Mounting Odd Sized Battery to PCB?

Nov 02, 2010 20 Replies
U

Hello all, I am working on a project with a group, and i am trying to design a power board for it. I am trying to find a method of mounting the batteries so that they will be easily replaceable. I am using 2 lithium ion batteries, with surface mount connections, with dimensions of 5.8*54*60mm. I was thinking about having a small sister board ,a little bit bigger than the batteries, that I could sandwich the batteries around, and put my thermistor in between the board and a battery. Then I would connect the sister board to my main board that has my charger on it through a header or connector.



My problem with that design is that I need to find a way to mount the batteries to the pcb while still making them easily removable. I was not able to find any mounting clips for that size of battery on digikey, or various other places online. I was contemplating having holes drilled into the pcb and using zip ties to hold the batteries down, while this is tacky, it also poses a problem if the batteries fail because they tend to inflate when they fail. I also wanted to try and avoid gluing the batteries if at all possible.



I was also thinking about using the sister board as a large ground plane...



I also need a method of attaching the sister board to the larger power board, I was contemplating using two headers on each end of the sister board to form a mount, I'm not sure how secure that would be, I was also contemplating drilling holes and using metal spacers and screws to hold the boards together.



I would appreciate any help you could give me on this project, I don't have any real experience with building pcb's, only designing circuits on paper, so I would appreciate any warnings of pitfalls you think I might run into with this setup.



The entire project is going to be put inside a 10cm^3 container, so space is at a premium, and later versions of the board will be weight sensitive, and of course this is a time and money sensitive project.....but aren't they all?



Anyways, I would greatly appreciate any advice, ideas, etc. you could give me on this project. Thanks.



*ps, could somone repost this so people who block gmail accounts might be able to help me out as well? thanks*
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T

Waltz into your local hobby shop and buy a 2-cell LiIon pack designed for model airplane use. Then put whatever power connector you want onto it, and go.

Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
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M

We don't do homework for others here. At the very least you should provide us details on the battery type, part number and manufacturer, a web link would suffice. Have you looked into Keystone? Or how about velcro and pogo pins? Use thin strips of PC board material to make a nest for the batteries to rest in, solder them perpendicular to the main board Regards, al

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K

I lift far fewer pads with SMT devices than I did with PTH. Pins in planes can be a PITA. OTOH, RoHS sucks the big one.

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T

PTH and internal planes are the worst. Without preheat, it's nigh on impossible to recap a faulty motherboard (what, ~8 layers?), even with a nice and toasty soldering iron.

PTH tends to be frozen on the top, so the pad (or PTH itself) tears out. When desoldering, I like to heat it from the component side when possible!

SMT on the other hand, stick the whole board under a torch, heat it up slowly (a few minutes...ha), then scrape or knock off your bonanza of assorted parts. ;)

Tim

Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
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R

Surface mount connections rule OUT the "easily replaceable" part, as a bit of ham-handed unsoldering can destroy the pads.

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T

Best way with PTH is to clip all the leads off and remove them one at a time. Then clean out the holes with a vacuum desolder tool. RoHS really does suck.

tm

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M

Do you know what a standard roll of solder of the Sn96.5 AG03 Cu.5 variety goes for? The mil spec stuff is even more.

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T

Only an idiot would reflow an entire board of hundreds or thousands of solder connections to service only a few. Then again, you did also say "torch".

The sad thing is that I know you to be smarter than that in other segments of the industry.

Yes, preheat is a must for servicing multi-layer through hole.

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T

"TheGlimmerMan" wrote in message news: snipped-for-privacy@4ax.com...

Poetic licence.... Tim's quite correct in his approach. We bake boards at 60 deg. for 4 hours before touching them. For BGAs it's 48 Hrs at 100 deg.

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U

UAFEEUndergrad schrieb:

Hello,

there are enough exchangeable lithium cells for which battery holders exist. Just select a combination of cell and holder available at digikey.

Bye

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J

MrTallyman wrote in news: snipped-for-privacy@4ax.com:

what happens if you use 63/37 Sn/Pb for the repair? does the RoHS police kick down your door? lose your license?

Jim Yanik jyanik at localnet dot com
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M

What would dimmie know about that?

Politicians should only get paid if the budget is balanced, and there is enough left over to pay them.
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E

Sometimes, with PTH - and frustration - a chainsaw comes to mind. :-(

Ed

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M

Cutting torch. ;-)

Politicians should only get paid if the budget is balanced, and there is enough left over to pay them.
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T

The ROHS Police is a figment of everyone's imagination...I know of at least two small companies that don't even know what lead free solder looks like....4 years down the road. Good luck to them... :)

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S

IOW, it's like cutting corners and bending the rules/laws anywhere- if you're small, low profile about it, and don't visibly hurt anyone too much, you can get away with it for quite a while.

Best regards, Spehro Pefhany

"it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
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K

Tim is also talking about reclaiming the parts, not the boards. Of course DimBulb is too dim to read.

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K

Yes. Your board is no longer RoHS if you as much as touch an iron that has touched Pb to the board.

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