SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jan 19, 2015, 12:47 PM
Registered User
Joined Mar 2006
181 Posts
Discussion
how do I check a Li battery without crashing the plane

I am like most of us the first nice day of spring or late winter you charge your batteries and check the batteries with your cell checker. Take out your pride and joy plane and take off you are on climb out and the battery goes DEAD
you know in your brain that you need to push the stick forward get up air speed, turn and land.
BUT brain dead .......... you hold in up till it crashes

There has to be someone or something that will tell us that the battery is gone, dead, kaput... besides taking off and crashing
I have read something about IR check and then other people say that that doesn't make any difference. what do really smart people do.

please help

tom
chem teacher2 is offline Find More Posts by chem teacher2
Last edited by chem teacher2; Jan 19, 2015 at 12:49 PM. Reason: said the wrong thing
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 19, 2015, 01:15 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,291 Posts
I don't know what the really smart people do but here's a simple test.


Measure the IR like this.
LiPo INTERNAL RESISTANCE (13 min 30 sec)


Run the test on the packs you have and compare the IR of the packs that work good and those that don't.
Now measure an unknown (performance wise) pack and measure the IR. Compare to the IR results you obtained on the good and not so good packs. It will be an indicator of how the pack will work in the air.

Note - All measurements should be made at nearly the same temperature.



I'd use it only for comparison of your packs and not as an absolute IR measurement for comparison to other members IR results.

Other IR testing info:
https://www.google.com/search?q=IR+t...utf-8&oe=utf-8

tom, remember that as a rough approximation for many reactions the rate of reaction doubles for every 10C rise in temperature and vice versa.
How cold was it?
Were the packs cold?
hoppy is offline Find More Posts by hoppy
Last edited by hoppy; Jan 19, 2015 at 01:24 PM.
Reply With Quote
Old Jan 19, 2015, 04:42 PM
Registered User
Joined Jan 2007
335 Posts
Quote:
Originally Posted by chem teacher2 View Post
I am like most of us the first nice day of spring or late winter you charge your batteries and check the batteries with your cell checker. Take out your pride and joy plane and take off you are on climb out and the battery goes DEAD
you know in your brain that you need to push the stick forward get up air speed, turn and land.
BUT brain dead .......... you hold in up till it crashes

There has to be someone or something that will tell us that the battery is gone, dead, kaput... besides taking off and crashing
I have read something about IR check and then other people say that that doesn't make any difference. what do really smart people do.

please help

tom
Question:
Was this battery used to run your electric motor up front, or was it used for receiver power? If it was to run your motor up front, does your ESC use a "Linear" voltage regulator, or a "Switch Mode" type of voltage regulator.

Some of those linear regulators can overheat, shutting down their 5 Volt DC output, shutting down your receiver, and your model goes in.

IR checks are quite valuable for LiPo battery types. The actual load test described in the above video is one way of doing it.

What I've done is to use a wattmeter in between your battery and ESC, and run up your motor and its prop to about 3C and about 10C. The exact value is not critical.

Measure the battery Volts and Amps at 3C, and again at 10C.

The total Ri for the entire battery pack will then be as follows:
Ri=(V3c-V10c)/(I10c-I3c)

For a 2200 Mah three cell pack, 3C would be 6.6 Amps, 10C would be 22 Amps.

So if you get 11.1 and 10.5 Volts at the two currents, Ri for the entire pack is as follows:

Ri=(11.1-10.5)/(22-6.6) which equals 0.038 ohms for the entire pack or about 0.012 Ohms (12 MilliOhms) per cell.
vollrathd is online now Find More Posts by vollrathd
Reply With Quote
Old Jan 19, 2015, 09:43 PM
Bombs away! Err...landing
Ira NZ's Avatar
Upper Hutt, New Zealand
Joined Apr 2006
2,412 Posts
Quote:
Originally Posted by chem teacher2 View Post
I am like most of us the first nice day of spring or late winter you charge your batteries and check the batteries with your cell checker. Take out your pride and joy plane and take off you are on climb out and the battery goes DEAD
you know in your brain that you need to push the stick forward get up air speed, turn and land.
BUT brain dead .......... you hold in up till it crashes

There has to be someone or something that will tell us that the battery is gone, dead, kaput... besides taking off and crashing
I have read something about IR check and then other people say that that doesn't make any difference. what do really smart people do.

please help

tom
The quickest and easiest is to just hold onto the plane and hit the throttle. No extra equipment needed. If the power is going to die off too much to fly it will be obvious.
Ira NZ is offline Find More Posts by Ira NZ
Reply With Quote
Old Jan 20, 2015, 03:30 AM
Registered User
United Kingdom, England, Southampton
Joined Oct 2013
2,317 Posts
Quote:
Originally Posted by chem teacher2 View Post
I am like most of us the first nice day of spring or late winter you charge your batteries and check the batteries with your cell checker. Take out your pride and joy plane and take off you are on climb out and the battery goes DEAD
you know in your brain that you need to push the stick forward get up air speed, turn and land.
BUT brain dead .......... you hold in up till it crashes

There has to be someone or something that will tell us that the battery is gone, dead, kaput... besides taking off and crashing
I have read something about IR check and then other people say that that doesn't make any difference. What do really smart people do.

please help

tom
"I don't know what the really smart people do but here's a simple test"
This. It is totally obvious to us smart people. And to every full-size pilot still alive. Both the learning and the full power run.

1) They learn how to do 'forced landings without power'

And if low, NEVER try to turn and get back to the runway!!!

