Lithium ion battery charger

[mayukh]

I am figuring on using a 12V 500mA adaptor to charge 3 lithium ion batteries in series  (each battery being 4.2V 2000 mAh therefore when put in series the total battery pack becomes 12.6 V 6000mA). A similar arrangement is described in the $50 robot. Would this work?

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Regards,
Mayukh.

[galannthegreat]

I highly recommend that you don't mess around with lithium batteries in general... the result could be very dangerous.

[mayukh]

Yep, that was exactly what I was thinking. There could be a fire hazard  .. Could get hold of a charger off the shelf or try building one myself, which would again take up too much of time. But I think the 12 V adaptor option is out of the window, although I would have tried with NiMH batteries..

[galannthegreat]

Yea, you're better off using NiMH batteries in my opinion. I will never use LiIon or LiPoly batteries in my projects because of the hazards that are very dangerous, and also the fact that you can get NiMH batteries for a much cheaper price, and the charging circuit envolved there is very simple and cheap to make or buy... compared to LiIon or LiPoly.

[blackbeard]

don't worry so much about the dangers of lithium ion batteries. honestly they are some of the most effective batteries i have ever used and contrary to popular belief they arn't ticking time bombs. charge them properly and they can be ideal for robotics or any other power consuming project. lipoly is a bit more dangerous but is great for it's size/weight to power ratio. the best precaution you can take is to buy a charger preferably for the specific battery you intend to use. another good thing to do is to test your circuit and make sure there are no shorts before connecting a lithium battery. save them for the final product.

[galannthegreat]

It's still not a good idea to mess around with them by making or using a charging circuit not designed with the intentions of charging a LiIon or LiPoly battery. Stick with what your knowledge bounds you to. I'm not saying don't use them, but just be careful when using them.

[madsci1016]

Lithium batteries  are one of the best batteries to use in robotics, and one of the most dangerous. I have seen videos of testing lithium batteries for worst case scenario (required for any battery we use at work; ie the Navy) and it is not pretty.

That said, you can make them relatively idiot proof.

Get something like this : http://www.all-battery.com/protectioncircuitmodulepcbfor111vli-ionbatterypack3cellswith65alimit-pcb111v65a.aspx

That is a circuit board the you attach every cell to in your battery pack and it takes care of everything, over/under voltage, current; all controlled. I have accidentally shorted my 14V DIY Li-Ion packs and the board protected them (and me) from exploding. 

Get a board like that attached to your cells, and then you should be ok.

[galannthegreat]

Definately a good buy there. But you should still take precaution when dealing with them.

Here is a method that will help with "accidental" explosions:

http://www.liposack.com/products.htm

[Joker94]

The good thing about lithium is that they have zero memory affects so that is a good point.

And remember if a lithium battery catches on fire don't use water to put it out it will just feed the fire.

http://www.societyofrobots.com/batteries.shtml

[madsci1016]

The good thing about lithium is that they have zero memory affects so that is a good point.

While having no memory effect, they do have diminishing returns. Ever notice the older your laptop gets, the shorter the battery life?

[Joker94]

While having no memory effect, they do have diminishing returns. Ever notice the older your laptop gets, the shorter the battery life?

yeh, i notice the life of my laptop battery shortening, but i suppose that happens with all batteries and in the endd lithium may still be the most effecient battery(when handled correctly and charged correctly).