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Old 04-10-2018, 01:33 PM   #1
kamel
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Default Need advice from experts for a cmos battery replacement

Urgent!

My MTX 3352 digital oscilloscope cmos battery got low and need replacement.

Original battery specs : varta brand Li-Manganese dioxide With PCB solder tags
1/2 AA 3V-950mah, non-rechargeable battery.

Found available on the market : NX brand Lithium-thionyl chloride ER14250 1/2 AA 3.6V 1.2Ah PP (Ref : PCL9005) without solder tags.

Question : Is it risky to use the 3.6V 1.2Ah battery instead of the 3V-950mah ?
If so, do I need to use a diode to drop the +0.7V excess and then what about the +250mah ?
Or is there any simpler and more efficient circuit to fit the 3.6V without risk for my oscilloscope.

Thanks
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Old 04-10-2018, 04:53 PM   #2
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Default Re: Need advice from experts for a cmos battery replacement

I think you should use the correct voltage if you can. I have a Tektronix 2440 that I had to replace the battery in - I tried 2xAA-alkaline, 3xAA-alkaline, LiMnO2 -- none produced satisfactory results (scope keeps complaining) until I put in another Li-Thionyl Chloride battery into it like the one that got replaced.

If you must use the 3.6V, you may be able to just stick that silicon diode in series, and other than mechanical fitting it should be fine.
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Old 04-10-2018, 04:54 PM   #3
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Default Re: Need advice from experts for a cmos battery replacement

The load dictates the current draw from the battery so in this case higher Amp rating of the battery has no effect.
Yes you can try using 1 or may be two diodes on the output of the battery, the Vf of the diode will depend on the If and the temperature, etc.
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Old 04-10-2018, 05:48 PM   #4
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Default Re: Need advice from experts for a cmos battery replacement

Lithium Thionyl chloride are rechargeable cells - totally different tech.
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Old 04-10-2018, 06:34 PM   #5
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Default Re: Need advice from experts for a cmos battery replacement

Lithium thionyl chloride is not rechargeable... it's an old high capacity, high internal impedance, low leakage lithium technology designed for memory backup.

Lithium ion and lithium polymer are rechargeable.
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Old 04-11-2018, 02:54 AM   #6
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Default Re: Need advice from experts for a cmos battery replacement

pretty sure i have a tube of lithium thionyl rechargeable cells here from server raid cards!
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Old 04-11-2018, 09:21 AM   #7
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Default Re: Need advice from experts for a cmos battery replacement

https://ntrs.nasa.gov/archive/nasa/c...9870007963.pdf
https://www.eetimes.com/author.asp?s...doc_id=1322276
http://www.tadiranbatteries.de/pdf/T...-Batteries.pdf
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Old 04-15-2018, 02:49 PM   #8
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Default Re: Need advice from experts for a cmos battery replacement

I wish to thank every contributor.

Problem was solved by soldering a 3V Li-Manganese dioxide battery 1200A instead of the 3V-950mah with PCB solder tags, and gluing the battery to the mobo for better security.

Please note that the initial issue was my oscilloscope refused to turn on : it always went to sleep mode, when switched on. Replacing the cmos battery solved the issue. This might help others having same problem.
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