that meter is performing a four wire Kelvin measurement. A known Current flows through one pair while the other pair measures voltage drop which will correspond to internal resistance.

Xtar tester does the same, never indicates the same value twice. I insert the cell 3 to 5 times to see the lowest value. I had cells from old laptop batteries that would not drop under 150 mili ohms and of course they got hot after 10 min of charging with 500 mili amp and brand new Samsung 25R that had lowest 11 mili ohms that charged with 2A without any problems

The reason for the dual probe and the inaccuracy of the charger is that there is some small amount of resistance at the contact points with the battery. The contact point resistance variable depending on the contact pressure and how clean the contacts are. This contact point resistance is very significant at this very small resistance readings. So it is extremely hard to get comparable readings between various batteries and test equipment. So the resistance in a battery is important, but for almost all users this data is inaccurate to the point of uselessness.

@lenslens7379

9 ай бұрын

Search for Kelvin probe

thank you for the video, i learned something

bro keep up the good work #UK

I tend to use old cells rated for 30 amps so I can arrange 10 amps discharge and look at the voltage drop. A digital meter across a single cell may change from 4.00V to 3.80V so 0.2V drop for about 10 amps load implying an internal resistance of 0.2/10 or 0.02 ohm. (I use 3 cells in series when testing and load them with 2x 12V55w car headlamp bulbs in parallel so about 9.2a.). If I build a 14S2P battery with peak current draw of 25A and use 0.02ohm cells I will have a battery internal resistance of 14x(0.02/2) or 0.14ohm. If I then draw 25A I lose 3.5volts which is what this is all about.

@Batteridoktorn

Жыл бұрын

That is good way to sort out bad cells, and its also a good way to test lead acid batteries to see of any cell is bad.

Does an expensive power supply like the HOTA do internal resistance measurements ?

Do you consider problematic receiving new lithium ion cells at 3.44v? I received my new 21700 Samsung INR 40T3 4.000mA, 35A cells with 3.44v. Is that too low? I've builded an 2.8 kw 24s8p battery for an electric paramotor and has a huge voltage drop at 10-17kw full throttle and it should handle it like other similar batteries. I'm trying to find out why. Thanks.

@GaryTheRCcar

11 ай бұрын

Lithium ions should be stored at 3.7-3.85 volts per cell... Where did you buy those cells because I'm not sure they are "new"... Please let us know so we can avoid.

@Seneslau07

11 ай бұрын

I've buyed them from Nkon - Nederland. A well known company from where I'm pretty sure many European builders buy. They can't be older than 2020 because that's when the 40T3 hit the market. Thanks.

@Kays_Customs

6 ай бұрын

I am a battery builder and sourcer. What I have learned is that cells are rejected by their manufacturer if they have a self discharge rate that is unacceptable. Those cells are usually supposed to be recycled for raw materials. But they usually end up being swapped for some other less valuable items and get documented as destroyed. But they were actually sold to the black/grey market. Such cells probably ended up with you eventually. It affects even famous and highly reputable brands such as Murata, Molicel, LG, Samsung etc

@Seneslau07

6 ай бұрын

@@Kays_Customs @KennethJustNowAtHere Thank you! It could be that or as others sugested that new regulations on lithium demand to be shipped at lower charge and other battery builders received theirs at the same 3.4v. I've asked on many youtube battery building videos. And the voltage drop might also be from the connections, I don't know. The capacity is right as on six individual cells cycle , I've got the full capacity and beyond like 4050-4120mA on the 4000mA cells. Now I don't even think about it, I can use it wery well as I don't need to go beyond 10kw power in which case the voltage drop is about 6-7v on the 2.8kwh 24s8p pack and already have 17 flights on it so I'm pretty happy.

Sorry for saying that, but even a beginner DMM user knows that never measure resistance in a live circuit. 🙂 You can completely destroy your DMM or just damage the "ohms" circuit and after the DMM will measures incorrect values. Fortunately, most modern DMMs have overload protection against this kind of misuse. These multimeters - like yours - have a thermistor in the “ohms” circuit. The purpose of this component is to rapidly increase the resistance along the heat from an overload current. About DC resistance and AC impedance: in all of the batteries datasheets there is AC internal impedance, which measured by 1kHz AC signal generator / crystal oscillator. However, sometimes they call this measurement result as AC IR (internal resistance). Usually high discharge rated batteries has very low IR (actually AC internal impedance). Most of them are 10-25 mR (mOhm). DC internal resistance value can be 5-6 times more than AC internal impedance and this measurement much more affected by the battery voltage state. Sorry for the long comment. 😁

@Batteridoktorn

Жыл бұрын

Thanks for your input, did not know it could dammage the DMM. Panasonic/Sanyo does not list IR in their datasheets, but i found it on LG Mj1. Initial AC Impedance (Cell shall be measured at 1kHz after charge): ≤ 40 mΩ, without PTC. Good to know. Do you maybe have an IR meter to recommend. FLUKE-BT510 costs like €4000 and UNI-T (UT701) about €300 is till a bit prices. Are the >€50 chinease ones decent?

@tg_privat

Жыл бұрын

@@Batteridoktorn I use YR1035+ for a few yars. Chinese. No complaints. Useful also for measuring resistance of cables, grounding, etc.

@norbithehun

Жыл бұрын

@@Batteridoktorn U don't have to buy "fancy" DMMs or any other devices. I use YR1035+ (like @tomazgorjup) for ages and it works fine. Your SM8124A is good and accurate enough to measure AC internal impedance of batteries.😉

@Batteridoktorn

Жыл бұрын

@@norbithehun Thanks, been looking at YR1035+ as well, but it has a small built in lipo battery, does not seem optimal. Can you recommend any brand IR meter?

