# Charging 4 with 6 ??????



## NCFRC (Aug 4, 2005)

I want to charge a 4 cell pack with an older high amperage pulse charger that was designed to charge 6-7 cells .

Does anyone have some knowledge on what type of resistor to put inline on the output side of the charger to make it think it has 6 cells connected to it.

I don't want to use an inline resistor on the power side as I want to keep the charge amperage between 8-10 amps.

I know BRP used to sell a simple light bulb set-up to chg a 4 cell aa pack from an old timed charger.

A mathematic formula would be great, its got to be able to be done fairly easily.

Thanks for your response


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## NCFRC (Aug 4, 2005)

there has to be somebody who knows how to do this :thumbsup:


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## RCMits (Jan 1, 1970)

with the prices of used good chargers (under 50 for some!) i wouldnt chance it with older "pulse". Should always charge linear on the newer batteries anyhow......

im sure someone else can pipe in...


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## NCFRC (Aug 4, 2005)

We're charging Sanyo 1900 SCR's which is still in production and one of their top sellers in other markets than RC.


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## OvalmanPA (Mar 21, 2000)

Try going to Tekins website and see if they still have the directions to download for the BC100L. Seems to me there was something in those directions about charging a 4 cell pack with that charger that should help.


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## Robertw321 (Apr 26, 2002)

OvalmanPA said:


> Try going to Tekins website and see if they still have the directions to download for the BC100L. Seems to me there was something in those directions about charging a 4 cell pack with that charger that should help.


I dug out the instructions for my old BC100L. It used a resistor, doesn't say what size, on the power input side of the charger. It reduced the input down to around 10V. He stated he didn't want to use one on the input side. If I'm reading his post right, he wants to use a resistor connected between the battery pack and the charger output to make the charger think it's charging 6 cells.


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## RCMits (Jan 1, 1970)

Robertw321 said:


> I dug out the instructions for my old BC100L. It used a resistor, doesn't say what size, on the power input side of the charger. It reduced the input down to around 10V. He stated he didn't want to use one on the input side. If I'm reading his post right, he wants to use a resistor connected between the battery pack and the charger output to make the charger think it's charging 6 cells.


http://rcdocuments.com/file_info/download.php?file=Tekin_BC100L_Manual.pdf

here....



engh.. im lost


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## OvalmanPA (Mar 21, 2000)

Honestly then I don't think the charger is going to care if it's charging 4 or 6 cells then, it'll just charge the pack. Of course I'm no rocket scientist when it comes to all things electrical either! :lol:


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## RCMits (Jan 1, 1970)

the cut off might be wrong  guess you'll have to watch temperature? egads....

buy my pitbull v1.. it'll do just fine!  hahahahah (shameless plug)


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## NCFRC (Aug 4, 2005)

OK , after some extensive research and putting a few brains together this is what I found.

First ,, Tekin says to use a voltage dropping resistor in the pos lead feeding the charger so when you charge at 4-5 amps the input voltage is about 10 volts to take the stress off the mosfet.
The resistor can't flow any more amps than that.

But as I said I wanted to charge a 4 cell nicad pack at 8-10 amps , so I wanted to add a HD resistor of some sort in the output side to keep the amps up.

After talking to Chris @ Tekin today he headed me in the right dirrection, he didn't have specific specs as they found it too expensive back then to do this and 4 cell racing wasn't that popular in the 80's.

With a pile of 1 ohm / 20watt resistors and some trial and error this is what i came up with and the charger stays nice and cool and I'm getting a full 10 amps to the battery.

A 320 WATT ,,, .25 OHM RESISTOR WORKS GREAT !!

The charger voltage metering ports read the voltage very close to a 6 cell battery and it peaks in the low 9's but the battery reads exactly like a 4 cell and peaks in the low 6's .

I'm not an expert either and if you try this its at your own risk but so far it seems to work fine.

I bought my 1 ohm resistors to build discharge trays years ago but I'm sure you can still find them dirt cheap on-line at electrical discount houses for like 5-10 for $1.00 pkg.

Hope this helps others also as there's lots of good chargers that could be used still today if adapted for 4 cell.


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## RCMits (Jan 1, 1970)

way to go!


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## NCFRC (Aug 4, 2005)

Thanks ,

For any of you racers running a 4 cell " NICAD " pack , probably a spec class ,this is a very inexpensive option and I'd suggest to pick up a Tekin BC-210 charger which you find on E-bay quite often and can usually get for $20-30 bucks.

Your Nicads will perform great and last longer than todays modern with most of tadays modern linier chargers.

Of course you have to use this resistor , 320 watt .25 ohm


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## cwinters (May 4, 2005)

NCFRC said:


> Your Nicads will perform great and last longer than todays modern with most of tadays modern linier chargers.


Not trying to start anything, but just be careful with that comment. Seems to me that you have only been using this technique for a few weeks at most. I don't believe you have the amount of data necessary to draw that conclusion.

Thanks,
Chuck


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## NCFRC (Aug 4, 2005)

cwinters said:


> Not trying to start anything, but just be careful with that comment. Seems to me that you have only been using this technique for a few weeks at most. I don't believe you have the amount of data necessary to draw that conclusion.
> 
> Thanks,
> Chuck



Hi Chuck ,

Not trying to be a wise guy but have been racing for over 20 years and was around when we only had 1200 nicads , not claiming to be an expert but alot of my comments are based off talking to other electrical techs that have also got that much experience.
Seems like the Nicad technics are fading away as fast as the new nimh cells are increasing in mah.
Thanks for responding :thumbsup:


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