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Forum Index : Microcontroller and PC projects : Capacitor smoothing question

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lizby
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Joined: 17/05/2016
Location: United States
Posts: 3875
Posted: 04:09pm 10 Mar 2025
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  Mixtel90 said  C=1500Ah It will discharge to end point voltage in 1 hour at 1.5A
C/20     It will provide 75mA for 20h


If the second is true, it's unlikely that the first will be true. As I understand it, that's why reliable ratings of rechargeable batteries are typically quoted for a C/20 discharge rate.

I have yet to see a Chinese 18650 battery or 12V 18650 battery pack which is rated accurately. I've been looking for a way to test this reliably--it looks like the circuit from @twofingers will do it. So there's something to be added to my already overflowing to-do list.

The LiFePO4 batteries seem generally much closer to spec.
PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on FOTS
 
twofingers

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Location: Germany
Posts: 1769
Posted: 04:31pm 10 Mar 2025
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  lizby said  ... --it looks like the circuit from @twofingers will do it. So there's something to be added to my already overflowing to-do list. ...





You might also look for zb2l3.I bought several from Ali-Express for about 2 EUR each. The circuit is trustworthy. The batteries to be tested can have up to 15 V. Two 7.5 ohm/5W resistors should be included. The threshold voltage (cut-off voltage is adjustable).
This is probably the cheapest solution.
Regards
Michael
Edited 2025-03-11 02:36 by twofingers
‚My name is Ozymandias, king of kings
Look on my works, ye Mighty, and despair!‘
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and ...
 
Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
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Posted: 04:46pm 10 Mar 2025
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Sorry lizby. :)
1500mAh of course. :)

The best bet is probably not to buy "high capacity" 18650s from China. Then you'll probably be less disappointed...
Mick

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lizby
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Joined: 17/05/2016
Location: United States
Posts: 3875
Posted: 06:38pm 10 Mar 2025
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  twofingers said  You might also look for zb2l3


Thanks. I ordered a couple of those. I do like the ability of your circuit to produce a graph.
PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on FOTS
 
twofingers

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Posts: 1769
Posted: 06:42pm 10 Mar 2025
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  lizby said   I do like the ability of your circuit to produce a graph.

Yes, it really is fantastic! I like it a lot!
Regards
Michael

BTW:
I use this:
https://www.printables.com/model/646235-enclosure-for-battery-capacity-tester-hw-586/related

model for 3d-printing.

And a 1 EUR charger as a holder for the 18650 battery.

Edited 2025-03-11 05:21 by twofingers
‚My name is Ozymandias, king of kings
Look on my works, ye Mighty, and despair!‘
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and ...
 
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