honeybadger
Just don't care
@Evolvd
This thread has taken a few turns but I'm at the point of replacing my battery. I want to thank Demonic for all the testing and info he's provided. After many hours researching over the past couple weeks — I have come to similar conclusions. I ordered a YTX20 and will be doing some testing to get it to hopefully run like OEM for everyone.
Antigravity YTX20
Antigravity's YTX20 appears to be one of the better options. It has cell balancing and one of the best true capacities for the price point/weight. I don't think I will have any problem following Demonic's experience and simply dropping it in, resetting the BMS with Forscan, and using it as a DD (being mindful it is of course a smaller lithium battery).
For example, I use Shorai batteries in all my motorcycles and they've performed flawlessly. I don't even think about it with my bikes even in stop and go traffic and 30 degree weather. For cars, the Shorai LFX36L3-BS12 is $100 cheaper than the YTX20. But it has a slightly smaller capacity at 12AH (true) vs. the 14AHish of the YTX20 (estimate, can't find an exact published value). Most importantly it does not have cell balancing. May not be a big deal but a definite plus to the Antigravity. Vette, Miata, Toyota guys run this battery all the time with no issues.
Smart Charging and Lithium
The only issue left is Smart Charging. Lithium batteries charge/discharge differently than FLA (Flooded Acid) or AGM batteries. Most notably they discharge at a constant rate. A lead acid battery discharges at a linear decreasing rate in terms of voltage. See example below:
LFP (Antigravity and similar batteries) pretty much hold a constant voltage. Think a new lithium power drill. It basically quits working once it's discharged rather than slowing down like an old drill.
So what's the big deal? Well Smart Charging makes sure the battery stays at a specific charge of say 85% for example. It may charge immediately at full volts after starting a vehicle but drop down on the highway once the battery is charged. This extends the life of the battery, improves MPG, and helps out with power in certain scenarios. Basically a more dynamic.. or smarter system. Pretty neat
The problem comes in the PCM knowing at what charge level the battery is. A big part of measuring this is just reading the voltages. There's a bunch of other factors but point is — Lithium batteries state of charge are read differently than lead acids.
Minor Problem
Demonic came to the same conclusion I did awhile ago. The Smart Charging system stock just doesn't know a Lithium battery is discharged enough to warrant charging until a little too late. A simplified hypothesis is likely due to constant voltage nature of lithium batteries explained above.
Demonic do you have any updates? I'd guess lithium batteries running under the stock settings may be running at 50-70% levels of charge. I'll confirm once I have mine in.
Possible Solution
The off the cuff solution is to just turn off Smart Charging.. There's some big benefits seen above and I think it's more of a case of misunderstood tech rather than "needless complicated technology."
As Demonic was looking into, basically the solution is to get the PCM to realize that there's a lithium battery in there and charge accordingly. If only there was another recently released Ford vehicle that uses a lithium battery that the PCM already has a profile for.... oh wait Batman! There is!
The Ford GT uses a lithium battery. Seeings as how plenty of S550 owners are using Ford GT Splash Screens, Sync Settings, and other non sense — the lithium Smart Charging battery type should be a valid option. Thanks to Mr. Leno and his GT's VIN (love the show!), the Smart Charging line is "726-04-01 0502 0000" where "05" is the battery type and "02" means that Smart Charging is indeed enabled stock on the Ford GT.
Obviously the battery is different and won't be a perfect match but hopefully it'll get us near enough. The other option is to purchase a Ford GT battery for the low price of $700 (HG7Z-10655-B)!
GT350 Programmed Battery Type
The stock value seen in forscan for my R is for a normal S550 Group 96R battery (incidentally not even the GT350's smaller battery). The code is "12" although interestingly some 350s come with "07" for a similar battery.
List of known batteries from the F150 forum. Yes it's for an F150 but the value of "12" found in my R correlates correctly as does the "07". There's a lot of shared values between vehicles.
Next Steps
Once I get the battery in I'll do some data logging — primarily the state of charge. I will have to find a tool that does this for Lithium Batteries. Hopefully it's running at an acceptable level of charge and we don't have to mess with anything else but I doubt it.
If that's the case I'll swap over to the GT Battery Type and repeat testing. Hopefully it's a valid option and the battery runs at an acceptable charge level. View attachment 331003
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