was thinking more that the resistance of the connections will decrease your performance due to it decreasing the voltage seen by the motor and it will therefore hit a slower speed and a bit less power because of this. the pack voltage will always be decreased due to the connection resistance and there’s no way around it other than better connections. No?
Carbon steel strip VS. Stainless steel strip VS. Pure nickel strip. Fake nickel strips tested! Practical performance test results
The voltage supply for this test does not matter. The resistance of the strip is constant. Power loss across strip = I^2 * R. Voltage drop across strip = I * R. Regardless of the voltage, the heat generated by the strip is constant. The voltage drop across the strip will always be the same for a given current.
In this test he ran 5A and the voltage drop was 0.27V Regardless of the source voltage being 50V or 11V, the voltage drop across the strip will always be 0.27V if you are running 5A.
If you build two packs, one 3S12P and the other 12S3P, with identical solder/weld joints and wire/nickel lengths. If you run 5A through both packs, the voltage drop and heat generated by wires/nickel tabs on both packs will be identical.
The difference is that the 3S pack will only output 1/4 of the power than the 12S pack, but this is purely due to the fact that one is a higher voltage source. The voltage drop however will be the exact same.
Higher voltage systems are by nature more efficient than lower voltage systems as heat generated is related to current and not voltage, so for the same power condition the higher voltage system will be running less current and therefore less heat is generated. This is absolutely irrelevant to the test he set up though.
thanks for clearing it up it makes sense now and the voltage drop is proportional to the current and resistance only and regardless of the applied voltage.
. None the less with the voltage drop it will be a reduced voltage seen by the motor no? and that reduced voltage will have all the downsides associated with it: reduced top speed and slightly reduced power and hitting low voltage cut off sooner. the greater current through will increase this voltage drop mimicking voltage sag.
Yes, it will indeed reduce the maximum voltage that the motor can see, as you are already losing voltage before it is applied the motor via the connector resistance, strip resistance and cell’s internal resistance and the lost voltage will be dissipated as heat by a function of current. Of course there will also be losses in the ESC’s transistor stage by pwm switching action and Rds(on) resistance, but those losses can’t be remedied as easily as making all your wiring beefy to minimize wire resistance.
Yes, but as I said, it is a constant. There’s nothing you can do about it except making your weld and soldering as clean as possible and your wires as large as possible.
You can measure this resistance if you have a really good rc charger. My icharger for example, will test my Pack’s internal resistance and also calculate line resistance, which is the resistance across the positive and negative minus cell resistance measured through the balance wires.
I have now ordered pure nickel strip from aliExpress and once that arrives I’ll test it and post the results here. Most of the strips available on aliExpress were either in 1 kg rolls or as 100 pcs of 100 mm strips of different widths and thicknesses depending on the product, but I found 1 offer for 0.15x8x5000 mm strip and ordered that.
EDIT: FUN FACT! 1 kg roll of 8 mm x 0x15 mm sized strip would be over 90 meters in length. for 70 $ -> 0.75 cents / m, it’s pretty cheap, but how often do you actually need that much nickel strip is the real question.
I’ve ran through about 150 feet of nickel strip in the past 6 months… Lol That’s about 45 meters?
Was bored today and decided to do a little test with the smallest AWG copper wire on my shelf. So here’s a test with a 24 AWG 600 mm length and the same 5 Amps test current as in the first post.
Power loss: 1,30 W Voltage drop: 0,26 V Wire resistance: 52 mOhm Wire AWG: 24 Wire length: 600 mm
IT PERFORMED BETTER! This super thin copper wire performs better than the carbon steel strip (the better one) tested in the first post! Can you imagine running a single run of this wire in your battery pack?! No? Well that’s what you’re basically using if you’re using the better one (carbon steel) of the tested strips.
Actually. This wire is better than either of the tested strips, because of the longer length and it still surpassed the carbon steel strip. And please let’s not even talk about the stainless steel strip…
All in all, people might be building decent battery packs, but then ruin them by using fake pure nickel strips and end up with sub-par performance and excessive resistive losses.
Copper rules. If only it could be more easily used on a pack. Still waiting for a copper compression pack with spring backed copper sheeting and conductive paste
Copper is 4x as conductive as nickel and 10x as conductive as carbon steel so that’s not surprising lol
I’ve purchased some pure nickel strips from a reputable supplier. I’ve also got what appears to be the stainless steel strip off of ebay. While both pass the corrosion test, I did notice that the stainless steel strip is noticeably stiffer that the nickel strip for the same thickness. This obviously isn’t very useful info unless you have a good nickel strip to compare to, but thought I’d put it out there nonetheless.
Pure nickel strip finally arrived:
I have updated the first post with the test results.
EDIT: My test setup has changed because I have placed the DC-DC modules in an enclosure and made it into my tabletop bench power supply, so I can no longer connect the strips straight to the power module’s output. I will do a better test in the weekend as I’ll be changing couple of parts in it.
Okay, I have now done the same identical test to the nickel strip as to the two earlier ones, so now the results are comparable.
Original post has been updated with the results.
I also calculated the resistivities of the tested strips and added them to the results and then compared them to a list of different metals/materials from https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity and included the closest sensible hit on the list.
EDIT: updated the original post conclusion
Hi. Wich battery are you using with. I just ordered 30 Samsung 30q to make 10s3p and I Wonder if 0.8x0.15 strip would be enough or would be better go for 0.2?
Thanks for your test Regards
I bought a used pack from a friend in order y build my Phoenix board and while I was disassembling it I discovered this:
It seems these strips are the bad ones.
It looks like the strip is very rusted, so it might be carbon steel. Resistance wise not the worst, but definite downside is the possibility for it to start rusting.