[overdream]

hi again.. say i want to add an LED indicator to indicate whenever the charger is charging the battery. where should i place it?

Anyone ?

 

[Avro_Arrow]

connect the resistor and LED at the power input jack.

 

[i_djoel2000]

how do i calculate the charging current rate? i'd like to set them to 25-30mA/hour. i'm using LM317T TO-220 style

 

[Fred_fred2004]

Use this formula
1.25/R = I
 
cheers
FRED

 

[i_djoel2000]

Quote:

Use this formula
1.25/R = I
 
cheers
FRED

thanks Fred!
 
in that case, the default configuration in the first page gives you 12.5mA charging current, correct?
 

 

[i_djoel2000]

i just made my charger, but it doesn't work, the amp won't turn on even though the battery is connected. i don't know what's the problem, and i'm pretty confident i followed the circuit correctly. both diode work well when i checked them with my multimeter. no idea about the LM317 though, but i assume it works decently as well since i've never used it at all until this moment. resistor is 1/4W 60.2 ohm
 
here are some pictures:


red wire is connected to battery, blue to amp (+) pole, black to (-) pole battery, and white to amp (-) pole
 
anybody can point what i did wrong here?

 

[Avro_Arrow]

Is your power jack shorted?

 

[i_djoel2000]

Quote:

Is your power jack shorted?

the lower pin is positive, upper and right pins are negative. i checked with my multimeter and there is no short between the lower pin to upper or right pin
 
i checked the charger last night and i still couldn't find what the problem is..

 

[Fred_fred2004]

Just trace out the positive path using your multimeter, start at the DC socket and work through the circuit at some point you will find it stops and theres the hole
 
cheers
FRED
 
 

 

[i_djoel2000]

Quote:

Just trace out the positive path using your multimeter, start at the DC socket and work through the circuit at some point you will find it stops and theres the hole
 
cheers
FRED
 
 

i just did..
 
should we have impedance reading across the diode? because i just traced the connection from dc socket, and stopped at the diode connected to LM317 because i didn't get any reading across the multimeter
 
i checked the diode using multimeter too, and they check out
 

 

[Fred_fred2004]

Are you saying there is no positive voltage at the junction of the diode and the lm317 ?

 

[i_djoel2000]

Quote:

Are you saying there is no positive voltage at the junction of the diode and the lm317 ?

i connect the black rod to + dc socket pin, and then work my way down using the red one throughout the positive path and then it stopped at the junction between diode 1 and diode 2
 
sorry if my previous comment misled you..
 

 

[Mullet]

I'm using this charging circuit for my PPA-S project. I'm having an issue though. I've hooked up everything correctly and get ~18v by connecting two 9v batteries in series. When I plug in my 24v 500mA Jameco wallwart my two Tenergy 250mA 9v batteries eventually get pretty damn hot. They also have started to disform. Any idea what can be going on here? I've used the standard parts including 75ohm resistor.

 

[MisterX]

How much current is your circuit putting into the batteries?
Should be somewhere around 16mA....
(disconnect the positive lead from the first battery, set the meter to read amps, connect the meter between the first battery and the charge circuit, power up the circuit, what's the meter read?)

 

[wakibaki]

From the numbers, you are running 24VDC into a battery with about ~16.5V depending on state of charge. So you're dropping 7.5V across 75 ohms, which is 100mA, far too much to trickle charge a 250mAh battery. You need ~330 ohms to get the current below 20mA, (less than C/10).

w