What the 4901 alarm means

Encoder backup battery voltage is below the warning threshold; absolute position will be lost at power-off if the battery dies. Codes 4900-4999 are warnings — the robot keeps running, but act now. This is one of the faults our repair team handles on EFORT EC2-S controller + TSINO drives systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • Battery past its service life
  • Poor battery contact
  • Long storage without power
  • Wrong battery type
Field note: the first item on this list is what we find most often on real machines. Check it before you go deeper.

Step-by-step field fix

  1. Replace batteries on all axes together
  2. Confirm type and polarity
  3. Verify absolute position data after replacement
  4. Log the date on the PM label
  5. Add battery replacement to the annual PM plan
Safety first: never bypass safety circuits or force contactors closed. If the alarm involves E-stop chains, brakes or drive power, and you are not a trained robot technician, contact a professional — wrong moves here can cost you a robot or an injury.

Still stuck? Get an engineer on the phone — right now

Tell us the alarm code, the robot model and what was happening when the alarm came up. Our engineers run these diagnostics every day, and remote diagnosis by phone or video call is free.

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Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related Maintenance alarms

1030 — Drive Overtemperature (TSINO) 4905 — Maintenance Interval Due (EC2-S)
Other brands: we also keep field-fix libraries for JAKA · AUBO · ROKAE and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the EFORT 4901 alarm mean?

Encoder backup battery voltage is below the warning threshold; absolute position will be lost at power-off if the battery dies. Codes 4900-4999 are warnings — the robot keeps running, but act now. In field practice it belongs to the maintenance family of faults.

QCan I clear a EFORT 4901 alarm myself?

Sometimes. Work through the step-by-step checks on this page — the first listed cause is what we find most often in the field. If the alarm returns after two attempts, or the fault involves power, brakes or safety circuits, stop and call a qualified robot service engineer.

QHow fast can a Henghuan engineer help?

On-site response in the Pearl River Delta within 30 minutes to 3 hours, across mainland China in 1-3 business days, and worldwide within 2-5 business days. Remote diagnosis by phone/WhatsApp/video is available immediately.

Written by the Henghuan Robotics repair team from field service experience. Alarm descriptions are our own summary for troubleshooting reference and may vary by controller and software version — when in doubt, check your EFORT documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by EFORT.