42V Charger for 36V li-ion battery ? Yes read this guide

I could call this article “how to choose the right charger for an electric scooter or electric bike or hoverboard” I do service for ebikes, e-scooters and similar products and here is my experience with chargers.


42V is the correct charging voltage

The first advice is to buy the charger with the correct charging voltage, the battery does not overcharge but charges correctly. Many stores sell chargers labeled as “36V Charger”. Attention 36V is only nominal voltage, the actual value of the charging voltage is higher for 36V li-ion batteries is charging voltage 42V ! 

36V are also labeled chargers for lead batteries and lifepo4 these chargers have a charging voltage even higher about 43.8V for a lead-acid battery can be even higher by 0.2V.

Why just charge by only 42V?

36V Li-ion batteries are made from smaller 18650 cells or prismatic cells , Each of these 18650 cells has a nominal voltage of 3.6V and a charging voltage of 4.2V, these cells are connected 10 in series, so it is 36V only as a nominal voltage and 42 is the charging voltage.

If there are 10 cells connect in serial it is referred to as 10S.

Higher voltage than 42V shortens battery life or complete destroy his, The BMS could stop the wrong charger but sometimes this electrical circuit also burns especially if the voltage is 92V as with aliexpress charger.

2A charging power or more power is better ?

More amps = shorter charging time = more heat …

If you have a small battery with a smaller capacity of 7.2Ah 5.2 Ah, up to about 11Ah i I recommend charger 2A output. The 2A current is optimal for smaller 36V Li-ion batteries I’ll explain why:

In you electric scooter have 7,8Ah 36V battery , manufacturer used Samsung 35E (INR18650-35E ) his the charging current is 1A per cell  (2A is maximum but not recommended by the manufacturer reduces the service life)

 You have two cels in paralel connections 2×3,4Ah=7,2 Ah and charging current can be about 2A. This also means that you can use a 2 A charger and not use a 5 A charger.

  • If you want to use a more powerful charger than recommended by the battery manufacturer, always check the battery cell parameters (type, manufacturer datascheet)
  • In some cases, the manufacturer delivers an unnecessary low charger along with the product, then it takes too long to charger

Cooling or not cooling ?

Fan chargers are good, especially at higher charging amperes such as 5A.Charger fan may not have if they are well designed while charging they are just a little warm. The biggest charging load is at the beginning, then the highest current flows.

  • Do not store the charging adapter in the pouch while charging the heat from it must be gone.

My other practical experience:

  • If you buy new charger , check with the multimeter before charging for the first time. A simple multimeter is enough here is my type XL830L
  • When charging for the first time, monitor the temperature of the charger as well as the battery, if possible,The charger may be warm but the battery should remain lukewarm
  • You can always replace the connector on, but check the polarity of the voltage with a multimeter.do not rely on the color marking of the drivers, often times it is nice.
  • The charger turns green after charging and stops charging when the voltage should be 42V (with 36V Li-ion charger)
  • If the green light does not light up and the charger is still charging the battery cannot reach the final voltage (it may not be a mistake but often it is a signal that it is something from the battery)

3 thoughts on “42V Charger for 36V li-ion battery ? Yes read this guide”

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    Hi i have lost my e_scoot’s battery so i have to make a new with cells 3*10 controled by the bms qs-b413anl-25a v1.03 and charger with 42v 2a
    The problème that i dont know where to plug the third wire in chargeur (indicator) so the charger is always on green light like the battery is disconnected

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