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Old Oct 18, 2001, 09:06 PM
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Curitiba , Brazil
Joined Oct 2001
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Charging packs

Hi Guys, I'm really new to this hobby, and I didn't even flight yet.
I've just received my radio this afternoon.
I've bought my foam plane (plane, motor, bat) here(Brasil) , and order from your country, the radio gear and a charger.
My problem is that the guy who sold the airplane said it would come with a 7 cell 800mah,but it came with a 8 cell 800 mha. so I bought a hitec 315+ peak charger. It says that it can charge from 5 to7 cell from 1200 to 200 mha.CAn I still use it to charge my 8 cell 800 mha??
Can I use the charger that comes with the radio ( hitec focus 4) to charge my bat pack?( I know tht it is not a peak ch. but can I use it?
Sorry about my broken english....
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Old Oct 18, 2001, 11:25 PM
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Kevin Murray's Avatar
USA, NC, Greenville
Joined Dec 1999
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First welcome to the EZone Cod.

Is your 8*800 pack a NiCad or a NiMH pack ?

If it is a NiMH the HiTec charger will not do a very good job.
If the supplier will take it back consider doing so.
The Super Nova 250S charger is a much better choice. It will charge all cells except lithium and will do larger packs. Up to 25 cells.

And yes the charger that comes with your radio will charge your 8 cell pack regardless of the cell type. (NiCad or NiHM. Don't use it for lithiums though) Use the transmitter side outputs. It will take a long time though. But it will get you in the air while you get your other charger issues resolved. The radios transmitters output is probably about 50 mAh, If so charge the drained pack 16 to 22 hours.
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Old Oct 19, 2001, 08:52 AM
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Curitiba , Brazil
Joined Oct 2001
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Hey kevin , thanks for your fast answer!!!!
The pack is NICad. It will be hard to exchange the charger since I've bought it in USA.I choose it becouse of the price...I know there are better chargers in the market, but I paid 30 and the super nova cost 120,00, Since I am new in this hobby I decided to take it easy on the wallet!!!
Can I still use to charge the 8 cell pack? How much time it will take to charge it? It has a auto cut off 30 minutes timer....
About the transm. charger...Do I have to monitor the charging or just leave it charging during 22 hours??
Here are the specs of the hitec 315+ charger:
No bells, no whistles, just simple and easy one button peak charging for 6.0v 8.4v 1200 400mah NiCad packs from a 12V power source.
Applications

Aircraft

5 cell, 1200 2400mah Receiver Packs

Surface

6 and 7 cell 1200 2400mah Motor Power packs

Specifications

Voltage range: 6.0v 8.4v (5 to 7 cell)

Capacity: 1200 2400mah

Current: 5.5 amps
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Last edited by CodFish; Oct 19, 2001 at 10:17 AM.
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Old Oct 19, 2001, 10:49 AM
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West Dundee, IL, USA
Joined Jul 2001
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I have that charger and I have used it to charge 8 cells. I know it isn't rated for this, but it did work for me (your mileage may differ, highway mileage significantly lower). You need to watch this charger though, because it continues to pulse the batteries after they have finished charging. You'll want to unplug the cells as soon as they are done. Figure about 15 minutes for the 1100mAH cells, and 6 minutes for the 600mAH cells.

I haven't measured it, but judging by the design and the symptom, I believe that it pulses the cells with the 5.5A charge pump after charge is complete and this will heat the cells up. Hitec should have picked a lower pulse rate to lower the average current. This charger has false peaked on me a few times too, but I believe that was caused by a bad lighter adapter that I had added to the input cord. At 5.5 Amps the chep connector was dropping too much voltage and finally heated up so much that it melted the connector all together.

So, I've gotten away with using the charger on 8 cells, but you do have to babysit.
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Old Oct 19, 2001, 01:28 PM
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N. Staffs, UK
Joined Jan 1997
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It will not charge 8 cells very well. If you run it from a car battery with the motor running it may just have a high enough voltage to do it but there is a real danger of it missing the peak and killing the battery.

Anyway the charge current is much too high for safety. At 5.5A it is very likely to damage any cell smaller than a sub-C size NiCd of about 1500mAh. It would probably kill any small NiMH battery the first time you tried it.

I'm sorry but that is a really good example of the old saying "Buy cheap, buy twice". This is a really good place to ask those sorts of questions BEFORE you buy anything.

