Better, better

The axes are still not auto-scaling, for example try selecting 208B and 20A for iset.

First impression is that there are indeed too many limit lines on the graph. Even with the legend it is very hard to tell which is which. I do not find that the Internal Power Max and External Power Max add any value and for me they are just clutter.

One suggestion is to add some marker symbols to some of the limit lines to make them easier to distinguish. I added and 'x' to the 'Set current Min' and a '+' to the 'Set current Max' and that helped me understand it more easily.

IMO the most useful by far is the max charger internal power line since the intersection of that line with the parabola defines the limits of safe/viable operation for the charger. Only currents to the outside of the bounding box formed by the max power intersection with the parabola are allowed.

I am having trouble understanding your definiton/derivation of Imin and Imax ? Imax appears to be the value at which the external resistor array hits its power rating. Imin I cannot figure out. For some input parameter sets it is a value to right of the apex of the parabola, for others, it is down at zero amps.

There are two sets of constraints, one is the current and power limits in the charger and the other is the power dissipation limit of the external resistors. My preference would be for the tool to highlight problems for the charger and let the user worry about getting appropriately rated resistors based on the data presented. The External Power Rating limit line makes it easy to see if the resistor array is being overloaded.

Thank you for listening to the feedback and doing all the hard work to refine your tool.

Originally Posted by kgfly

Better, better

The axes are still not auto-scaling, for example try selecting 208B and 20A for iset.

First impression is that there are indeed too many limit lines on the graph. Even with the legend it is very hard to tell which is which. I do not find that the Internal Power Max and External Power Max add any value and for me they are just clutter.

One suggestion is to add some marker symbols to some of the limit lines to make them easier to distinguish. I added and 'x' to the 'Set current Min' and a '+' to the 'Set current Max' and that helped me understand it more easily.

IMO the most useful by far is the max charger internal power line since the intersection of that line with the parabola defines the limits of safe/viable operation for the charger. Only currents to the outside of the bounding box formed by the max power intersection with the parabola are allowed.

I am having trouble understanding your definiton/derivation of Imin and Imax ? Imax appears to be the value at which the external resistor array hits its power rating. Imin I cannot figure out. For some input parameter sets it is a value to right of the apex of the parabola, for others, it is down at zero amps.

There are two sets of constraints, one is the current and power limits in the charger and the other is the power dissipation limit of the external resistors. My preference would be for the tool to highlight problems for the charger and let the user worry about getting appropriately rated resistors based on the data presented. The External Power Rating limit line makes it easy to see if the resistor array is being overloaded.

Thank you for listening to the feedback and doing all the hard work to refine your tool.

Thanks, I tried getting the axis to scale using conditional data and macros for hours to no avail. Maybe an excel wizard can help us along with this deficiency. For now users will just have to recognize when and how to scale the axis to fit their needs.

Thanks for your recommended modifications. I'll include them in my next update.

The derivation of imax and imin is shown on the "notes page" they are values such that all 4 constraints are satisfied:
1) i <= selected charger's max current rating
2) Pc <= selected charger's internal power dissipation rating
3) Pr <= external resistor's power rating
4) Vc >= 0V

If you go through a few different setups with the spreadsheet, you'll see that imax is limited by either #1, #3, or #4, depending on which is smaller. I have found many practical cases where Pr stays much less than the resistor rating, and imax is limited by #1 or #4 (try 2cell/2ohm/50W/n2).

imin is much harder to explain. imin is either limited by #2 or it has no limit (0A). There are actually some cases where Pc never exceeds the internal power rating. In these cases the minimum set current is in fact 0A. The graph clearly shows that for all i up to imax, the paraboli(?) are always under the internal power rating. Note that in these cases a very large range of current is possible.

In cases where the parabola clearly exceeds the internal power rating, the spreadsheet looks at the second intersection of the parabola and Pcmax to determine imin (intersection with negative slope). If you zoom in on this, you'll notice that the spreadsheet is correctly picking the largest imin (so we safely consider resistor tolerances). It doesn't select the first intersection (positive slope side) because then imin would include currents that put the parabola over the internal power rating.

There may be rare cases where the internal power rating is tangent to the apex of the parabola, but these singularities are still valid. In reality, I've only been able to find one case that looks tangential, but in fact has 3 points where Pc>Pcmax (3cell/2ohm/50W/n2). It looks like it's finding the apex of the low tolerance curve, but if you zoom in really close (or look for the red values in the "Pclo" column of the table), it's still in fact finding the second intersection.

I have mixed feelings about these "tangential" results. The calculator is doing it's job 100% literally, and it is not allowing you to go below that intersection because if your resistors are on the low end of their tolerances, you'd technically be over powering the charger. However just as well the resistor could be on the high end it's tolerance; then you'd be safe down to 0A. Another possibility is the charger's tolerance might allow slightly more than the rated dissipation. Then again the charger's tolerance could be slightly less than rated. Either way you look at it, the chart does give that feel of how far you're pushing your charger. If you feel lucky, ignore imin for tangential cases. If not, go with imin. I'm never lucky, so I just go with what the robot is telling me to do, and then add a 5% or so safety factor.