2) First day of the season and any other time you see fit ? Do a full power test for half a minute or so at home. You don't have to use 'instruments', measure IR, and all that nerdy stuff.
Mark Powell is online now Find More Posts by Mark Powell
Last edited by Mark Powell; Jan 23, 2015 at 05:16 AM.
Reply With Quote
Old Jan 20, 2015, 03:45 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,638 Posts
When it happens and it happens to most people at some time or another - despite what they say !

The shout of 'OH SH** !!' is made ....

You then slam throttle closed and then open again to get that last few secs of any juice left ...

Down elevator and glide into the bushes / corn / crap !

Then go on the "Hunt a Model" trek !

Hi Denny : OP did say he was holding UP elevator - so that indicates his Rx is working ... so I would think he's talking motor power has died ...

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Jan 20, 2015, 04:26 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,638 Posts
Here's my T45 'dieing' shortly after launch ....

22-07-2012 Lanyu T45 (2 min 16 sec)


Note the keep her level and let her land as she needs ...

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Jan 22, 2015, 08:41 AM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,390 Posts
Telemetry.
Julez is offline Find More Posts by Julez
Reply With Quote
Old Jan 22, 2015, 08:53 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,638 Posts
Quote:
Originally Posted by Julez View Post
Telemetry.
That's fine ... but given the scenario OP mentions - it would make little difference. As I read it ... basically all great on launch, sec's later no motor power .... batterys dead but he had Rx power.

??

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Jan 22, 2015, 02:31 PM
Registered User
Joined Jan 2007
335 Posts
Quote:
Originally Posted by solentlife View Post
When it happens and it happens to most people at some time or another - despite what they say !

The shout of 'OH SH** !!' is made ....

You then slam throttle closed and then open again to get that last few secs of any juice left ...

Down elevator and glide into the bushes / corn / crap !

Then go on the "Hunt a Model" trek !

Hi Denny : OP did say he was holding UP elevator - so that indicates his Rx is working ... so I would think he's talking motor power has died ...

Nigel
Way off topic, but I've been using those overweight, oversized, undervoltage A123 cells for power in my models. And, after more than 6 years of flying with over 100 cells, I've never had one quit in flight. As long as you don't fly more than 75% of the battery or so.

I've got one cell from a club member that was left dead, 0.5 Volts for over a year. It still puts out 15 Amps at rated voltage, but won't hold a charge for more than a month.
vollrathd is online now Find More Posts by vollrathd
Reply With Quote
Old Jan 22, 2015, 05:49 PM
Registered User
Joined Mar 2006
181 Posts
thank you I have more ideas
and I have a better understanding of IR
I have kept three flight packs that have taken a dump but came off the charger looking good on the cell checker. I did the 60 second full power test described above and I think I have found a winner. In every one of the "bad" batteries gave a clear indication of a problem in that 60 second test. A good battery did not seem to sag in the first 60 sec test.

I do know that you should just glide in and not turn around but our field is on a canyon rim so gliding straight forward is not an option

wallradthd thank you for your input I have not tried to fly the A123 because of their energy density but might be fun to try a pack

thank you all again all knowledge is power

tom
chem teacher2 is offline Find More Posts by chem teacher2
Reply With Quote
Old Jan 22, 2015, 08:17 PM
Registered User
Joined Jan 2007
335 Posts
Quote:
Originally Posted by chem teacher2 View Post

vollrathd thank you for your input I have not tried to fly the A123 because of their energy density but might be fun to try a pack

thank you all again all knowledge is power

tom
Just got some new A123 2500 Mah cells today from EVDM Corporation.

They are located at
http://assets.buya123batteries.com
http://www.buya123batteries.com/ANR2...300475-306.htm

These cells do put out 2500 Mah, compared to the 2100 Mah of the older A123 2300 Mah cells.

Just a note. These cells do NOT come with solder tabs, so trying to solder copper tabs to them with a 40 watt iron won't work. Period.

My Weller 100 Watt temperature regulated soldering iron did the job well.

In a model application, it takes four A123's to replace a three cell 2200 Mah LiPo. At 2.5 ounces each, that is 10 ounces. These cells put out 2.85 Volts per cell at 25 Amps. So, four cells times 2.85 volts per cell equals 11.4 Volts. I don't run mine much over 35 Amps per cell.

The actual voltage on these cells is around 4% higher, due to the voltage drop on the #12 test lead wires.
vollrathd is online now Find More Posts by vollrathd
Last edited by vollrathd; Jan 22, 2015 at 08:26 PM.
Reply With Quote
Old Jan 23, 2015, 01:34 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,638 Posts
Quote:
Originally Posted by chem teacher2 View Post
.......I do know that you should just glide in and not turn around but our field is on a canyon rim so gliding straight forward is not an option .......
tom
In that case - then it's try keep nose down and forward speed and keep turns FLAT ... use the rudder more than the ailerons ....

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Jan 23, 2015, 05:27 AM
Registered User
United Kingdom, England, Southampton
Joined Oct 2013
2,317 Posts
---
Mark Powell is online now Find More Posts by Mark Powell
Last edited by Mark Powell; Jan 23, 2015 at 05:36 AM.
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion How well do accounts get checked for double registration? SoloProFan Site Chat 12 Jan 22, 2015 04:41 PM
Discussion How often do you CRASH your plane? Petepala1961 Sailplane Talk 47 Sep 06, 2014 11:53 PM
Discussion How do you guys do a range check? Demo7 FPV Talk 5 Jan 24, 2014 05:38 PM
Discussion Accucell-8150 - How to check voltages of my pack without doing any (dis)charging? kaon Batteries and Chargers 13 Sep 05, 2010 01:09 PM
How do you Crash a plane without flying it ? OzzieFlyer Electric Plane Talk 25 Feb 20, 2004 03:52 PM