Internal Resistance Meters. Any recomendations?

Ampster

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I have an order of 280 Ahr cells arriving in the next month. I was going to test a random sample for capacity and if okay I did not feel it was necessary to test every cell.
My BMS does calculate IR which will be useful for diagnostics, once the pack is assembled. I thought having a meter might be useful to do a quick verification of quality before i assemble the pack. I did a quick check on Amazon I see there are several for under $50.

Does anyone have any recommendations? I searched but did not find a video that Will has done?
 
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Ampster

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I did buy the iCharger x6 to do some capacity testing with. It does give an internal resistance measurement but I don't know if you have to cycle through a test to get IR. I will see and report back. In the meantime I am not seriously looking for IR meters but still interested if anyone is using one.
 

Airtime

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Thanks for starting this thread, I'm interested in this too. I mean I know how to do a delta current and measure delta voltage and calculate internal resistance. But it would be nice to have a tool to do it quick and easy. So far I've found these:

Battery Beak
$80, measures DC using delta V over delta I. 1mohm resolution, OK but not great.

EM3610
$32, Measures AC at 1kHz, 4 wire. Also 1mohm resolution, OK but not great.

SBS-6500
$5000, included just for fun :)
Range: 1 mΩ to 400Ω
Resolution: 0.001 mΩ
Accuracy: +/-1%
I guess you get what you pay for...

I decided to try the EM3610. Seems like an AC measurement would be a bit more non-intrusive and from what I've read will correlate pretty well with DC, and price is right.
 
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Barry N

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if you want a good IR meter try the YR1030 from vapacell i did my 18650 powerwall with this meter and works very good.
i run my powerwall with no BMS and all my 14 packs stay in balance .
IR is very important for good balanced packs
 

Airtime

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And if you still don't want to pay the five grand: 25 bucks
Looks like a good price for a battery monitor, I already have some similar ones. What I want is a tester with probes that I can use to quickly test individual cells, vs. a device I need to cable up with a shunt.
 

100FUEGOS

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if you want a good IR meter try the YR1030 from vapacell i did my 18650 powerwall with this meter and works very good.
i run my powerwall with no BMS and all my 14 packs stay in balance .
IR is very important for good balanced packs

This is a good advise. I own myself the YR1035 and it is a nice piece of hardware.
 

Ampster

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I am disappointed with my IR tester. So far everything reads 1 or 2 mOhms. That includes my new 280 Ahr cells and several different Nissan Leaf modules of different chemistry and vintage.
So much for my plan to bin the leaf modules by IR in order to sell them. I am going to try a few more settings.
 

BiduleOhm

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I recommend you use the money to buy a current clamp meter and use Ohm's law; it'll be far more precise for measuring the IR and you can use your meter for lots of others things ;)

The method is very simple: measure the cell voltage (right at the posts) at rest, and do it again while loading it heavily and measuring the current too. Then just do (Urest - Uloaded) / I to have the resistance. You can also measure the resistance of the whole pack if you want (so it includes the busbars and connections) using the same method ;)
 
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smoothJoey

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The method is very simple: measure the cell voltage (right at the posts) at rest, and do it again while loading it heavily and measuring the current too.

Can you quantify "loading it heavily"?
Perhaps as a fraction of c?
 

Airtime

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I've got an EM3610 on the way, I'll post a report after I try it out.
Well I did buy this one so I'll report back. I don't have much to say about it other than I tried it briefly, and the 1 milliohm resolution is too low to be interesting. For measuring in the 5-10 milliohm range or higher it would be OK. But my total system resistance (including cables, connections, Class T fuse, shunt, bus bars, battery switch and battery internal resistance) seems to be about 2.5 milliohms based on measuring voltage drops while discharging 100A. About half of that is the battery IR and half is the cables and components. This is with a 24V 1p8s 280Ah pack, 6mm X 25mm tinned copper bus bars, 2/0 AWG cable, quality tinned copper lugs.

So I can't recommend it for measuring IR of cells. That SBS-6500 would do the job but I think I'll pass on the $5k price!
 

grey nomad

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I recommend you use the money to buy a current clamp meter and use Ohm's law; it'll be far more precise for measuring the IR and you can use your meter for lots of others things ;)

The method is very simple: measure the cell voltage (right at the posts) at rest, and do it again while loading it heavily and measuring the current too. Then just do (Urest - Uloaded) / I to have the resistance. You can also measure the resistance of the whole pack if you want (so it includes the busbars and connections) using the same method ;)
I intended to use the internal cell voltage drop( no load - load voltage) to find the cell IR= V drop with load/ current in load.
And with the higher test current you may get a more accurate figure because the cell voltage drop to load current may not be linear at lower currents.

Is this cell IR ohm's figure the same value as the cell impedance that is calculated at a frequency (I think around 1khz with a cell impedance meter).
Or would you only be checking that all your cell's IR are close to the same resistance for matching.
I think the cell specification sheet states the cell independence at a particulate freq.
Can you use your calculated DC IR and compare that to the spec sheet's a/c Z figure to judge the cell age and condition.
 

Luthj

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AC resistance and DC resistance are typically related by a fairly constant value. The difference of course is that capacitance has a significant effect on AC but no effect on DC. Typically DC is bigger and is a multiple of AC. A rough estimate would be 1.1 to 1.3 times AC resistance.

To measure compare the resistance observed from a battery under constant load for 1 second to that of it under constant load for 10-20 seconds. This is tough to do though unless you can graph the voltage/current in real time at a ~100-500ms resolution.
 

BiduleOhm

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Is this cell IR ohm's figure the same value as the cell impedance that is calculated at a frequency (I think around 1khz with a cell impedance meter).

No, it's not the same. But the two values should be relatively close.

Or would you only be checking that all your cell's IR are close to the same resistance for matching.

Yes, but you can also use the the DC IR to calculate the short-circuit current for example, it's actually more useful than the AC impedance ;)

Can you use your calculated DC IR and compare that to the spec sheet's a/c Z figure to judge the cell age and condition.

Not really; it would be a lot better to measure the cells when they are new and note the value somewhere to compare with a future measure ;)
 

grey nomad

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Just wanted to know the difference between a/c Z and DC IR because if i purchased some cells from Alibaba, i would only be able to test DC IR and compare it to the a/c Z value in the manufacturers spec sheet EG EVE 290ah 0.25 m ohm a/c.
To determine if the cells are new and A grade or used seconds
 
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