Battery IR question...
 

What should I be seeing for total internal resistance on my Protek Graphene 6500mah 4s LiHV batteries? I bought 4 over the last few weeks, 2 have about 15 cycles while 2 have about 6. Anytime they will sit for longer than a few hours they go into storage mode, always charged at 1c other than a couple times at 9 amps, or just under 1.5c. I have my shutoff in my esc's at 3.45 v per cell. 3 of them my charger is showing about 45 mOhms, and one of them is just under 20mOhms. Just curious as to what normal is. These batteries are awesome, best I've ever had, I just want to make sure I'm taking care of them best I can.

Most of my brand new packs start out around 1 mΩ and tend to go up to around 3 mΩ within the first 6 months, then hit around 8 mΩ after a year or so, typically around 20 mΩ is when I start to see swelling of the cells and performance/capacity starts to degrade to the point where I only use the packs for practice and I start shopping around for some new packs.

Are you quoting those readings per cell, or total?

Following this thread because i just got a charger that measures IR and have no idea what to do with the numbers.

I check the IR after a full charge, my charger reads individual cells and that's what I take into consideration... I will notice that when 1 cell starts to increase resistance then it takes longer for my packs to balance out too :(

and that's a per cell reading you are talking about? I wonder if it makes a difference the type and size of battery? I know that none of mine were ever below 10 total for the 4 cells even when new. I dont think they have changed much either. I did notice yesterday that my 2 cell life pack for my 7px is around 300mOhms, and it is 6 weeks old with about 4 cycles. I guess I just have no idea what "high" or "low" or good or bad numbers are...

When are you taking the readings? I noticed that mine get cut almost in half when reading freshly charged or warm after a heat, as compared to a cold battery sitting in storage mode. No idea if that's normal, though.

So I contacted AMain about this to try and find out what numbers I should he seeing using their batteries and their charger and this was their response...

"The information this charger is giving off regarding the IR of these batteries is a bit misleading. The charger is measuring the internal resistance of battery as well as all the connections and cables along the channel between the battery and the charger, there are many variables come into play when showing that number with a graphene battery. These numbers are normal and as long as the batteries are showing any puffing or other physical damage they should be fine. ​Please let me know if there is anything else I can help you with!"

not sure that really jives with me even though I understand the added resistance of the connectors etc between the actual cells and the charger, but how else is someone supposed to measure them? I'm super happy with the performance of the batteries and charger, but I just dont want to have 4 $175.00 paperweights in 6 months if something is wrong...

That response was totally bogus, they completely skated around your question and did not give a direct answer, I did pose a similar question over here:
https://www.rctech.net/forum/radio-e...rd-low-ir.html

that's exactly what I thought. All I was looking for was them to tell me what I should be seeing, not to tell me that unless my batteries are puffed that they are fine. Not sure "Kate S." Even works in the tech departments haha.

I have the x6 charger that reads IR. If i use my normal long (12 inches) charging leads to measure IR I get IR in the mid 40s (45 mOhms) if I use a high quality short leads like I would use in the race car I get closer to ~ 5 mOhms and on some packs down to 3 or 2.5 depending on temperature.

So many things go in to IR, the temp of the battery and the resistance of the cable and connectors, calibrations of the tool your using to measure. we are talking about micro numbers here, my reading of your pack with my tools may be different than your readings of your pack with your tools. you should be looking to make sure your testing the same way every time and the same temp, once you establish a baseline you can track and monitor trends.

to the OP: I would do more testing of other packs that you have a known IR and get your baseline for your testing setup, also have other people test your packs that know their own base line and see what you get and work from there.

Temperature of the cells is probably the biggest factor when getting IR readings. I know my charger's IR meter may not be the most accurate thing in the world, but certainly gives good insight to health of cells when I have a baseline of cells being ≤ 7 mΩ, then the next time I check the cell's IR, I have one cell with a reading of 20 mΩ or greater...something's going on.

I try to take IR readings when my LiPo batteries come off a balance charge and the pack is between 70°F ~ 80°F. That's my baseline for my packs. Like it's been said in other post(s), one can usually tell when a pack is starting to get "funky". I start to question a cell's life once my packs take longer than 90 minutes (from storage voltage) to balance @ 2C charge rate , Actually, I start closely monitoring a pack's IR when my packs take longer than 50~60 minutes to balance charge @ 2C charging rates.