Is this acceptable IR for brand new Multistar Lipo?

Hi All,

First post. I've been lurking for about 4 months now and thank you for everything you have taught me.

I purchased 6 packs of the Multistar 4s 10AH lipo from HK. They were delivered fine and all the cells came in at mostly .01 v of each other. around 3.94 ish. My concern is the IR that I measured off of those cells.

In particular, I am concerned if the first cell reading is some measurement anomaly that I haven't read about here yet, or a side effect of the Multistar Low C structuring, or something I should contact HK about. It is weird that it is in all of the 6 cells.

lets see if I can figure how to link some pics here....



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Thank you for any help you can provide.

Jim

It looks suspiciously like a "total" IR figure for the 4 series cells ?
Do you have other packs you can cross check with ?
If not you can always do an individual IR test on those single cells.

The photos above are showing the iR for the individual cells. The chargercan also show the whole pack resistance as well and it seems to add up the four cells:

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I have some brand new Turnigy 4s 20-30c 5AH but I haven't switched the wires to XT90 yet. I guess if I switch one over and it does not show a large (is 13 large?) IR for the first cell then that will somewhat rule out a weird charger anomaly.

...getting out the soldering iron...

I personally don't trust the RC chargers method of Ri measurement at all. In my experience, it's been about as good as rolling a dice and picking a value completely un-related to whatever the cell's Ri may be.

liveforphysics said:

I personally don't trust the RC chargers method of Ri measurement at all. In my experience, it's been about as good as rolling a dice and picking a value completely un-related to whatever the cell's Ri may be.

Click to expand...

Ditto....

Calculate IR using voltage drop against known load for about 10s. Basic Ohms law.

Well it turns out that the brand new hardcase reads pretty much the same as the multistar including the high reading on the first cell so it is likely an oddity with the charger.

Thx all.

Good thread about IR testing:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=48739&hilit=

Here's the video that inspired me to learn IR testing from that thread:

[youtube]usRE3gLFnOc[/youtube]

As you're learning, those built-in IR functions often provide weird results. Best use dummy Amp load, calculate voltage drop (pack or individual cell) and use Ohm's law for useful values.