@norbithehun

Жыл бұрын

@@Batteridoktorn YR1035+ has a 18650 battery inside, so it is ideal for me. 🙂 I have some.😁😅 Maybe you checked YR1035 without "+", because it has lipo battery inside. But, if U want to by a brand IR meter, I recommend the Uni-t UT3563. If U want even more professional, buy one of the Hioki products. Hioki makes battery analyzers and impedance meters like BT4560, but this meter is more than 6000 USD. In my opinion, I think, Uni-t is more than good enough for U.

Can the charger measure the internal resistance correctly just by inserting the battery? Doesn't it need to charge and/or discharge for more reliable results? I have one lousy cheap charger and the internal resistance changes a lot while charging

@SharvilSawargaonkar

2 ай бұрын

Should not change doesn't depend on charge depend on battery material

Te LitoKala measure the resistance with DC current. But the 4 wire resistance meter use 1 kHz... this is the reason why results are different. Generally battaery manufacturer give internal impedannce (resistance) at 1 kHz... see an LG CHEM datashett...

XTAR Dragon VP4L Plus is good?

a side note, ive been using the nimbot bluetooth label printer to make clean labels for my 18650s and powerbanks. much better than my own handwritting. maybe i should make a video. i think the printer was like 10$ or something and the refills are like 2$ each

Hi battery doctor ...what would be the good number of resistance for a battery pack .like 36v ....

@ericklein5097

Жыл бұрын

Entirely depends on how many cells you have in parallel and what type of cells you are using to begin with. You have to have 10 cells in series so lets just use 20 milliohms, it is a good IR for a moderately powerful cell. So thats 20X10=200 milliohms....but if you have 10S2P well then 100milliohms. 10s4P will be 50 milliohms. 10S8P will be 25 milliohms.

@Rcfishingagadir

Жыл бұрын

Thanks battery doctor ...i appreciate the help.

I calculate the internal resistance with a multimeter and a shunt resistor..so i guess the battery analyzer does the same with the 2 prongs. One meassures normal voltage and the other got a precice shunt as load and the device does the calculations i do on paper.

@dantronics1682

10 ай бұрын

the analyser use 1khz square wave for measuring the impedance, if you do a resistor load test you will get different reading depending on SOC

@josepeixoto3384

17 күн бұрын

@@dantronics1682 Ok, but does the internal resistance itself, not vary with the SOC, even when measured with the analyzer?

@dantronics1682

17 күн бұрын

@@josepeixoto3384 yes it does

Is it possible to measure an entire battery packs IR?

@gamingSlasher

5 ай бұрын

yes

Internal resistance vs. internal impendance... Resistance is tested with DC current (probably 1A) and calculated out of voltage drop. Internal impendance is tested with 1000hz AC current. They are never the same. Internal Impendance is what the manufacturer refers as IR so for comparison only this is OK to use. Let's say it's standard. You have to use double wire probes. Probably one for current, other for resistance (not sure). And it is much more accurate. The probes must be sharp to make good contact, and the springs result the same force. Chargers use DC voltage drop for testing, so the results are way off. It is different type of IR. SkyRC tester is pretty OK for this, but SOC is very important factor here. And not test just after charge. Cell must settle first. For basic orientation it is just fine. If IR is over 200, then Impendance is most likely over 50, and the cell is "kaput". But not necesary. Some new cels have higher internal resistance. Higher energy density cells, higher resistance, lower max current. So you have to check technical paper for new cell first, before you say "it is kaput". :-) BTW: if you push up/down arrows at the same time, SkyRC measures IR on all ports, that are not charging.

@Batteridoktorn

Жыл бұрын

Thanks for the explenation and input

@RocZi

Жыл бұрын

Is the XTAR Dragon VP4 Plus a good internal resistance ohm checker? It comes with 2 probes connected via USB

@tg_privat

Жыл бұрын

@@RocZi Don't know. It seems to me the probes are not 4-wire probes. Try to find some comparison with YR1035+ on YT.

@travispratt6327

7 ай бұрын

Are battery chargers that use voltage drop fine for matching cells to use in an 18650 vape mod? This is what I want to do, I have a bunch of random 18650s and I just want to match them for that use only.

@tg_privat

7 ай бұрын

@@travispratt6327 There are high currents at vapeing. So it is very important to use high current cells. If there are more cells paralleled in vape, they should be closely matched. Both; by capacity and resistance. Chargers could measure capacity pretty OK, but resistance is not consistent. I would try to measure voltage drop ar higher curents. At least 2C. This could be 4A or more. More amps bigger voltage drop and easyer to measure.

The video misses several important insights: DC vs AC, test methods, charge state, variability, and purpose! * One of the tests is DCIR, the meter you have uses ACIR. (DC resistance, measured any of several ways, vs AC resistance at 1 kHz. VERY different). * Int'l test standards are for testing at 85% and 20% charge. Depending on the battery type, that matters a LOT! * The red meter with double probes is +/- 3%. Don't have spec on accuracy of the other. * For use in electronics, ACIR is much better. For high power such as a vehicle, or RC device, DCIR is better.

Search for "Kelvin 4-wire probes" and you can read about why there are two wires on each probe ...

@Batteridoktorn

Жыл бұрын

Thank you!

I have the same meter but not with dual plugs

My new Sony / Murata US18650VTC6 3000mAh - 30A have an internal resistance of 12.6 mA

@999szt

Жыл бұрын

A is for current... ohm for resistance