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Old Dec 03, 2011, 01:44 PM
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Rugby, UK
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Originally Posted by Aviefly View Post
Got mine today, thanks Wayne.

I'm very impressed with the appearance and feel of the meter and the very easy operation. I love the fact that it is very cottage industry and not mass produced, the designer himself has sat there and built them by hand and then calibrated each individual one, that in itself is worth the money to me.

When I got out to the shed the first thing I did was change the Deans connector to my chosen 4mm gold connectors for my bigger packs and made up some adapters so I can use my charge leads for other connectors such as the jst's on my smaller packs. This should also mean it will be easy to use it on other peoples packs who might use different connectors though it will mean there is extra resistance to take into account from the extra wiring in pack mode.

I then set about testing my packs which had all been sitting together so temperature difference didn't effect it when comparing my packs like for like. I will need to get myself an accurate thermometer so I can attempt to take readings at the same temperature over time.

Instead of trying to type out all my readings I've attached a picture of my scribblings. Notice the Max Poly 900mah 20C 3S packs, these are my oldest packs and though they still have enough power to fly the model they are for I had been thinking about replacing them. The other thing I notice is the difference of the sum of cell resistance and the pack resistance is much higher on my small packs with jst connector, maybe it's time to switch over to 2mm golds? or is this just down to using my charge lead to connect it to the meter? it is a high quality lead though it is quite long.

If you can make any sense of my scribblings I would be interested in hearing your thoughts on them. Unfortunately the only other bit of information that would be useful for you is the ambient temperature but unfortunately I can't measure it at the minute.
Dan,
Glad to hear it's all ok.
Re the connector problem. If you look at the photo which is my own meter you will see that I have cut the leads short and put a pair of 5.5mm solid connectors in it which is the big bulge in each lead. They are so low in resistance (about 0.14milliohms) that they can be ignored and I have made up adapter leads for various connectors. I don't like the Deans knock offs and would rather fit the XT60 which is a good connector, the contacts being small scale models of the 5.5mm solid bullet. I am tempted to just leave the connector off as everyone seems to change it.
The results are interesting (see below) but despite what it says below you are right about the JST connector which is quite unsuitable with a resistance of 7milliohms/pole and a current rating of 3A; I don't understand why lipo assemblers use them. Suggest Deans micro connectors are a good replacement and ok for 15A.
The figure for the old Max poly pack are not valid as the max. specified range on "Cell" for the meter is 25milliohms. It will actually measure up to about 35milliohms but the values you are seeing are effectively 'overange'. ie the measuring circuit is saturated and the IR of each cell is well above 38milliohms. The measuring pulse of 16A is too high for an old 450mAh cell which is why I have specified 500 - 6000mAh. That is why there is such a large difference between Pack and Cell total.

All your other figures look fine. It is worth looking at the FOM (Figure Of Merit) values based on Mark Forsyth's original formula stating that the product of cell capacity in mAh and cell resistance in milliohms should be less than 12000 for a really good lipo. ie 12000 divided by that product should be 1 for a really good cell. If you calculate these figures you will see that the Billowy is 0.58, the Overlander is 0.59 and the Gens Ace is 1.24.

Wayne
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Old Dec 03, 2011, 05:44 PM
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Thanks Wayne that gives me some ideas.

I did read about the FOM rating a while ago and thought what a great idea it was but didn't do anything with it as I didn't have a way to measure my cell IR's. Even if it never stands a chance of becoming an industry standard it would still be a great way for us modellers to rate the performance our packs for ourselves.

Let me see if I'm getting the right end of the stick, to arrive at the FOM's you stated you took the individual cell IR's for a pack, added them together then divided by the number off cells to arrive at an average cell IR for the pack, right so far? multiply this number by the pack capacity in mah, the FOM is the number of times this number will go into 12000 so in other words 12000 divided by the end figure?

Does this mean that the suggested FOM doesn't take into account the resistance of any leads and connectors?

Take the Gens Ace 25C 450mah 2S pack number 7 from my photo. I picked this one as it looks to be the worst of the bunch. That would be 29.96+29.16/2 giving 29.56, multiply this by the capacity 29.56*450 giving 13302. Then take the 12000 figure and divide by 13302 giving an FOM of 0.9.

