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Old Feb 14, 2011, 04:58 PM
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So. Cal.
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Quote:
Originally Posted by jaccies View Post
Only thing suprised me and dont understand why is there a difference, between the Pack IR and the sum of all cells IR? It's around 10mOhm difference.
In cell mode, it measures the IR of the cell at the solder tabs of the cell. In pack mode, it measures the resistance of all wiring (including wiring within the IR meter) and connectors.

For this reason, there will always be a difference between the aggregate cell IR and measured pack resistance. Any large discrepancy between these two measurements will denote a bad connection somewhere, be it solder joint, connector mating interface, or other. As such, measuring both cell IR and pack IR is not a bad idea.

Mark
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Old Feb 14, 2011, 06:03 PM
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Rugby, UK
Joined Feb 2007
883 Posts
Jac,

Thanks for posting the results on your packs.

Mark is exactly right, the difference is because of the sum total of the resistances of the terminations, leads and connectors. With a Deans I always expect 6 - 8 milliohms extra of resistance between cell totals and pack reading. Your pack with Deans shows 7.4milliohm difference. Can't comment with authority on 4mm cage connectors as I hardly use them, but I would expect just slightly more than Deans.
It is surprising how the difference builds up as it includes the interconnecting resistance between the cells as well as the external leads, connectors and all the solder joints. Nonetheless it is a practical reading because in practice this is what the ESC + motor see in series with a perfect voltage source ( ignoring discharge effects.)
Your readings all look sensible at a glance; I will look at them in more detail , compare with your original readings and comment again in the next day or so.

Wayne
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Old Feb 14, 2011, 10:00 PM
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Melbourne
Joined Aug 2010
449 Posts
Just tested some of my packs for info

All tested at storage voltage, ambient 80f
Most are 12 months old with 20 - 40 cycles on them
They all balance charge fine
I use 5.5mm bullets for discharge leads

6s 5100mah 35c Voltz
Pack 23.1
2.72, 2.72, 2.68, 2.96, 2.68, 2.76

4s 5000mah 40c Turnigy
Pack 12.6
1.36, 1.48, 1.52, 1.64

3s 6000mah 25c Nano
Pack 13.8
2.0, 2.2, 2.08

3s 5000mah 40c Turnigy
Pack 11.7
2.04, 1.36, 1.44

2s 6000mah 25c Nano
Pack 11.1
2.08, 2.20

2s 5000mah 40c Turnigy
Pack 9.9
1.52, 1.48


Cheers
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Old Feb 15, 2011, 04:05 AM
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The Netherlands, LI, Venray
Joined Dec 2008
1,403 Posts
Quote:
Originally Posted by crusey_aus View Post
Just tested some of my packs for info

All tested at storage voltage, ambient 80f
Most are 12 months old with 20 - 40 cycles on them
They all balance charge fine
I use 5.5mm bullets for discharge leads

6s 5100mah 35c Voltz
Pack 23.1
2.72, 2.72, 2.68, 2.96, 2.68, 2.76

4s 5000mah 40c Turnigy
Pack 12.6
1.36, 1.48, 1.52, 1.64

3s 6000mah 25c Nano
Pack 13.8
2.0, 2.2, 2.08

3s 5000mah 40c Turnigy
Pack 11.7
2.04, 1.36, 1.44

2s 6000mah 25c Nano
Pack 11.1
2.08, 2.20

2s 5000mah 40c Turnigy
Pack 9.9
1.52, 1.48


Cheers
Hi,
you measure very low values, what brand of lipo''s are you using?
Put the brand of lipo in your list.
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Old Feb 15, 2011, 04:08 AM
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Melbourne
Joined Aug 2010
449 Posts
The brands are listed mate

Hobbyking Turnigy
Hobbyking Turnigy Nanotech
Voltz

Cheers
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Old Feb 15, 2011, 04:20 AM
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The Netherlands, LI, Venray
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Quote:
Originally Posted by crusey_aus View Post
The brands are listed mate

Hobbyking Turnigy
Hobbyking Turnigy Nanotech
Voltz

Cheers
yes i saw it sorry
your readings are very low values, i use only 1 turnigy which readings are also low.
Why you choose for Turnigy instead of Zippy flightmax?, i know Turnigy;s are more expensive then Zippy's

you measured at storage level, its summer overthere lipos should be full for cars
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Old Feb 15, 2011, 04:23 AM
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Melbourne
Joined Aug 2010
449 Posts
I use them for cars and usually just grab whatever is in stock

Have used plenty of smaller Zippy's over the past few years and never had a bad pack

Cheers
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Old Feb 15, 2011, 03:55 PM
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Rugby, UK
Joined Feb 2007
883 Posts
Jac,

Having looked at you results I was intending to say that I notice that the Turnigy IR was low which I have also noticed in my measurements and Scott's (Crusey) results confirm it also, although his temperature is rather higher.
Notice his difference between Pack and total cells is about 6.6 - 6.8mOhms because he is using 5.5mm solid connectors which are only about 0.15mOhms each.
I see your 30C FPs are noticeably lower than the 20Cs but not as low as the Turnigy, again as I have found.
I have noticed in doing comparison high power continuous discharges that the higher IR packs show greater voltage drops initially but then finish up at the end with the same IR due to the self heating, but a lot hotter and presumably will not live as long.
All your packs look OK; if one is dying you will see one cell much higher than the others, which is a runaway situation. The poor cell gets hotter and the rate of damage accelerates.

