magudaman
Posts: 46
Joined: Tue Feb 18, 2014 9:40 pm

Re: Better 12V battery option?

Sun Dec 28, 2014 10:56 am

I the tech manual says that it needs to be replaced with a battery of equal capacity and size. You can buy a CD version of the manual for about $160 from http://www.helminc.com

triangles
Posts: 1139
Joined: Tue Aug 16, 2011 11:40 am
Location: Toledo, Ohio

Re: Better 12V battery option?

Fri Apr 09, 2021 9:09 am

So I got a bit over 3 years out of my warranty replacement Motorcraft battery. I'm not sure what the FFE does to abuse these so much besides running them flat every so often.

Anyway I had planned on shoehorning in an Optima Yellow Top deep cycle AGM but I know how bad it is for the battery every time our FFE's run the battery flat dead. However I think I'm gonna go LiFePO4 for my next 12V battery. I've had a bad experience with LiFePO4 batteries in my motorcycle but even riding that almost daily in winter temps down to about 10F for 3 or 4 winters. That battery is still going strong today after 8ish years. I actually don't remember when it was that I bought it. The cells on it have never been balanced and repeatedly abused by charging at subfreezing temps yet they keep on keeping on.

I made this decision in light of the following:
- FFE occasionally completely draining the battery which is very bad for lead acid (even worse for lithium without a BMS)
- The claim that modern LiFePO4 batteries can provide cranking amps for an ICE in sub freezing temps.
- I found a deep cycle LiFePO4 battery with a BMS that cuts off at 10 volts to provide over discharge protection.

I decided to go with this battery: https://www.amazon.com/MOSEWORTH-Phosph ... B08QMQHY8S

My only concern is the max charge rate of 50A since the DC-DC converter will supply up to 100A. If you are not aware, Lithium batteries have very little internal resistance and will take about as much current as you can feed them. This can be a bad thing if you're giving it more current than what it is rated for.

Well I'll find out what happens. Supposedly the BMS won't allow over current charging, but I'm not sure how that will all work out. I might end up frying the BMS.
2014 Blue Candy FFE
http://www.fuelly.com/car/ford/focus/2014/triangles/303811 (since this forum doesn't allow BBcode in sigs)

Anti_Climax
Posts: 79
Joined: Fri May 20, 2016 12:22 pm
Location: The Valley of the Sun

Re: Better 12V battery option?

Fri Apr 09, 2021 8:20 pm

It's my understanding that the BMS is very picky about voltage. As soon as it hits mid-summer, my AGM droops just enough that it will refuse to remote start because of the low 12V warning that triggers. Be prepared for a different chemistry to register incorrect status. Even different types of lead acid seem to do it.

I'm actually considering feeding the voltage sensor with a boost circuit that will prevent it from reading low enough to trigger that 12V error. I'll still let it drop just above that, so it doesn't think the battery is fully charged when it isn't, just never let it see that last .1V that makes it think the world is ending.
2012 Candy Blue FFE
33.5kWh battery pack
CHAdeMO DC Fast Charging

Heima
Posts: 144
Joined: Thu Feb 21, 2019 11:46 pm

Re: Better 12V battery option?

Sat Apr 10, 2021 7:07 am

So why not a deep cycle battery? Doesn't have to be Lithium based. Aren't those supposed to be able to go flat repeatedly?
And I thought pulling fuse 3 stops the TCU from draining the battery? Also, didn't Ford release a firmware update to fix the TCU draining the battery problem?

Considering the new Tesla 12V batteries are not much more than a laptop battery pack, I wonder if a laptop battery pack, or one of those jump starters could be used as the 12V battery for our cars.

triangles
Posts: 1139
Joined: Tue Aug 16, 2011 11:40 am
Location: Toledo, Ohio

Re: Better 12V battery option?

Mon Apr 12, 2021 11:00 am

Heima wrote: So why not a deep cycle battery?
I was going to go with a cylindrical cell AGM (Optima Yellow Top) These are about as good as it gets as far as lead acid goes. They are deep cycle batteries. I opted for the LiFePO4 because they are about the same cost and the LiFePO4 suppsoedly has about 10x the cycles, so neglecting calendar life the LFP battery should last much longer and they are similarly priced. Also no they are not able to go flat repeatedly. IIRC a normal starter battery shouldn't be drained more than 20% A deep cycle just extends that to 80% so running them flat is still very bad for their longevity. The LFP has a BMS that disconnects at 10V so you literally cannot run them flat. That is why I went LFP.

Also if they did indeed fix all the 12V issues my car wouldn't have had a flat dead 12V the two times that is has unrelated to the TCU. It's the F1 fuse for the TCU. I had that out for over a year and had no 12V issues. I only enable the TCU in the winter for the GO times and I have it on a low voltage disconnect that cuts it off if the 12V drops below 12.1V which is about 40% SOC for lead acid.
Anti_Climax wrote: It's my understanding that the BMS is very picky about voltage. As soon as it hits mid-summer, my AGM droops just enough that it will refuse to remote start because of the low 12V warning that triggers. Be prepared for a different chemistry to register incorrect status. Even different types of lead acid seem to do it.
Not sure what you're talking about there is no BMS for the 12v system. Also oddly enough after they "fixed" my 12V issues, I no longer get MFM warnings about low 12V when the battery dies. Also If your AGM voltage is low that means your battery is going bad or the DC-DC isn't charging it. My FFE will give no indication of a problem until you get down o 11.5-11.8V where it doesn't have enough voltage to turn on the car.

