Author Topic: measuring battery capacity used (Read 2896 times)

FLOYD CARTER · « **on:** March 22, 2013, 11:08:10 AM »

It seems like the best way to determine battery power used for one flight would be have a charger that integrates charge current*time to record total power delivered for a charge.

My charger only tells me when "full". I would like to buy a charger with more "bells &n whistles".

Can you provide a recommendation? (did a search, but no joy!)

Floyd

Tim Wescott · « **Reply #1 on:** March 22, 2013, 11:11:24 AM »

My Triton charger from Electrifly does just that -- it reports on the charge stuffed back into the battery. I can't tell you which currently-available ones do, though.

LiPo cells have a very high charge efficiency, so the charge put back in is a good indication of the charge taken out.

Ron Hook · « **Reply #2 on:** March 22, 2013, 04:41:11 PM »

Go to ProgressiveRC.com. They are in the Seattle area and are great guys to work with for chargers. I bought the ICharger 306B along with the Mean Well 1000 watt power supply. The charger will tell you everything about your battery's condition including how many mAH you put back into the battery. Has internal balancer so that all cells are charged to the same level. With this combination of power supply and charger and the purchase of one of their parallel charging boards, I can charge 6 Flight Power 4200mAH batteries at one time. Great time saver. Any questions, please email me for help

Ron Hook

Dan Bregar · « **Reply #3 on:** March 22, 2013, 05:05:23 PM »

Floyd

Ron gives you good info.

http://www.buddyrc.com/icharger-306b.html
http://www.progressiverc.com/icharger-306b.html

James Strickland · « **Reply #4 on:** March 22, 2013, 08:45:53 PM »

another great source is EP Buddy r/c and THE top of the line charger is IMO the FMA Power Lab 8 up to 6 8s packs at once I think 1340 watts max and every feature one could ever imagine and completely PC integratable/ compatable with all kinds of setting memories and menu's

John Rist · « **Reply #5 on:** March 22, 2013, 10:21:33 PM »

Cheep is B6 from Hobby King. I have one of these and so far it works. Have seen reports that some do not do a proper job of balancing the cells. Mine seems to be spot on as checked with a digital volt meter. It does report total charge put back into the battrey. I also like it because it will charge lead acid and nicad battries.

http://www.hobbyking.com/hobbyking/store/__5548__IMAX_B6_Charger_Discharger_1_6_Cells_GENUINE_.html

Cut and paste comment from Hobby King customer revue.

This is just IMAX charger. It's cheap, but all of them suffer the same problem. Voltages they report differ from reality. My charger shows 4.20V on all cells when there is 4.19V, 4.17V, 4.21V, 4.16V, 4.22V, 4.27V. The last value is much too high.
So before you buy one - read threads on rcgroups.com describing how to make it more reliable (resistors change and/or charger calibration).

Like I said mine does not have a balance problem. I guess I just got lucky.

William DeMauro · « **Reply #6 on:** March 23, 2013, 01:47:58 AM »

My last column in Stunt News discussed chargers. James and Ron both make great suggestions. I have 2 I-chargers (306B and 206B) and a Powerlab 8. Those are Some of the better ones. Be careful with anything with the name I-Maxx on it. There are many counterfeits and I would question the safety of any of those. There are many threads on the RC forums on just that topic. I still have some power supplies left if you need one.

John Hammonds · « **Reply #7 on:** March 23, 2013, 08:29:54 AM »

Hi Floyd,
Although you are looking for a better charger. For your immediate question I would recommend the EOS Sentry Battery checker. In my opinion one of these or something very similar should be part of every electric flyers arsenal. It tells you plenty about the state of your packs immediately after a flight.

http://www.amazon.com/Hyperion-EOS-Sentry-Battery-Checker/dp/B003YI94KM

TTFN
John.

FLOYD CARTER · « **Reply #8 on:** March 23, 2013, 01:16:52 PM »

It appears that Hyperion EOS Battery Checker is what I really need. I only want to know the total Amp-hour drain for one flight. Plug this thing into battery and it is supposed to tell me how much capacity is used or remaining.

So I ordered one!

Thanks to all for your help

Dan Bregar · « **Reply #9 on:** March 23, 2013, 03:24:48 PM »

http://www.buddyrc.com/epb-volt-meter.html This is a great little tool I use at the flying field.

Dean Pappas · « **Reply #10 on:** March 23, 2013, 05:39:35 PM »

Hello Floyd,
None, and I do mean NONE of the plug-in-afterward capacity gauges are worthwhile for an accurate measurement.
You need a charger that does exactly what you said: integrates the charging current. My personal choice is anything from the FMA line of chargers.
FMA are the first guys in the entire industry, domestic or import, who did balance charging right, and they are also first who provided cell resistance measurements to tell you how your batteries are aging.
In addition to the real charge measurement, they also have a "fuel gauge" that is based, like ALL others, on a typical voltage/discharge curve.
It too is useless for accurate measurements, but for a given battery brand, once you have calibrated yourself, gives useful RELATIVE instant feedback on how hard this last flight hit the batteries.

Other brands are perfectly fine too!

Regards,
Dean P.

