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diy solar

Internal Resistance Meters. Any recomendations?

I had been trying to use my icharger to measure internal resistance but it doesn't seem very reliable
You will get two numbers of internal resistance, one for charging and one for discharging. At least that is what I got from my PowerLab6. I bought a meter and it did not give me the precision I got out of the PowerLab6 or from my BMS.
 
You will get two numbers of internal resistance, one for charging and one for discharging. At least that is what I got from my PowerLab6. I bought a meter and it did not give me the precision I got out of the PowerLab6 or from my BMS.
It will only give resistance when its not charging or discharging. At least that is how mine works.
 
It will only give resistance when its not charging or discharging. At least that is how mine works.
What is unreliable about the numbers you are getting? Have you compared the capacity of those cells to the IR numbers to see if there is any coorelation?
 
What is unreliable about the numbers you are getting? Have you compared the capacity of those cells to the IR numbers to see if there is any coorelation?
its not a stable reading, I can test it 10 times and not get the same reading twice or even close to the same reading.
 
Thanks, I have an iCharger x6 that I haven't used yet for capacity testing. I have some used Nissan Leaf modules I am going to sell and since they are used, I want to give buyers an idea of remaining capacity. In that case it is capacity that they will be buying and IR may be a way to better match similar capacities.
 
Hobby chargers including PowerLab are not going to give a meaningful IR number unless it's just for comparison purposes. Charging and discharging shouldn't have significantly different readings for TRUE IR.

While this seems like a gimmicky unit, I have several, and while their correlation isn't fantastic (fuzzy at the 0.3mΩ level), they do provide meaningful IR measurements. Search for YR1030 or YR1035. They tend to run $40-60. Personally, I prefer the YR1030 as it requires zeroing every time. The YR1035 retains its zero, but I find I can't trust it without periodic re-zeroing.

These units use the ±1V 1kHz method via 4 wires. They apply a ±1V 1kHz sine wave to the battery and measure its response to compute IR. I use this tool to build small batteries that charge and discharge at 20-25kW and require matched IR.
 
The time variable makes that method unreliable. Additionally, the flat discharge curve of LFP makes this even more challenging. This method necessitates testing the voltage change between two currents in the flat portion of the curve vs. no current and a current.

If one is extremely consistent in their method, they can produce meaningful IR numbers for comparison, but they are only accurate on a relative basis, not absolute.

Equipment that produces accurate load IR tests applied to an unloaded cell/battery measure the voltage drop over milliseconds.
 
The time variable makes that method unreliable. Additionally, the flat discharge curve of LFP makes this even more challenging. This method necessitates testing the voltage change between two currents in the flat portion of the curve vs. no current and a current.

If one is extremely consistent in their method, they can produce meaningful IR numbers for comparison, but they are only accurate on a relative basis, not absolute.

Actually the flat discharge curve is an advantage here as you want to measure the voltage drop from the IR and not let the discharge voltage changes come into play.

It only takes seconds to read the voltage, so even at 1 C the voltage will not change much because of the battery discharging, especially on the flatest part of the curve.

Obviously it's not perfect but it's still far better than your 300 µOhm accuracy example (you can easily have a few 10s of µOhm accuracy with a decent meter, and even single digit µOhm accuracy with a nice meter) and don't necessitate specialised equipment as most people already have a DMM and a shunt monitor (or a current clamp meter). It's also a true DC IR measurement and not an AC impedance one.

Equipment that produces accurate load IR tests applied to an unloaded cell/battery measure the voltage drop over milliseconds.

That's probably more because there's no need to have longer loading times and they don't want to deal with dissipating kW for a long time; if you keep your timing short you can use thermal inertia at your advantage and have little to no heatsinking, even at hundreds of A.
 
Hobby chargers including PowerLab are not going to give a meaningful IR number unless it's just for comparison purposes. Charging and discharging shouldn't have significantly different readings for TRUE IR.

While this seems like a gimmicky unit, I have several, and while their correlation isn't fantastic (fuzzy at the 0.3mΩ level), they do provide meaningful IR measurements. Search for YR1030 or YR1035. They tend to run $40-60. Personally, I prefer the YR1030 as it requires zeroing every time. The YR1035 retains its zero, but I find I can't trust it without periodic re-zeroing.

These units use the ±1V 1kHz method via 4 wires. They apply a ±1V 1kHz sine wave to the battery and measure its response to compute IR. I use this tool to build small batteries that charge and discharge at 20-25kW and require matched IR.

all of the YR1030 or YR1035 I could find forsale were shipping from china so that's a bummer, really don't want to wait 8 weeks for this.
 
Search for YR1030 or YR1035.

Some of the sellers on Alibaba are using that same meter. Not surprising. Shenzhen Basen Technology Co., has a video with the YR1035 in action testing batteries.

 
Some of the sellers on Alibaba are using that same meter. Not surprising. Shenzhen Basen Technology Co., has a video with the YR1035 in action testing batteries.


i have also the YR1030 and it works good
 
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