HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jul 19, 2012, 12:46 PM
Registered User
bob_nj's Avatar
Vineland, N.J.
Joined Sep 2003
664 Posts
Understood, thanks!
bob_nj is offline Find More Posts by bob_nj
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 22, 2012, 10:13 AM
Registered User
Chicago, USA and Manila, Philippines
Joined May 2007
153 Posts
Hi Wayne, a suggestion...

1s and 2S 70 to 300 mah cell and batteries are popular now a day. On your next version of your ESR, can you make them standard? Of course we are willing to pay the extra cost of components and labor..

Elmer
yurstruly is offline Find More Posts by yurstruly
Reply With Quote
Old Jul 24, 2012, 06:53 AM
Registered User
Rugby, UK
Joined Feb 2007
838 Posts
Quote:
Originally Posted by yurstruly View Post
Hi Wayne, a suggestion...

1s and 2S 70 to 300 mah cell and batteries are popular now a day. On your next version of your ESR, can you make them standard? Of course we are willing to pay the extra cost of components and labor..

Elmer
Elmer,

Unfortunately that would require a major redesign as the PIC is already fully utilised and another current setting and reading range would demand a change of PIC and new PCB.
I originally did the low current modification and single cell mod. to fulfill the needs of a customer who is conversant with electronics. The low current mod is a compromise as the actual reading now has to be multiplied by a factor of 10x so the unit could not be sold with the mod included as it exists at present.

Wayne
Wayne Giles is offline Find More Posts by Wayne Giles
Reply With Quote
Old Aug 01, 2012, 04:53 AM
Registered User
Rugby, UK
Joined Feb 2007
838 Posts
Sorry for delay; Windows latest updates somehow crashed my compter, but am now back on line and here are the mods requested.

To dissemble the unit it is only necessary to split the case (2 screws) and unsolder the pushbutton connections on the PCB. You MUST use either a desoldering tool or desoldering braid to remove the solder and avoid stripping copper from the PCB. The whole assembly will now unplug from the display and come away attached to a side panel.
The older unit with the switch can also be modified. Dissembly is similar but you must remove the switch clamp nut.


ESR Meter Mods. Details for single cell operation and measuring small cells

Single Cell Mod.
This is intended to enable the meter to measure single cells. It has no effect on normal use.
The electronics within the meter require >6V to drive it which normally comes from the lipo under test but needs to be fed from an external source to measure single cells. The simple mod is to add a lead (I normally use a JST connector so that the external feed can be a small 2S or 3S lipo) which feeds the circuitry via a 1A schottky diode for reverse voltage protection. The current demand is 20mA.
The photo below shows how to connect this; the +ve via the diode to the cathode of D1 and the –ve to 0V rail. You need to feed the leads through the grommet in the side panel as shown.
For measurements it is better to connect the voltage search leads in parallel with power leads to measure small cells. Connect them directly to the cell if possible with large cells ie on the cell side of the power connector.
After use don’t forget to unplug the auxiliary lipo otherwise it will eventually become overdischarged.

Low Current Mod.
The normal measurement current of 16A is too large for very small cells (<300mAh) as the max Cell range is 30milliohms. It can be reduced to 1.6A with a simple mod described below and a small slide switch added to make the unit dual range.
The display is a compromise as the meter will now read one tenth of the actual ESR so that the reading must be multiplied by 10 on the 1.6A range.
The two photos show the modification on the board and the overall layout. The slide switch can be mounted through the side panel.
R22 needs to be shunted by 19.3ohms to reduce the current to 1.6A. Connecting two 39ohm resistors in parallel will give 19.5ohms which is the easiest way to achieve this. Ideally use 1% tolerance resistors. (I know the two in the photos are 56ohms BTW!)

If measuring very small single cells for indoor flight (70 - 160mAh) you need to add both mods.
Take care with the very small connectors which are used as they will add to the ESR readings if not clean and/or properly mated.
This apart, all the real “C” ratings measurements and John Julian’s Lipotool (www.jj604.com/LiPoTool) all still apply and work well with the results.
See his findings at http://www.rcgroups.com/forums/showp...75&postcount=5
Wayne Giles is offline Find More Posts by Wayne Giles
Reply With Quote
Old Aug 01, 2012, 12:39 PM
Registered User
Aviefly's Avatar
United Kingdom, Aviemore
Joined Feb 2005
3,244 Posts
Thanks Wayne that is great. I will attempt to do both mods and make myself a label for the switch showing 16A and 1.6A X10 to remind myself to correct the readings. This will make an already great tool even better for my purposes.

