Ryobi 9.6v Charger...

[Odomus]

Sadly, been working on this Project for over a year.... and Asked on many forums, and NOONE seems to even have any answer or HAS them yet doesnt want to, OR has the Charger, and doesnt want to take it apart and give me a PIC or THe info I need.

Here is my Problem, My Charger Stand for eh 9.6v cordless drill fried....well the PCB did. (see below)

  - Top
  - Traces 
Yeh BURNT....

The PCB isnt the Problem I can make another one, better than the orginal really.... my question is... What WERE the resistors that were ON the PCB, take in part heat damage and the fading of the Resistors, the GUESSES below are approximate for the bands.  I dont know if they are correct that Is why I am asking anyone to take apart their Charging base to give me the NON-FADED resistors of the charger... yes this is an OLD charger, and prob used millions of times, it was just old and fatigued, Iam not complaining as I got the whole set for free, and all I want to do is fix it, and getting as close as possible to the orginal resistors is my best bet in trying to fix this.


And I think it is gold Not the Silver as I described. GOld just burnt off is all.
(BUt again these are ALL GUESSES due to heat fading and bleaching out)

Now unless you guys have a better resistor combo for this PCB... So I can get it back up and running so I can use my drill again I would be most appreciated.  Noone seems to really want to help anywhere else out there at all. 

Base:
Ryobi 9.6v #1400673     I hope this helps.

[Uncle Vernon]

I think you'll find once you replace the restors that your battery is fries.
R1 is the LED dropping resistor. 330 ohm ¼ Watt 5%
R2 sit's in series with the battery charger. 34 ohm 10% 2 Watt would be my guess. To work it out you would be aiming for a charge of C/10. This resistor should really have been a 5 Watt item to handle the excessive temperature rise.

These chargers are rubbish. they will fry any battery left connected for any length of time (14hrs absolute max). They are built for a price. In short avoid any power tool that has a wall wart supply most have no form of battery monitoring or protection.

You'll probably find that if batteries need replacing it will be cheaper to scrap the tool and get a better item. 

[Odomus]

I figured it was 330 But With heat, and such... right about now, I wouldnt put it past it being 1M... that is just how my life goes type of scenario.
34ohm Would never have guessed that one at all..... would have seemed to me alot more than that low... but oh well.

Well it came with it, and since you cant beat the price of FREE, I dont mind thinking of feeling it is rubbish.
Even so, the batteries are fine, have been actually, and totally 100% ok. Just cant charge them worth a dang in a year.... I just hope the nicd batteries themselves are not too low form not charging at all in a year.
Yeh it may be a wall wart one, but again it doesnt bother me, since I didnt pay for this one.

As for scrapping it, no, I have better ones AND more powerful ones... but this is my mid range/sized one that is jsut right for jobs that dont need all that torque, and I have a small one but it doesnt have any torque... this one is just right. Especially it being free I cannot deny nor do I care about the price and wasting money on another tool for me is kinda wasteful without even trying to fix the old one which is possible.

Though IF you have any suggestion for a small PCB for a charging circuit that I can put inside, I am all ears too... if you cant do it maybe someone else can come up with one?

But again as long as I can get the right resistors then I am fine.... I will look for a 5w one though... but I figure the 5w wont really fit... that would be my only problem *shrug* Oh well Maybe I can mod it to fit.

Thank you....
Still would like to have other opinions and ideas and thoughts though.

[Uncle Vernon]

I figured it was 330 But With heat, and such.......34ohm Would never have guessed that one at all.

Around 30 ohms was an educated guess, it depends on the voltage and regulation of the wall wart, the capacity of the batteries etc. I'm assuming the wall wart is nominally 9.6V unregulated.

Even so, the batteries are fine, have been actually, and totally 100% OK.

The state of that resistor says something different. That is assuming the battery has been the only thing placed into the charger.

Though IF you have any suggestion for a small PCB for a charging circuit that I can put inside, I am all ears too... if you cant do it maybe someone else can come up with one?

Google is full of designs for chargers, do some searches, just remember the cost of parts often exceeds the cost of a made up charger with a free drill.

I will look for a 5w one though... but I figure the 5w wont really fit... that would be my only problem *shrug* Oh well Maybe I can mod it to fit.

You may have more luck fitting 5 by 1 watt resistors wired in parallel. For 36 ohm use 5 by 180 ohm.

Have fun.

[amspire]

I think it will be 34 ohms 3W to 5W power rating.

The drill would have used NiCd batteries that can withstand extended charging as long as the current is 1/10th the battery Amp-hour rating.

With good batteries, then voltage very quickly rises on the battery to over 1.2V per cell, and at that voltage the resistor should be able to survive.

What happened in this case is that one or more of the 8 series NiCd cells had shorted. With, say, 2 cells shorted, the voltage when the charger was attached would have only risen to something like 7.2v, and the resulting extra current through the resistor did all the damage. Shorting is a very common problem in old NiCd cells, and so for simple resistor based chargers, this sort of problem is also pretty common.

Don't try and fix the battery pack with NiMH batteries - you have to use NiCd batteries as NiMH cannot really sustain extended overcharging the way NiCd batteries can.

Richard