Scott, thanks for posting those; Turnigys do come out low generally. No experience of Volz.

Wayne
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Old Mar 04, 2011, 02:45 AM
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United Kingdom, Wales, Swansea
Joined Jun 2010
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Quote:
Originally Posted by Wayne Giles View Post
Jac,

Thanks for posting the results on your packs.

Mark is exactly right, the difference is because of the sum total of the resistances of the terminations, leads and connectors. With a Deans I always expect 6 - 8 milliohms extra of resistance between cell totals and pack reading. Your pack with Deans shows 7.4milliohm difference. Can't comment with authority on 4mm cage connectors as I hardly use them, but I would expect just slightly more than Deans.
It is surprising how the difference builds up as it includes the interconnecting resistance between the cells as well as the external leads, connectors and all the solder joints. Nonetheless it is a practical reading because in practice this is what the ESC + motor see in series with a perfect voltage source ( ignoring discharge effects.)
Your readings all look sensible at a glance; I will look at them in more detail , compare with your original readings and comment again in the next day or so.

Wayne
Hah Hah. I went to quote some connector resistance values that I'd read on another forum then when I looked I noted that it was YOUR data.

http://www.rcmf.co.uk/4um/index.php/...915455.html#37 post #37
Valid nonetheless.
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Old Mar 04, 2011, 12:45 PM
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Rugby, UK
Joined Feb 2007
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Quote:
Originally Posted by Kozmyk View Post
Hah Hah. I went to quote some connector resistance values that I'd read on another forum then when I looked I noted that it was YOUR data.

http://www.rcmf.co.uk/4um/index.php/...915455.html#37 post #37
Valid nonetheless.
Kozmyk,

That is what the statement was based on!
I know it is off - topic, but I avoid 4mm cage connectors for two reasons:
1) When fumbling in a fuselage at the field it is all too easy to pick up the wrong connectors and plug the pack +v into the pack -ve. - Yes, I did it once!
That objection applies to any single pole bullet connector.
2) The cage connector has little surface area and is effectively two connectors in series, which is why a 3.5mm solid connector is 3 x better than a 4mm cage connector. I must say I was surprised how good that little 3.5mm solid connector was; enough to make me double check the results, not far behind the 5.5mm solid bullet.

Wayne
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Old Mar 04, 2011, 04:30 PM
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United Kingdom, Wales, Swansea
Joined Jun 2010
53 Posts
Wayne

I agree that the single cage type are risky in terms of pack safety but I must admit that I was surprised how well they did in the resistance stakes, still well behind the solid bullets but not as bad as I had expected.
The EC# design of course prevents such pack shorting accidents by mounting it's 3.5mm bullets in polarised housings.
Now if only we could get solid bullets to fit into EC# housings; that would be perfect.

Getting back on topic, I look forward to you getting enough interest to be able to make some more IR Meters.
Such a precision device would be a prized addition to my arsenal.
So refreshing to see so much care and attention to accuracy in a design these days.
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Last edited by Kozmyk; Mar 04, 2011 at 04:41 PM.
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Old Mar 04, 2011, 04:39 PM
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Rugby, UK
Joined Feb 2007
883 Posts
Quote:
Originally Posted by Kozmyk View Post
Now if only we could get solid bullets to fit into EC# housings; that would be perfect.
Koz,

If you look at an XT60 connector (which I have changed over to for normal use, ie up to 60A) you will see that it uses solid bullets which look very nearly identical to the 3.5mm solid bullets. I would have difficulty in telling them apart out of the housings, so they sound exactly what you want. Don't ask me to explain why they don't perform as well as the bullets - I can't, but even so they are very good. This is why I was so surprised how good the bullets were.

Wayne
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Old Mar 04, 2011, 05:21 PM
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United Kingdom, Wales, Swansea
Joined Jun 2010
53 Posts
I'm happy enough with the EC3s for now despite them being cage types (in a shroud) but any bigger current and I'd prefer solid to cage for sure.

So far I've got 3 helis, 2 planks and 8 packs on EC3 and I'm reluctant to change unless any of them start getting hot.
In retrospect I'd have done as well to keep the packs on XT60 and changed the birds but it's done now.
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Old Mar 06, 2011, 11:52 AM
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United States, IL, Peoria
Joined May 2003
810 Posts
Do you have any of the IR meters left? and how do I pay you-Paypal or Int Money Order?
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Old Mar 06, 2011, 11:53 AM
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Joined May 2003
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I ran out of British Sterling...LOL
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