Just ordered Antigravity Lithium Battery

[Less Weight]

Ok, idiot alert here

I just got back from a drive. Parked the car in the garage and hooked it up to my OptiMate battery tender.

The only problem: I swapped the terminals and hooked the negative cable to the positive terminal and the positive cable to the negative terminal.

I know; a real idiot move and not one I’ve ever done before but I’ve been real sick for the past month and it has affected me.

Right when I connected it, the lights on the battery tender lit up all red. No sparks or and thing. Just the indicator light on the tender lit up all red

Right when my slow brain finally registered the flashing red light a second later, I quickly unplugged it from the wall outlet. Switched the cables to the correct terminals then plugged it back into the wall outlet. All green

Question is: Did that split second of stupidity damage anything?

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[Evolvd]

Ok, idiot alert here

I just got back from a drive. Parked the car in the garage and hooked it up to my OptiMate battery tender.

The only problem: I swapped the terminals and hooked the negative cable to the positive terminal and the positive cable to the negative terminal.

I know; a real idiot move and not one I’ve ever done before but I’ve been real sick for the past month and it has affected me.

Right when I connected it, the lights on the battery tender lit up all red. No sparks or and thing. Just the indicator light on the tender lit up all red

Right when my slow brain finally registered the flashing red light a second later, I quickly unplugged it from the wall outlet. Switched the cables to the correct terminals then plugged it back into the wall outlet. All green

Question is: Did that split second of stupidity damage anything?

No, most tenders have a polarity sensor built in and shouldn’t damage the batt.

 

[galaxy]

Nope. Almost all battery tenders today are smarter than you are.

 

[Tomster]

Nope. Almost all battery tenders today are smarter than you are.

Ouch

 

[Less Weight]

Well, thank goodness that these tenders ARE smarter than I am, lol.

Thanks for alleviating my fears @Evolvd and @galaxy

 

[galaxy]

Ouch

LOL...I meant "you" collectively.

 

[Gt350procharged]

Ive been running the atx20hd on my previous 17 gt350 and now on 21 gt500 and even tried the atx30hd

Ran great but after every 6months the battery would trip the psmand cause overvoltage and major engine faults....I haven't tried the forscan reprogramming to fix has anyone tried per below?

See ai response;

You’re hitting a known issue on the 2020–2022 when running lightweight lithium batteries:


“PSM / Charging System Overvoltage” = the car is seeing voltage spikes (often 15.2–15.8V)
Lithium batteries (like Antigravity) don’t buffer those spikes like AGM does
After months → BMS degrades → errors start appearing (exactly your 6-month pattern)


What’s actually happening (root cause)

The GT500 uses a smart charging system:

• PCM dynamically raises voltage during acceleration / regen
• Normal for car: up to ~15.5V spikes
• Problem:
  • AGM battery = absorbs spike
  • Lithium battery = rejects spike → triggers PSM fault

Over time:

• Battery BMS weakens
• Internal resistance changes
• System becomes unstable → PSM overvoltage warning

Symptoms you’re seeing (confirm)

• PSM / charging system warning
• Happens at higher RPM or hard pulls
• Works fine for months → then suddenly starts
• Same behavior on ATX30 + ATX20HD (you already proved this)

That confirms: not a bad battery — it’s incompatibility


Real fixes (ranked by what actually works)
1. BEST FIX (reliability)
Switch back to AGM battery

• Odyssey / Motorcraft AGM
• Heavier (~30 lbs) but:
  • absorbs voltage spikes
  • no PSM errors
  • no tuning needed

This is what Ford designed the system for.


2. Keep lithium but make it work (advanced fix)
A. Change battery profile using FORScan

Set charging system closer to AGM behavior:


Steps (high level):

1. Connect OBD (your adapter works)
2. Open FORScan
3. Go to:
   • BMS / BCM module
4. Change:
   • Battery type → AGM (NOT lithium)
   • Reset battery monitoring system

This reduces aggressive voltage spikes


B. Add voltage stabilization (VERY important)

Install:

• DC-DC regulator OR
• Voltage clamp device

Prevents spikes >14.8V reaching battery


C. Choose better lithium (if you insist)

Best options:

• Braille Lithium (race series) → strongest BMS
• Antigravity RS (restart) → slightly better protection

But even these can fail without voltage control


What will NOT fix it

• Trying another similar lithium brand (Bosch, NOCO, etc.)
• Same size/spec battery swap
• Resetting codes only

You already proved this with ATX30 → ATX20HD


Your exact situation (diagnosis)

Based on everything you told me:

• GT500 alternator = aggressive charging
• South Florida heat = worsens lithium stability
• Hard driving once/week = voltage spikes
• Batteries last ~6 months = BMS degradation

Conclusion: system mismatch, not bad batteries


My straight recommendation (no fluff)
If you want ZERO headaches:

Go back to AGM and forget about it

If you want lightweight + performance:

Do ALL 3:

• Braille lithium
• FORScan AGM profile
• Voltage stabilizer

 

[xXANCHORMONXx]

Ive been running the atx20hd on my previous 17 gt350 and now on 21 gt500 and even tried the atx30hd

Ran great but after every 6months the battery would trip the psmand cause overvoltage and major engine faults....I haven't tried the forscan reprogramming to fix has anyone tried per below?

