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Batteries, what the?

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Batteries, what the?

Old 07-26-2012, 11:19 PM
  #1  
djmp69
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Default Batteries, what the?

Ihave a plane running a DLE55, with a 4.8v, 2400mah NiMh batt for ignition. If I remember right, I used to be able to get at least 4 flights out of that config. Now days, After one flight on a "full" overnight charge, the voltage check reads just like it always has, just over 6 volts. However, after one flight, voltage drops down to the 5.39 range. I figured, ok, maybe I fried the battery, so I get a new one, same specs. Overnight charge at 125 mah, got to the field about a 1/2 hour later, voltage had dropped to about 5.7, and after one flight, you guessed it, right around 5.4. I haven't tried to fly beyond this point, should I? Maybe the voltage will hover around after the drop, but should I take the chance?

And please, to some of you this may have been asked before, and may be a rookie question, but all of our learning started somewhere, so please no snippy comments about how I should know this already, or check the search engine, or "dude, just use an IBEF, why are you screwing aroud with..."

I'd really just like to know if there's something I'm missing or if this is normal...

Thanks in advance!
Old 07-27-2012, 02:50 AM
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Kaos Rulz
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Default RE: Batteries, what the?

Your battery is looking good if your getting an initial voltage reading of over 6v for a 4.8v battery. It is not uncommon to lose a few tenths of a volt initially, and after a couple of flights the volatge should read at, or above, the battery's rating. In this case 4.8v. In fact you should be able to fly after the voltage dropps to 4.6v. With a good battery, properly charged, you will notice its voltage will stay at the 4.8v for a good while before dropping below 4.8v.
Now the main thing I noticed with your post is you're not getting the best charge for your batttery by charging at the 125 ma rate. Even for an onernight charge you should be at least at a c-10 charge rate. In this case 240 ma. I usually charge at the c-10 rate plus 10%. That equates to about 265-275 ma, depending on how accurate your charger is. These batteries can take a higher charge rate, but I like to baby my batteries and charge slow in hopes of battery longivety.
Old 07-27-2012, 02:51 AM
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tomfiorentino
 
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Default RE: Batteries, what the?

On the upside there is probably a lot less variation with the electrical demands of an ignition than say your servo set up. So this shouldn't be too hard to figure out.

I know you stated that there is a change from your personal experience and history with this battery. But as an additional check, I would find out about what the DLE ignition uses in mah per 10 minutes or whatever...that should be pretty standard and someone here probably knows that answer from experience. It wouldn't matter what airplane the engine was in and it would be a good reference because everyone using that engine would have a similar experience (not much variation).

Also, regarding your specific battery, I would record and verify capacity by putting it through 3 charge/discharge routines. It is either a capable little chemical engine or it isn't! What you are seeing with it now may simply be telling you that the battery isn't good anymore!

Very good that you are aware of what is going on with your equipment and you may have caught an issue with your power system!

Let me know should you get additional information, and don't "try" additional flights...it isn't worth the risk.

Tom
Old 07-27-2012, 03:02 AM
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telejojo
 
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Default RE: Batteries, what the?

I use 4.8 2500 packs I put from eneloop and can fly all day on a full charge.
Old 07-27-2012, 05:30 AM
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JohnBuckner
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Default RE: Batteries, what the?

As Kaos Rulz pointed out already you are are likely not fully charging the battery at 125ma overnight you need to charge at C/10 or perhaps slightly over that rate.

John
Old 07-27-2012, 06:04 AM
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Mustangman40
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Default RE: Batteries, what the?


ORIGINAL: Kaos Rulz

Your battery is looking good if your getting an initial voltage reading of over 6v for a 4.8v battery. It is not uncommon to lose a few tenths of a volt initially, and after a couple of flights the volatge should read at, or above, the battery's rating. In this case 4.8v. In fact you should be able to fly after the voltage dropps to 4.6v. With a good battery, properly charged, you will notice its voltage will stay at the 4.8v for a good while before dropping below 4.8v.
Now the main thing I noticed with your post is you're not getting the best charge for your batttery by charging at the 125 ma rate. Even for an onernight charge you should be at least at a c-10 charge rate. In this case 240 ma. I usually charge at the c-10 rate plus 10%. That equates to about 265-275 ma, depending on how accurate your charger is. These batteries can take a higher charge rate, but I like to baby my batteries and charge slow in hopes of battery longivety.

I agree,
those are good numbers out of a 4.8.....
I wouldn't worry at all with them above 5, that is still a good number on 4.8... I am setting up a DLE55 on a pitts right now, I will let you know what battery I go with and what kind of numbers I get...Good thread.

Jimbo
Old 07-27-2012, 07:11 AM
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raptureboy
 
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Default RE: Batteries, what the?

Taken from the Hangtimes.com web site. Great info, great batteries.




