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Silver oxide Battry selection

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Mosaic

Well-Known Member
hi,
I have an app that draws 16 to 22mA under max load and 72uA when asleep.

Due to space constraints I am looking at SR936 Silver oxide batts.

They claim around 75 mAH. At my max load would that realistically translate into about 3 hours usage?

At the 72uA quiescent drain, what type of shelf life would be realistic?


thx!
 
I doubt it, because those small batteries are designed for very low leakage, and that implies that they have a rather high internal resistance if they are running very lean on the KOH, water, and whatever else they put in there.

https://www.azom.com/work/0JP6xJ3v83Lq13oVb36q_files/image004.gif

i would figure that you need minimum 40-60 hours discharge rate to get the nameplate rating on the amp hours. (as you might know, lead acid is 20 hours, but the 8 hour discharge is as high as 90% of the 20 hr discharge total amp hours)

Do you have a battery to test the short circuit current? the short circuit current should be as high as it is for nickel cadmium batteries, as it is a very similar chemistry.
 
So far i've seen Silver oxide are best for high drain devices due to it's voltage stability. My app calls for drains of perhaps 20 minutes at a time max, mostly it's an intermittent drain. I'm just hoping to characterize the battery run time. A discharge rate of .3C is kinda large. I don't know the internal resistance of the chemistry. If it has low then the impact of a higher discharge rate is mitigated.
 
Also Colin the PR4401 pic from: **broken link removed**
The picture of the PR4401 is not mine. I would never suggest using a button cell to illuminate a LED.

Notice how all the date on these tyes of cells tries to omit the most important detail: How much current can be taken from the battery.
 
Last edited:
The open circuit voltage of silver oxide batteries is 1.6 volts. The
operating voltage at typical current drains is 1.55 volts or more.
well that explains it right there.
so if you need 100 h discharge you'd better have a KOH battery and you're going to get 60% of nameplate amp hours.
i'd be willing to bet most watch batteries are NaOh because its cheaper, and according to the pdf much easier to seal.
and if the only thing you can get is NaOH silver oxide batteries then you'd best have enough capacity for 1000 hour operation.

I figured these cells were a couple orders of magnitude better than that. :(
 
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