Lipo resistance figures

[tonydevon]

I just got myself a decent charger for the first time ever.

Pulsar touch conpetition.

Anyway it displays a resistance figure.

What figures should i expect to see and what does a high or low reading mean?

[jayst]

ive been cycling some saddles that are 3yrs but new. there started off at 35m@ and done 2 cycles and there comin down. now at 15m@

[neallewis]

It will vary from charger to charger. I've tried measuring IR figures on difference charger platforms, and the same pack will give different readings on different chargers. You can't therefore use the actual values measured on one pack as good or bad. In theory a lower IR value is better, but I've taken a pack with a value reading of 7-8mOhms one one charger, and it come back with 20-30mOhms on another. The higher value is a consistent measurement on that charger and lead set, not wrong.

Measure your packs and look for consistent figures (or significant changes), not what the actual value is, as it doesn't really matter. Knows what's good and whats not by measuring your known good packs and keeping note of the values.
Some chargers measure the pack as a whole, others measure each cell in the pack, which can be useful in detecting a failed or failing cell.

Edit: Additionally a low reading is a low internal resistance, which is desirable. A higher reading is worse. if you are getting 5-50mOhms measurements on your charger, then i'd not be worried. if they were consistently reading say 8-15mOhms, and then you suddenly got readings of 1Ohm, i'd say it was duff or failing, or very out of balance.
As was mentioned above cycling packs can help with measured IR figures. If a pack has rested for some time, your first charge may give a high(ish) reading, but after a few charge, race/discharge cycles, it will drop to its typical lower value.
Just observe what you normally get, and look for the times when it's off that typical reading.

[5tone]

you also have to pay attention to the charge leads, clean the inner battery plugs and check the clearance of the male plugs.
this way you can get a coherent value to compare time after time.
some chargers really measure the IR others calculate it.

in my experience, with my charger (a D200), I can't point the most powerfull pack with the IR measurment, only a dying one.
the charging curve seems to be more revealing of it.
(in my case, the goal is 5mn without lost of power)

[tonydevon]

Ok thanks for replies will try to read and understand better later on.

I run 5 shorty packs. 1 per heat and a final.

All bought at same time. And all showing 15.1 to 15.3 on that charger.

So they all similar. Guess thats good news.

I need to read up more on storage etc as i came back to buggy racing after a long gap. Nicads were my power lol

[mark christopher]

Lower ir. Means more punch,

The biggest factor when measuring ir is cell temp, a warm cell will have lower ir, so when comparing chargers your Lipo should be same temp.

I can get my 1s packs around 1ohm, by discharging and charging at 40amp. Only really need low ir in stock racing, off road with mod motors batteries are not the limiting factor