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wall charger and 6V - NiMH battery

Old 07-13-2013, 09:44 AM
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jcvt
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Default wall charger and 6V - NiMH battery

My wall charger is rated 4.8 V. , but is actually producing 5.25V ,I don´t understand how I am able to charge a 6V - NiMH battery .
The battery is marking 7.05 V.
Could some one explain it to me.
Old 07-13-2013, 10:33 AM
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Rodney
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Default RE: wall charger and 6V - NiMH battery

If you measure the voltage output on your charger with no load connected (output leads have nothing other than the voltmeter on them) you will find that the voltage is quite a bit higher than you think. If that voltage is greater than the fully charged voltage of the battery you connect to it, it will charge it. How fast? Hard to say without knowing the internal resistance of the charger and the open circuit voltage. It will take longer to charge the 5 cell battery than it did to charge the 4 cell battery if both are equally discharged.
Old 07-13-2013, 11:02 AM
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jcvt
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Default RE: wall charger and 6V - NiMH battery

That is the thing, I measured the voltage output on my charger using a voltmeter and is 5.25 for the futaba and 4.75 for the airtronics. I am lost here.!!
Old 07-13-2013, 11:38 AM
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Default RE: wall charger and 6V - NiMH battery

Neither one have high enough voltage to charge it.
Old 07-13-2013, 12:23 PM
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jcvt
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Default RE: wall charger and 6V - NiMH battery

Well, the battery is showing 7.05 V and I have been flying for over a year... We are missing something here...... Others people are using the same thing, I just don´t get it..
Old 07-13-2013, 02:10 PM
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Default RE: wall charger and 6V - NiMH battery

Maybe the charger puts out more voltage under load?
Old 07-13-2013, 02:16 PM
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A.T.
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Default RE: wall charger and 6V - NiMH battery


ORIGINAL: jcvt My wall charger is rated 4.8 V. , but is actually producing 5.25V ,I don´t understand how I am able to charge a 6V - NiMH battery . The battery is marking 7.05 V. Could some one explain it to me.
Not possible to measure the voltage without the battery being attached, this to provide some load/resistance,
and varies greatly between brand of charger. (see graph attached pic #1).
Wall chargers can be used to charge both 4 & 5 cell NiMHBattery packs as also attached.

Much more information available under sub section:
"Battery Care, Performance & DIY Battery Packs."
at
Alan's Hobby, Model & RC FAQ Web Links

Alan T.

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Old 07-13-2013, 08:20 PM
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jcvt
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Default RE: wall charger and 6V - NiMH battery

After reading all possibles posts in all the Internet forums, I got two conclusions:

1)Wall chargers can be used to charge both 4 & 5 cell NiMH.
2)Wall chargers can´t be used to charge both 4 & 5 cell NiMH.

Why so many opinions with this topic!!
Old 07-13-2013, 08:34 PM
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Default RE: wall charger and 6V - NiMH battery


ORIGINAL: jcvt
After reading all possibles posts in all the Internet forums, I got two conclusions:
1)Wall chargers can be used to charge both 4 & 5 cell NiMH.
2)Wall chargers can´t be used to charge both 4 & 5 cell NiMH.
Why so many opinions with this topic!!
There are many old school stories spread around by a few who know a little about many things,
but have never actuially spent time within the particular industry nor been qualified to talk about it.
Reason for variance in performance was explained in the article attached previous post.
The many different chargerswere not built to the same standards.
e.g. Those prior to switchmmode regulator typesprovided by Futaba were ofmuch cheaper constructionthan those
included with the JRsystems.
Chargers alsovaried between countries as with many systems,each distributor would buy in chargers from a company in Korea or Taiwan
to suit the sockets, voltages and by laws of their own country and simply stick say a Futaba labelon the charger being their right
as the authorised distributor. No known brand has ever manufactured their own chargers.

Alan T.
Old 07-13-2013, 08:37 PM
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Default RE: wall charger and 6V - NiMH battery


ORIGINAL: jcvt

After reading all possibles posts in all the Internet forums, I got two conclusions:

1)Wall chargers can be used to charge both 4 & 5 cell NiMH.
2)Wall chargers can´t be used to charge both 4 & 5 cell NiMH.

