Stereo Dual Battery - BMS Questions

[raydulce]

I found a lot of BMS threads, but none that really answered my question. I'm hoping this thread can grow into a pinned/sticky that will help many others too.

I upgraded my 2023 stereo system with a subwoofer and amplifier. We ran 1/0 Copper (both positive and ground) to behind the seat. I'm going to be putting a 1500W RMS amplifier back there and am beginning to worry about voltage support. I found a a great little sealed AGM battery I can put back there for power stability. So my question is rather general: "Can someone please teach me how the BMS system works in detail?".

I currently have the battery in parallel (fused, but no isolator). On my last truck (Silverado) I had an isolator in the circuit to disconnect the battery when the truck was off to avoid any parasitic drain since they're not identical batteries. I may do that here, but want to learn more about Ford's system first. I have a very strong background in electricty and power, but almost zero experience with Ford's setup.

- Will changing the 80% SOC in ForScan result in ~14.4 volts always?
- Do I need to change my battery Watt-Hour setting with Forscan?
- Please share any other tips, tricks, or thoughts about Fords BMS and a 2nd battery.

THANK YOU!!

 

[Shane361]

Your stock system can easily support a 1500rms amp. I do believe the magic number is somewhere around 2800 actually. I run a D3400 under the hood and 112ah of Headway Lithium in the bed with no ISO. I do believe I disconnected the smart charge part of the system. Also have Mechman370 alt. Done the "big three"? Where did you bring your zero into the cab? I need to get external voltage regulator for the Alt but apparently they don't make one that won't throw a dash code. Ford vehicles with the smart charge are not exactly ideal for larger stereo systems.

 

[The Car Stereo Company]

1500 watts isnt enough to warrant the need of a second battery. and a second battery is the last thing you need to add anyways, unless you plan on using the sound system with the truck off. bigger alternator is more important than a battery.

 

[raydulce]

@FordTechOne

I saw a few of your posts in other threads, and it sure sounds like you know your stuff. Is this a topic that you're able to share some knowledge? I'd like to know everything I can about these newer BMS systems.

Thanks!

 

[goblues38]

1500 watts isnt enough to warrant the need of a second battery. and a second battery is the last thing you need to add anyways, unless you plan on using the sound system with the truck off. bigger alternator is more important than a battery.

Do you all still do BIG Capacitors? Back in my day (early 90's) we would beef up the system with a 1 or 2 farad capacitor. Didn't require an isolator, but solved the problem with voltage drop when the bass was hitting hard.

 

[Shane361]

Do you all still do BIG Capacitors? Back in my day (early 90's) we would beef up the system with a 1 or 2 farad capacitor. Didn't require an isolator, but solved the problem with voltage drop when the bass was hitting hard.

Not still a thing to be honest.

 

[The Car Stereo Company]

Do you all still do BIG Capacitors? Back in my day (early 90's) we would beef up the system with a 1 or 2 farad capacitor. Didn't require an isolator, but solved the problem with voltage drop when the bass was hitting hard.

caps are almost obsolete now days. i had a 50farad capacitor back in 2004ish that helped with the power discharge, but with how alternators have been built better these days, its not necessary anymore. back when i was in spl competitions a high output alternator was anything over 165amps. and these high output alternators did not give a charge at idle. had to be above 2k rpms to get power from it. they also cost $700 or more (20 years ago, that was a shit load of money) and they only lasted about a year because they were wound so tight. not sure what high output (250amp or more) alternators cost these days, but with most sound systems its not necessary. im about 3k watts with my sq system but i dont have it cranked up loud most of the time so im not drawing maximum current. you will know if you need to upgrade if you start going through batteries. if you system is drawing more than you vehicle can produce, you draw from the battery. as capacity gets worn down, it diminishes the life of the battery. but nobody i know uses caps anymore. especially with these new batteries which can discharge just as fast as caps.

