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Charging a 36V battery with a Luna 48V charger set at 80%

fond of bikes

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Jul 16, 2020
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I wonder if it would be safe to charge a 36V Li-ion battery with a Luna 48V Li-ion battery charger set at 80%. The 48V Luna charger will charge a 48V battery to 54.6V when set at 100%. 54.6V multiplied by .8 = 43.68V. The 36V battery should be fully charged at 42V. The 36V battery has a BMS. The Luna charger will charge at 1V, 2V, 3V, 4V or 5V.
 

Walt

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Jul 12, 2020
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Always use a charger that is designed for you pack. If you use the wrong charger you not only risk the long life of your pack it can also become a fire hazard. Make sure the charger’s maximum voltage matches the maximum voltage of your pack.

Theoretically it would work however if you forget to select 80% you'll come home to a cooked battery at the least or a pile of rubble where your house used to be at the worst! You'll notice that at 80% you're still over the maximum recommended voltage for your pack which is 42V and hence the risk of an exploding battery pack or fire. Here is an example of maximum voltages for popular Luna Cycle 18650 packs:
  • 10S (36V pack) – 42V max voltage
  • 13S (48V pack) – 54.4V max voltage
  • 14S (52V pack) – 58.8V max voltage
 

fond of bikes

New member
Joined
Jul 16, 2020
Messages
4
Points
1
Always use a charger that is designed for you pack. If you use the wrong charger you not only risk the long life of your pack it can also become a fire hazard. Make sure the charger’s maximum voltage matches the maximum voltage of your pack.

Theoretically it would work however if you forget to select 80% you'll come home to a cooked battery at the least or a pile of rubble where your house used to be at the worst! You'll notice that at 80% you're still over the maximum recommended voltage for your pack which is 42V and hence the risk of an exploding battery pack or fire. Here is an example of maximum voltages for popular Luna Cycle 18650 packs:
  • 10S (36V pack) – 42V max voltage
  • 13S (48V pack) – 54.4V max voltage
  • 14S (52V pack) – 58.8V max voltage
Walt, Thank you for the excellent advice. I did not attempt to charge the 36V battery with the 48V Luna charger at 80%. I was patient and waited for the 36V battery charger I had previously ordered to arrive. After it arrived, I had to be patient once again as it took 10 hours to charge the 36V 10AH battery with a 2Amp charger. I expected it to take only 5 hours. The charger was probably overrated.
 

fond of bikes

New member
Joined
Jul 16, 2020
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@fond of bikes If you would like to test your theory, Luna sells a charge safe for ebike batteries which would prevent a battery fire from spreading:

Thanks. I checked those out. I use something similar already. It is a heavy duty small to medium barrel shaped steel can with a spring loaded lid that was designed to house oily rags to prevent spontaneous combustion. I will still take Walt's advice and use the appropriate charger for the battery.
 
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