Need help for building a 24v nicad battery charger

[protocol217]

what input voltage should i use, can i use this 24V 0,8 A transformer ( rectified and filtered of course )
and what capacitor ( filter cap ) should i use on input on this LM317 circuit ?

and how will i know when the battery is full can an led be added for that if so where ?
and lm317 will be getting hot i guess so it will be needing a heat sink, how large ?

and i don't quite understand your last sentence: "Input to Output Voltage Can NOT Exceed 40 Volts"

 

[chemelec]

The Output of the Full wave Bridge goes in to that Cap.
That is the 470uf Cap as shown in your previous drawing.

The LM317 Might require a Small Heatsink, But I doubt a large one is necessary.
If you can Hold on to it Continuous, Than it is Not too Hot.

With the 28 Volts Rectified, It will be LESS than 40 Volt.
Also That 470uF cap should be rated at 50 Volts.

Sorry that LED Circuit will not work with this circuit.
Not that it was really that Accurate to determine a full charge anyway.

But Since the Charge Current of this is Less than 1/10 of battery Capacity, it will Not Overcharge or Overheat the Batteries.

If the batteries are Fully Discharged, They should be Recharged in about 12 -14 Hours.

 

[protocol217]

thanks, just one more thing you didn't answer can i use for input 24 V 0.8 A transformer ?
i found a 470 uf 40V rated cap.

 

[chemelec]

Check POST 16

 

[protocol217]

ok, i see, i thought that was for previous circuit. will report back how it works when done.

 

[protocol217]

i finished building it, it works, without the battery it gives out 31,5 v
when charged battery has 27-28 v but when i use it 2 cells get down to 0,5 v together and the rest 18 cells are all 1,3 -1,6 v.
so i think those two cells probably need to be replaced, until i replace them do they mind for charging ?

thanks for all the help, i am using this battery's for audio amplifiers taken out from pc speakers. i make a coyote game call for hunters. And they say that it gives perfect sound.

if you would give me a circuit diagram ( with LM317 ) for 12 v and 14,4 v nicd charger ( all nicd cells are 1,2 v 1200 mah )
or if it is the same like this one just the resistor and AC transformer is different tell me what resistor and transformer ac voltage that is needed. and i guess the capacitor for filtering the voltage is the same 470 uf am i right ?

 

[chemelec]

If your Batteries DO NOT ALL READ THE SAME at Just giving them a FULL CHARGE, You have Problems.

GOOD Fully Charged NiMH or Nicad batteries, JUST Finishing the Charging should be about 1.5 Volts.
And they should ALL Maintain a LOW of 1.2 Volts till Needing a Re-Charge.
If Any Go Lower than the 1.2 Volts Before the Others, They are going Bad.
IDEALLY in Such a SERIES Connection, You should Start with ALL NEW Batteries of the Same Type and A/H Rating.

To make a charger for those 1200 mA, 12 or 14 Volt pack, Just use a 14 Volt transformer on the SAME Circuit.
The 12 Ohm Resistor Determines the actual Charge Rate.
(Formula is: 1.2/12 Ohms = 0.1 Amps or 100 mA.)

 

[protocol217]

they all read the same after the charge, but when i use the for a little while two of them get below 1 v and drooping, the others stay the same, but the charger does work because it charges them up all,
and the charging is complete at lest for those 18 other cells, am i right?
all the cells are the same voltage and mah but not the same manufacturer.

 

[protocol217]

i replaced two bad cells now all is good.

so with LM317 i can build like this also drivers for LED diodes, i just need to put a right resistor across ADJ and OUT of lm317.

i need a driver for this led: https://uk.farnell.com/osram/sfh4235/ir-emitter-850nm/dp/1827025

what resistor should i put on lm317 so that i can get 90 % of power for led , and what input voltage should i use. i will be running it from a battery's

 

[tvtech]

I tried to warn about this...

Charging UNMATCHED cells in Series is always risky...

Even matched Cells are problem....unless it is a purposely built battery pack (little PP3 comes to mind)

Regards,
tvtech

 

[chemelec]

they all read the same after the charge, but when i use the for a little while two of them get below 1 v and drooping, the others stay the same, but the charger does work because it charges them up all,
and the charging is complete at lest for those 18 other cells, am i right?
all the cells are the same voltage and mah but not the same manufacturer.

Sorry for the Delay, but it seems this site was Down.

