Explanation of Charging Stages on MEAN WELL Intelligent Battery Chargers

Charging Stages on MEAN WELL Intelligent Battery Chargers

MEAN WELL’s intelligent battery chargers are usually available with two or more selectable charging stages.  

These are referred to in the product data sheets as: 

  • Stage 2 Charging 
  • Stage 3 Charging 
  • Stage 8 Charging 

The options are found on the below MEAN WELL battery chargers, which are stocked by ADM: 

Battery Charger Model

Float / Boost Voltage

Rated Current

Charging Stages


13.8V / 14.4V (for 12V batteries) 

40A 2 / 3 / 8 


27.6V / 28.8V (for 24V batteries) 21A 2 / 3 / 8 


13.8V / 14.4V (for 12V batteries)  60A 2 / 3 / 8 


27.6V / 28.8V (for 24V batteries) 34.7A 2 / 3 / 8 


55.2V / 57.6V (for 48V batteries)  17.4A 2 / 3 / 8 



MEAN WELL PB-600 Series Battery Charger
MEAN WELL PB-1000 Series Battery Charger


Selecting the Required Battery Charging Curve 

The charging curve is selected via a slide switch on the front panel of the battery charger: 

MEAN WELL PB-600 Battery Charging Curve Selection Switch
Position of switch on PB-600 series battery charger


MEAN WELL PB-1000 Battery Charging Curve Selection Switch
Position of switch on PB-1000 series battery charger


Stage 2 Battery Charging 

This is a 2-stage charging cycle that can be used to fast charge batteries in industrial applications, such as forklift batteries or a battery in a car that is in storage and needs an occasional charge.  

Stage 1 is the battery charger operating in constant current mode. The voltage increases as the charge cycle progresses. 

Once the battery reaches the boost voltage of 2.4V per cell, the charger switches to constant voltage mode.

As the battery charges, the current will drop gradually. When the current drops to about 10% of the rated output, the charger switches off. 

Stage 2 battery charging curve
2 stage battery charging curve


The LED indicators on the front panel of the battery charger will glow orange until the battery is fully charged, at which point the LED indicator will switch to green. 

Stage 3 Battery Charging 

The 3-stage charging curve can be used for the cyclic charging of batteries and is ideal for battery backup applications and UPS systems.  

Stages 1 and 2 operate in the same manner as the Stage 2 operation outlined above.  

However, once the battery charger's indicator turns green the battery charger switches to ‘float charging’ mode. This will maintain the battery at full charge at a voltage of 2.3V per cell.  


Stage 3 battery charging curve
3 stage battery charging curve


Stage 8 Battery Charging 

This is a full function charging program that analyses the battery at certain points during the charging cycle, to achieve optimum charging capacity.  

This mode cannot be used if the battery is under load, as this will influence the analysis functions and could result in the battery being over charged. If you are using the battery charger in a caravan application, do not select Stage 8 charging. Select 3-stage charging instead 

The below table sets out how the PB-1000-12 would operate charging a 12V battery. 

Stage 8 battery charging curve
8 stage battery charging sequence


When initialised, the battery charger will check the battery voltage. It will then start pulse charging with an output of 40A, the frequency of the pulse is determined on the battery voltage detected. 

The battery charger will then switch to soft-start mode, maintaining an output of 20A until the voltage reaches 12V. Once that happens the battery charger will use constant current charging, followed by constant voltage charging (as per Stage 2 charging outlined above).  

The next stage is for the charger to conduct further analysis. If the battery voltage is above 12.6V the charger will switch to recondition mode to maximise the capacity of the battery. Once this stage is complete the LED indicators will switch from orange to green. 

The battery charger will then switch to float voltage for a period of time. This allows further charging to be absorbed as gently as needed. This is sometimes called the Absorption Stage. 

The last stage, or Maintenance Stage monitors the battery voltage and switches on occasionally to maintain the state of charge, while not unnecessarily stressing the battery (also reducing the energy consumption of the charger) 

If you have any questions concerning the use of MEAN WELL battery chargers, then do not hesitate to contact ADM. A member of our expert team will gladly answer any question that you may have.  

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15 October 2021