Why so many opinions with this topic!!
We have been using wall chargers for many years to charge both 4.8v and 6v NiCad and NiMh batteries. The wall charger charges at such a low rate (50ma-100ma) it is basically a trickle charge for most Tx and Rx batteries used today. Don't use it for Lithium batteries. The Wall charger gives you no feedback as to what the state of the charge is, so it is possible to Overcharge a pack. It still is adequate. I prefer to use a Peak charger that can Cycle the batteries when necessary and anticipates when the pack is close to peak voltage.

I have no idea why anyone would suggest that it could not be used for both 4.8v or 6v packs commonly used today.
Old 07-14-2013, 01:55 AM
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Default RE: wall charger and 6V - NiMH battery

Excellent description of what is occurring. I use a charger made by ACE R/C that is adjustable to suit the battery pack being charged. Other manufacturers make similar units all you have to do is a internet search. Once you find a charger than go to EBay and purchase it from a vender.
Old 07-14-2013, 03:30 AM
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Default RE: wall charger and 6V - NiMH battery



Common on people, in the past wall chargers That came with transmitters had an extra port to charge NiMh batteries, it is trickle charge so you have to leave it overnight. But it works.



I change now to LiFe for my receiver packs, but when I was using NiMh never had a problem charging them overnight w the wall charger the transmitter came with.

Old 07-15-2013, 05:55 AM
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Default RE: wall charger and 6V - NiMH battery

I use the DVM from ace Rc. They work great. So if you can locate any of those your will be golen. They have two charge outlets and you can set how many mah you want to charge your packs! For 0 to 250 mah. So you can charge up to 2500 mah pack. 4 or 5 cell. I have been using them for years and never had a problem what so ever.. Hope this helps some..
Old 07-15-2013, 07:25 AM
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Default RE: wall charger and 6V - NiMH battery

The charger in question is most likely rectified AC without much if any filtering. The average voltage you read with a DC voltmeter is quite a bit lower than the peak voltage. The peaks will charge a battery to a level higher than what you read a
s the average voltage
Old 07-15-2013, 07:35 AM
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Default RE: wall charger and 6V - NiMH battery

+1!
When I was still running 5 cell Nicd's for receiver packs, I used the Futaba wall-wart that came with the 9C, (110mA on the receiver output) it fully charged the 5 cell 1100mAh Nicds I was using at the time with no problem, as confirmed by my good old Digipace II.
The only Nixx cell I use today is a glow igniter!
Pete
Old 07-15-2013, 05:13 PM
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Default RE: wall charger and 6V - NiMH battery

Jvt, Take it from an old tech. Over 50 years now. Started in the Navy. The only way you can tell how well the wall charger is charging a five cell pack is to put an ampmeter in series while you are cahrging it. If it says 50 ma at 4.8 it will be lower for a 6 volt pack. How much depends on the charger. It will charge a 6 cell pack. It just takes longer. If you are using a 5 cell 600 ma pack, It won't be fully charged in the same amount of time as a 4 cell pack. Any way it works. It just takes longer. Sam
Old 07-16-2013, 04:42 AM
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Default RE: wall charger and 6V - NiMH battery

If you want to know what your peak voltage is on the charger, just put a small capacitor on the output leads (no other load) and measure the voltage with a DC voltmeter. The capacitor will charge to the peak voltage as long as no other load is on it. If the voltage is not regulated, a conventional ammeter will not accurately measure the current being put into the battery. If you have an RMS (root mean squared) ammeter, you will get the correct reading but such an instrument is not commonly available.
Old 07-16-2013, 09:37 AM
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Default RE: wall charger and 6V - NiMH battery