Would it be reasonable to take the same method but use the Pack IR divided by the number of cells to start off with to see how much difference your chosen connectors can make. Taking the same pack would give you 97.5/2=48.75*450=21937.5 then the 12000/21937.5=0.55 giving and FOM difference of 0.9-0.55=0.35

Do the same for Billowy number one pack and although the pack has a worse FOM the difference is a lot smaller. Individual cell FOM would be 0.57 the second figure would be 0.52 giving a difference of only 0.05

On another note I have a couple of my mates Gens Ace 25C 2200 3S packs, I'm going to let them settle next to my Billowy 2250's so that I can compare them tomorrow.
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Old Dec 03, 2011, 06:04 PM
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On another note I have a couple of my mates Gens Ace 25C 2200 3S packs, I'm going to let them settle next to my Billowy 2250's so that I can compare them tomorrow.
Would be very curious to know how your results compare to my results. My measurements were taken with an iCharger so the raw IR or FOM numbers won't be directly comparable but the deltas sure will be. Need to get me one of Wayne's nifty meters... (hook me up Wayne! )

Mark
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Old Dec 03, 2011, 08:26 PM
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Anybody here that has both the PL8 and Wayne's meter? How do the IR values compare on the same lipo and conditions?
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Old Dec 03, 2011, 09:21 PM
ancora imparo
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Melbourne, Australia
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I have attached the first comparison I did with the new meter against the PL8 and a SuperDuo.

A selection of batteries that were lying around.

All were charged from storage to fully charged with a PL8 then discharged to storage with the SuperDuo. IR was measured with the Waynemeter at full charge and at storage after allowing the meter to settle for 5 secs after connection. The PL8 only measures individual cell IR and only while charging above 75% capacity. The Duo measures battery IR charging or discharging but I only measured the discharge value.

You should compare the summed cell values from the PL8 with the cell sum numbers for the Waynemeter. (The figures in red look odd. Didn't have time to recheck them so am calling them anomolous for now.) The SuperDuo numbers should be compared with the Battery numbers from the Waynemeter.

I think the conclusion is (based on this very quick first test) that there is a lot to be said for IR - and it hasn't all been said yet.

Certainly these three methods are all different. My understanding is the SuperDuo measures the voltage between the charge/discharge period and the relatively long rest period which occurs frequently. In the PL8 the current is turned off for 300uS and the at-rest battery voltage is compared to the charging battery voltage on a cell by cell level. Both are measuring the IR based on the difference between the set charge/discharge current (which will vary depending on battery capacity and charge rate) and no load. The PL8 measures only during charge. The Waynemeter measures discharge IR at a standard 16A vs no load.

Note: The Thunderpower 325mAh battery was tested at 1.6A not 16A.

All testing done over a 3 1/2 hour period at about 23C.

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Originally Posted by alexf1852 View Post
Anybody here that has both the PL8 and Wayne's meter? How do the IR values compare on the same lipo and conditions?
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Old Dec 03, 2011, 10:36 PM
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@jj604

Thanks for the comparison.
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Old Dec 03, 2011, 11:22 PM
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Anybody here that has both the Icharger and Wayne's meter? How do the IR values compare on the same lipo and conditions?
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Old Dec 04, 2011, 12:44 AM
ancora imparo
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Melbourne, Australia
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I just measured the Turnigy 30-40C 4S 3.6Ah #7 which from my from my previous post at Storage Charge on the Waynemeter was:

Cell 1 = 3.08 mOhm
Cell 2 = 2.72
Cell 3 = 2.6
Cell 4 = 2.76

On the iCharger 3010B
Cell 1 = 3
Cell 2 = 3
Cell 3 = 2
Cell 4 = 2

It's about 4 degrees cooler today, and the storage charge level might be slightly different.

The iCharger, like the SuperDuo, only reads to a resolution of 1mOhm of course.

I'm guessing from the way it works that the iCharger does a constant current discharge like the Waynemeter. Anyone know for sure?

John


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Anybody here that has both the Icharger and Wayne's meter? How do the IR values compare on the same lipo and conditions?
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Old Dec 04, 2011, 01:09 AM
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I'm guessing from the way it works that the iCharger does a constant current discharge like the Waynemeter. Anyone know for sure?
John,

Yes, the iChargers do measure in similar fashion as the Wayne-o-meter. I have placed a current shunt in series with the main discharge lead of a lipoly and witnessed a current 'blip' when measuring IR with my iChargers. Unfortunately I don't have a scope readily accessible at my 'home lab' to accurately capture the current and pulse duration but my testing was sufficient to prove to me that it works in a similar manner.

