Espritmodel.com Telemetry Radio
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Old Jul 14, 2012, 05:23 PM
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Originally Posted by Aviefly View Post
Yep I'm loving the meter too, had it for a while now and finding I'm using it more and more. As Wayne says, combined with jj604's tool it's super easy to start to get an idea what the packs are really capable of instead of what the manufacturer claims or even just those packs that you haven't had a use for in ages. You can pull them out check them out and decide if they are up to the task or not, I've been surprised at how well some old packs that have sat for long periods have come out. It really impresses me that once you've tested out some various packs and then check them out on the wattmeter the ones you expect to perform better actually do and the one's you thought might be border line for your application end up being shelved for a less demanding application. I'm sure it's saved me puffing a good few lipo's already.

Wayne, I know we've spoken about it before but I'm interested in being able to test smaller sized packs, down to the UM packs and even 1S packs. I know you said that it was pretty easy to change something on the meter to make it handle lower capacity packs but as the idea of damaging my meter scares me wondered if you'd be interested in modifying one for me. I'd like to purchase another meter from you for this purpose and obviously would pay for any extra costs.

Dan
Dan,

If you are reasonably handy with a soldering iron and have a DMM, I can give you details of how to add the mod to make the meter dual range for the small lipos. Component cost is negligible as you just need a small slide switch a pot and one resistor.
As John says, the connector resistance is difficult to eliminate but is not that significant compared with the IR of these tiny cells.

Wayne
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Old Jul 14, 2012, 05:40 PM
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Melbourne, Australia
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Wayne, If you do make a good connection, the IR values are little affected by the connector as you say. However that is true for new cells and connectors. I have found that after a time the connections can get quite variable and higher resistance with these little cells and their Molex pico blade connectors. This is particularly a problem for the meter side connector as it is the one that gets far more action. Fortunately it is the blade side as the flexible sprung sockets are in the battery connector.
I suspect the biggest problem is that the blades become loose in the housing after a few insertions and tend to push back out of it when the battery is connected.

Dan if you hold the adapter connecting wires as you push the battery in then they have to go in all the way.

Corrosion may also be an issue with my original cells some of which are almost two years old. I used D-Toxit last time and that seemed to help with consistancy.

John
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Originally Posted by Wayne Giles View Post
As John says, the connector resistance is difficult to eliminate but is not that significant compared with the IR of these tiny cells.

Wayne
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Old Jul 15, 2012, 04:15 AM
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I've asked this before but want to ask again.

I have two of the meters and like them a lot.
The testing I do is with small two cell packs primarily, from 325 to 450 mAh.
These packs have mostly XH and TP connectors.

Are the readings I'm getting useful, or am I wasting my time?

Thanks
Bob
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Old Jul 15, 2012, 05:26 AM
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Originally Posted by Wayne Giles View Post
Dan,

If you are reasonably handy with a soldering iron and have a DMM, I can give you details of how to add the mod to make the meter dual range for the small lipos. Component cost is negligible as you just need a small slide switch a pot and one resistor.
As John says, the connector resistance is difficult to eliminate but is not that significant compared with the IR of these tiny cells.

Wayne
That would be great Wayne if you can give me a component list and some details on what to do I'll give it a go. If it all goes wrong I'll just have to buy another meter.

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Originally Posted by bob_nj View Post
I've asked this before but want to ask again.

I have two of the meters and like them a lot.
The testing I do is with small two cell packs primarily, from 325 to 450 mAh.
These packs have mostly XH and TP connectors.

Are the readings I'm getting useful, or am I wasting my time?

Thanks
Bob
I don't think your wasting your time especially if you look into the FOM concept and/or use Mark Forsyth's simple tool. I think the problem for the size of packs your testing would be the 16A load used for the test could be a little on the high side, that's why I'm looking into modifying it. The problem with the single cell um packs we have been talking about is as there is only one connection point you can't eliminate the resistance of the connector via the cell probe and four wire system. If your 325 to 450mah packs are conventional packs with balance tabs this isn't a problem, though it might be a good idea for you to look into doing the mod too.
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Old Jul 15, 2012, 05:34 AM
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Melbourne, Australia
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Bob, if you use both connections - that is connect up the battery power lead to the ESR meter to power it and take cell readings through the XH or TP balance connectors the readings you get for IR are absolutely accurate for the temperature you measure them at and for the conditions of the meter. However that is a 16A load.

For 325 - 450 mAh cells that equates to a 50C - 35C load which these small cells are not really capable of supplying. 25-30C would be the highest rate I would expect to get while maintaining a useful voltage from a very good 450mAh cell such as a Thunderpower 65C.The meter pulse is short and will not damage the cells but I would not regard the IR numbers as useful in absolute terms. Probably fine for comparison between cells and packs, just do not use the IR number in the LiPo tool for example. Certainly for the 325mAh ones.

In short the meter applies a current that is more than most of these cells can be expected to deliver. I think you might consider getting Wayne to supply a modified 1.6A version or converting it yourself if you have those skills if you are serious about sub 400mAh batteries.

Wayne may want to give an opinion. He is the expert on the functionality of the meter and and what affects the results.

John

Quote:
Originally Posted by bob_nj View Post
I've asked this before but want to ask again.

I have two of the meters and like them a lot.
The testing I do is with small two cell packs primarily, from 325 to 450 mAh.
These packs have mostly XH and TP connectors.

Are the readings I'm getting useful, or am I wasting my time?

Thanks
Bob
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Old Jul 15, 2012, 06:32 AM
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Rugby, UK
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Quote:
Originally Posted by bob_nj View Post
I've asked this before but want to ask again.

