R/C Tech Forums - Internal Resistance

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Internal Resistance

What is considered High IR for a 2s Shorty pack, and how big of on IR mismatch between cells is cause for concern?
4 of my 8 shorties are getting up to about 1 year old, but show no signs of swelling, and never get above 100 degrees after a Heat or Main in my 2wd & 4wd buggies or stadium truck

Quote:

Originally Posted by Scott R (Post 14912467)

Find someone at the track with a i charger nad have them cycle it for you

Honestly when I run the pack and the car has plenty of punch and no fade thru the run I could care less how old the pack is

the IR's of my batteries are below...anything I should be concerned about? Mismatched IR or High IR?

............Cell1 ...Cell 2
Batt 1......6......6

Batt 2......7......6

Batt 3......3......2

Batt 4......2......1

Batt 5......5......6

Batt 6......6......7

IR is a perfect trap for those of us with OCD :D

I stopped caring too much about IR when I realized that readings usually weren't repeatable. In other words, the variance with back-to-back readings was high enough that it cast too much doubt over the integrity of any given reading. However, I do like that the cells within each of your packs are evenly matched in terms of IR.

There are several great articles out there on IR... here's one of them.

He states:

Quote:

This begs the question: how low should it be? Unfortunately, there's no easy answer for this. It's all dependant on your use case and battery. What is great for one battery may be terrible for another. Based on my online research, combined with my own experience and findings, I would say, as a general rule, a per cell rating of between 0-6 mΩ is as good as it gets. Between 7 and 12 mΩ is reasonable. 12 to 20 mΩ is where you start to see the signs of aging on a battery, and beyond 20mΩ per cell, you'll want to start thinking about retiring the battery pack. But this is only a guide - there is no hard rule set here. And if your charger doesn't give you the per cell measurements, you'll have to divide your total count by the number of cells in your battery to get an approximate per cell rating.

Based on that, you're good to go. Like Marco said: if you're getting good performance out of the pack and it's not puffing or getting hot, carry on.

What charger are you using?

Quote:

Originally Posted by Chris Brown (Post 14915638)

What charger are you using?

Hitec X2 AC Plus

Quote:

Originally Posted by Jason B (Post 14914759)

This is what I'm finding out as well. Still in all, I will use the readings and watch them over the life of my packs.

I have chased IR for awhile, the hitec chargers are not the greatest for this as the numbers are not very repeatable,and it does without current running threw it.
Now I was using the ac pro (the one with the soldiering station) I now have a icharger which is alot more consistent.
Biggest facter for consistency I found was that you must have good leads and wires.

For true performance test was when I use a gfx turbo 35.
Those numbers that I got from that machine, reflected the performance on the track.