My LFP will be here Wednesday so I'll report back how it goes.
2014 Blue Candy FFE
http://www.fuelly.com/car/ford/focus/2014/triangles/303811 (since this forum doesn't allow BBcode in sigs)

Anti_Climax
Posts: 79
Joined: Fri May 20, 2016 12:22 pm
Location: The Valley of the Sun

Re: Better 12V battery option?

Tue Apr 13, 2021 6:43 am

There is a 12V BMS that has separate settings for flooded lead acid, AGM, etc as they each have slightly different charge characteristics, giving slightly different voltages when fully charged. They've had to reset it each time they've replaced my 12V battery.

Folks that put optimas in can run into this awesome behavior where the car will see the normal fully charged voltage of the battery and treat it as if it's dangerously low.

You'll see this when you switch off the car but don't open the door. The fans and console will normally stay on for 30 minutes but it will almost immediately give a message about preserving the battery and cut off. I get this frequently even with the Ford standard AGM battery.

https://youtu.be/KE97854wYLo

On the gas version, you can pull the 12V sensor plug off but on our EVs it will just refuse to work like that.

https://youtu.be/1rxGS06ETR4

Feel free to mess around, just letting you know folks have tried exactly what you've been considering and it's not as simple as swapping them out.

In a perfect world we could find BMS commands that would set the proper float voltage values and low voltage cut off for any given battery but I'm not holding my breath.

If you have a copy of the service manual that's floating around, there's a little more detail in "414-00 Charging System - General Information". While it does mention a 12V battery management system it doesn't go into further detail. I believe the "BMS" they always check when my AGM droops is the Battery Monitoring Sensor that reads into the BCM.
2012 Candy Blue FFE
33.5kWh battery pack
CHAdeMO DC Fast Charging

triangles
Posts: 1139
Joined: Tue Aug 16, 2011 11:40 am
Location: Toledo, Ohio

Re: Better 12V battery option?

Wed Apr 14, 2021 7:24 pm

Interesting. They must have disabled this on mine. Whatever "software update" they did my my TCU went bad must have eliminated it. My OEM battery has a resting voltage of about 11.8v. It still starts the car fine but doesn't have enough to jump my motorcycle.

Battery went in fine. There was a bit of a clearance issue with the negative terminal. Had to bend up the plastic above it to get the negative terminal on. The positive terminal just touches the Underwood insulation. This battery is almost too tall. But seems to work just fine the few minutes I've used it.

Other than i need to fab up a new hold down since the new battery is taller, there were surprisingly no issues installing it.

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We'll see how it goes.
2014 Blue Candy FFE
http://www.fuelly.com/car/ford/focus/2014/triangles/303811 (since this forum doesn't allow BBcode in sigs)

Anti_Climax
Posts: 79
Joined: Fri May 20, 2016 12:22 pm
Location: The Valley of the Sun

Re: Better 12V battery option?

Thu Apr 15, 2021 7:41 am

I'd have to double check, but I think my car pitches a fit when the AGM hits 12.5V (nominal for flooded lead acid being 13.8V). Maybe not that exact voltage but not nearly as low as I'd expect.

If yours goes that low and the car doesn't complain, something had to have been changed. If you ever figure out what, please - for the love of god - tell me.

It pisses me off to no end that my car will refuse to remote start during the hottest part of the Arizona summer WHILE PLUGGED IN and the best the dealer can do is make me waste time to bring it back for a warranty replacement battery that doesn't actually fix the root cause...
2012 Candy Blue FFE
33.5kWh battery pack
CHAdeMO DC Fast Charging

triangles
Posts: 1139
Joined: Tue Aug 16, 2011 11:40 am
Location: Toledo, Ohio

Re: Better 12V battery option?

Thu Apr 15, 2021 8:43 am

That sucks. I have never gotten any sort of low voltage indication other than reading DTCs or a notification thru MFM that the 12V is low AFTER the 12V has already expired. After they "fixed" it and replaced my TCU I never got a MFM notification that the battery had died (12V low). Even after the 3rd replacement TCU has failed. Other than mine being a '14 model, I wonder what is the difference.

You might try a LTO I was going to make a 6S LTO battery for the 12V I was going to go this route but LTO is still stupidly expensive. I was going to build a LTO with no BMS as they can tolerate being run flat without being ruined and can tolerate charging in freezing winter temperatures. Not sure about the other end that you would need to be concerned with. Not sure if that would make any sense for you but might be worth looking in to.

Oh and I'm pretty sure the nominal voltage for any lead acid battery is 12.6V or 2.1V/cell. so I don't see why it would make any difference for you, flooded, gel, or AGM. I could be wrong but I'm also pretty sure the gizmo on the negative terminal is a current sensor not a voltage sensor.
2014 Blue Candy FFE
http://www.fuelly.com/car/ford/focus/2014/triangles/303811 (since this forum doesn't allow BBcode in sigs)

Anti_Climax
Posts: 79
Joined: Fri May 20, 2016 12:22 pm
Location: The Valley of the Sun

Re: Better 12V battery option?

Fri Apr 16, 2021 6:27 pm

Apologies, it's float voltage, not nominal. Float varies between gel (13.05V), flooded (13.4V) and AGM (13.6V) but it also varies by temperature.

It's not much between flooded and AGM but it's enough for my car to complain. Strangely, the car doesn't post a DTC other than "I didn't start because something else errored". Doesn't post it when my HV battery overheats either.

I'm really starting to love-hate this car.
2012 Candy Blue FFE
33.5kWh battery pack
CHAdeMO DC Fast Charging

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