See ai response;

You’re hitting a known issue on the 2020–2022 when running lightweight lithium batteries:


“PSM / Charging System Overvoltage” = the car is seeing voltage spikes (often 15.2–15.8V)
Lithium batteries (like Antigravity) don’t buffer those spikes like AGM does
After months → BMS degrades → errors start appearing (exactly your 6-month pattern)


What’s actually happening (root cause)

The GT500 uses a smart charging system:

• PCM dynamically raises voltage during acceleration / regen
• Normal for car: up to ~15.5V spikes
• Problem:
  • AGM battery = absorbs spike
  • Lithium battery = rejects spike → triggers PSM fault

Over time:

• Battery BMS weakens
• Internal resistance changes
• System becomes unstable → PSM overvoltage warning

Symptoms you’re seeing (confirm)

• PSM / charging system warning
• Happens at higher RPM or hard pulls
• Works fine for months → then suddenly starts
• Same behavior on ATX30 + ATX20HD (you already proved this)

That confirms: not a bad battery — it’s incompatibility


Real fixes (ranked by what actually works)
1. BEST FIX (reliability)
Switch back to AGM battery

• Odyssey / Motorcraft AGM
• Heavier (~30 lbs) but:
  • absorbs voltage spikes
  • no PSM errors
  • no tuning needed

This is what Ford designed the system for.


2. Keep lithium but make it work (advanced fix)
A. Change battery profile using FORScan

Set charging system closer to AGM behavior:


Steps (high level):

1. Connect OBD (your adapter works)
2. Open FORScan
3. Go to:
   • BMS / BCM module
4. Change:
   • Battery type → AGM (NOT lithium)
   • Reset battery monitoring system

This reduces aggressive voltage spikes


B. Add voltage stabilization (VERY important)

Install:

• DC-DC regulator OR
• Voltage clamp device

Prevents spikes >14.8V reaching battery


C. Choose better lithium (if you insist)

Best options:

• Braille Lithium (race series) → strongest BMS
• Antigravity RS (restart) → slightly better protection

But even these can fail without voltage control


What will NOT fix it

• Trying another similar lithium brand (Bosch, NOCO, etc.)
• Same size/spec battery swap
• Resetting codes only

You already proved this with ATX30 → ATX20HD


Your exact situation (diagnosis)

Based on everything you told me:

• GT500 alternator = aggressive charging
• South Florida heat = worsens lithium stability
• Hard driving once/week = voltage spikes
• Batteries last ~6 months = BMS degradation

Conclusion: system mismatch, not bad batteries


My straight recommendation (no fluff)
If you want ZERO headaches:

Go back to AGM and forget about it

If you want lightweight + performance:

Do ALL 3:

• Braille lithium
• FORScan AGM profile
• Voltage stabilizer

AGM all the way, it’s been 8 years since I posted on this thread and I’ll never go back.

The reality is that unless you are trying to squeeze an extra 10th, are at the limit of your capabilities on the car and want to extract more it’s just not worth it.

For most, spending the money on driving instruction, tires etc will yield better results.

While I still have my GT350 I now have gone through a few other sports cars with a current Porsche and will not be wasting the money on an unreliable battery

Ever since this thread started, and I switched back to AGM I’ve had zero battery issues with that car and the other 8 cars I own.

 

[volcanogod]

Ive been running the atx20hd on my previous 17 gt350 and now on 21 gt500 and even tried the atx30hd

Ran great but after every 6months the battery would trip the psmand cause overvoltage and major engine faults....I haven't tried the forscan reprogramming to fix has anyone tried per below?

See ai response;

You’re hitting a known issue on the 2020–2022 when running lightweight lithium batteries:


“PSM / Charging System Overvoltage” = the car is seeing voltage spikes (often 15.2–15.8V)
Lithium batteries (like Antigravity) don’t buffer those spikes like AGM does
After months → BMS degrades → errors start appearing (exactly your 6-month pattern)


What’s actually happening (root cause)

The GT500 uses a smart charging system:

• PCM dynamically raises voltage during acceleration / regen
• Normal for car: up to ~15.5V spikes
• Problem:
  • AGM battery = absorbs spike
  • Lithium battery = rejects spike → triggers PSM fault

Over time:

• Battery BMS weakens
• Internal resistance changes
• System becomes unstable → PSM overvoltage warning

Symptoms you’re seeing (confirm)

• PSM / charging system warning
• Happens at higher RPM or hard pulls
• Works fine for months → then suddenly starts
• Same behavior on ATX30 + ATX20HD (you already proved this)

That confirms: not a bad battery — it’s incompatibility


Real fixes (ranked by what actually works)
1. BEST FIX (reliability)
Switch back to AGM battery

• Odyssey / Motorcraft AGM
• Heavier (~30 lbs) but:
  • absorbs voltage spikes
  • no PSM errors
  • no tuning needed

This is what Ford designed the system for.