I have two of the meters and like them a lot.
The testing I do is with small two cell packs primarily, from 325 to 450 mAh.
These packs have mostly XH and TP connectors.

Are the readings I'm getting useful, or am I wasting my time?

Thanks
Bob
Bob,

As John has said, the 16A pulse is high for these small lipos but it will not damage them as it is so short in time. The IR of a lipo is virtually independant of current over the ranges we are talking, so that the results will be valid providing that the meter is not going into over - range.
The Cell mode is the better measurement as it ignores connector resistance but the meter is only specified up to 30 milliohms as a maximum reading in Cell mode. In practice it will measure accurately up to about 37 milliohms or so, but I would be suspicious of readings over 35 milliohms, especially if all the cell readings are the same. At values over 37 milliohms the meter measurement range 'saturates' so that any higher value will be shown as this saturated reading.

Wayne
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Old Jul 15, 2012, 07:05 AM
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Originally Posted by Wayne Giles View Post
Bob,

As John has said, the 16A pulse is high for these small lipos but it will not damage them as it is so short in time. The IR of a lipo is virtually independant of current over the ranges we are talking, so that the results will be valid providing that the meter is not going into over - range.
The Cell mode is the better measurement as it ignores connector resistance but the meter is only specified up to 30 milliohms as a maximum reading in Cell mode. In practice it will measure accurately up to about 37 milliohms or so, but I would be suspicious of readings over 35 milliohms, especially if all the cell readings are the same. At values over 37 milliohms the meter measurement range 'saturates' so that any higher value will be shown as this saturated reading.

Wayne
That's interesting to know Wayne I probably have some more packs that I can sort through till I get the mod done then, thanks.
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Old Jul 15, 2012, 11:28 AM
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Thanks for all of the useful replies.
I am using both connections, and the taps are XH and TP connectors, so the readings are easily obtained.

I was hoping to use the readings as someone commented as comparisons between packs, and to make sure the cells are reasonably close to one another in milliohms.

That's what I'm looking for right, to make sure one of the cells isn't way out of whack in relation to the other?
From what I remember, that indicates a cell that's going south etc.

The readings are in the 30's, but they are not the same so I'm guessing I'm getting decent readings, all between 25 and 35.

My soldering skills are decent, so is there a tutorial or something on modifying the meter?

Thanks again
Bob
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Old Jul 15, 2012, 02:13 PM
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Originally Posted by bob_nj View Post
Thanks for all of the useful replies.
I am using both connections, and the taps are XH and TP connectors, so the readings are easily obtained.

I was hoping to use the readings as someone commented as comparisons between packs, and to make sure the cells are reasonably close to one another in milliohms.

That's what I'm looking for right, to make sure one of the cells isn't way out of whack in relation to the other?
From what I remember, that indicates a cell that's going south etc.

The readings are in the 30's, but they are not the same so I'm guessing I'm getting decent readings, all between 25 and 35.

My soldering skills are decent, so is there a tutorial or something on modifying the meter?

Thanks again
Bob
Bob,

That sounds OK. You must be using 2S or larger packs.
If the cell readings are below 35milliohms they will be valid measurements, so that there is no need to modify the meter.
The mod is really to enable the meter to the tiny 70mAh and 130mAh cells which indoor models use.

Wayne.
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Old Jul 18, 2012, 10:14 PM
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Canada, AB, Edmonton
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Quote:
Originally Posted by Wayne Giles View Post
...I can give you details of how to add the mod to make the meter dual range for the small lipos.
Wayne, could I also take you up on your very kind offer of those details? (No problem with soldering, test equipment availability, etc.)

Reason I ask this is I've recently become interested in small models and have been making up my own 2S 200mAh packs (with balance taps) from single cells. On checking some of those with your meter, I was surprised and delighted to see that they apparently had very low IRs, equivalent to FOMs of around 1.6.

That didn't really seem right, and discharge tests and flying experiences didn't indicate anything exceptional. Then your posts above rang some bells. I looked back over my IR readings and - sure enough - they were around 37 milliohms per cell.

I knew about that limit all along, but it had somehow slipped my mind.

So I would like to be able to use your marvellous little meter with small cells too. Thanks, Wayne, for such a great device and for your offer of info on how to do the small-cell mod.
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Old Jul 19, 2012, 01:47 AM
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Dan, Bob and Harry,

Give me a few days, as I have a computer problem at present, and I will write up a few notes on the "Small cell modification" so that you can add it to your meter.

Wayne
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Old Jul 19, 2012, 10:41 AM
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Take your time

Not sure if this was covered previously, but I've used my meters on LiFePO4 batteries with good results.
These are generally 2 cell 1100 mAh packs or bigger.

Is the meter useful for this chemistry too?
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Old Jul 19, 2012, 11:13 AM
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ABSOLUTELY!

The ESR Meter is fantastic for all battery chemistries. The electrons do not care much of the chemical reactions that are allowing their movement.

Mark
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Old Jul 19, 2012, 11:15 AM
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Excellent!

I was looking at the title of the thread and started to wonder...
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Old Jul 19, 2012, 11:38 AM
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Originally Posted by bob_nj View Post
Not sure if this was covered previously, but I've used my meters on LiFePO4 batteries with good results.
These are generally 2 cell 1100 mAh packs or bigger.

Is the meter useful for this chemistry too?
Bob,

Just one note of caution. The on-load voltage of an 2S LiFeP04 pack is not high enough to supply the electronics within the meter so that the reading is likely to be optimistic ie low.
3S packs or larger up to 8S are fine. As Mark says, the electrons don't care what type of cell is moving them.
Equally the meter will measure Nicad or Mimh packs (and individual cells if you connect the search lead) provided you respect the minimum and max pack voltages of 7V and 30V.

Wayne
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