Testing an Aux batt solution...

[Shane150]

Is the truck capable of charging the LFP battery and which trickle charger will I need to charge it?

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[Snakebitten]

Is the truck capable of charging the LFP battery and which trickle charger will I need to charge it?

Yes, the normal AGM charging strategy will charge the LFP. Although if you want it charged all the way to 100%, you will need to use the fanspeed 5+ trick for a few miles at least. The reason is that, as far as I understand it, the LFP increases the LV SOC value seen by the BMS. And Ford's charging strategy isn't interested in maintaining what it considers 100% SOC. So it will be very conservative with both charging voltage and charging current.
The fanspeed 5+ triggers 14.x Volts, rather than ~12.7 Volts. And the LFP will gulp down every Amp available for those fanspeed 5+ miles.

And if you park the truck and discover the a couple of hours later, the resting voltage is below 13.25 Volts, a typical Noco 5 AGM charger does charge at 14+ Volts and the LFP onboard BMS will fill the little LFP back up.

But all of that is beyond what I really need from the LFP. I just need the LFP to be a superior auxiliary battery to the 7AH AGM. And so far it props up the resting voltage of my ~3 year old truck far better than the AGM possibly could.

Resting at 12.8-13.25 Volts for multiple days on end is a piece of cake.

 

[Spiffy]

Wow I wish I had found this thread way before. These technical observations cleared up a few things.
The last fewxdays I have been working on programing. I have that smart charger thatcwas recommended that puts out 20amps power supply.
I also replaced the brand new 7 agm that my dealer put in a couple weeks ago with a new new 7 agm from Duracell. I also isolated the defective modual that just wouldn't sleep.
My resting voltage went from 12.4 to 13
But last night when I shut off my truck I got the sleep message instantly.
Damm....

During my fdrs sessions with the aux power supply I noticed the battery level in the fdrs show 12.3 one second then 13.6. Some of the variations were coming from my head lights that would automatically come on after I did some on off that were required from fdrs. I keeper forgetting to turn off the lights each time.

So if I now understand it's the aux battery that's giving me the sleep message?
Not so much as the agm?

 

[Snakebitten]

Let's just say that since the 2 AGM batteries are connected in parallel, it's possible that that either or both are contributing to a low voltage SOC shortcoming.

Unless you were to check each one individually, disconnected, you can't just assume the health of either.

I did discover that my factory oem 7AH AGM auxiliary battery was absolutely healthy, when I removed it a few weeks ago. A couple of hours after disconnecting it from the underhood H7 AGM, I put a voltmeter across it and it's resting voltage had increased to 12.8V.
I was surprised to see that since when it was in parallel with the underhood AGM, the voltage was about 12.4V. So I guess the big AGM was a bit of a drag on the little AGM?

And since I now have the LFP (~25AH) as the auxiliary, you could say the LFP has more lifting power(?) than the little AGM did, because that same underhood AGM can't draw that LFP down enough to get the resting voltage, combined-parallel, below 13.X ?

I guess almost 4X's the Amp Hours, and the higher resting voltage of an LFP, means the auxiliary battery in the Powerboost is more influencial at assisting the underhood AGM?

 

[Samson16]

I guess almost 4X's the Amp Hours, and the higher resting voltage of an LFP, means the auxiliary battery in the Powerboost is more influencial at assisting the underhood AGM?

I suspect the mismatch will flow current into the AGM draining the LFP even when the system is not “on”. The LFP has no need of the constant float voltage, and because it’s low for LFP, a chronic LFP undercharge may develop. That being said, since we’re battling a chronic main AGM drain situation with the truck, knowingly offering up a sacrificial auxiliary LFP battery to bolster main AGM performance might be just the ticket. The auxiliary’s sole purpose is to isolate the DC bus from main AGM / Bendix starter operation which only takes seconds to accomplish, after which it can resume propping up the suspect battery management logic.
I’m still running what the factory provided. Didn’t the BMS OTA change help eliminate this issue? Are you just curious or actually solving a remaining problem?

ps. I remembered the update right at the end of my discussion lol. Apologies for the duality

 

[Snakebitten]

I'm just having fun keeping a Factory Motorcraft H7 going.

