Testing an Aux batt solution...

[Snakebitten]

Will you continue to run the Lithium piggyback on your new H7?

I intend to

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[Jmitchelltfo]

I know it's April Fools Day, but you could have found something more believable to bait us with . . .

This was from over a month and a half ago…..so I’m probably closer to 1470 now. I’ll probably end up replacing my original before it gets really cold again…….maybe.

 

[Porpoise Hork]

I finally got around to reading this thread and I have one thing to say..

@HammaMan Dammit man now I have a 20ah LifPo4 battery and charger in my Amazon cart that I really didn't want to buy...

 

[Double-A]

Thanks for this thread, my '21 PB lariat 502a that has 56k miles now still had the original 12v batteries and I started getting the classic "system off to save battery"/remote start disabled errors in sure everyone here is familiar with lol...

So I just went ahead and bit the bullet this weekend and upgraded the main battery to the Everstart H7 AGM from Walmart and the @Tank recommended 14ah Super Start AGM from oreillys and she runs like a top again!

 

[Tank]

Thanks for this thread, my '21 PB lariat 502a that has 56k miles now still had the original 12v batteries and I started getting the classic "system off to save battery"/remote start disabled errors in sure everyone here is familiar with lol...

So I just went ahead and bit the bullet this weekend and upgraded the main battery to the Everstart H7 AGM from Walmart and the @Tank recommended 14ah Super Start AGM from oreillys and she runs like a top again!

Awesome to hear!

 

[tsigwing]

How's this for a SOC?

Went camping on the 29th. Lots of door openings, in and out of the car. Just happened to check it out yesterday evening and it was at 18%. Had no issues starting it up this morning, bu twas rather interesting. This is after replacing the aux battery with a lipo4.

 

[Snakebitten]

How's this for a SOC?

Went camping on the 29th. Lots of door openings, in and out of the car. Just happened to check it out yesterday evening and it was at 18%. Had no issues starting it up this morning, bu twas rather interesting. This is after replacing the aux battery with a lipo4.

I inadvertently drained my Lifepo4 auxiliary to the point it shut down to protect itself. I only noticed because the ICE wasn't turning off in generator mode and the truck threw a code that pointed me in the right direction.

Looked up the battery isolation code and it hinted at a potential auxiliary battery problem. When I checked the auxiliary, I discovered it was off. I also confirmed that the DC/DC converter was supplying 12.7V because I didn't have the FOB in the truck, nor did I have the HVAC fan at 5.
Basically, while sitting in generator mode for about 5 days straight, the Lifepo4 was slowly getting drained down to what Ford's BMS would consider as safe for an AGM battery.

I unhooked it and plugged it into a charger. It woke up almost instantly and started gulping down current. I also put the FOB in the truck and turned the fan to 5, forcing the DC/DC converter to increase to 14+V.

Put the Lifepo4 back in the truck and the truck started cycling ICE on/off again normally for generator mode.

Lesson learned!

Every camping trip since (2), I now keep the DC/DC converter voltage up so the Lifepo4 auxiliary can get some food. ?

 

[Porpoise Hork]

I've been watching this thread closely and decided to go the LFP route. My battery arrived last week and while it will fit in the oem box with modification, I don't want to do that.

I also keep my rear seats folded up and keep the under seat storage folded down. The amount of open space is surprising. Anywho, that means I can't put the battery in the under seat storage either.

So, I'm going to make a custom, 3d printed battery enclosure to fit where the oem enclosure is now. It'll take me a while to get it done.

First thing I'll do is take out everything that's there now to get measurements of the oem enclosure and mount points. (If anyone has that info or knows where to get it feel free to save me the trouble.)

It'll take me a while to get it done.

Then it'll be design and prototyping. I'll be making it to fit the battery I purchased, but the basic design should be easily modified for size.

I will not be trying to monetize this or sell the design. This is just me doing something I'm interested in. So if any of you have any design ideas throw them out here.

It'll take me a while to get it done.

I'll take photos and all that other stuff people like to see as I go along. If there's enough interest I'll start my own thread.

It'll take me a while to get it done.

Did you ever get the 3d print design completed? I'd be interested in seeing the STL for it.

 

[HammaMan]

Factory battery is 1200 days old now, LFP is 2 years old now. Nothing to report. Truck works as I want it to (can't really say as it should because as it should sent me down this path). It currently gets about 10 sub 5 minute drives a week which is the ultimate killer of SOC and it's still resting at 13.2v

 

[Snakebitten]

You know @HammaMan , without the fan5 hack that I first heard about from you, I'm not sure the LFP Auxiliary would be as good an idea for my truck. Thank goodness we can "trick" the DC/DC converter into supplying the necessary voltage to leverage the LFP advantages.