Q: What's up with 'Formation Charging'? Can't I just charge and fly a new pack?
*
A: The term 'Formation Charging'describes the initial charge/discharge 'forming'process that fully activates the 'chemical engine' and balances the cells in a new pack. NiMH packs have a particular need for repetitive c/10 charge/cycle conditioning, a 'break-in' procedureneeded to get them to full rated capacity.Both NiMH and Nicad packs benefit from the process and the intent is to make sure that any new pack has been verified to be fully operational and that a 'start-up' capacity number is established for the pack before it's put into service. To 'Form' a new NiMH packdo three10% 16-24 hour charges followed by a 300 to 500 ma discharge routine between each charge.In other wordsoa slow charge at the slow charge rate (or as close to it as you can reasonably get with your equipment) as shown on the pack label. Charge till the pack is warm, followed by a controlled discharge with a cycler. Do it 3 times. The recommended Formation Charge/ Slow Charge rate for our packs is printed right on the label of the pack as well as on the data card the pack was shipped with. New Nicad packs should get at least oneslow charge followed by a 300 to 500ma discharge.Record the capacity numbers reported by your equipment for comparison cycling as the pack ages. Never check your brain at the door! As one respected modelerput it, "There's nothing more suspect than anew battery pack." Before you fly anybody'spack be certain it's fully operational and safe to fly.
*

Q: How do I know if my pack is fully charged?
*
Temperature is the key.. always, always, always! IF THE PACKAIN'T WARM AT THE END OF THE CHARGE ROUTINE, IT AIN'T CHARGED! NoteI said 'warm'. Not HOT! Hot is NEVER GOOD at the end of the charge routine.. but warm is OK. If using a temp probe, set it for 10 degrees above AMBIENT. If it's a peak controlled charger and the charger shuts down before the pack is slightly warm to the touch.. IT AIN'T FULLY CHARGED. If it's a timer controlled charger and at the end of the charge period the pack is not warm.. it's NOT fully charged yet! By far and away the biggest reason for low capacity numbers is undercharging.. if you have a 5 gallon pail with only 3 gallons in it, your only gonna get 3 gallons out of it. Engage your brain.. check temperature at the end of the charge routine!
*
Q: Temperature??I thought voltage washow you could tell the pack was charged??
*
A: More packs have been fried by guys looking for a 'number' instead of temperature on a chargerthan any other causeof premature battery failure. The 'finish' voltage of a pack will vary under an astounding number of variables.. but temperature rise ALWAYS signalsthat the cells arechargedin a slow charge routine.Why? Because when the cells can no longer absorb the energy being shoved at them by the charger, they begin to give the unstored energy off as heat.
-
Taking the Temperature story to the next level.. fast charging. Here we can generate even more heat. Some high-impedance cells like AA NiMH's can get warm when being charged at 'normal' 1C (fast)or even 10% (slow) rates. They can get warm BEFORE they get to full charge.Why? Because high-impedance cells don't absorb energy as efficiently at high current levels.. just like they don't give up energy efficiently at higher discharge rates. So.. before you crank up the current on your charger on your new NiMHTxpack.. check the pack label on our packs.. and set the charge rate recommended; which is often LESS than the 'industry standard' forNiMH cells.
Finalword on temperature: Aside from being a key indicator for correct charge time, rate and final charge condition bear in mind that heat is the bitter enemy of NiMH Cells. Drive the pack into thermal overload (hot) on the charger andit's likely you'll ruin it. Pay attention to the temperature!
Old 07-27-2012, 07:38 AM
  #8  
djmp69
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Default RE: Batteries, what the?

Thanks everyone, really good info! 

This was happening on a batt that I'd had for a while, and I thought maybe the battery was fried or just bad.  I'd bought a brand new one, "formed" it, watching the temperature, and even that one was doing the same thing.  I totally agree with Tom's advice, not "trying" additional flightsforget the fact that I really like the plane, it's just not plane safe (pun intended).

The first battery I know was probably bad because I'd had it for a while and did more quick charges than I should I'm sure.  I'm going to continue to get another new one, and keep the current one if for nothing else as a backup.

PS, I will say that as a few of you have pointed out, I suspected the wall charger I have just wasn't enough, so I set up my field charger to  charge at 200-300.  The result was the same.  Cycled it.  Same thing...
Old 07-27-2012, 01:14 PM
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Default RE: Batteries, what the?

We used to have a Nicd supplier here in town. I got a tour one day. The tour guide said no less than 1 volt per cell. 1.1 volt was even better for a bottom voltage.

Ken
Old 07-27-2012, 01:58 PM
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Gray Beard
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Default RE: Batteries, what the?

Cycle!!!!!!!!! I have found that all brand new NIM and NICAD packs need to get cycled at least four times then follow the C rating, your not getting a full charge. Different ignitions also draw different rates, I recall the original Zinoah G-20 ignition would suck the life out of a fully charged pack.
Anyway, charge and cycle.

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