 

[HammaMan]

I suspect the mismatch will flow current into the AGM draining the LFP even when the system is not “on”. The LFP has no need of the constant float voltage, and because it’s low for LFP, a chronic LFP undercharge may develop. That being said, since we’re battling a chronic main AGM drain situation with the truck, knowingly offering up a sacrificial auxiliary LFP battery to bolster main AGM performance might be just the ticket. The auxiliary’s sole purpose is to isolate the DC bus from main AGM / Bendix starter operation which only takes seconds to accomplish, after which it can resume propping up the suspect battery management logic.
I’m still running what the factory provided. Didn’t the BMS OTA change help eliminate this issue? Are you just curious or actually solving a remaining problem?

ps. I remembered the update right at the end of my discussion lol. Apologies for the duality

I haven't verified it but the system is described as a transient buffer for "rolling starts". The traction motor starts the truck while in park. Rolling starts in the 21-3s is handled by the OBIGS which opens the isolator per the system's description. I'm quite surprised they haven't already deleted the aux batt and just placed a capacitor near the BCMC.

 

[Jmitchelltfo]

And since I now have the LFP (~25AH) as the auxiliary, you could say the LFP has more lifting power(?) than the little AGM did, because that same underhood AGM can't draw that LFP down enough to get the resting voltage, combined-parallel, below 13.X ?

I guess almost 4X's the Amp Hours, and the higher resting voltage of an LFP, means the auxiliary battery in the Powerboost is more influencial at assisting the underhood AGM?

I just noticed that after getting my X2 battery installed. My resting voltage was 12.4 with the OEM auxiliary battery (immediately after turning the ignition off).

Only modification was a small amount of trimming to the positive terminal cover to give some clearance for the cable. I haven’t touched the top cover yet since I’m not sure where my final mounting location will be.

4awg cables hooked up and slid the battery into the adjacent compartment and now my resting voltage shows 13.2 after turning everything off. I’m impressed so far.

I’ll keep an eye on it and report back after I get some more time with this setup.

 

[Snakebitten]

Very similar resting voltage as I get with each combination.

But when I was all AGM, and the truck was sitting parked for a few days, each time the truck was awakened by a door opening or an approach trigger, the resting voltage never completely recovered to the pre-awakened voltage.

With the LFP Auxiliary, it can recover completely multiple times. Much less degradation and perhaps never requiring me to Noco 5 again?

We'll see.

 

[HammaMan]

Everyone going the tri-batt route now, LOL.

Gotta love the LFP!

 

[Snakebitten]

Everyone going the tri-batt route now, LOL.

Gotta love the LFP!

You da pied piper.

LFP Auxiliary + a few miles of fanspeed 5 = no more low voltage worries.

Thanks again

 

[Jmitchelltfo]

Everyone going the tri-batt route now, LOL.

Gotta love the LFP!

I had been considering it just for the reason that it is completely reversible. I might still remove the OEM AGM, but I’ll keep an eye on this for a week or so and see how it performs.

 

[Spiffy]

Let's just say that since the 2 AGM batteries are connected in parallel, it's possible that that either or both are contributing to a low voltage SOC shortcoming.

Unless you were to check each one individually, disconnected, you can't just assume the health of either.

I did discover that my factory oem 7AH AGM auxiliary battery was absolutely healthy, when I removed it a few weeks ago. A couple of hours after disconnecting it from the underhood H7 AGM, I put a voltmeter across it and it's resting voltage had increased to 12.8V.
I was surprised to see that since when it was in parallel with the underhood AGM, the voltage was about 12.4V. So I guess the big AGM was a bit of a drag on the little AGM?

And since I now have the LFP (~25AH) as the auxiliary, you could say the LFP has more lifting power(?) than the little AGM did, because that same underhood AGM can't draw that LFP down enough to get the resting voltage, combined-parallel, below 13.X ?

I guess almost 4X's the Amp Hours, and the higher resting voltage of an LFP, means the auxiliary battery in the Powerboost is more influencial at assisting the underhood AGM?

Absolutely!
I forgot until this thread that I forgot to reset the bms. That might of caused the sleep mode not

I just noticed that after getting my X2 battery installed. My resting voltage was 12.4 with the OEM auxiliary battery (immediately after turning the ignition off).

Only modification was a small amount of trimming to the positive terminal cover to give some clearance for the cable. I haven’t touched the top cover yet since I’m not sure where my final mounting location will be.

4awg cables hooked up and slid the battery into the adjacent compartment and now my resting voltage shows 13.2 after turning everything off. I’m impressed so far.

I’ll keep an eye on it and report back after I get some more time with this setup.

I expected to see gorilla tape.

 

[Spiffy]

I haven't verified it but the system is described as a transient buffer for "rolling starts". The traction motor starts the truck while in park. Rolling starts in the 21-3s is handled by the OBIGS which opens the isolator per the system's description. I'm quite surprised they haven't already deleted the aux batt and just placed a capacitor near the BCMC.

I'm asleep surprised that they don't use the traction batteries to keep the agm charged.

 

[Jmitchelltfo]

I expected to see gorilla tape.

I even used the fancy heat shrink along with TechFlex but only had the red/black. I need to find the plain black to clean the ground wire up.

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