Question about Li-Ion and battery choice for project

[SkinnyV]

Hi guys!

I was lurking the forum after searching for a DIY Li-Ion charger and found the forum to be much more useful than I thought! I am trying build a new product intended to be sold in small quantity to a couple of people around my area and I was looking into adding a rechargable power source to that product(special dog collar).

But after reading alot on the forum, it turn out that the battery choice I had made earlier might not be the best idea for such an application. I had choosen Li-Ion for its ability to work under extreme condition (like the really cold canadian winter for example), probably the CR123a which can output 3.6v and sometime more which would be useful for what I'm trying to power up. I need to supply between 6v and 12v, the closer to 12v the better but 6v should be enough. The battery also need to be small enough to be weared on a dog collar without making the collar too incomfortable for the dog.

So, my questions are:

Is stacking two CR123a to produce more than 6 v dangerous if always charged at the same time?

Is the simple DIY charger from this thread http://www.candlepowerforums.com/vb/showthread.php?t=57999
would be safe to use with CR123a Li-Ion battery and would it cause problem to leave the battery on the charge after thay are charged?


Would it be unsafe to charge the battery while they are installed permanently inside a circuit?

I found out about the AW R123 while on the forum and they appear to be capable of doing what I want them to do without any safety concern but they are more expensive though and would add to the cost of the product which I try to keep as low as possible

I am not sure yet if I'm gonna end up using rechargeable battery or regular as of yet. I wanted to have them rechargeable if possible and with the CR123a, it was not really that much more expansive to add. But on the other hand, the product might be used by peoples without much or any knowledge about battery and battery charging and I don't want to add something that could be a safety concern or explode in the dog neck either or that would be too complicated to use for someone who just want to plug the thing and forget it.

I also need to be able to construct and integrate a small charging circuit or else I'm gonna need to scrap the rechargeable battery idea and stick to regular battery.

So is there any option that I have overlooked or thing I should know?

Thanks for your help and time guys, it's apreciated

Vince

 

[mdocod]

Welcome to CPF!

I think you might want to make sure you have your terminology all figured out straight...

A CR123 is a primary lithium cell and is not rechargeable. Charging them will make them very unsafe.

Charging li-ion cells in series requires a balance charging setup to really maximize safety, which I would say is pretty important if you are planning on having this device be worn on a pet. Series packs are perfectly safe if you implement them according to manufacture guidelines (must have global protection and balance taps for charging).

How much stored energy do you need? It's not easy to make a recommendation based purely on voltage needs, I could easily suggest a stack of watch batteries to meet your voltage requirements if that's all you need, but the power requirements of the device and time you want between recharges would be important to know to make the best possible recommendation.

Eric

 

[45/70]

mdocod is correct in that more information on your requirements is needed. One thing for sure, if you're talking about the Canadian winters I'm familiar with (east shore Superior), Li-Ions won't work. Your best bet would probably be lithium primaries, although, I'm not sure how well those will work at -40 (take your pick, F or C ).

Dave

 

[SkinnyV]

Thanks for your answer guys. I was refering to the rechargeable battery that look like a CR123a I guess. After reading the forum more and looking at different chemistry battery, I am beginning to think that rechargeable might not be the way to go for what I am trying to achieve... It's either too expensive to add to the product with a proper charger, or to troublesome to use in that particular application. Li-ion is supposed to work well in temp bellow 0 but might be a safety concern. I tought of maybe convering the battery area with fire proof fabric . AW R123 are safe but lose their juice in the cold aparently. Also, my goal was to install the rechargeable battery permanently inside but from what I understand, that kind of rechargeable battery can fail after a couple of cycle sometime so it would be alot of trouble for a regular person to change the battery after that.

So my best bet would be to use primary like I suspected, I wanted to go rechargeable and save some battery from being thrown in the dumpster but I guess this might not be realistic. I'm gonna continu to look around the forum just in case though but do you have any experience with rechargeable CR2032 battery or other button cell rechargeable?

Thanks!