By the way I was at the LMA Cosford airshow at the weekend and was tempted to pull the meter out at some of the stalls selling lipo's. If I really needed some new one's I would have given it a go to see if any of them would let me test before I buy.
Aviefly is offline Find More Posts by Aviefly
Reply With Quote
Old Aug 01, 2012, 01:40 PM
Registered User
Rugby, UK
Joined Feb 2007
838 Posts
Quote:
Originally Posted by Aviefly View Post
Thanks Wayne that is great. I will attempt to do both mods and make myself a label for the switch showing 16A and 1.6A X10 to remind myself to correct the readings. This will make an already great tool even better for my purposes.

By the way I was at the LMA Cosford airshow at the weekend and was tempted to pull the meter out at some of the stalls selling lipo's. If I really needed some new one's I would have given it a go to see if any of them would let me test before I buy.
Dan,
I nearly went but backed out at the last minute.
I have often been tempted to ask to try a lipo on the meter before buying, paricularly at a stand at an airshow but have never had the nerve. I fear the result would be forceful advice from the salesman involving love and travel!

Wayne
Wayne Giles is offline Find More Posts by Wayne Giles
Reply With Quote
Old Aug 01, 2012, 04:27 PM
Since 1952
Harry D's Avatar
Canada, AB, Edmonton
Joined Oct 2004
1,247 Posts
Thanks for the info, Wayne. I'm in the middle of doing those mods on mine right now but before I go any further, I have a question.

I have one of the earlier versions (board Rev A) which (of course) has a completely different layout to the current one shown. Would I be correct in assuming R22 and D1 have the same functions, and I just connect to those numbered components as described?

That is, the 19.3 ohm resistor in parallel with R22, and the external power positive lead to the cathode of D1, as they appear on my board?

I'm pretty sure that will be the case, but thought I should confirm. I'd hate to wreck one of my favorite and most-used tools.

Thanks!
Harry D is offline Find More Posts by Harry D
Reply With Quote
Old Aug 01, 2012, 04:57 PM
Registered User
Rugby, UK
Joined Feb 2007
838 Posts
Quote:
Originally Posted by Harry D View Post
Thanks for the info, Wayne. I'm in the middle of doing those mods on mine right now but before I go any further, I have a question.

I have one of the earlier versions (board Rev A) which (of course) has a completely different layout to the current one shown. Would I be correct in assuming R22 and D1 have the same functions, and I just connect to those numbered components as described?

That is, the 19.3 ohm resistor in parallel with R22, and the external power positive lead to the cathode of D1, as they appear on my board?

I'm pretty sure that will be the case, but thought I should confirm. I'd hate to wreck one of my favorite and most-used tools.

Thanks!
Harry,

Yes, you are correct in your assumptions. R22 is the same identity and value (220 ohms) and D2 is also unchanged in the newer version.

Although the unit accuracy will be subject to component tolerances on the low current range, you can get an approximate check by measuring a mid sze pack on both ranges. The low current reading should be one tenth of the normal full current reading.
Any errors will be swamped by the variations in the connectors that are used on these very small cells.

Wayne.
Wayne Giles is offline Find More Posts by Wayne Giles
Reply With Quote
Old Aug 01, 2012, 05:16 PM
Since 1952
Harry D's Avatar
Canada, AB, Edmonton
Joined Oct 2004
1,247 Posts
Thanks, Wayne. I'll get right back to it. Shouldn't take long to finish off. I'll post some results when I try out the new setup. I'm sure everything will work just fine.

[I assume "D2" in your response was just a slip of the finger and should have read D1.]
Harry D is offline Find More Posts by Harry D
Reply With Quote
Old Aug 01, 2012, 05:23 PM
Registered User
Rugby, UK
Joined Feb 2007
838 Posts
Quote:
Originally Posted by Harry D View Post

[I assume "D2" in your response was just a slip of the finger and should have read D1.]
Yes Harry you're right; more a slip of the brain, what's left of it.

Wayne
Wayne Giles is offline Find More Posts by Wayne Giles
Reply With Quote
Old Aug 05, 2012, 06:24 PM
Registered User
Aviefly's Avatar
United Kingdom, Aviemore
Joined Feb 2005
3,244 Posts
I got the mod done today, went as smooth as I could expect considering my novice abilities and I checked, double checked and then checked again that I was putting things in the right place.

I have attached a screen shot showing a set of tests on my 8X Gensace 25C 450mah 2S packs, the first set of results is with the 1.6A test and the second set with the standard 16A, I hope these are within acceptable range. They do show up that my number 7 pack has seen better days but I'm quite happy with the others.

