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Old Jul 11, 2014, 04:04 PM
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Originally Posted by AeroKen View Post
The two new batteries I ordered arrived - these are identical to the four I was asking about the IR of above. I checked the IR of the new batteries and one of the old ones after letting them sit overnight with the other ones so they'd all be at the same temperature (~75 F, been hot here recently, even the basement floor has warmed up). The highest cell IR in the new ones measures less than half of the lowest cell IR in the old ones. Much more inline with what I was expecting, I'm guessing I'm in for a real pleasant surprise this weekend when I throttle up with a new battery.

I guess the higher IR of the old ones is just what comes of a couple years storage at storage charge in the 60-75+ temps in my basement.
Ken, (?)

The IR of the new packs will almost certainly fall after the first couple of cycles so that should be better than half of the old ones.
Whether you see an obvious difference in flight performance between the new and old will depend on how hard you are pushing them and also how low the IR is on the better ones.
Remember that the IR dictates how high the losses are, so that if the losses are very small as a percentage of total power, then doubling them might not be obvious.
As the lipo ages the IR rises so that the losses and the pack heating increases.
The extra heat does more damage which increases the IR so we have an accelerating failure rate. Usually the weakest cell will go into a runaway failure when the IR goes very high and the pack is effectively dead.

Wayne
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Old Jul 11, 2014, 04:17 PM
3D? I only got two thumbs!
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I'll be checking the IR regularly on the old and new packs. I like to push both ends of the flight envelope, I think I should see a difference at the higher end of the throttle especially in the larger of the two planes I use these in. It'll be interesting to see if I actually do notice a difference.

(Yes, it is Ken, and thanks for all the info Wayne.)
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Old Jul 12, 2014, 03:07 PM
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Hi
I got my Wayne Giles ESR Meter, but I need another measurement cable/ search wire with smaller distance between the pins so that I can measure all the kinds of balance connectors. How do I do it the best way?
Is the meter calibrated with the mounted Deans connector and does it become uncalibrated if I change to another contact, such as XT60?

/Ville
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Old Jul 12, 2014, 03:13 PM
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The easiest means of ensuring compatibility is to get a balance plug adapter that adapts the balance tap on your pack to JST-XH. e.g. - The same balance plug adapter that you use to balance charge your packs on nearly all balancing chargers.
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Old Jul 12, 2014, 03:28 PM
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Originally Posted by mrforsyth View Post
The easiest means of ensuring compatibility is to get a balance plug adapter that adapts the balance tap on your pack to JST-XH. e.g. - The same balance plug adapter that you use to balance charge your packs on nearly all balancing chargers.
Embarrassing ease, thanks so much!

/Ville
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Old Jul 12, 2014, 05:27 PM
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Originally Posted by liukku View Post
Hi
Is the meter calibrated with the mounted Deans connector and does it become uncalibrated if I change to another contact, such as XT60?

/Ville
Hi,

Just to clarify this point. Changing connectors or leads will have no effect at all on the Cell readings as the search wire connection eliminates any extra voltage drops. If you change the power connector, the difference in Pack readings will be negligible
If you add an adapter cable to the power lead, it will add the extra resistance to Pack readings, but will still not affect Cell readings.

Wayne
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Old Jul 13, 2014, 11:15 AM
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Originally Posted by Wayne Giles View Post
Hi,

Just to clarify this point. Changing connectors or leads will have no effect at all on the Cell readings as the search wire connection eliminates any extra voltage drops. If you change the power connector, the difference in Pack readings will be negligible
If you add an adapter cable to the power lead, it will add the extra resistance to Pack readings, but will still not affect Cell readings.

Wayne
Thanks Wayne, not only for this reply, but also for all the work you and other put on informing and educating us with less knowledge of the subject, and to sort out the chaos in LiPo swamp.

/Ville
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Old Jul 13, 2014, 04:42 PM
3D? I only got two thumbs!
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I flight test compared the new lipos to the old ones yesterday (the new ones measured less than half the IR of the old ones). There was a slight difference in the air, I'm not sure I'd notice in a double blind test but it did seem to me like it was real. The more telling difference was in the voltage telemetry for the larger of the two planes - the min voltage recorded was a volt higher for the new lipos.
I leaning toward retiring the old ones - they're at the point where if I flew long enough to land @ 3.7 volts per cell it's quite possible the min voltage in flight would get too low. With new lipos I just wouldn't have to worry about that.

So, to summarize this whole experience. The ESR meter and the simple lipo performance tool were telling me exactly what was going on all along, I just wasn't quite ready to believe them because I didn't want to believe the four lipos I'd never flown were already past their prime. I won't make that mistake again - this is clearly an excellent early warning tool that can tell you very clearly about lipo problems which might be harder to notice by other means.

