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-   -   Load checker without using motor / ESC etc. (https://www.wattflyer.com/forums/showthread.php?t=82279)

solentlife 03-15-2022 11:35 AM

Load checker without using motor / ESC etc.
 
I am sure that I am not only LiPo user that has a lot of LiPos' and amongst the many - are odd ones that at times do not perform. I try to mark them as ?? to avoid using again ... but one or two can get used again and occasionally seem to be OK.

I have a bench set-up .... motor mounted to a flat plate I can clamp in a vice ... ESC and Servo Tester .... I can connect wattmeter and run up to observe / listenm and read results. But its a pain having to charge up the LiPo - then connect - run and then storage discharge.

I've tried using the Internal Resistance values to check - I have a dedicated IR meter as well as on the chargers ... but that has not proven to be solution.

So ? Question is - what is there out there that can be used to reliably determine a LiPo's condition without too mucxh work involved ... lets say charge up to average 4.0v per cell .. plug into XXXX ... load is imposed and you get direct result ?? I know that sounds like a Wattmeter exercise - but I'm looking for something that does not need ESC / Wattmeter / Servo Tester etc.

Any ideas Guys and Gals ??

Wildflyer 03-16-2022 06:51 AM

I saw someplace that if a fully charged Lipo is loaded to a point that the voltage output drops anything over 0.3 volts per cell then that is the current limit for that particular battery. Basically the C rating of that battery at that time.
The guy explained that if a 4 cell battery dropped over 1.2 volts in total then that would be the limit of current for it.

I don't know if this is all true, it seems a bit harsh to me. If it is true, then many of my batteries are over the hill.

I haven't heard of anything new other than the SkyRC BD250 Battery Discharger & Analyzer and similar devices

solentlife 03-16-2022 09:16 AM

0.3V per cell .... blimey - that's not much ..... IMHO - thats being super kind to the battery.

Wildflyer 03-16-2022 07:47 PM

I fully agree Nigel,
I don't know how much of an "Expert" the author is on batteries, but he made it into the book.

solentlife 03-16-2022 08:15 PM

My reason for looking is that I am currently going through my huge collection of LiPo's ...

First charge up to max 4.2V per cell.
Read of Charger the Internal Resistance of each cell. I know temp makes a difference - but I'm looking for big differences not small.
I have test motor with 11x5.5 prop on board clamped in a vice. Sevo Tester control and ESC /BEC

I have found before that IR results are not as reliable as some claim ...

Example : Cells are in mOhms ... Motor test is bad * ... fair ** Good ***

LiPo # ...... Cell 1 ........ Cell 2 ......... Cell 3 ............. Motor test
#4 ..............066 ........... 021 ........... 023 ................***
#5 ............. 066 .......... 008 .......... 011 ................ **

They are same size / capacity / brand .... I would expect #5 to perfo0rm as good as or better than #4 ... but it did not. It was plainly less capable.

CHELLIE 04-05-2022 11:54 AM

maybe this Lipo tester might help,
https://www.rcdronegood.com/best-lip...istance-meter/

pmullen503 04-07-2022 10:11 PM

On the subject of voltage drops under load.

Before I had telemetry, I set a timer so I'd land at around storage voltage. That way I could pack up batteries and go home without having to mess with them. Now, I set my telemetry alarms for 3.3V/cell. If they go off under power, it's time to land. I want to have at least 3.7V/cell resting (again, pretty much storage voltage).

The point is if my alarms are going off but I still have more than say 3.8V/cell I know that battery is getting weak and it gets "de-rated" for use in less demanding planes. So while I may get one or two years in an EDF, but the same battery can still be fine for use in prop planes for several more years.


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