Cheers,
Kev

{edit: OK, changes made and uploaded as of this edit. Go to my blog and download it now if you want the latest version.

To see how everything works, I like (106b/lipo/3s/1.95ohm/5%/n2/prmax50). it spreads out the curves so you can more clearly see how it works. Now drop Prmax to 35W. Cool, now change R to 2.5ohm. Too much, now drop Prmax to 15W. Sweet! }

YeeHaw!!! I finally figured out a way to auto scale the axis. The updated file is now on my blog.

BTW, I had to change the formatting of the imax and imin lines since my new method put too many marks to tell the difference between say + and o. So I made them different colors, with a bright teal for imin so we can easily see it when imin=0. I also changed the formatting of the Prrating and Pcrating lines. Now I think it's easier to tell they're both max's and which set of curves they go with (external is all dots and internal is all solids).

As usual, let me know what you guys think about the latest iteration so I can improve it. Fortunately, I think this may very well be the final release of my tool. I wouldn't have done all this work without the help and guidance of rcg members!

Cheers,
Kev

Excellent work Kev, well done and thank you for your dedication to getting it right.

Excellent work Kev! Do you ever sleep? I have deleted my spreadsheets from this thread because they were solving a different problem: I was trying to pick the external resistance such that any valid current could be chosen to keep the iCharger below it's recommended power level.

I also have a recommendation for your spreadsheet: create an error flag when imin > imax which can happen when the power ratings of the resistors are too small. [FYI Kev - if you would like a copy of your spreadsheet that I modified, PM me your email. I do not want to post it here to avoid confusion to others.]

I have created a resistor value table using your spreadsheet as help. The table assumes you have up to 24 of 50W 1 ohm 1% resistors. I found these to the be most economical (in my opinion) for this application because they are about $4. each. Note that you only need more than 12 of these for some specific cell counts and current levels. I have used the same parallel/serial nomenclature as is used with LiPo batteries. For example, 3S2P means 2 strings of 3 resistors connected in series. Both of the strings are then connected in parallel. Also I have supplied some alternate choices if you want to use a smaller number of resistors for some cell counts.

[I can't get the columns to line up right. I thought the CODE tags would use a fixed space font but the "space" seems wrong? ]

Array of 50W 1ohm 1% resistors

  106B+ (6 cell, 7.0A max)
 1010B+ (10 cell, 7.0A max)

LiPo		 n  Current
 1	2S3P   6  6.2A
 2	5S4P  20  6.7A
	 (4S3P  12  6.2A)
	 (3S2P   6  5.5A)
 3	2S1P   2  6.2A
	 (4S2P   8  6.2A)
 4	5S2P  10  6.7A
 5	3S1P   3  7.0A
	 (6S2P  12  7.0A)
 6	4S1P   4  6.2A
 7	9S2P  18  6.5A
	 (5S1P   5  5.8A)
 8	5S1P   5  6.7A
 9	6S1P   6  6.2A
10	6S1P   6  7.0A


LiFe		 n  Current
 1	2S3P   6  6.2A
	 (1S2P   2  7.0A)
 2	5S4P  20  5.7A
	 (4S3P  12  5.3A)
	 (3S2P   6  4.8A)
 3	5S3P  15  6.4A
	 (2S1P   2  5.3A)
 4	7S3P  21  6.1A
	 (5S2P  10  5.7A)
	 (3S1P   3  4.8A)
 5	3S1P   3  5.9A
 6	7S2P  14  6.1A
	 (4S1P   4  5.3A)
 7	4S1P   4  6.2A
 8	9S2P  18  6.3A
	 (5S1P   5  5.7A)
 9	5S1P   5  6.4A
10	6S1P   6  5.9A

---------------------------

Array of 50W 1ohm 1% resistors

  208B (8 cell, 20.0A max)

LiPo		 n  Current
 1	1S4P   4  16.6A
 2	2S4P   8  16.6A
 3	2S3P   6  18.7A
 4	3S3P   9  16.6A
 5	5S4P  20  16.6A
	 (4S3P  12  15.6A)
 6	4S3P  12  18.7A
 7	6S4P  24  19.4A
	 (5S3P  15  17.5A)
 8	6S3P  18  16.6A


LiFe		 n  Current
 1	1S4P   4  14.3A
 2	2S4P   8  14.3A
 3	2S3P   6  16.0A
 4	3S4P  12  19.0A
	 (3S3P   9  14.3A)
 5	3S3P   9  17.8A
 6	5S4P  20  17.1A
	 (4S3P  12  16.0A)
 7	4S3P  12  18.7A
 8	6S4P  24  19.0A
	 (5S3P  15  17.1A)
 9	5S3P  15  19.2A
10	6S3P  18  17.8A

i remember someone from here blowed up his icharger when used external resistance load.
What happened then?

Originally Posted by alex.guzun

i remember someone from here blowed up his icharger when used external resistance load.
What happened then?

