Through the years I’ve changed coin- and button-cell batteries in numerous merchandise and have needed to repair or enhance the marginal battery holders utilized in a lot of them. It’s comprehensible however irritating that many low-end merchandise use cell holders with an absolute minimal of electrical-contact and mechanical-attachment floor space, which is rarely good for long-term reliability in addition to resistance to regular wear-and-tear.
The cell holders for these merchandise are sometimes simply stamped steel items for the PC board. They connect with the battery backside for one contact and the highest (or edge rim) for the opposite, Determine 1. Each time you take away and exchange the battery, you place stress on the tiny contact space between the steel stamping and the board.
Determine 1 Coin cell holders are sometimes simply fundamental stamped-metal contacts soldered on to the PC board. (Picture sources: diyleyuan.com, PCBoard.ca)
It might probably simply be twisted inadvertently twisted and ripped off, particularly when there’s little clearance to achieve the battery and you must sort-of twist the contacts to do the elimination and substitute. I’ve tried to resolder these minuscule contacts with combined success, since entry is proscribed, and the world is fairly tight.
Let’s face it, these stamped-metal battery holders are very cheap. Maybe the product producer assumes that the general product is so low cost that nobody will trouble to switch the battery, which itself prices between $2 and $4. Possibly, however possibly not.
That’s why I act with warning once I want to switch a coin or button cell in one in all these merchandise. If I see a kind of low cost battery holders in there, I take it sluggish and delicate with the battery elimination and substitute.
However it doesn’t need to be like this. There are many broadly accessible, pretty strong battery holders for coin and button cells accessible from many sources, together with ones with actual bases plus tabs to solder to the board; some actually have a retaining clip holding issues in place, Determine 2. Sure, they’re a couple of cents extra and take a tiny bit extra room, however it might be good if even cheap merchandise used them…hey, we will all dream, proper?
Determine 2 Higher-quality cell holders embody a discrete base for higher mechanical and electrical connections. Some actually have a top-side latch which retains the battery however will be launched for battery substitute. (Picture sources: West Florida Elements; MTI Company)
Typically, the battery holder is a supply of shock. I wanted to switch the CR2032 coin cells in a small, cheap (~$25) Salter 2001 kitchen scale that’s a minimum of 20 years previous (and nonetheless accessible used at Amazon and eBay), Determine 3. As with most such scales, the unit is “closed up” pretty tight to keep up the mechanical integrity of the cantilever-weighing beam, load-cell, and platform meeting.
Determine 3 When it got here time to alter the batteries in cheap kitchen scale, I used to be anticipating an affordable battery-holder proper on the PC board.
I anticipated the batteries could be onerous to achieve, however as an alternative they have been situated beneath a small door on the underside. I opened that door not figuring out what to anticipate for battery placement and connections, and assume it might an affordable, barely reachable association.
As an alternative, nonetheless, I discovered a really elegant method. The 2 coin cells have been in their very own considerably “elegant” detachable holder in a pocket away from the PC board, and linked to the board by a pair of modest-gauge wires so they’re considerably unbiased, Determine 4.
Determine 4 The 2 CR2032 batteries are in a detachable case.
This holder, in flip, had a totally detachable slide-out “drawer” which held the cells in place, making them simply accessible but full protected, Determine 5. All I needed to do was take the battery holder out of its pocket on the size’s backside, slide out the drawer, take away and exchange the 2 cells, and reverse the process.
Determine 5 To take away/exchange the batteries, you merely slide their holder out from the case—actually elegant in its personal small method.
Not solely did it take only a few seconds for the complete course of, however there was no stress on the inner circuit board, because the wires between holder and board had sufficient slack. Whoever designed this scale and authorised the invoice of supplies (BOM) was considerate sufficient to make it simple but rugged, even when it added a couple of cents to the BOM value—and I used to be grateful to that unknown designer or staff.
Too usually we see the place value pressures lead to a design, which is barely satisfactory with respect to mechanical and thus electrical comfort and reliability, in client merchandise equivalent to these kitchen scales, low-end distant controls that come free with TVs, or different mass-market units. Typically, we pay the worth, because the unit is tossed out too quickly when what ought to be an simply replaceable half isn’t. From an engineering perspective, once I see one which’s made “proper” with that little bit of additional consideration, I give silent shout out even whereas figuring out they’ll by no means hear me.
Do you give the coin/button cell holder in your design a lot consideration or consideration? Have you ever ever used a barely higher and extra expensive half to attain a big improve in product life or consumer ease, solely to have your BOM ripped aside at assessment by the fee staff? Have been you capable of make the case and win, or did a couple of cents get in the best way of a extra useful and longer-lasting part or design method? Have usually needed to requested your self “what have been they pondering right here?” or “why didn’t they select one other method?”
Reference
Artwork Pini, Digikey, “Learn how to Choose a Coin Cell Battery Holder for Most Shock and Vibration, and Ease of Substitute”
Invoice Schweber is an EE who has written three textbooks, a whole lot of technical articles, opinion columns, and product options.
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