2. Keep lithium but make it work (advanced fix)
A. Change battery profile using FORScan

Set charging system closer to AGM behavior:


Steps (high level):

1. Connect OBD (your adapter works)
2. Open FORScan
3. Go to:
   • BMS / BCM module
4. Change:
   • Battery type → AGM (NOT lithium)
   • Reset battery monitoring system

This reduces aggressive voltage spikes


B. Add voltage stabilization (VERY important)

Install:

• DC-DC regulator OR
• Voltage clamp device

Prevents spikes >14.8V reaching battery


C. Choose better lithium (if you insist)

Best options:

• Braille Lithium (race series) → strongest BMS
• Antigravity RS (restart) → slightly better protection

But even these can fail without voltage control


What will NOT fix it

• Trying another similar lithium brand (Bosch, NOCO, etc.)
• Same size/spec battery swap
• Resetting codes only

You already proved this with ATX30 → ATX20HD


Your exact situation (diagnosis)

Based on everything you told me:

• GT500 alternator = aggressive charging
• South Florida heat = worsens lithium stability
• Hard driving once/week = voltage spikes
• Batteries last ~6 months = BMS degradation

Conclusion: system mismatch, not bad batteries


My straight recommendation (no fluff)
If you want ZERO headaches:

Go back to AGM and forget about it

If you want lightweight + performance:

Do ALL 3:

• Braille lithium
• FORScan AGM profile
• Voltage stabilizer

I'm curious for the folks that are having issues with LIPO type batteries if you are running any high power stereo/amps? Has anyone looked at the high voltage spikes with a O-scope? How long is the duration of the voltage spike? I'm curious if the spike is load related with the differences in LIPO and AMG? Is this something that can be filtered out?? Large capacitors are used in high amperage stereo applications to filter out droops in voltages. Seems this should be something fixable.

 

[Evolvd]

I'm curious for the folks that are having issues with LIPO type batteries if you are running any high power stereo/amps? Has anyone looked at the high voltage spikes with a O-scope? How long is the duration of the voltage spike? I'm curious if the spike is load related with the differences in LIPO and AMG? Is this something that can be filtered out?? Large capacitors are used in high amperage stereo applications to filter out droops in voltages. Seems this should be something fixable.

I had the base stereo in mine when I had the problems. The problem is with the BMS. Once the LiPO batt stops taking a charge the car spikes voltage thinking there’s an issue with the battery charge. There is no fix unless you figure out how to reprogram the BMS.

 

[galaxy]

Maybe reprogramming the BMS is a critical step. Should be accomplished with any new battery, but...But as I've posted in several threads on the topic, I have countless years and just as many miles completely 100% trouble free with my 20HD. No, I have no amps, suspension controller, nor any other aftermarket high demand voltage/currency load items which certainly seems to play a factor on the topic. My point; stock car, I would not sway away from this battery if it's what you want.

 

[Evolvd]

Maybe reprogramming the BMS is a critical step. Should be accomplished with any new battery, but...But as I've posted in several threads on the topic, I have countless years and just as many miles completely 100% trouble free with my 20HD. No, I have no amps, suspension controller, nor any other aftermarket high demand voltage/currency load items which certainly seems to play a factor on the topic. My point; stock car, I would not sway away from this battery if it's what you want.

You cannot reprogram the BMS. The only thing you can do is change the battery type from LA to AGM with FORscan….but that doesn’t prevent the system from screwing up the charge logic with LiFPO batteries.

 

[honeybadger]

You cannot reprogram the BMS. The only thing you can do is change the battery type from LA to AGM with FORscan….but that doesn’t prevent the system from screwing up the charge logic with LiFPO batteries.

I don't remember the exact command, but I know you can tell the system to use the "Ford GT" profile and that's setup for lithium.

 

[Evolvd]

I don't remember the exact command, but I know you can tell the system to use the "Ford GT" profile and that's setup for lithium.

Would like something a little more than a maybe….if you can find that info it might be worth testing. But this is the first time I’ve ever heard that, and even the guys at Antigravity don’t know about it.

 

[honeybadger]

Would like something a little more than a maybe….if you can find that info it might be worth testing. But this is the first time I’ve ever heard that, and even the guys at Antigravity don’t know about it.

I know its a thing. it what I did when I ran one. I've mentioned it a few times. its documented somewhere around here

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