2 protected LiIon batteries in parallel. Possible?

[slimest]

My friend purchased these miniature batteries in purpose to use them in parallel in his small mod:
2 X 3.7V Li-Poly Battery For Syma RC Helicopter New | eBay
They are protected, i.e. each has its own protection board. My question is:
What's better: just to connect them in parallel using output wires or remove the board from one accumulator and connect two accumulators in parallel using the remaining board?
Load capabilities of one board are enough for vaping.

Colleagues, your opinion? I intuitively don't like to connect two protection boards in parallel...

 

[BuzzKilla]

Li-Poly is a more violent and temperamental chemistry.
I wouldn't mess with the boards on them as you may overheat the battery trying to unsolder the board.
The skin is a very thin foil, and if punctured the internals will short causing a big BOOM! if you try to charge it.
So be carefull when you handle these cells, any serious deformation to the casing can cause an internal short.

considering each cell can only take 240mAh i really dont think it is worth while.

If you are set on sticking with this style cell, just get a single larger capacity cell, use the existing leads and solder them to a mod chip(many to choose from on this forum).
You would have to get creative, when it comes to charging.

If you browse around @ hobbyking.com you can find pre-made 2S1P(2 cells in series) packs 7.4V .
Dimensions on these packs are listed, so it makes it easier to find one that fits in your mod. But most of these dont have protection, as the RC electronics take over that function. then just get a regulator board to bring down the voltage as per your liking.

i would personally stick to lithium-ion or IMR cells. put a battery holder within the mod and charge the batteries separately, and this will alleviate any extra bulk from having a built in charger or separate leads to a charger.
Makes the wiring in the mod a lot simpler.

But that is just my opinion...

Someone soon will probably come along with a more helpful suggestion.

 

[slimest]

BuzzKilla, thanks for your answer. I have some experience to work with different lithium batteries and understand risk and needed precausions. My question mostly concerns boards and their correct work if they connected in parallel.
And I don't need a batteries in series, I need to use already existing batteries in parallel.

P.S. I thought so: the question is not simple, so no more answers...

 

[The Lukester]

Just my 2 cents but why use two batteries when one can do the job and be much safer for everyone!

 

[slimest]

One battery has 240 ma-h

 

[skipdashu]

I've got a box mod that uses two 14500s in parallel (protected or IMR) and works fine as long as the two are matched pair. Putting one in that's lower charge will cause the higher batter to rapidly try to charge the lower one. I use pairs that are within .05v of each other at full charge. I haven't seen any problems with the protected ones in parallel. The box will work on a single battery also so u know they're hardwired in parallel.

 

[slimest]

skipdashu, thanks for answer. Seems that no problems with a such connection...

 

[skipdashu]

skipdashu, thanks for answer. Seems that no problems with a such connection...

BTW, "The worst sin is greed"... see THIS? I'm partial to "Pride" but "Greed" will do in a pinch ;-)

 

[CraigHB]

I don't know why people have such a hard-on for LiPo cells. They're no more volatile than LiCo cells. I think they get a bad rap becasue the RC guys work them hard with no protection and blow them up a lot. They're plenty safe enough when properly protected. After all, they are used by the billions in cell phones and digital cameras.

I wouldn't be concerned about running two protection boards in parallel. As much trouble as it is to remove the boards and rewire protection for the cells, I'd just leave it as is. People run protected round cells in series or parallel all the time with no issue. That's essentially the same thing. Though, you'll need to check your drain limits. It's not unusual for LiPos to come in a 2C drain limit.

 

[asdaq]

Uh Craig, Lipo's don't really do it for me. Neither does liposuction. Now just suction, sometimes yes.

 

[slimest]

Thanks Craig. About drain limit - these cells are 20C each, it's enough

 

[CraigHB]

20C cells are nice, usually have ample drain capability even for the smallest cells. They're bigger than their 2C or 10C counterparts though.

 

[skipdashu]

240mAh x 3 = 720mAh = about 1 14500 Protected Trustfire 'flame' battery. 3 x @3.08 = $9.24 out of China. Huge drain capacity but more than u could use on a PV.

A pair of Trustfires out of China = $9.38, in parallel about 1500mAh. 'nuff drain capacity to run 1.5 ohm atties and a bit more durable.

But kewl stuff to see! If they dropped another buck I'd have to think abut putting 4 of them in parallel in some sort of box. Maybe an Altoids box.

 

[slimest]

skipdashu, in my case (my friend's case) the main criteria is dimensions. He wants to make e-pipe using two small batteries in parallel. Trustfires etc don't fit, but described batteries fit perfectly.

 

[skipdashu]

skipdashu, in my case (my friend's case) the main criteria is dimensions. He wants to make e-pipe using two small batteries in parallel. Trustfires etc don't fit, but described batteries fit perfectly.

Oh. Well that does make quite a difference.

 

[Para]

Since he's making an e-pipe and space is critical....have you considered using 2 14250's in parallel? They are similar in mah and protected. Just a thought.....