Top 10 Common AGM Battery Issues (and How to Fix Them)

Modified on Wed, 1 Oct at 11:02 PM

Absorbent Glass Mat (AGM) batteries are a reliable choice for solar systems, caravans, RVs, boats, and off-grid power setups. They’re durable, maintenance-free, and designed to perform well in demanding conditions. But like all batteries, AGM batteries can experience problems over time.

In this guide, we’ll walk you through the 10 most common AGM battery issues — and more importantly, how to fix or prevent them.

1. Low Voltage or Battery Not Holding Charge

Symptoms: The battery drains too quickly, or voltage drops below 12V.
Causes: Over-discharging, poor charging practices, or leaving the battery unused for long periods.
Fix:

Recharge using a compatible AGM battery charger.
Avoid letting voltage fall below 50% state of charge.
If stored, top up charge every 1–2 months.

2. Sulfation (Crystal Build-Up on Plates)

Symptoms: Reduced capacity, poor charging acceptance.
Causes: Leaving the battery discharged for extended periods.
Fix:

Use a charger with a desulfation mode if caught early.
For advanced sulfation, the battery may need replacing.
Prevent sulfation by always recharging after use.

3. Overcharging

Symptoms: Excessive heat, bulging case, or electrolyte loss.
Causes: Incorrect charging voltage, faulty charge controller.
Fix:

Ensure charger/solar regulator is set to AGM mode.
Keep charging voltage within manufacturer specifications (typically 14.4–14.7V bulk/absorption, 13.5–13.8V float).

4. Undercharging

Symptoms: Battery never reaches full capacity.
Causes: Undersized solar panel, short charging cycles, or incorrect charger settings.
Fix:

Increase charging time or use a larger solar array.
Confirm charger is correctly programmed for AGM batteries.

5. Battery Self-Discharge During Storage

Symptoms: Voltage drops when not in use.
Causes: Self-discharge or small parasitic loads (LEDs, monitors, alarms).
Fix:

Disconnect the battery during storage.
Recharge every 1–2 months.
Store in a cool, dry place away from direct heat.

6. Swelling or Bulging Case

Symptoms: Battery casing expands or warps.
Causes: Overcharging, overheating, or internal failure.
Fix:

Stop using the battery immediately.
Replace — swollen AGM batteries are unsafe and cannot be repaired.
Check your charging equipment to prevent repeat issues.

7. Reduced Runtime / Shorter Operating Hours

Symptoms: Battery drains faster than expected.
Causes: Natural aging, frequent deep discharges, or high loads.
Fix:

Test capacity with a load tester.
Reduce depth of discharge (avoid going below 50%).
Consider upgrading to a larger battery bank or lithium for longer runtime.

8. Corroded or Loose Terminals

Symptoms: Poor connections, intermittent power, or visible corrosion.
Causes: Moisture, improper installation, or lack of cleaning.
Fix:

Clean with a baking soda + water solution.
Tighten connections to manufacturer torque specs.
Apply terminal protectant spray.

9. Battery Won’t Charge at All

Symptoms: Charger won’t start or battery stays flat.
Causes: Voltage too low for charger to detect, or battery completely failed.
Fix:

Use a manual charger (that doesn’t require voltage detection) to “wake up” the battery.
If still unresponsive, the battery has likely failed and needs replacement.

10. Shortened Lifespan

Symptoms: Battery reaches end-of-life earlier than expected.
Causes: Deep cycling, high heat exposure, over/undercharging.
Fix:

Follow correct charging voltages.
Minimise deep discharges (keep above 50%).
Keep batteries cool and well ventilated.

? Tips to Prevent AGM Battery Issues

Always use a smart charger or quality solar regulator with AGM settings.
Avoid high heat — install in a shaded, ventilated area.
Never leave the battery sitting flat.
Match battery size to your energy needs.

⚡ When to Replace an AGM Battery

If your battery is swollen, fails to hold charge, or shows consistent poor performance despite troubleshooting, it’s time for a replacement. Recycling is important — always dispose of old batteries responsibly at an authorised recycling centre.

⭐ Need More Help with Your AGM Battery?

If you’ve tried the steps above and are still experiencing issues, our support team is here to help.
Email: support@starpoweradvancesolartechnology.com
Live Chat: Available on our website during business hours

Chat online: www.starpoweradvancesolartechnology.com.au