Author Topic: BM235 Lithium Battery "mod"...  (Read 776 times)

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Offline sequoia

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BM235 Lithium Battery "mod"...
« on: October 03, 2018, 02:47:14 am »
BM235 isn't happy camper with 1.8V AAA Lithium cells (https://www.eevblog.com/forum/testgear/the-bm235-does-not-accept-lithium-batteries/).

This is my "backup" meter that sometimes doesn't get used for weeks or more, and I've noticed that even slightly discharged Lithium Batteries tend to have voltage creep up slowly (when meter is switched "off") over longer period of time, enough to set the over voltage error when meter is turned on again. To get meter operational again, one can leave meter in diode measurement mode with back light on for few minutes to bring voltage down enough, but this gets annoying quick, if you're working on something and needed quick measurement....


When I came across some "ultra low forward voltage drop" diodes: SBR10U40CT
That  seemed to have about 0.2V drop at 30mA  (these are rated for 10A) which seemed perfect for BM235....  After installing this "mod", I haven't had issues using the meter with Lithium Batteries...



« Last Edit: October 03, 2018, 02:51:18 am by sequoia »
 

Offline bitseeker

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Re: BM235 Lithium Battery "mod"...
« Reply #1 on: October 03, 2018, 06:35:26 am »
That's a big diode. Nice that it fit in there so well. I like the way you used that small square of PCB to slip into the battery circuit.
I TEA.
 


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