 

[Shane361]

caps are almost obsolete now days. i had a 50farad capacitor back in 2004ish that helped with the power discharge, but with how alternators have been built better these days, its not necessary anymore. back when i was in spl competitions a high output alternator was anything over 165amps. and these high output alternators did not give a charge at idle. had to be above 2k rpms to get power from it. they also cost $700 or more (20 years ago, that was a shit load of money) and they only lasted about a year because they were wound so tight. not sure what high output (250amp or more) alternators cost these days, but with most sound systems its not necessary. im about 3k watts with my sq system but i dont have it cranked up loud most of the time so im not drawing maximum current. you will know if you need to upgrade if you start going through batteries. if you system is drawing more than you vehicle can produce, you draw from the battery. as capacity gets worn down, it diminishes the life of the battery. but nobody i know uses caps anymore. especially with these new batteries which can discharge just as fast as caps.

My Mechman370 cost right around $700. My Lithium was over a grand but I built it myself. Should support a 10K system together...but only running a Sundown Audio SALT-4 to one 15" Zv6 at 1ohm.

 

[Shane361]

caps are almost obsolete now days. i had a 50farad capacitor back in 2004ish that helped with the power discharge, but with how alternators have been built better these days, its not necessary anymore. back when i was in spl competitions a high output alternator was anything over 165amps. and these high output alternators did not give a charge at idle. had to be above 2k rpms to get power from it. they also cost $700 or more (20 years ago, that was a shit load of money) and they only lasted about a year because they were wound so tight. not sure what high output (250amp or more) alternators cost these days, but with most sound systems its not necessary. im about 3k watts with my sq system but i dont have it cranked up loud most of the time so im not drawing maximum current. you will know if you need to upgrade if you start going through batteries. if you system is drawing more than you vehicle can produce, you draw from the battery. as capacity gets worn down, it diminishes the life of the battery. but nobody i know uses caps anymore. especially with these new batteries which can discharge just as fast as caps.

What's crazy is it seems we did so much with so little back in the 90's. I was running an Orion HCCA 275 at 1 ohm on two 15" RF HX2 15's on stock electrical and it was crazy bass. I'm not sure today I could get that much bass on stock electrical....doesn't seem possible but should be even easier.

 

[FordTechOne]

@FordTechOne

I saw a few of your posts in other threads, and it sure sounds like you know your stuff. Is this a topic that you're able to share some knowledge? I'd like to know everything I can about these newer BMS systems.

Thanks!

Here’s the information published on BMS.

The Electrical Energy Management system utilizes a load shed strategy to help control discharge of the battery and prevent, when possible, an excessively low battery state of charge. The BCM uses a battery monitoring sensor to monitor the battery state of charge.

• Generator current sensor
• Battery current sensor

These sensors serve as input to the Electrical Energy Management system software. If the sensors malfunction due to wiring issues or failure, a DTC will be set. In most cases the Electrical Energy Management system functions will be turned off until the sensor operation is restored.

To maintain correct operation of the load shed system, any electrical devices or equipment must be grounded to the chassis ground and not the negative battery terminal. A connection to the negative battery terminal causes an inaccurate measurement of the battery state of charge and incorrect load shed system operation due to the current being used bypassing the battery monitoring sensor. Refer to the Battery Monitoring Sensor component description in this section.

Battery State of Charge

The battery monitoring system charges the battery current flow and voltage to determine the battery state of charge. During the drive cycle the battery monitorning system software monitors the charge and discharge current and increases the state of charge during charging, and decreasing it during discharge. During rest periods (key off with no electrical loads) when the vehicle enters sleep mode, the battery voltage is sampled to calibrate the state of charge. The sensor automatically executes this calibration anytime the vehicle enters sleep mode and when the total vehicle current draw is below 400mA. It takes 4 to 6 hours in the sleep mode to calibrate the battery state of charge to high accuracy. If the system draw does not allow the battery state of charge calibration over the previous 7 to 10 days the state of charge quality factor changes to flag this and some battery monitoring system functions, which rely on the accuracy of the battery state of charge, may be temporarily turned off until a calibration takes place.

NOTE: Any devices left attached to the power socket that draw in excess of 200mA (or less depending on other battery loads), prevents a battery monitoring sensor from calibrating the battery state of charge