lithium ion battery tech

kaaoszx · 25th April 2007, 07:06 PM

im trying to install a new battery in a mp3 player and had a different capacity one on hand. can i use the same protection circuit for the higher capacity battery? im guessing that the higher capacity batery wont work with a lower capacity circuit? anyone know where i can find information on building your own lithium ion charging circuit?

I_Forgot · 25th April 2007, 08:21 PM

SparkFun Electronics has a $15 Li-Ion charger kit (well, assembled PCB) that gets power from either a wall wart or USB port on a computer.

I_F

Mailliw · 25th April 2007, 08:33 PM

Assuming the lithium-ion charging circuit detects when the voltage reaches a specified value (Wikipedia), the capacity change shouldn't matter.

What's the worst that could happen, a small fire?

Pjotr · 27th April 2007, 08:09 PM

Hi,

Li-ion batteries have almost the same charging profile as lead acid batteries: That is, constant current / constant voltage.

But there is a big difference: They cannot stand overcharge. When the cell voltage becomes higher than 4.2 V the electrolyte will be destroyed permanently rendering the battery useless then. Therefore they need a battery management system (BMS) when more cells are in series to watch each cell. So no one will be overcharged.

Putting a new single cell battery in with a just higher capacity means only charging will take a little longer. Provided the current charger is in good working order.

Here is some good reading: http://www.batteryuniversity.com/

Cheers

25th April 2007, 07:06 PM	#1
kaaoszx diyAudio Member Join Date: Nov 2005	lithium ion battery tech im trying to install a new battery in a mp3 player and had a different capacity one on hand. can i use the same protection circuit for the higher capacity battery? im guessing that the higher capacity batery wont work with a lower capacity circuit? anyone know where i can find information on building your own lithium ion charging circuit?

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25th April 2007, 08:21 PM	#2
I_Forgot diyAudio Member Join Date: Jan 2005 Location: Phoenix, Az.	SparkFun Electronics has a $15 Li-Ion charger kit (well, assembled PCB) that gets power from either a wall wart or USB port on a computer. I_F

25th April 2007, 08:33 PM	#3
Mailliw diyAudio Member Join Date: May 2005 Location: Canada	Assuming the lithium-ion charging circuit detects when the voltage reaches a specified value (Wikipedia), the capacity change shouldn't matter. What's the worst that could happen, a small fire?

27th April 2007, 08:09 PM	#4
Pjotr diyAudio Member Join Date: Nov 2002 Location: Netherlands	Hi, Li-ion batteries have almost the same charging profile as lead acid batteries: That is, constant current / constant voltage. But there is a big difference: They cannot stand overcharge. When the cell voltage becomes higher than 4.2 V the electrolyte will be destroyed permanently rendering the battery useless then. Therefore they need a battery management system (BMS) when more cells are in series to watch each cell. So no one will be overcharged. Putting a new single cell battery in with a just higher capacity means only charging will take a little longer. Provided the current charger is in good working order. Here is some good reading: http://www.batteryuniversity.com/ Cheers