The one thing I'm still wondering about is what exactly happened with the old lipos. The sat never used in the basement between 60-75 F for close to 2 years. I measured the IR before flying them for the first time, so I know in flight abuse didn't kill them - they were already tired. I have lipos that are older than that which I've flown regularly from day one which are still going strong and reporting decent IR numbers. What I'm wondering is if leaving them stored without ever putting some cycles on them may be worse than storing them for the same time with regular use?
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Old Jul 13, 2014, 06:45 PM
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Originally Posted by liukku View Post
Thanks Wayne, not only for this reply, but also for all the work you and other put on informing and educating us with less knowledge of the subject, and to sort out the chaos in LiPo swamp.

/Ville
/Ville,

Thanks for your kind words.
I don't have a great knowledge of lipos themselves, but an enthusiasm for power electronics, which has led me to try to understand their performance characteristics.
Mark Forsyth and John Julian have the same target and we thought up the Lipotool between us which works on a very simple principle of limiting heat dissipation within the cell, but seems to be able to forecast maximum safe load current ( ie real 'C' value) with surprising accuracy and consistency.
It also helps to quantify the difference between real 'C' ratings and the marketing hype which we are constantly subjected to.


Ken,

I have two 4S 2250 25C LoongMax lipos which I bought four years ago for a specific project and have never used. I came across them the other day and notice that they are both slightly puffed . I will measure their IR values and post them; hopefully I can find records of the same cell type when new for comparison.
I guess storing at 65/70*F doesn't help. I have a non-working freezer cabinet in an outside garage which I store lipos in, so the average temperature is probably about 50/55*F.
At any temperature, they will deteriorate, presumably the cooler the better, within reasonable limits.

Wayne
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Old Jul 21, 2014, 06:56 PM
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Wayne sent me the parts to fix my old meter. It is over 5 years old. It is working good as new. His customer service is excellent.

Thanks!!
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Old Jul 22, 2014, 04:55 PM
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Originally Posted by Wayne Giles View Post


Ken,

I have two 4S 2250 25C LoongMax lipos which I bought four years ago for a specific project and have never used. I came across them the other day and notice that they are both slightly puffed . I will measure their IR values and post them; hopefully I can find records of the same cell type when new for comparison.
I guess storing at 65/70*F doesn't help. I have a non-working freezer cabinet in an outside garage which I store lipos in, so the average temperature is probably about 50/55*F.

Wayne

I have now measured the above packs which I foolishly charged and left fully charged for four years as specified above.

Cells in both packs have self discharged to between 3.9 and 4.0 volts per cell.

IR values at 22*C are:-

Pack 1-----8.32----8.60----7.96----9.84 milliohms
Pack 2-----8.16----8.00----8.40----8.12 milliohms

They are LoongMax 2250mAh. 20C cells. ( not 25C as I thought)

A new LoongMax 2250mAh 20C 3S pack I measured at the time showed an average Cell IR value of 4.1milliohms so that it looks as if the cell IR values have approximately doubled after four years storage at full charge.

Quantifying this with the Lipotool, it suggests that the real 'C' rating has fallen from 25C. (57A max current). to 18C. (41A max current)

I don't know how much this can be read across to other lipo types; not that much at a guess, the LoongMax were very good cells at the time.


Wayne
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Old Jul 22, 2014, 05:10 PM
3D? I only got two thumbs!
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Interesting, the four packs I stored for 1-2 years at storage voltage seem to have degraded just as much as the packs you stored fully charged for four years. I'd guess the average temp mine were stored at is around 60 in the winter and 75 in the summer. Sounds like that's 15-20 degrees warmer than yours were stored at, which kind of confirms that temperature is important. Maybe I should find some cooler lipo storage.
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Old Jul 26, 2014, 05:49 PM
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Can anyone answer this question for me. If I have a motor that is rated at 20amps max, how high of an esc can I use? I estimate a 25 or 30 amp esc would do fine, however what if I used a 60amp, would effect the system in anyway?
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Old Jul 26, 2014, 06:09 PM
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Can anyone answer this question for me. If I have a motor that is rated at 20amps max, how high of an esc can I use? I estimate a 25 or 30 amp esc would do fine, however what if I used a 60amp, would effect the system in anyway?
Ermilo,

This is not really the right thread for this question, but the answer is simple.

Using a higher rated ESC in a system will have no effect on the sytem; just your wallet. It would just mean that you are buying unwanted capacity; a bit like buying a 10 ton jack to lift a 5 ton weight.
Having said that it is always wise to leave a margin. If you think you will be drawing 20 - 25A, always use a 30A ESC. The same applies to motors and particularly Lipos.

Wayne
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Old Jul 26, 2014, 09:42 PM
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Tks nice metaphor
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