Excellent summation of your testing above, BTW. I've long thought that the FMA chargers measure on the low side and your testing corroborates this. My theory is that this may be due to the measuring methodology of the FMA chargers and perhaps heating during charging is contributing to lower measured results.

Mark
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Old Dec 04, 2011, 01:16 AM
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Birchleigh, South Africa
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Originally Posted by jj604 View Post
I just measured the Turnigy 30-40C 4S 3.6Ah #7 which from my from my previous post at Storage Charge on the Waynemeter was:

Cell 1 = 3.08 mOhm
Cell 2 = 2.72
Cell 3 = 2.6
Cell 4 = 2.76

On the iCharger 3010B
Cell 1 = 3
Cell 2 = 3
Cell 3 = 2
Cell 4 = 2

It's about 4 degrees cooler today, and the storage charge level might be slightly different.

The iCharger, like the SuperDuo, only reads to a resolution of 1mOhm of course.

I'm guessing from the way it works that the iCharger does a constant current discharge like the Waynemeter. Anyone know for sure?

John
I measured a Zippy 4S 5000mAh pack:
3010B 7,7,8,7 total 29
208B 8,8,10,10 total 37
Waynemeter 7.76, 7.80, 8.04, 7.40 total 38.1

Hennie
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Old Dec 04, 2011, 02:36 AM
ancora imparo
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Mark, Wayne may want to comment - he knows much more about this than I do - but the duration of the pulse is also critical.

My understanding is that he spent a great deal of time making sure the discharge pulse was long enough to ensure an accurate reading. There is a "settling curve" before IR can be accurately measured and I was surprised that the PL8 uses such a short resting period to calculate IR. On the other hand the Marks boys know a lot more about this than me as well, so they may have incorporated some clever algorithm that compensates.

John
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Originally Posted by mrforsyth View Post
John,

Yes, the iChargers do measure in similar fashion as the Wayne-o-meter. I have placed a current shunt in series with the main discharge lead of a lipoly and witnessed a current 'blip' when measuring IR with my iChargers. Unfortunately I don't have a scope readily accessible at my 'home lab' to accurately capture the current and pulse duration but my testing was sufficient to prove to me that it works in a similar manner.

Excellent summation of your testing above, BTW. I've long thought that the FMA chargers measure on the low side and your testing corroborates this. My theory is that this may be due to the measuring methodology of the FMA chargers and perhaps heating during charging is contributing to lower measured results.

Mark
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Old Dec 04, 2011, 02:48 AM
ancora imparo
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Hennie, that's useful. It's hard to draw any serious conclusions about cell IR of big modern packs when the meter reports only to 1 mOhm resolution/accuracy.

I should have used an old pack with larger IR numbers.

The one conclusion we can all agree on I think is that the numbers aren't very consistent between methods.

I am curious why some people are adamant that the FMA charger is somehow "more accurate". I wonder if it is colored by the fact it is a US product from a company with a long, well deserved, reputation rather than from any theoretical justification.

Not saying they are wrong, just wondering what the reasoning is. Certainly in relative terms I suspect the PL8 and Waynemeter are probably reliable - in absolute terms it becomes perhaps a "more heat than light" discussion.

John
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Originally Posted by hethjo View Post
I measured a Zippy 4S 5000mAh pack:
3010B 7,7,8,7 total 29
208B 8,8,10,10 total 37
Waynemeter 7.76, 7.80, 8.04, 7.40 total 38.1

Hennie
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Old Dec 04, 2011, 02:51 AM
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Note: The Thunderpower 325mAh battery was tested at 1.6A not 16A.
How did you do this with the Wayne-o-meter?
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Old Dec 04, 2011, 02:56 AM
ancora imparo
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I have a modified one with a 1.6A test capacity.

John
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How did you do this with the Wayne-o-meter?
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Old Dec 04, 2011, 03:04 AM
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I have a modified one with a 1.6A test capacity.

John
mmm I think I'll leave that to someone who knows what their doing

Just have some um 1S packs at between 130mah and 200mah. What would happen if I connected them in parallel to the main leads so they could take the 16A and used the probe to take the cell IR?
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