Steve
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Old Oct 19, 2001, 04:39 PM
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USA, NC, Greenville
Joined Dec 1999
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I would use the radio charger for 22 hours only the first charge or if the pack is completly emptied, otherwise go 16 hours. And you don't need to monotor the voltage, 50 mAh won't damage the 800 mA pack - just don't leave it on forever. 30 hours frequently may shorten your packs lifespan but is still safer than the 5500 mAh the HiTec will hit them with.
See Steves post above.
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Old Oct 20, 2001, 03:10 PM
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Curitiba , Brazil
Joined Oct 2001
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That's right slewin, but as I said, I was a bit short of money at the time!I will problably buy another one soon...
Kevin I already charged the trans. pack 22 hours as you said , but the needle didn't go all way till full charge in the display...I't marks 90%.
I'm bit worried about that.I will see in the next charge if it's go all the way...
Is there any way of lower the the charge current of the hitec charger???
I will give it a try like tekochip did, at the max I will loose the bat pack...there goes another 30 bucks...I'm crazy to do my first fly!!!!
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Old Oct 20, 2001, 04:55 PM
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USA, NC, Greenville
Joined Dec 1999
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I don't understand what 90% needle mark you mean.

Yes you can lower the amount of output that the charger will send to the battery pack. I don't recomend physicaly altering the charger but you can add a resistor in serise with the battery pack in the charge circute.
It will take a hefty resistor though, probably with a cooling fan or some type of heatsink. (Or perhaps several resistors in series combined to that the amperage then placed in series as I noted above)
If you do thes about 70% of the power from the charger will be burned up in the resistors and that would leave 30% for the pack or about 1.5 amps ( 2C ).
The calculation of the resistors size is beond my capability / knowlage.
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Old Oct 20, 2001, 08:49 PM
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Curitiba , Brazil
Joined Oct 2001
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I charged the transmitter pack and the meter on the transmitter marks 80% of charge , It should go all the way (100%) , isn't it?
Can I charge it again?? even with the 80% charged?
Great! I thought the same way , puting resistors It will lower the charger current , I will ask a friend who works with eletronics about it.
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Last edited by CodFish; Oct 20, 2001 at 08:54 PM.
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Old Oct 20, 2001, 09:26 PM
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Steve Fehr's Avatar
Chesapeake, VA
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Unfortunately, putting a resistor in series will also decrease the voltage across the battery, which won't work for charging.
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Old Oct 20, 2001, 10:26 PM
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Kevin Murray's Avatar
USA, NC, Greenville
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Putting a resistor in line was recomended both here and in The Battery Clinic Forum over at RC OnLine. But you are right, It is placed in parallel.

I don't remember the ohm value of the resistor recomended but I bought a 10 turn 1000 ohm potentiometer and made up a charging lead out of a servo lead extension. I use it to charge a 4.8 volt 50 mAh receiver pack for my RC/RG 's. I put the lead in line with the receiver output on the wall wart transformer that came with my radio set up. I charge the pack at 5 mAh.
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Old Oct 20, 2001, 11:40 PM
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Chesapeake, VA
Joined Sep 2001
528 Posts
Ah, parallel does make a lot more sense! Does a battery perform like a typical resistor, though? Since a charger isn't a constant voltage device- it's a constant voltage *and* constant current device, that means only the resistance is variable... kinda goes against the grain of all those circuitry classes, lol. It's easy to use Ohm's law to see that if it were a resistor, it would be about a 1-25 Ohm resistor, depending on current. If you put a 6 Ohm resistor in parallel with a battery on a charger pushing .1A at 12V, you will theoretically be putting 50ma into the battery. Is this true in practice?
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Old Oct 21, 2001, 09:19 AM
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West Dundee, IL, USA
Joined Jul 2001
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If you want to reduce the charge rate of a peak charger you need to place the resistor in parallel, not series. The reason for this is that peak chargers are constant current pumps. If you place the resistor in series the charger will still attempt to pump the full current through your load. At some point the drop across the resistor in series with the battery will be larger than the Open Circuit Voltage of the charger. Some chargers shut off if the Closed Circuit Voltage is near the OCV, because something is certainly wrong and you don't want to pump all that power into something that's gone bad. Other chargers may limp along but won't be able to detect the peak and time out.

Anyway, for peak chargers you'll need to place the resistor in parallel to reduce the charge current into the pack.
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Old Oct 21, 2001, 01:22 PM
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N. Staffs, UK
Joined Jan 1997
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Quote:
Originally posted by tekochip
Anyway, for peak chargers you'll need to place the resistor in parallel to reduce the charge current into the pack.
That's correct but you should also be careful. Since the resistor doesn't "peak" like a battery does having resistor in there can prevent the charger detecting full charge correctly. If you're just reducing the current a little you would be o.k. but in this case you need to get rid of around 4A of those 5.5A.

With an 8 cell pack at around 12V you are looking at a 3 ohm resistor and it is going to dissipate nearly 50 watts. It would get very very hot and would almost certainly stop the peak detection circuit from working. I wouldn't recommend it personally.

Steve
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Old Oct 22, 2001, 09:12 AM
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Curitiba , Brazil
Joined Oct 2001
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It seems that putting a resistor in paralel it will prevent the charger from peak detecting the bat pack...Anyway I should reduce the current to something 4c, ins't that right?
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