage by itself, rather than being told what to put out by the BMS. So whatever I draw with the stereo, the alternator puts out. This keeps me at a happy 14.3-14.8 no matter how loud the stereo is.
This is how the car ran before, so I am thinking the car lost communication with the BMS a long time ago, then it suddenly regained communication and started to regulate the voltage down.
So for anyone with an aftermarket stereo, disconnect the small red wire from the positive terminal on the battery and you will be good to draw up to 150 amps.

 

[djt5278]

I agree, most will not need as much power as I do. But if you are having issues with voltage not staying up, this is the way I found to fix that. Dropping down in the 10v range is not good!