Yes, that was Speedflyer who blew his up using 3.15ohms on a 20V pack at 2A. That was the incident that motivated me to analyze the D+ mode. Now with this spreadsheet, we can see how Speedflyer fried his iCharger 106b+.

Kev

Happy Easter Everyone!

Chip Geek, very nice follow up! That list is indeed very useful for those hunting for resistors for D+ mode. Next thing you know, the vendors are going to sell prewired complete resistor kits; I want a cut in the profits if they do, lol.

Normally I get 6hrs of sleep, but once I have my mind set on a challenge, sometimes it's hard for me to put my pen down and go to sleep, lol. I think I inherited my dad's OCD!

Cheers,
Kev

So what's the latesting thinking on Icharger quality, both as to design and workmanship?

I read a comment from Everydayflyer in the Hyperion thread which, I think, said something like, "Just when everything looks good for the Icharger, some new issue comes up."

Now, bear in mind I have a bias for the Icharger (I have a new 1010b+), and so far, (a few days), it seems to be a good "second" charger (after my Hyperion Duo II), with a great price from a very fine American retail seller (progressiverc.com).

So, again, what comments do folks have, good, bad or indifferent (if you don't have one, please say so in your comment)?

Originally Posted by Truglodite

Chip Geek, very nice follow up! That list is indeed very useful for those hunting for resistors for D+ mode. Next thing you know, the vendors are going to sell prewired complete resistor kits; I want a cut in the profits if they do, lol.

Thank you. I will take my "cut" (if there is one) in the form of a 208B.

- Dan

Originally Posted by Mighty Manfred

So what's the latest thinking on Icharger quality, both as to design and workmanship?

I have an iCharger 106B+ and a Hyperion 610i net. I like them both and each one has features that I like the other one does not have. I think the iCharger design is very good and what few workmanship problems there are get taken care of under warranty quickly and easily. I bought the Hyperion first and just recently bought the iCharger for 2 reasons: 1) the 7.0A discharge capability and 2) the Hyperion is in for repair and I couldn't fly without a charger.

Originally Posted by Chip Geek

Thank you. I will take my "cut" (if there is one) in the form of a 208B.

- Dan

LOL Dan, great minds do think alike. Last night I was thinking the exact same thing. The 208b would be suitable compensation!

Kev

Originally Posted by Mighty Manfred

So what's the latesting thinking on Icharger quality, both as to design and workmanship?

I read a comment from Everydayflyer in the Hyperion thread which, I think, said something like, "Just when everything looks good for the Icharger, some new issue comes up."

Now, bear in mind I have a bias for the Icharger (I have a new 1010b+), and so far, (a few days), it seems to be a good "second" charger (after my Hyperion Duo II), with a great price from a very fine American retail seller (progressiverc.com).

So, again, what comments do folks have, good, bad or indifferent (if you don't have one, please say so in your comment)?

I have only owned my 106b+ for little over a week. My other lipo chargers include a Multiplex 5014, Apache 2030, and a pair of cheapy chargers that came with $100 helicopters (one from esky and one from eflight). So for me, the 106 is my primary charger rather than a backup. I won't comment on durability since it's so new, but for sure the precision is great (~0.5% verified by my 0.1% BK Precision 390A multimeter), the features are unbeatable for my purposes (<4s), and it costs less than half of what the competition offers. Not sure what else the duo2 has over the 1010 besides 12s, but I'm sure most ppl running 12s are using 2x6s packs, so a pair of 106's sounds like much a better deal to me.

The only "ding" I'd put on iCharger is the fan. It seems like a cheap one. I bought 3 106b+'s at the same time, one for myself and 2 for my buddies. After a few hours of running, all 3 fans have developed a mechanical clicking noise. It definitely sounds like the bushings are already going bad, rather than PWM pulses. No biggie, since I have an extra ball bearing fan from my pc projects that I plan on dropping in after the stock one fails. Even if I didn't have an extra 40mm fan, I could go to Fry's and get one for a nice ball bearing one for around $5, so IMO this is a non-issue considering the price of iChargers.

Other than that mine has had 0 problems, and I've used it anywhere from 3-12 times per day, leaving it on 24/7. I regularly use the balance, store, expanded discharge, and internal resistance features. It runs cool. I even noted on a very low humidity day last week, my wife and I discharged static electricity (large amounts, that weren't exactly "painless" ) on my iCharger's case at least 10 times without a single glitch.

So far so good,
Kev

I had the 106b+ for a week or so, and I moved to the 1010b+ since the former had an IR measurement peculiarity.

I noticed immediately that the 1010b+ buttons had a firmer mechanical feel, the fan is quieter (a little) and runs far less often.

So far, so good!

The Duo II was bought some time ago to use at home, and to charge or "store charge" large numbers of batteries so I can get to the field faster or reduce the time for storage charging.

I find the Icharger's settings far more intuitive or easier to access.

We have added iCharger Expanded Discharge tool--Spreadsheet in the first page of this post, you can download it there.

Thank you for what Trug have done for it, and thanks for the members here who support us all the time.

Regards,
Junsi