Author Topic: Shock proof coin cell holder for DS3231M  (Read 459 times)

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Offline Simon

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Shock proof coin cell holder for DS3231M
« on: June 03, 2019, 01:50:16 am »
I'd like to include a coin cell in my project. This needs to be a decent capacity so i was thinking CR2450. But the available holders don't look like they will hold the battery if the board is up on its side. The product will go vertical in a vehicle so i am not sure about the battery staying in.

I am using this for backup to a DS3231M so am I going over the top and is a CR2032 adequate for sensible retention time?
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Offline Arjunan M R

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Re: Shock proof coin cell holder for DS3231M
« Reply #1 on: June 03, 2019, 02:00:22 am »
Why don't build an enclosure for the battery.Which can be removed when battery is needed to be replaced.
 

Offline Simon

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Re: Shock proof coin cell holder for DS3231M
« Reply #2 on: June 03, 2019, 02:07:44 am »
Well there is the matter of cost and ease of replacement. I can easily get this item: https://www.mouser.co.uk/ProductDetail/Keystone-Electronics/1061?qs=sGAEpiMZZMtT9MhkajLHrnU1d13jcSgSD%252BrGIhHEbuk%3D for a CR2032 and that is sturdy enough but they don't seem to make that style for CR2450 cells. If a CR2032 will provide enough power for the RTC then I can use one of those.
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Online JackJones

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Re: Shock proof coin cell holder for DS3231M
« Reply #3 on: June 03, 2019, 02:13:11 am »
I've always just used CR2032.

Looking at the datasheet it says: "Timekeeping Battery Current (I2C Inactive) 3.5µA". That includes the average temperature conversion current.

You're looking at years and years of battery power, at which point you're probably pretty close to the shelf life of CR2032 anyway.
 

Offline wraper

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Re: Shock proof coin cell holder for DS3231M
« Reply #4 on: June 03, 2019, 02:19:19 am »
You should be more concerned about SMD soldering failure (which I've seen a lot of times) rather about battery falling out.
 

Offline ogden

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Re: Shock proof coin cell holder for DS3231M
« Reply #5 on: June 03, 2019, 02:20:47 am »
Slide-in holders often used in keyfobs are holding battery very well.

 

Offline Simon

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Re: Shock proof coin cell holder for DS3231M
« Reply #6 on: June 03, 2019, 02:24:00 am »
You should be more concerned about SMD soldering failure (which I've seen a lot of times) rather about battery falling out.

Happy to glue it down.
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Offline Simon

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Re: Shock proof coin cell holder for DS3231M
« Reply #7 on: June 03, 2019, 02:24:38 am »
Slide-in holders often used in keyfobs are holding battery very well.



Yea that sort of thing like i posted.
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Offline Arjunan M R

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Re: Shock proof coin cell holder for DS3231M
« Reply #8 on: June 03, 2019, 02:31:08 am »
Slide-in holders often used in keyfobs are holding battery very well.



Yea that sort of thing like i posted.
I found  this type holder for CR2450 in RS components
https://uk.rs-online.com/web/p/battery-holders-mounts/4814162/

https://uk.rs-online.com/web/p/battery-holders-mounts/4814140/
« Last Edit: June 03, 2019, 02:32:42 am by Arjunan M R »
 

Offline Simon

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Offline ruffy91

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Re: Shock proof coin cell holder for DS3231M
« Reply #10 on: June 03, 2019, 02:44:36 am »
These are very sturdy: https://ch.farnell.com/renata/nh5077-lf/batteriehalter-vertikal-f-r-cr/dp/1216360

Gesendet von meinem MI 9 mit Tapatalk

 

Offline floobydust

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Re: Shock proof coin cell holder for DS3231M
« Reply #11 on: June 03, 2019, 01:30:38 pm »
Slide-in holders often used in keyfobs are holding battery very well.

I've used those in a product and they are crap!
PCB as the (-) contact to the battery, you get a bad connection (oxides, corrodes) unless ENIG finish on the PCB.
You need a lot of paste and heat in reflow. I had many the solder didn't really hold to the tab. Quite a few broke off.
edit: to clarify, the PCB pads and paste have to be just right, and the holder's plating is weird metal.
« Last Edit: June 03, 2019, 01:48:59 pm by floobydust »
 

Offline ogden

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Re: Shock proof coin cell holder for DS3231M
« Reply #12 on: June 03, 2019, 06:04:52 pm »
PCB as the (-) contact to the battery, you get a bad connection (oxides, corrodes) unless ENIG finish on the PCB.

If you can't "manufacture" proper negative terminal on PCB, you can consider holder with negative spring.

Quote
edit: to clarify, the PCB pads and paste have to be just right, and the holder's plating is weird metal.

Weird metal claim is consistent with cheap contacts you get from Ali/eBay. Many can't solder cheap crocodile clips as well - it does not mean that all crocodile clips are crap.
 

Offline floobydust

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Re: Shock proof coin cell holder for DS3231M
« Reply #13 on: June 03, 2019, 07:08:44 pm »
I used a Keystone Electronics, not low end ones. view catalog page.

They come in phosphor bronze tin-nickel plate or matte tin finish (for low temp soldering). I used tin-nickel in production, very low cost. MPD holders appear to be the same.
Other battery holder contacts are nickel-plated stainless steel with gold plating overall. Gotta wonder.

It could have been the process at the board assembler. A tab sometimes popped up when you put the battery in. The wetting did not work out, and the recommended pads are the same size as the tabs so the solder did not form a fillet. There is a hole in the tab, I guess that is supposed to help.
 
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Offline Simon

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Re: Shock proof coin cell holder for DS3231M
« Reply #14 on: June 03, 2019, 10:40:07 pm »
Well there is the matter of cost and ease of replacement. I can easily get this item: https://www.mouser.co.uk/ProductDetail/Keystone-Electronics/1061?qs=sGAEpiMZZMtT9MhkajLHrnU1d13jcSgSD%252BrGIhHEbuk%3D for a CR2032 and that is sturdy enough but they don't seem to make that style for CR2450 cells. If a CR2032 will provide enough power for the RTC then I can use one of those.

I think i will go back to my original choice, easier to glue down and I am not forced to use gold plating or worry about how to get a footprint without solder paste ending up where it should not go.
https://www.simonselectronics.co.uk/shop
Varied stock of test instruments and components including EEVblog gear and Wurth Elektronik Books.
Also, if you want to get ripped off: https://www.ebay.co.uk/usr/simons_electronics?_trksid=p2047675.l2559
 


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