Battery Voltage High, Charging System Over-Limit
What does ATLAS-COPCO-E011 mean?
The ATLAS-COPCO-E011 (Xc4002 / Xc2003 / Xc4004) diesel fault code means: Battery Voltage High, Charging System Over-Limit. This is a moderate severity code.
Common Symptoms
- Controller LCD on the side panel displays E011 and the unit shuts down or holds in a warning state
- Battery or charging indicator light stays on after engine reaches full RPM
- Measured voltage at battery terminals reads above 15V DC on a 12V system or above 30V DC on a 24V system
- External battery tender or trickle charger was left connected to the compressor battery before startup
- Onboard electrical accessories (lights, solenoids) feel warm or behave erratically
- Unit starts normally but trips the E011 fault within a few minutes of running
- Repeated fuse or relay failures in the control circuit shortly before or after this code appears
Probable Causes (Ranked by Likelihood)
- Alternator voltage regulator stuck in high-output or open-circuit mode, overcharging the battery Very Likely
- External battery charger or jump-start pack left connected while the engine is running, stacking voltage on top of the alternator output Very Likely
- Faulty or corroded battery voltage sense wire giving the Xc4002 / Xc2003 / Xc4004 controller an inflated reading Likely
- Failed or sulfated battery with high internal resistance causing surface-charge voltage spikes under low or no load Likely
- Loose or broken alternator ground strap creating a floating reference that reads artificially high at the controller Possible
- Wiring short between the alternator B+ output and a higher-potential circuit on a 24V system Possible
- Controller calibration drift or a bad analog input channel on the Xc4002 / Xc2003 / Xc4004 board misreading actual voltage Less Likely
Step-by-Step Diagnostic Procedure
Step 1. Disconnect any external battery charger or jump-start pack before doing anything else. Leaving it connected while the engine alternator is also running is the single most common cause of E011. Clear the fault on the controller LCD, restart, and watch whether E011 returns.
Step 2. With the engine OFF and the battery rested for five minutes, measure DC voltage directly at the battery terminals with a multimeter. A healthy 12V system should read 12.4-12.8V. A healthy 24V system should read 24.8-25.6V. Anything over 13.0V (12V) or 26.5V (24V) at rest suggests surface charge or a prior overcharge event.
Step 3. Start the engine and let it reach normal RPM. Measure DC voltage at the battery terminals again. For a 12V system, alternator output should be 13.8-14.4V. For a 24V system, expect 27.5-28.5V. A reading above 15V (12V system) or 30V (24V system) confirms the alternator or its regulator is overcharging.
Step 4. Inspect the alternator ground strap. It connects from the alternator body to the engine block or chassis. Look for corrosion, cracking, or looseness. A bad ground makes the alternator appear to produce higher voltage than it really is. Clean and tighten if needed.
Step 5. Trace the battery voltage sense wire from the battery positive terminal back to the Xc4002 / Xc2003 / Xc4004 controller connector. Look for chafed insulation, a pushed-back pin in the connector, or corrosion inside the connector housing. Measure voltage at the controller end of the sense wire and compare it to what you read directly at the battery. If they differ by more than 0.3V, the sense circuit has a wiring problem.
Step 6. Load-test the battery using a carbon pile tester or have the rental yard test it. A battery that fails a load test can show inflated open-circuit voltage while being unable to deliver current, which confuses the controller. Replace if the battery does not hold voltage under load.
Step 7. If all wiring and the battery check out but charging voltage is still too high under Step 3, the alternator voltage regulator is the likely culprit. On most Kubota and Deutz-equipped XAS models the regulator is integral to the alternator. You will need to swap the alternator or take it to an alternator shop for bench testing. This step requires moderate electrical skill.
Step 8. If the hardware all tests normal, connect DiagPro service software via the J1939 / CAN data port and check the live battery voltage reading inside the controller against your multimeter. If they disagree by more than 0.5V, the Xc4002 / Xc2003 / Xc4004 analog input channel may need recalibration or the controller board may need replacement. Call an Atlas Copco service tech for that step.
Frequently Asked Questions
What does Atlas Copco code E011 mean?
E011 means the Xc4002 / Xc2003 / Xc4004 controller measured battery voltage above the upper limit it is programmed to accept, typically above 15V DC on a 12V system or above 30V DC on a 24V system. The most common reason is an external battery charger left connected while the engine is running, but a failed alternator voltage regulator can cause the same fault.
Can the compressor still run with E011 active?
It depends on how the unit is configured. Most Atlas Copco XAS and XATS platforms will allow a short warning period before shutting down to protect the controller and solenoid wiring from sustained overvoltage. You may get limited operation, but do not ignore the fault. Sustained overvoltage can damage the Xc4002 / Xc2003 / Xc4004 controller board and other electronics.
How much does it cost to fix E011?
If an external charger caused it, the fix is free. Just disconnect the charger and clear the code. A new battery runs $80-$180. An alternator or voltage regulator swap is $150-$450 in parts if you do it yourself, or $300-$700 at a shop. Controller board issues are the expensive scenario at $500-$1,200 and require an Atlas Copco service tech.
Will the compressor start again after I clear E011?
Yes, in most cases it will restart once you clear the fault on the controller LCD. But if the root cause is still there, the fault will come back within minutes of the engine reaching normal RPM. Fix the charging issue before putting the machine back into service. Clearing and ignoring it risks permanent damage to the controller.