I have a 11.1 V Li-ion battery pack that I use for a 9-12V device as backup power. When I charge the battery pack, it draws 1-1.25 A of current from the DC charger which has caused more than 1 charger to burn up. How can I limit the current to 0.5 A? I tried using a 47 ohms resistor in series with the battery but it dropped the current to 10 mA. What am I doing wrong?
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\$\begingroup\$ What battery is it and what device you are using to charge it? \$\endgroup\$– JustmeFeb 17, 2021 at 7:02
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\$\begingroup\$ It is a li-ion battery pack with BMS. I am using it to run a led board driver. I use a run of the mill 12V - 1A DC charger to charge it. \$\endgroup\$– RagoFeb 17, 2021 at 7:52
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2\$\begingroup\$ Do you mean a power supply or a charger? A power supply is not a charger. A BMS is not a charger either. You can't charge lithium batteries without a charger, or something is going to blow up. You can be glad it was the power supply that blew up first, instead of the battety exploding or catching fire. The battery may also be damaged already so it may not be safe to use it any more. \$\endgroup\$– JustmeFeb 17, 2021 at 8:17
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2\$\begingroup\$ That is NOT a charger, it is a power supply. Stop connecting it to your batteries immediately. \$\endgroup\$– JustmeFeb 17, 2021 at 9:01
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1\$\begingroup\$ I sense a lithium fueled fire in the making. \$\endgroup\$– winnyFeb 17, 2021 at 9:42
2 Answers
The problem is that you don't have a lithium battery charger, and you are directly connecting a 12V power supply to your batteries.
Don't do that, as it will damage the power supply and the lithium batteries, and they may explode or burst into flames.
Only charge the lithium batteries with a lithium battery charger.
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\$\begingroup\$ I got the datasheet of the battery pack from the manufacturer - imgur.com/yX4m4uh \$\endgroup\$– RagoFeb 17, 2021 at 11:28
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\$\begingroup\$ It does not matter as you don't have a device which is suitable for charging. \$\endgroup\$– JustmeFeb 17, 2021 at 11:36
A Lithium ion battery pack must be charged with a circuit specifically designed to do so, and should be discharged with a protection circuit as well. Batteries with multiple cells in series(like yours) should be charged with an appropriate BMS(Battery management system). If you're using Lithium ion for a project, do your research. You might want to check out batteryuniversity.com.
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\$\begingroup\$ Hi, the battery pack I am using has an attached BMS with OC / UC protection, overheating & charge protection. It is just that it draws too much current. Anyway to limit that to 500 mA? \$\endgroup\$– RagoFeb 17, 2021 at 6:55
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\$\begingroup\$ many charging chips have settable charging current (via external resistor) \$\endgroup\$– IlyaFeb 17, 2021 at 7:18
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1\$\begingroup\$ I think you have it the wrong way around. The battery is not allowed to draw any more current than the charger it is connected to is set to provide the current. It sounds like @Rago has no charger and the battery is directly connected to a power supply, and the devices cannot handle that. \$\endgroup\$– JustmeFeb 17, 2021 at 7:24
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\$\begingroup\$ Yes if the BMS and battery protection are built into the pack it would appear you just need an appropriately sized charger board. The current ratings and adjustability of the charger board should be listed in its documents. \$\endgroup\$– K HFeb 17, 2021 at 7:27