John Hammonds · « **Reply #11 on:** March 24, 2013, 06:31:17 PM »

Quote from: Dean Pappas on March 23, 2013, 05:39:35 PM

[Snip] None, and I do mean NONE of the plug-in-afterward capacity gauges are worthwhile for an accurate measurement. [/snip]

Hi Dean,
I'm not going to dispute your statement for a second. (You have probably forgotten more about ECL than I will ever learn). But just how inaccurate do you consider products like the EOS sentry to actually be? I have 2 chargers (Both Hyperion) and a sentry unit. (Also made by Hyperion). All 3 give me a different %age left reading after a flight. The voltage per cell though agree (To 0.01v). Strangely enough after charging the pack the Sentry unit seems to have given me the most accurate %age left starting figure. For me the important thing seems to be to trust one of them and stick with it. At least that should mean I am comparing apples with apples so to speak. Comparing figures for a fully charged pack gives me identical figures for %age charged and again agrees with the chargers figures to 0.001v resolution per individual cell. I did question the different %age figures I was seeing straight off a model in another thread soon after I bought the Sentry unit but no one commented at the time.

Assuming you are using a charger which is doing it's job correctly I still consider the Sentry unit to be a viable alternative to one of the more pricey chargers, at least for someone like me who is essentially a sport flyer who just happened to go down the electric route and perhaps flys in 3-4 competitions a year.

TTFN
John.

Igor Burger · « **Reply #12 on:** March 25, 2013, 02:38:53 AM »

You can still extend your diplayless charger by such unit which will show you all you need and you can still use it as a measuring equipment for testing your power train :- )))

http://www.hobbyking.com/hobbyking/store/__10080__Turnigy_130A_Watt_Meter_and_Power_Analyzer.html
http://www.hobbyking.com/hobbyking/store/__6380__Watt_Meter_Power_Analyzer_Watts_up_Ver_2_.html

Dean Pappas · « **Reply #13 on:** March 25, 2013, 08:55:07 AM »

Hi John,
I've seen the instant fuel gauges read something like 15% left and then the battery took only 65 or 70% to fully charge it. That's missing by a factor of 2.
Other times they were pretty close. Exactly why I couldn't say, except that a one size fits all batteries and post-flight temperatures approach is fundamentally lacking.
In an attempt to make this better some manufacturers are providing for selectable discharge vs voltage curves in the calibration memory.
I think that's way too much fuss. If flying 4 cells, then cost is not a problem.
Putting that integrating coulometer in front of the battery as Igor suggests sure will work, though.
Regards,
Dean

Mark Scarborough · « **Reply #14 on:** March 25, 2013, 10:52:12 AM »

Dean,
went to the website for FMA products,,
I see "battery workstations" versus chargers,,

do you have any personal experience regarding the specific units?
Ultimatly I would like to be able to charge two packs ( with separate start times)
so as I finish a flight, I can plug in and start charging the pack after it cools
I had a Hyperion, but one channel took a dump so now its just an expensive one channel charger,,

Dean Pappas · « **Reply #15 on:** March 25, 2013, 09:03:52 PM »

Hi Mark,
If you are willing to charge at 1C, two CellPro 4S'es at $60 apiece is what I'd do.
Dean

Mark Scarborough · « **Reply #16 on:** March 25, 2013, 09:47:31 PM »

Thanks Dean, I appreciate your response,
I will look those over a bit closer

John Hammonds · « **Reply #17 on:** March 26, 2013, 05:06:11 PM »

Hi Dean,
Thanks, I might buy another Sentry just to see if it at least agrees with the original. I guess most manufactures have there own way of calculating state of charge, and at least sticking with the figures from just one of my available options will give me a consistent baseline. Slightly perplexing though that in my case it's all Hyperion gear but I suppose calculation parameters are constantly updated (My chargers are a bit long in the tooth now).

Thanks again.

TTFN
John.

Dean Pappas · « **Reply #18 on:** March 27, 2013, 07:21:56 AM »

Hi John,
Whatever works is good, right?
As long as battery chemistries and constructions keep subtly evolving, those calculations will always be out of step.
It's nice to be able to count on things like that.

take care,
Dean

FLOYD CARTER · « **Reply #19 on:** March 27, 2013, 02:23:42 PM »

So, if nothing else works right, or is accurate, then I will put up a 5 1/2 min flight. Back on the ground I will run the motor until the same battery starts to poop out. That will give me all the information I need, and without any special electronic gadgets!

Floyd

Dean Pappas · « **Reply #20 on:** March 27, 2013, 08:11:27 PM »

Except that you risk wounding your batteries by doing that.
later,
Dean

Howard Rush · « **Reply #21 on:** March 27, 2013, 10:09:14 PM »

I don't think it will tell you much. A prop running at 0 airspeed takes a whole lot more power than one running in an airplane. You could either pony up for a charger that integrates charge or do it yourself with an ammeter, a clock, and a pencil.

Dean Pappas · « **Reply #22 on:** March 28, 2013, 07:54:15 AM »

True though static running current is typically between 133% and 150% of the in-flight average.

Dean

FLOYD CARTER · « **Reply #23 on:** March 29, 2013, 09:35:44 AM »

My charger current tapers off when it gets something approaching full charge. Then it takes 15 min or more charge and current steadily drops off. I charge with a AC-powered lab power supply that has V and A meters. Kind of hard to do an integration when charge current is so variable.

Floyd

Howard Rush · « **Reply #24 on:** March 29, 2013, 05:16:18 PM »

Here's what you need: http://labjack.com/u3 . As a EE, you should have one anyhow.

Even better would be to record voltage and current during discharge. I got me one of these, but I haven't done anything with it yet: https://www.sparkfun.com/products/8627 .