Antigravity ATX-20-HD

[Cory S]

Here’s the ATX-30HD with the battery cover in place after a couple of hours of creativity. It wasn’t very difficult.

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[galaxy]

How is the base secured to the bottom of the battery box? Did you have to make any mods to the floor of the stock battery box to get it all to work?

 

[Cory S]

How is the base secured to the bottom of the battery box? Did you have to make any mods to the floor of the stock battery box to get it all to work?

Some pilot hole drilling and big screws. 4 in total. It’s never coming out on it’s own. That’s for sure.

 

[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 psm and 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

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