Can a battery that shows a red LED on the charger be repaired?

In most cases, yes. The cause is usually BMS protection after a deep discharge. After replacing the cells we activate the BMS and the battery charges again in the GKL charger.

Could the problem be in the charger?

Yes, so it is worth checking the charger with another battery. If other batteries charge correctly, the cause is in the battery.

Can I use the original charger after regeneration?

Yes. We keep the original Leica BMS, so GKL211, GKL221 and GKL311 chargers recognise the battery as a factory one.

Red LED on the GKL211 / GKL311 charger: causes

Axis Baterie · Updated: 2026-10-16

A red LED on a Leica GKL charger means the charger cannot start charging the battery. Most often the cause is BMS protection, which activates after a deep discharge or long storage. In most cases the battery can be regenerated: after replacing the cells we activate the BMS and the battery charges again in the GKL charger.

How the GKL charger detects a problem

Leica GEB batteries have a built-in BMS that communicates with the charger and protects the cells against overcharging and excessive discharge. If the cell voltage drops below a safe level, the BMS blocks charging, and the GKL211, GKL221 or GKL311 charger signals an error.

The meaning of the individual LED signals is described in the charger manual. This article covers the situation in which the charger signals an error with one battery while charging other batteries correctly.

The most common causes

Deep discharge. A battery left in the instrument or in storage for several months discharges below the safety threshold.
Off-season storage. After a winter spent in a car or an unheated room, the cells may be discharged and chilled.
Uneven cell wear. In older packs one cell loses capacity faster than the others, and the BMS detects a voltage mismatch.
Damaged thermistor or contacts. The charger cannot read the temperature or has no reliable connection to the battery.

What you can check yourself

Make sure the battery and the charger are at room temperature. Charging a cold battery is blocked.
Check that the contacts of the battery and the charger are clean and undamaged.
Insert another battery into the charger. If it charges correctly, the problem is with the battery.

We do not recommend trying to "wake up" the cells with a laboratory power supply or opening the housing. Deeply discharged lithium-ion cells may be damaged, and interfering yourself carries risk.

What the repair involves

During free diagnostics we measure the voltage and internal resistance of the cells and check the BMS and the thermistor. If the electronics are in good order, we replace the cells with new ones, activate and calibrate the BMS, and then run a load test. After regeneration the battery charges in the original GKL charger without errors.

To avoid the problem in future, follow the recommendations in the article on using and storing batteries in winter.

Good to know

Axis Baterie is an independent service, not affiliated with Leica Geosystems AG or Hexagon AB. Leica, GEB, FlexLine, Viva and Captivate are trademarks of their respective owners.

Order diagnostics and regeneration

FAQ

Can a battery that shows a red LED on the charger be repaired?: In most cases, yes. The cause is usually BMS protection after a deep discharge. After replacing the cells we activate the BMS and the battery charges again in the GKL charger.
Could the problem be in the charger?: Yes, so it is worth checking the charger with another battery. If other batteries charge correctly, the cause is in the battery.
Can I use the original charger after regeneration?: Yes. We keep the original Leica BMS, so GKL211, GKL221 and GKL311 chargers recognise the battery as a factory one.