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Is my Chinese voltmeter correct?

Old 02-12-2021, 11:52 PM
  #1  
Mustangdude
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Default Is my Chinese voltmeter correct?

Does this voltage agree with the % capacity? Shouldn't it read 6.0v or less?

I suspect one figure is wrong, if so, which should I trust?

Please be aware that I ran this near new 3500 Mah Li-Ion battery down too low on one occasion but don't know how low it actually went. (inexperienced)

But I'm now very kind to it since that incident.

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Old 02-13-2021, 12:29 AM
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ron_van_sommeren
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You could check with another meter.
Are using LiIon or LiPo batteries? 0.1volt difference between the two, per cell.
Note also that voltage is a very poor indicator for capacity(percentage) left/used. And vice versa.
Nature and physics don't use/feel percentages
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Old 02-13-2021, 06:00 AM
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Hi Ron,

Yes definitely Li-Ion 3500 mah 2s.

No I don't have access to another meter except my charger.

When at home it had 27%

7.33v

3.69v per cell

and I balance charged it at .5A, it took on 1911ma

How does that sound?

Jim
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Old 02-13-2021, 02:03 PM
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solentlife
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There are different forms of LiIon ... that have different max voltage.

The standard LiIon such as in many 18650 cells is the 4.2V variety .... a LiPo just has a Polymer strata in it .. hence the Po part of the name ...

Here's a typical table for a LiPo ... and if you have LiIon of the usual 4.2V form - then it applies as well.



Here's a run down of LiIon batts as there are different types :

https://batteryuniversity.com/learn/...of_lithium_ion

As you see - your display output is strange as the % is not in keeping with voltages shown. ... BUT we need to know what LiIon you are using - the data supplied with the cells indicating max charged voltage etc.

As regards Voltage indicating charge level etc. It is the ONLY practical way as hobbyists we have to determine level of charge. It bhad survived for many years as a quick way to check cells, at home and on the field. Its a debate that gets dragged out regularly and there are those that swear by mA in vs mA out ... fine except for a serious flaw : mA in is derived as a calculation of TIME and AVERAGED amps supplied by charger ............ so in fact its as poor in accuracy as voltage !
Unless you have expensive gear or indulge in Laboratory derived system of charging ... you are stuck with practical means - voltage !!

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Old 02-13-2021, 08:57 PM
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Thanks Solent, Good stuff.
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Old 02-13-2021, 09:16 PM
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Sorry guys...last word on my battery I promise :-)

See my battery specs below. From that I see I can discharge this battery down to 5 volts, is that correct?

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Old 02-14-2021, 07:08 PM
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solentlife
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Interesting that they quote 4.1V max .... that is generally what some advise to increase life of the cells ... the 0.1v reduction is said to extend life significantly ....

Personally - I believe how we discharge has more effect on life than a reduction of 0.1V in charge.

I think TBH - that you could just carry on and let charger do its job and not worry too much about what's displayed .. as long as your settings are correct and it terminates at set point ..
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Old 02-14-2021, 10:31 PM
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Thanks for that
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Old 02-15-2021, 06:56 PM
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Mustangdude
I note you stated that the battery took 1711 mAh to full from a figure of 27% capacity..
That charge does not represent 63% of 3500 which suggest either the battery had more in than 27% left in it or more likely its capacity is not, or is no longer, 3500 mAh.
You need to be careful about claimed battery capacities.
In practise it comes down to first limiting the flight duration and then slowly extend flights checking not only the final voltage but also the mAh to recharge it to full.



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Old 02-16-2021, 10:37 AM
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Thanks for your answer. I'm buying a 3s battery next and will definitely take your usage advice. It makes sense. I may have damaged this 2s battery as I posted earlier, I believe the ZOHD battery is a reliable name, I hope so anyway.
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