Auxiliary 12v Battery

[Sig Oris]

Other than replacing the battery as a result of failure, why would I want to replace this battery with a higher amp/hr battery? I get the reasons for a larger battery in the engine compartment but what does one gain with this battery?

I don't need an explanation of what amp/hr means

Sponsored

 

[Gros Ventre]

Given the intermittent nature of this battery's drain, I see no utility in putting in a larger battery. It's a "keep alive" battery to sustain system voltage during the start cycle dip in main battery voltage.

 

[FaaWrenchBndr]

With the battery I got (https://www.oreillyauto.com/detail/...op-post-battery-group-size-btx14ah/ssbn/etx15) I was able to leave it in. However the strap doesn’t fit around the battery any more and I had to leave the top part of the cover unhooked in the back I also added the gold washer things that came with the battery as a spacer. The positive ford terminal hook up is large and in order to thread the bolt in, the terminal got caught in a little ledge on the battery. I tried to add this in the pictures. You can also reset your battery management system (bad) by getting in your truck, pressing the start button without your foot on the brake (or turning your key to the aux without starting), flashing your brights 5 times, then pump your brakes 3 times. The battery icon on your dash should flash three times. You don’t have to do this though, it resets after 8 hours of being parked any ways.

I used a longer bolt when I changed to the larger battery. I think I went with a 40mm longer flanged bolt.

 

[HammaMan]

Other than replacing the battery as a result of failure, why would I want to replace this battery with a higher amp/hr battery? I get the reasons for a larger battery in the engine compartment but what does one gain with this battery?

I don't need an explanation of what amp/hr means

Why would you want more reserve capacity? It should be self evident, no?

I switched Aux batt chemistries to significantly increase the time before modules sleep. I've found after 10 days the BMS will stop exterior lighting but will not sleep modules / enter low power mode. I'm going to test removing the CT from the aux batt so the BMS can no longer see its current as there's been no positives associated with allowing it to see the aux batt's current flow. I suspect this to yield a welcome change as there's no need to shut off the welcome lighting with 13v on the 12v bus.

(Edit, there is a welcome lighting timeout count between key cycles, as in you only get so many wakeups before needing a key cycle to reset this. While you may not believe you're waking up the welcome lighting, it may still be triggering if the key is within 20' of the truck. On my list to look into further)

 

[Spiffy]

Man I'm confused. My interior lights not coming on are connected to this aux battery? What state is this battery in when my lights won't come on?
Again I'm asking about resetting the bms. Does that reset the aux battery?
Also is there a pid for that battery?

What soc does that battery need to be when the truck decides not to let my lights light ?

 

[HammaMan]

Man I'm confused. My interior lights not coming on are connected to this aux battery? What state is this battery in when my lights won't come on?
Again I'm asking about resetting the bms. Does that reset the aux battery?
Also is there a pid for that battery?

What soc does that battery need to be when the truck decides not to let my lights light ?

no, it's limited to so many wakeups per key cycle

 

[Spiffy]

Mine doesn't wake up at all. I can leave my truck overnight with a charger on the main battery. That battety is soc of 90+ % unlock the truck, open door and no interior lights. Press start button and lights turn on. They never turn on opening the door.
They worked for a day after I received a new battery. Is the interior lights tied to the aux battery condition?

 

[Spiffy]

I just checked my ford pass. I got a message that I need to drive the truck to exit battery saver mode. WTF? it's on a smart charger and I have a remote battery level meter that shows the battery is 100% at 14.2 volts. I just started it this morning..

 

[HammaMan]

Try resetting the BMS?

 

[safety_3rd]

I just checked my ford pass. I got a message that I need to drive the truck to exit battery saver mode. WTF? it's on a smart charger and I have a remote battery level meter that shows the battery is 100% at 14.2 volts. I just started it this morning..

Man a lot of us are telling you the same thing. You replaced your under hood battery, that’s great. General I replace my aux battery at the same time. Also do a bms reset. Your computer will relearn the battery charge and hopefully reset the power save function… which includes your interior lights. However if you haven’t replaced your aux battery and it’s below where it should be, then the bms reset will just relearn that your aux battery is still dead. For 70 bucks and less time than it took for you to type a dozen messages you could have your problem fixed.
If you’re using a battery charger there is a special way to hook it up so that the BMS is monitoring that it’s charging. I imagine you have your trickle attached to your main battery. I “think” that should also charge your aux battery but I’m not sure. I don’t understand why you’re so hesitant to replace the aux? Obviously it was time to replace the under hood battery, it was probably time to replace the aux. Not trying to be an ass, just want you to get your truck working. There is a YouTube video of someone showing you how to hook up a trickle, discussed the bms system, and the aux battery. He discusses the amp draw our trucks pull. My understanding is while the hybrid is on, the aux is running your electrical. Also sitting in your truck with the doors closed and everything on with get engine off, pulls a buttload (yes that’s the technical unit of measurement) or power.

 

[safety_3rd]

Given the intermittent nature of this battery's drain, I see no utility in putting in a larger battery. It's a "keep alive" battery to sustain system voltage during the start cycle dip in main battery voltage.

I understand the aux battery also supplements the power draw while the engine is off, or in hybrid mode.

 

[Gros Ventre]

I understand the aux battery also supplements the power draw while the engine is off, or in hybrid mode.

Unless the Engine is being started, it is paralleled with the main battery. It will supply current to the truck in proportion to its respective sizing relative to the main battery. While it's true it "supplements" the main battery, it's not there for that purpose and is unnecessary in that respect. Also note that the truck is "in hybrid mode" when running. The DC-DC converter is also supplying power to the truck when it is on. Recall that there is a relay that opens when starting the engine so that the voltage dip occurring in the main battery when powering the starter motor is not seen by the rest of the electrical system.

 

[Spiffy]

Ii didnt say i was opposed to replacing the aux battery. I'm still not convinced that a bms reset actually resets the aux bms. Is there any info on this?
The more i learn from this thread the more clear it it that no one really knows the exact porpoise of this battery. In not one to throw money into a hopeful repair.
I have a specific issue and no one has said it's definitely caused by my aux battery. Just now someone was suggesting that a trickle charger on the main battery also charges the aux battery.
That means if my main battery is reporting 13.5 volts then the aux should be the same.

 

[Gros Ventre]

Ii didnt say i was opposed to replacing the aux battery. I'm still not convinced that a bms reset actually resets the aux bms. Is there any info on this?
The more i learn from this thread the more clear it it that no one really knows the exact porpoise of this battery. In not one to throw money into a hopeful repair.
I have a specific issue and no one has said it's definitely caused by my aux battery. Just now someone was suggesting that a trickle charger on the main battery also charges the aux battery.
That means if my main battery is reporting 13.5 volts then the aux should be the same.

The shop manual purpose is to support truck voltage during a start cycle. The starter motor current draw is large enough to cause dip in main battery terminal voltage to something like 10.5VDC. That's a normal characteristic. Ford set up a special starter circuit with a relay that separates it from the rest of the truck. Thus the aux battery then supports system voltage during the starting cycle.

 

[HammaMan]

Is it a comprehension issue
Perhaps a language barrier

Sponsored