I'm sorry, but the current going into the battery is DC. There is a diode in the wall wart along with a AC transformer. The transformer is wound so that the voltage on the secondary side is high enough to deliver the the charge rate that the manufacturer intended the batteries be charged at. Typically this is a C10 rate or one tenth of the capacity of the battery. For a 600 Ma battery that would be 60 ma. The output of the charger is rated by power and if you charge a battery with a higher voltage the current will go down. You can only charge a battery with so many volts as the secondary winding will only put out so high a voltage. Ohms law has never changed. You can measure the current with a DC meter. I do it all the time. These are trickle chargers so as not to ruin a battery if you forget and leave it on charge all week. The diode in the charger will only let current flow one way and typically drops approximately .6 of a volt across it. What you will se if you look at that voltage wih an ocilliscope is DC with AC ripple on it. When you hook up the battery, it will fillter out the ripple and you end up with DC. I just measured two of my Futaba wall wart chargers. One is rated at 50 ma, the other at 100ma. On a 4.8 votlt pack the 50 ma charger delivered 60 ma and the 100 delivered 118 ma. On a 6 volt battery the 50 ma charger delivered 45 ma and the 100 ma charger delivered 95 ma. Not a great difference. So feel free to charge a 6 volt battery. Just remember it will take a little longer.
Old 07-17-2013, 10:07 AM
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Default RE: wall charger and 6V - NiMH battery

Sorry Hellcat1, unless the laws of electricity have change since I got my degree in EE and spent some 50+ years in the practice, the output of an unregulated/unfiltered rectified AC charger is pulsating DC which can not accurately be measured with the typical DC ammeter. Depending on the circuitry within the meter, the current will usually read 1.44 times higher than the actual current if it looks at the peak instantaneous current. In any case it will NOT be a measure of the actual average current. Now you can get a meter that will account for the pulsating current but they are a bit more expensive and complicated than your typical run of the mill VOM. Also, that 50 or 100 milliamperes is not a trickle current. Trickle current is defined as that amount of current that just compensates for the leakage current which can vary from few microamps to a milliamp or two. The actual value will depend on age of the battery and the temperature. The 50/100 or ??? current put out by the typical wall wart is better defined as slow charge current, definitely not trickle current. Of course, in spite of all this, that wall wart will effectively charge either a 4 or 5 cell battery very adequately given the time. I still charge my receiver batteries using them in liu of the fast chargers as it is much easier on the battery. I have some NiCads that still perform well after 10 years of use.
Old 07-19-2013, 08:10 PM
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Default RE: wall charger and 6V - NiMH battery

Rodney, I agree with you that the wall wart is easier on the batteries than a fast charger. I don't agree that the current is pulsating DC with the battery connected. The battery filers out the ripple and the current becomes DC. Then the charger is no longer unfiltered. You and I will continue to disagree on this so there is no need to continue my intrepretation of things anymore. Just take a look at the voltage on the battery with a scope and you can see what I am saying is true.
Old 07-20-2013, 07:17 AM
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Default RE: wall charger and 6V - NiMH battery

What you need to look at is the current flow. If you do that you will see that current only flows when the voltage out of the transformer is greater than the battery voltage. This will show up as small bursts of current when the rectified AC voltage out of the transformer exceeds the battery voltage. These burst of current will be at 60 bursts per second if a half wave rectifier is used, 120 bursts per second if full wave rectification is used. The real current (not accurately measurable with most ammeters) will be the average of those periodic bursts of current. If you have access to a very sensitive clamp on ammeter and an oscilloscope you can easily see the bursts of current by monitoring the clamp on meter.
Old 07-21-2013, 12:53 PM
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Default RE: wall charger and 6V - NiMH battery

Rodney, I will concede to your higher education. With the equipment that I have, I looked across the battery with a scope and see a 20 mv 60cps pulse. I do have a AC clamp meter. It reads the same current as I read with a DC meter in series with the battery lead. I don't think a 20mv ac pulse will make my clamp AC ampmeter that accurate as it isn't that senitive. I'm sure it has a sample rate and that is why is is reading anything at all. I really think my ignorance is probably what started all this and we were both trying to make things too technical. It has been stated several times in this forum that you can use a wall wart to charge the higher voltage battery and that was the question in the first place. I apolize. Sam
Old 07-22-2013, 06:31 AM
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Default RE: wall charger and 6V - NiMH battery

You are right Hellcat, we tend to get to technical at times but I do not think that is to bad in most cases. I know I make a lot of mistakes and appreciate it when someone politely corrects me. My dissertations were in no way meant to be abusive or degrading and I'm sorry if they were so taken.

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