cheap 9v battery connector - Page 1
Forum section: electronics / projects

author: OM222O
author_rank: Frequent Contributor
timestamp: April 22, 2019, 01:51:13 pm
content: HelloI had designed a few boards as potentially commercial products and now I've decided to go ahead with that idea and sell them.My only issue is surface mounts snaps for 9V battery are super expensive for what they're worth (a few $ per connector, and you need a male and a female one!) so that was a no go. for prototyping I just used battery clips with wires soldered onto the PCB which worked fine, but if the wires are moved a lot, they tend to break as they are fairly small. the product can also use up to 1A so the connector should be able to handle that (preferably a bit more as a safety measure). or if you have recommendations on how to protect the wires so they don't break off so easily, that would be great too. (maybe use more solder? somehow secure them to the board so the actual joints aren't stressed?)

author: rhb
author_rank: Super Contributor
timestamp: April 22, 2019, 01:56:40 pm
content: I recommend soldered wires with two holes and a zip tie to secure the wires. A blob of epoxy will also work, but is less repairable. I rather fear that surface mount would will eventually pull the board traces up. I've encountered some cases where I broke the connector trying to separate it from the battery..

author: Psi
author_rank: Super Contributor
timestamp: April 22, 2019, 02:00:21 pm
content: Put 3 holes in the PCB in a line, 2 are a little bigger and non-plated and the last one is plated.Push the wire with insulation through one hole the back up through the 2nd hole.Then have some insulation removed and push the wire only through the last plated hole and solder it.This will provide some retention and stop the wire from flexing at the rigid part.Wires break when flexed because the solder wicks up the wire and you lose the flexibility of stranded wire at that point.You can try only 2 holes, but i found 3 works better.One disadvantage of this method is it takes a bit of manual labour time to perform during assembly.If this is too long for you then you can use this second method below. It isn't quite as good but is much faster.Cut 3x L slots into the pcb on the edges. Then you can just push the loose wire into the slots in a similar up down up style and the L shape traps them from easily getting back out. This is much faster to thread the wires into the retention areas because the slots are open ended, unlike a hole.

author: OM222O
author_rank: Frequent Contributor
timestamp: April 22, 2019, 04:42:19 pm
content: unfortunately I can't use through hole. The board must be surface mount because the other side is used as front panel and must be clean looking (routing the circuit on a single side was a nightmare but I managed to do it). In one of dave's teardowns I saw something which looked like a 0.1 inch header, looped into a semi circle which was used to tie down some cables. I wonder if I can use those instead?

author: mariush
author_rank: Super Contributor
timestamp: April 22, 2019, 04:58:03 pm
content: the product can also use up to 1A so the connector should be able to handle that9V batteries can't really sustain 1A over long periods of time. You'll have the voltage of the battery drop and indicate low voltage prematurely.Check 9v datasheets, most batteries list charts and graphs and values for max 250-500mA :1.https://www.celltech.fi/fileadmin/user_upload/Celltech/Prod.sheets/Duracell_Ultra-Power_9V.pdf2.http://data.energizer.com/pdfs/522.pdf3.http://data.energizer.com/pdfs/max-eu-9v.pdfHave you considered using 2-3 AAA or AA alkaline batteries instead of a 9v battery, along with a step-up regulator to whatever internal voltage you need?A 9V battery is ~ 49mm x 18mm while an AAA battery is ~ 45mm x 11 mm, so two AAA batteries would not take more space.Here's battery holders and clips for AAA :https://www.digikey.com/short/pp2ppvHere's a 3 x AAA battery holder, basically takes 53mm x 38mm x 13mm and costs almost 1$ when you buy 50+ :https://www.digikey.com/product-detail/en/keystone-electronics/2479/36-2479-ND/303824Probably can get them cheaper at other stores or lcsc (whatever it's called)Here's a 2AA , 63mm x 33mm x 16mm ..https://www.digikey.com/product-detail/en/keystone-electronics/2462/36-2462-ND/303811... at least you know you can get 2-3A from each AA battery for short periodsThe step-up regulator could be less than 50 cents, including the inductor and ceramic capacitors it may need, and considering the mass use of AA/AAA batteries, the clips for batteries would be super cheap

author: OM222O
author_rank: Frequent Contributor
timestamp: April 22, 2019, 05:18:37 pm
content: yes, I said up to 1A as it's small burst loads, not sustained. the product design is not the issue here, it's just the connectors that aren't easy to deal with. I didn't find any decent SMT 9V battery holder

author: SeanB
author_rank: Super Contributor
timestamp: April 22, 2019, 05:31:38 pm
content: Then a pair of largish pads on the board, and then have a small circle of bare board which is the landing spot for the blob of hot glue to retain the wires. Instead of hot glue regular contact adhesive, acetoxy free silicone or even superglue gel will work as well. No holes, but a strong connection.

author: MosherIV
author_rank: Super Contributor
timestamp: April 22, 2019, 05:39:04 pm
content: HiI know you said no through hole but a knot in the cable is a great and very cheap strain relief.Put the cable through the hole in the board with the knot on theright side.Then solder the cable ends to your pads.

author: OM222O
author_rank: Frequent Contributor
timestamp: April 22, 2019, 05:44:00 pm
content: how well will hot glue or epoxys hold up in long term? I agree that it's the cheapest best solution.

author: rhb
author_rank: Super Contributor
timestamp: April 22, 2019, 06:22:35 pm
content: I would not depend upon hot melt. Epoxy should hold well. If you have space, a pad just for a strain relief connection soldered to the pad should be OK. I'd probably back it up with epoxy just in case soldering weakened the foil to board bond.

author: soldar
author_rank: Super Contributor
timestamp: April 22, 2019, 08:34:11 pm
content: Less than ten cents apiece on eBay.

author: Heartbreaker
author_rank: Unknown
timestamp: April 24, 2019, 02:24:17 pm
content: I have recently used these from Keystone.https://www.keyelco.com/category.cfm/9-Volt-Battery-Contacts/9-Volt-SMT-Contacts/p/404/id/422/c_id/1241They are outsider my definition of cheap, but I did not find any alternatives. For god solderability use the recommended footprint and propper wetting of the soldering is important for mechanical strength.Sverre

author: OM222O
author_rank: Frequent Contributor
timestamp: April 24, 2019, 03:07:26 pm
content: Quote from: Heartbreaker on April 24, 2019, 02:24:17 pmThanks! I've already seen these but they are not suitable as they don't actually snap to the battery so I need to use some sort of trick in order to get the battery to stay in placeI think just using epoxy on the joints is the best solution here.

author: Psi
author_rank: Super Contributor
timestamp: April 25, 2019, 11:59:12 am
content: Is this of any use?If the wires are part of the holder they wont move much and can be very short before attaching to PCB.So the risk of movement causing a wire break is very low.https://www.aliexpress.com/item/Practical-DC-9V-Battery-Support-Box-Connector-Coupler-Battery-Holder-with-Lead-Wire/32806205166.html

author: kjr18
author_rank: Regular Contributor
timestamp: May 07, 2019, 11:10:39 am
content: Quote from: OM222O on April 24, 2019, 03:07:26 pmHow about using third one on the other side of the battery to keep battery nicely positioned and a bit of double sided tape on the board to glue battery on?