 

[Porpoise Hork]

Installed the 20AH LFP on Friday after charging and 14.4v balancing it for 3 days. At that time the 12v SOC was hovering around 80% and would easily drop 5-7% a day since I don't drive it much. After 24 hours the 12v SOC rose to 95% with the system off. Then drove it for about 30 min. Day 2 with the LFP installed and the 12v SOC hit 100% and hasn't budged since. The wife and I drove across town for Sunday brunch a little over an hour round trip with fan on speed the whole time. Got home and the truck sat in the driveway untouched until this morning since I had to move it so she could go into the office and was shocked to see the 12v SOC still sitting at 100%. Normally it would have been at best 70% after not having been started for nearly three days even if it was at 95% or hjigher SOC. Eventhough it was at 100% I decided to leave it idle for 30 min with the fob in it so the system would put a bit of juice back into the LFP. Have to say best mod Ive done to this truck. @HammaMan very nice job sluthing this out.

 

[HammaMan]

You know @HammaMan , without the fan5 hack that I first heard about from you, I'm not sure the LFP Auxiliary would be as good an idea for my truck. Thank goodness we can "trick" the DC/DC converter into supplying the necessary voltage to leverage the LFP advantages.

Reading your situation on your battery shutting off, I suspect it was another variable. LFP shouldn't enter protection until ~10.5v. I suspect another variable to have been a factor and not total voltage. Even with the truck trying to run AGM float around the 12.8v range, that's well within the LFP's operating voltage UNLESS, the cells have become out of balance

If I had to guess, by not using fan 5 you've been charging/discharging well inside of its curve and a cell could be drifting. A daily cycled LFP needs to be fully charged to balance the cells every 8 weeks or so (daily top balancing is also acceptable). Most chemistries have linear curves for voltage/SOC, but LFP's flat curve requires regular top balancing. If a cell reached the lower or upper protection threshold, that wouldn't be visible on total batt voltage alone. Given that charging it brought it back it sounds like a cell is on the lower side. Fan 5 may eventually top balance if you didn't trickle charge it.

The one thing to keep in mind is that the BMS has absolute limits for cells and that's really the wall that gets hit before total battery voltage. Mine was out of balance when I got it where it turned off charging at ~13.8v. The BMS has no way to talk to it but I knew from experience that at least one of the cells was reaching 3.65v limit thus requiring a trickle charge at the BMS's balance clamping limit. I believe the truck watches the aux batt current flow as when it's fully charged, fan 5 only results in 14.2v or so. When it's taking in energy it'll be around 14.6 which is the upper limit for LFP and it shuts off the charging mosfets. Typically the balance clamping will start around 3.45v on a cell so the 14.2v the DC/DC settles at on longer trips is able to allow the BMS to equalize the cells without needing a complete top balance. Goodnuff as I like to call it.

I don't monitor mine at all outside of looking at the cheapo BT voltmeter thingy a lot of us have, and even then I'm only looking at the history once a month. I'm of the opinion that it should just work and I don't care to babysit it.

 

[Snakebitten]

Makes total sense.
I only ASSUMED 12.7v was below some LFP BMS parameter because I found the battery "off". (an AGM doesn't have an off )

The truck not cycling ICE on/off isn't really that rare if you use ProPower as often as I do. And it's just a habit of mine to harvest codes when it happens, before I attempt to "reset" ProPower with a key-cycle. Which does often solve the issue as long as it wasn't a ProPower load factor that has ICE on continuously.

Anyways, I harvested the codes and had never seen P2C44 before. Ever.

Looked it up and briefly reviewed the Pinpoint test procedures. It obviously led me to look at the Auxiliary battery and I found the onboard LCD display off and the display button for cycling between voltage and SOC % unresponsive.

Now knowing that a total voltage of 12.7 Volts is well above the LFP's BMS shutoff, I'm not going to ever know exactly what triggered the shutdown.

No big deal though. I still have and will continue to run ProPower with the FOB in the cabin & the fanspeed at 5. It's not even necessary to have air conditioning on. The DC/DC converter provides the 14+V current even with the compressor turned off.

 

[HammaMan]

No big deal though. I still have and will continue to run ProPower with the FOB in the cabin & the fanspeed at 5. It's not even necessary to have air conditioning on. The DC/DC converter provides the 14+V current even with the compressor turned off.

I'm still slightly amused that to put the 12v system into 'proper' voltage mode is simply put the blower on 5 or better.
?‍

 

[Snakebitten]

I have to admit that I would be very pleased to be told by someone at Ford why the fanspeed 5 voltage trigger exists. Of course that would assume that someone at Ford knows the trigger exists and it isn't something unintended or meant.

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