Internal Resistance 6s Nanotech's

[enterpryse]

Has anyone got some figures for these batteries?

I have 4 new ones that are showing about 8mohms per cell with the exception of one cell in one battery showing 17. Clearly it's dodgy but is it still usable?

Tested using I charger.

Ta & merry Christmas. :-)

[Andy from Sandy]

Has anyone got some figures for these batteries?

Which batteries?

[enterpryse]

Re: Internal Resistance 6s Nanotech's

Which batteries?

Nanotech's 3300. 65-130

[Planehazza]

Sounds high to me, although I don't know what adverse affects it'll cause. They may puff earlier and not reach their rated C discharge?

My normal blue 6S 3300s have 3-4mOhm per cell. They're 30C packs.

[enterpryse]

Re: Internal Resistance 6s Nanotech's

Sounds high to me, although I don't know what adverse affects it'll cause. They may puff earlier and not reach their rated C discharge?

My normal blue 6S 3300s have 3-4mOhm per cell. They're 30C packs.

Thanks, how are you measuring the IR?

[GIXERMAN]

3300-4500 nanos approx 2-3

Using a pl6 or pl8

[Planehazza]

Thanks, how are you measuring the IR?

Just via the measure ir section of my icharger.

[Mark_T]

It would help if people could state how they are measuring the IR as the PowerLab chargers tend to read low whereas the iCharger and Wayne Giles meter tend to be a lot closer to each other.

To answer the original question though, yes the pack is usable, and it may even improve a little with use, but it is probably going to be the first of those packs to fail and the edge may go off the performance quicker during flight than the others.

I should add though that a 3300 pack even with a measurement of 8 is only effectively a 15C pack, so definitely not what you thought you'd bought really ...

[mahbouni]

I have 10 x Turnigy 6s 3600 30C packs with cell IR's in the range 2.0-3.6mOh. Measured at end of charge on a PL8.

[xygax]

The measurement of internal resistance can be done on a battery in many different ways. The classic method is to inject ac into the cell or collection of cells and measure the ammount of refelected energy across a reference resistor. That actually takes quite a bit of electronics and is unlikely to be employed in any of our chargers. More likely this is done using a pulsed DC method and the on load / charge voltage measured on each cell in turn.

The method employed really dosent matter its the comparison between the cell under test and its peers. What you are looking for is the difference. lets say on a 6S pack you mesure 10mR 11mR 9mR 10mR 9mR 11mR then the grouping is close enough to indicate the pack is servicable if one of the cells in the group is double the mean value of the rest say 20mR the that battery cell will fail before the rest. The failure mechinisam would be that that cell would discharge to 0v faster than the rest of the pack and in the event of a complete discharge it can go reverse polarity this in lithium based cell is a fire hazzard.

Now because a battery has an element of resistance inductance and capacitance the key thing when measuring its resistance is to ensure that the inductance and capacatance are rejected as far as posible and these elements make them very frequency dependant. So a charger that measures at say 1Khz will give a different reading to a charger that measures at 100Hz. although both of the readings are valid its makes the comparison between a say PL8 and an Icharger invalid because the frequency / method of measurement is unstated or unknown.

All that asside in the comercial world we condem cells / blocks when their internal resistance is double that of their piers. When batteries fail this is really easy to spot. Take a 100Kva UPS that has an 80Kw demand from a battery say 360v thats a current of 222A for say 20 mins you would need a 160Ah battery (aproxamatly) to do this duty. when you load test this system for half that time photograph the whole battery with a thermal image camera then test the hot blocks... always the ones that have / are failing because they have high resistance they get hotter than the rest.


Here endeth the crimble sience lecture for 2012


Have a goodun all
Steve

[helimadness]

my pl6 measured my new gens ace 6s 2600's at about 5 when first time charge from new but after a few cycles they are down to about 2. Maybe keep an eye on them after a few charges. I also noticed a mate who was charging using a pl8 in parallel with 2 6s 5000 mah and choosing high power no parallel packs and was just setting the current to suit the 2 packs was getting half the IR number. I stopped the charged and got him to do the same rate charge but selecting 2 packs in parallel then it showed the correct value which was between 1.2 to 2 ohms.

[Mark_T]

The PL8 figures are great for direct comparisons between cells and packs on the same charger, but don't use them as a basis for comparison with iCharger numbers though as the PL8 will always display lower numbers.

Also don't forget that temperature has a significant impact on the results you see, so charging in the cold will show significantly higher IR figures than when you charge in a warm room.

I do agree though that you'll see some improvement over the first few cycles, but I doubt it will 'cure' the weak cell so that one is likely to remain out of step with the others.

Which cell in the pack was it btw?

[iceuk]

If your internal resistance is 17 on a new battery send it back.

[Mark_T]

If your internal resistance is 17 on a new battery send it back.

Good luck explaining that to HK

The voltages will be fine and I doubt they will be interested in much more than that.

Worth noting that the acceptable IR is proportionate to the capacity, so 17 on a pack below 1000mAh would be perfectly reasonable, clearly not in this case on a 3300 pack though.

[iceuk]

New batteries should be less than 5. Useable batteries less than 10, old batteries 10+

If your happy to give someone your money for junk then goodluck to you. At the very least you
Should complain to them!