Lipo internal resistance # ?

[Andris Golts]

Hi all i notice after i have charged a lipo on my Hyperion charger and scroll through the menu i get milli ohm readings on new lipo's numbers between 5-10 and on older packs as high as 215 milli ohms. Im assuming the higher the number the more the internal resistance . At what point would the numbers tell you to discard the pack ? Is there a way to reverse the internal resitance balancing ect ? Andris Golts.

[fweasel]

I thought I recalled reading once 15 was the warning point. Most of my Revo and Turnigy Graphene packs read 1.9 or lower on my Hyperion chargers

[srislash]

I thought I recalled reading once 15 was the warning point. Most of my Revo and Turnigy Graphene packs read 1.9 or lower on my Hyperion chargers

About same readings here. Once again on Hyperion. Do have some batteries up at 3-4 and maybe 5.

[Bp9145]

I don't remember where exactly I got these figures but I had this written on one of my cheat sheet and I seem to agree but to a certain degree with the findings. Also, with these figures remember to use the total IR value to get the real health or condition of the pack. . . .for example for a 3S battery . .cell 1: 4mΩ cell 2: 3mΩ cell 3: 4mΩ . . .totals to 10mΩ will be your real value of the pack. GUYS, THIS IS JUST FOR WHAT I SOMEWHAT FOLLOW/JUDGE/GUIDELINES BUT IT MAY NOT BE TRUE FOR OTHERS. . .maybe someone else may have a real definitive IR facts for lipo batteries

1. 0 - 5mΩ : Packs that are as good as new (although I've gotten BRAND NEW PACKS with total value of over 10mΩ and performed great. Also, many BRAND NEW PACKS may have higher IR values but still perform as new so don't be alarmed when you see that. I've had some that got better as I cycled them or used them. .IR values got lower)
2. 5mΩ - 10mΩ : packs that have been used dozens of times, but are still very good
3. 10mΩ - 20mΩ : Packs that have been used even more, and start to feel slightly weaker
4. 20mΩ - 25mΩ : Packs that are tired and won't have that great punch
.......and packs with much higher IR values that still work but will no longer hold a full charge, have significant sag in performance and only runs less than 50% of what it used to run, these packs are really tired and perhaps consider disposing them unless you want to use it for bench testing where it doesn't require much power. But, like I said I agree to a certain degree because I have packs that should be disposed but they still have a considerable amount of run time when used in some of my rc cars and a couple of slow boats, but it just doesn't have that punch but plenty enough time for enjoyment. .especially for the little kids to use and they have a good time and I'm not worried about ruining my batteries if they go too low on voltage. But, overall, you should be the one to be able to tell the difference in performance as time goes by and how many cycles you have used them. . .it's up to you to decide if you have any use for them or simply dispose them.

[srislash]

That’s a good little read.
And yes I think Ryan’s and my statements were based on a ‘per cell’ resistance. Mine anyway.

[Bp9145]

That’s a good little read.
And yes I think Ryan’s and my statements were based on a ‘per cell’ resistance. Mine anyway.

Thanks Shawn, like I said I don't completely agree in determining the health of the pack by adding the IR. Let's take a brand new 6 cell battery. If each cell has 4mΩ which as an individual cell is "good as new" then multiply that by 6 you get 24mΩ total. As I indicated above a pack with a total IR value of 20mΩ -25mΩ is a pack that is tired and won't have that great punch. Then this new battery falls in the category of a poor battery but in fact it is new. So I too mostly look at each individual cell. So I use the chart for each individual cell to determine the health of the pack. So like you and Ryan I look at each individual cell because if all the cells in a particular battery are almost the same, lets say in the 1mΩ - 2mΩ range and then you have one that has 8mΩ then certainly you have one mismatched cell and possibly defective. The math, however, is correct in calculating the IR because the cells are run in series. . .for example to get 4S you have to add 4 individual cells together or wire in series, so in turn you would have to add the IR values as well. I would rather divide the total IR value by the number of cells to get the overall IR value. . .so again, I use the chart above my own way in determining the health of a pack. . .well, it's a good place to start anyway.

[Andris Golts]

Thanks to all for the great information. Regards Andris Golts.

[Speed3]

I think 3miliohms to 4 miliohms per cell is a good for a low c rating cell like a 4200 to 4500 30c.

Having 3 to 4 miliohms per cell for let's say a 5000 50c is not a healthy battery.

I have found in my experience that a 2000kv motor on 4s need a pack with cells of 1.3 miliohms per cell.

I had an experience where I was using a tp 4060 1950kv on 4s with cells around 3 miliohms per cell and my leopard 4092 1730kv was out performing the 1950kv 4060 tp with the same prop in the same boat.

Then later on I decided to try the tp again but with better cells 1.65 miliohms per cell and the tp wake up in a way I can't explain the speed increase was insane.

I found that some cells get damage charging them to the 4.2 volts per cell at least on my charger so I charge to 4.1 or 4.15v per cell and some ESC lower voltage cut off is set to lower so they can over discharge the battery and damage the cell. A cut off of 3.4v per cell is a safe limit in my experience.

[fweasel]

I had an experience where I was using a tp 4060 1950kv on 4s with cells around 3 miliohms per cell and my leopard 4092 1730kv was out performing the 1950kv 4060 tp with the same prop in the same boat.

Then later on I decided to try the tp again but with better cells 1.65 miliohms per cell and the tp wake up in a way I can't explain the speed increase was insane.

This experiment is flawed. All that you have shown, in limited sample size, is that your Leopard motor is a better performer for your setup than the TP on 3milliohm cell batteries. Running the TP motor with batteries that measure 1.65milliohms and gaining "insane" speed, only tells us that lower IR battery readings (higher quality cells) equates to more performance (speed).

[Speed3]

The same leopard did not gain any increase with the better batteries.

Lower amp draw setups can perform well with the weaker batteries. But to get really see the true potential of a higher amp setup you need the better batteries.

I think a 1900kv motor and up would require better cells.

And strangely doing maths on paper cannot explain what is really happening.

[fweasel]

OK, wasn't aware the leopard made no increase. The 4060 is certainly an amp hog, perhaps that specific wind more so than others. All in all, lower IR batteries will perform best regardless