I tested another 8 Desire Power 35C 380mah 3S packs, these came out at a true 22 to 23C with an FOM of 1 and slightly above and a max current of 8 to 9 amps. These match up to previous results with a watt meter which I have also attached.

The single cell mod is great too, I got 18 single cells for my McpX tested of different sizes, 200's 250's 300's and a couple of 500's. Again the results matched up with the ones which hold up better in flight having the lowest IR but even so they all fell well short of the rated C. I am going to have to make up some better leads for testing them though, I noticed that the pack voltage read lower than the cell voltage and I can only presume it is my conglomeration of leads and adapters to get them hooked up

Thanks again Wayne, your a topper
Aviefly is offline Find More Posts by Aviefly
Reply With Quote
Old Aug 13, 2012, 03:55 PM
Registered User
Aviefly's Avatar
United Kingdom, Aviemore
Joined Feb 2005
3,244 Posts
I made myself a little experiment this weekend and lay all my 2S 450mah packs out with the pack numbers facing down and made sure I didn't see them when fitting them into the plane. The idea was to see if I could pick out which pack was the number seven pack, guess what? I could pick it out no bother at all. Just goes to show that the meter and the lipo tool can tell you what performance to expect from your lipo's and prevent you inflicting undue wear and tear on them.

I seem to be getting addicted to taking readings though, anyone that turns up at the field with some lipo's and out comes the meter. It's a good way of finding out which packs I'm going to invest in next though and people seem to appreciate getting a free health check on their lipo's.
Aviefly is offline Find More Posts by Aviefly
Reply With Quote
Old Nov 18, 2012, 06:27 AM
Registered User
Rugby, UK
Joined Feb 2007
838 Posts
Hi All,


I have had three people contact me recently to ask if the ESR Meters are still available and the answer is definitely “YES”
As I build them all myself I struggled early on to keep up, but by streamlining the assembly, test and calibration somewhat I have managed to reduce the overall effort and time involved.
This has enabled me to keep the price the same despite component price increases. (How does the price of a Powerfet double in 12 months when we are supposedly in a world recession?)

The net result is that I have now built another batch which are available still at the original price.
See: http://www.rcgroups.com/forums/showp...&postcount=249
The major advantage over taking IR readings from a charger is that the meter has a much better resolution than most chargers, which becomes increasingly important as cell size increases and IR values fall.
Some of the best packs are now showing cell IR values of 2milliohms and below.
The meter also reads the value instantly at a realistic discharge current level and without charging the pack which introduces a temperature change and consequent source of error.
A Kelvin 4 – wire measurement is system used for cell measurements which eliminates all connector and lead errors.
Measure the cell IR at 22degC (72degF), put the value into John Julian’s calculator at: http://www.jj604.com/LiPoTool/
and it will give you the real “C” value of the lipo with surprising accuracy.
An extension of this is that it can be used at low temperatures to forecast the safe current you can take from a lipo under winter conditions as the result from the LipoTool will always be a max. current at the temperature at which the IR was read. So if you are at the flying field with a meter and any portable link to the net, you can instantly find the max current that you can safely draw.

Wayne
Wayne Giles is offline Find More Posts by Wayne Giles
Reply With Quote
Old Nov 18, 2012, 09:31 AM
Stop scaring my donkey!
JohnathanSwift's Avatar
Greenland
Joined Mar 2012
7,514 Posts
I recommend this to anyone who doesn't have one or is on the fence-fantastic product from a nice guy.
JohnathanSwift is offline Find More Posts by JohnathanSwift
Reply With Quote
Old Nov 18, 2012, 09:38 AM
Registered User
Prof100's Avatar
Canton, Michigan USA
Joined Jul 2007
16,275 Posts
I will go one step further. I would like the ESR meter to be used by all battery makers / distributors and drop the phony "C" ratings that proliferate the market.
Prof100 is online now Find More Posts by Prof100
RCG Plus Member
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Best fo the West Jets Schwemmer Inland Slope Rebels 0 Oct 14, 2010 05:02 PM
Discussion Motor fo UH Haoye EDF Ducted Fan Unit 7 Blade 3.5inch RJPIoW Electric Ducted Fan Jet Talk 1 Sep 08, 2010 12:05 PM
Question New Low IR Lipos Cells nxtdoor High Performance 75 Sep 06, 2009 04:47 PM
Discussion ESR meter to test Nicad/NiMH ?? 1101 DIY Electronics 3 Jun 15, 2009 04:08 AM