If not all the cells are the same manufacturer, that can cause problems.
And Just adding Two New batteries is also not really a good idea.

Nicads are also subject to Developing MEMORY Problems.
Before Recharging them, They should be used down to Just Under 1.2 Volts per cell.

 

[chemelec]

i replaced two bad cells now all is good.

so with LM317 i can build like this also drivers for LED diodes, i just need to put a right resistor across ADJ and OUT of lm317.

i need a driver for this led: https://uk.farnell.com/osram/sfh4235/ir-emitter-850nm/dp/1827025

what resistor should i put on lm317 so that i can get 90 % of power for led , and what input voltage should i use. i will be running it from a battery's

Seeing as it is rated at 3 Volts and One Watt, I would assume Full Current is 333 mA.
1.2 Volts / .333 Amps = 3.6 Ohms. (For 90%, Possibly use a 3.9 Ohm Resistor, 1 or 2 Watt.)

WHAT SUPPLY VOLTAGE are you going to use?
HOPEFULLY NOT THAT 28 VOLTS!

Your LM317 should have a Heat Sink on it.
That LED Should Als have a Heat Sink put on it.

 

[chemelec]

so with LM317 i can build like this also drivers for LED diodes, i just need to put a right resistor across ADJ and OUT of lm317.

Adding that LED and Resistor, Can cause the Circuit Limit to INCREASE in CURRENT.
I Don't Think you want to do this.

 

[protocol217]

i don't understand your last post,

Adding that LED and Resistor, Can cause the Circuit Limit to INCREASE in CURRENT.
I Don't Think you want to do this.

Did you mean that if i would use it like this:

how would you recommend to drive this LED with LM317 if i would want to run it of two 3,7 v battery's connected in series (7,4 V) ?

and on Product Information about this led on that page it says:

• Forward Current If(AV): 1A ---( i thought that if i want to run it on 90 % power that it needed 900 ma )

• Forward Voltage VF Max: 3V

• Voltage Vf Typ: 3V

explain to me what does all 3 things mean especially the first one.

 

[chemelec]

i don't understand your last post,

Did you mean that if i would use it like this:

how would you recommend to drive this LED with LM317 if i would want to run it of two 3,7 v battery's connected in series (7,4 V) ?

and on Product Information about this led on that page it says:

• Forward Current If(AV): 1A ---( i thought that if i want to run it on 90 % power that it needed 900 ma )

• Forward Voltage VF Max: 3V

• Voltage Vf Typ: 3V

explain to me what does all 3 things mean especially the first one.

Yes Like That.

Sorry I thought it was a ONE WATT LED, Not a 1 Amp.
So for 90% it would be a 1.33 Ohm.
But that isNot a Standard Size, So use a 1.5 Ohm, 2 Watt Resistor.
(for 80% Power.)
And Definately put a Heat Sink on the LM317 and on the LED.

 

[protocol217]

ok, but what about the input voltage, when i use it with two 3,7 v battery's connected in series (7,4 V), hov much will it give out, and will the led handle 7 v ? i am asking this because in Product Information says:

• Forward Voltage VF Max: 3V

 

[chemelec]

When you LIMIT the Current, The Voltage Will automatically Correct itself for the LED.

 

[protocol217]

i build lm317 driver for my led and it works, when i installed everything inside housing i had it connected like this:
cathode (-) directly to the battery minus, anode (+) to the output of the lm317 driver, and the heatsink which is also the anode (+) was connected directly to the battery minus - by accident because of the housing, and by the time i realized that the anode is also connected to heatsink the diode died it wont lite out even when outside of the housing and connected properly.
the driver still gives 820 mamps when shorted out connected as described above.

is that the reason why my diode died or is it something else?

 

[chemelec]

Not sure I understand what your saying?

What do you mean by DRIVER?, The Transformer and Rectifier?

Yes the HEAT SINK is HOT.
It MUST BE ISOLATED from the CASE, GROUND and OUTPUT to Battery.

You May have Damaged the LM317!

 

[protocol217]

I was talking about my infrared diode, driver is the lm317 with 1,5 ohm resistor. on my led diode in datasheet says that the heatsink and the anode (+) are electrically connected.

here is how it was connected.
**broken link removed**
the lm317 still gives out 820 ma of current when shorted out like that, but when i take out the diode from housing and connect cathode (-) to minus of the battery and output of lm317 to anode (+) the ampmeter stays on zero.

so i gues the diode died because of that housing connection.