DIY 18650 battery pack

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kje

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I`ll make a battery pack with 3x18650 in series powering some 12v led lights.

1) Do I need a balancer in the battery pack?

2) Do I need a 11.1v pcb protection circuit?
 
HKJ

HKJ

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I`ll make a battery pack with 3x18650 in series powering some 12v led lights.

1) Do I need a balancer in the battery pack?

Depends on your charger, hobby chargers has balancing connections.

2) Do I need a 11.1v pcb protection circuit?

No, you need a protection for 3 batteries in series, i.e. it checks the voltage for each battery, not only for the series connection.
 
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kje

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Depends on your charger, hobby chargers has balancing connections.

I`ve ordered a iMax B6 charger...

No, you need a protection for 3 batteries in series, i.e. it checks the voltage for each battery, not only for the series connection.

What is it called and where do I get it?

I`ve heard lithium batteries can be damaged or make a fire if discharged under 3v. What happens if one of the three batteries is discharged under 3v? Will the protection give me some alarm so I can charge it?
 
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lightseeker2009

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I`ve heard lithium batteries can be damaged or make a fire if discharged under 3v. What happens if one of the three batteries is discharged under 3v? Will the protection give me some alarm so I can charge it?

From practical experience..
Lithium batteries does not catch fire even if you use it to below 1.0V. But if the voltage drop too low you have damaged your battery. It will not accept charge then. When you try to charge a damaged cell, that is where a fire can occur.
The protection circuit wil prevent that from happening. It does not give a warning, but power supply will be stopped.
 
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BringerOfLight

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What is it called and where do I get it?
It's called PCM (Protection Circuit Module) or BMS (Battery Management System). Some have a balancer built in. (Just do a search for "lipo pcm", you will find plenty.)
I`ve heard lithium batteries can be damaged or make a fire if discharged under 3v. What happens if one of the three batteries is discharged under 3v? Will the protection give me some alarm so I can charge it?
The protection circuit will shut down the battery pack. That's typically done when any cell reaches around 2.5V.
From practical experience..
Lithium batteries does not catch fire even if you use it to below 1.0V. But if the voltage drop too low you have damaged your battery. It will not accept charge then. When you try to charge a damaged cell, that is where a fire can occur.
With a 3S setup and an unbalanced pack, you can easily have 2 cells reverse charging the 3rd one - that's playing with fire.
 
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yvonne_chan

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if you assemble a battery pack, a pcm or bms is necessary needed.
battery is dangerous so you need sth. to prevent it from causing dangerousness.
you can choose a 3s or 4s pcm.
explain: 12V/3.7≈3 or 4
 
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kje

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It's called PCM (Protection Circuit Module) or BMS (Battery Management System). Some have a balancer built in. (Just do a search for "lipo pcm", you will find plenty.)

The protection circuit will shut down the battery pack. That's typically done when any cell reaches around 2.5V.

With a 3S setup and an unbalanced pack, you can easily have 2 cells reverse charging the 3rd one - that's playing with fire.

When my battery pack power some led lights over time, one of the cells can be discharged under 2.5V? So if I have 3 cells unbalanced in series and one of the cells is discharged under 2.5V, that will give me some trouble?

Balancing and protection circuit is two different things? Do I need both?

This 3x18650 holder has pcm installed. Do I need balancing as well with this?
 
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kje

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Do I need to buy balancing leads?
 
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lightseeker2009

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If you can easily disasemble the pack to charge the batteries seperately, then no. Otherwise I would seriously recommend it. The holder you linked to won't balance the cells when used in series. I've bought these holders for myself, but the parallel version. They are meant for unprotected batteries. Protected batteries are too long for it. I had to force mine in, now I can't get them out.
 
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kje

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Ok. 1) What balance leads do I need? 2) The balance leads are just for the charging process, right?3) What if one cell dont work (discharged) while powering the leds, that means extra work for the other two cells? Is that dangerous?
 
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kje

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Is there many types of balancing leads?
 
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kje

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If i connect balancing leads to my 186500 battery pack and use the Imax to balance each time I charge the pack, there is no need for a PCM?
 
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kje

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Can i use some of the pcb from a laptop on my 3s2p batterypack? Here are some picture of 4 laptop pcb's I have: (the two first are from mac, the other two from pc)

https://dl.dropboxusercontent.com/u/17206911/Public Photos/20130618_190013.jpg

https://dl.dropboxusercontent.com/u/17206911/Public Photos/20130618_190110.jpg

https://dl.dropboxusercontent.com/u/17206911/Public Photos/20130618_190042.jpg

https://dl.dropboxusercontent.com/u/17206911/Public Photos/20130618_190203.jpg


Your images are oversize, when you post an image please remember Rule #3

Rule #3 If you post an image in your post, please downsize the image to no larger than 800 x 800 pixels.

Please resize and repost. - Thanks Norm
 
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K

kje

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If i connect balancing leads to my 186500 battery pack and use the Imax to balance each time I charge the pack, there is no need for a PCM?
 

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