Smart Charger 29 volts @ 1 amp how do I change it 25 volts

[sam_sam_sam]

I bought these chargers to charge 24 volt li-ion battery packs I could not find one that would be at 25 volts and the close I could come up with is this

What resistors would I have to change to make it work at 25 volts not 29 volts

The ic chip that is KTG3646 has a logo of ( IG ) I can not find a data sheet for it

[redwire]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

It's very cheap power supply - there is no opto-coupler+voltage reference (i.e. TL431) to provide feedback to the SMPS IC and control the DC output voltage.
It might just regulate from the aux winding, not the output. That leaves only R5, R6 and the top resistor by EC2 to tinker with.
In other words, it is regulating the voltage on EC2 which is proportional to Vout, on the mains side.
The LM358 and all those parts are just for the LED. You'd have rto find the IC datasheet and sketch the schematic a little, but I would not use it for lithium ion battery charging because it will always have poor regulation and it's not really a 29W power supply. The parts would overheat.

[Andrew F. Ali]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

Use a step down buck converter. That is the safest thing.

[R_J]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

The ic maker is Kintago, This may or may not help

[sam_sam_sam]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

The ic maker is Kintago, This may or may not help

Thank you for finding the data sheet for me it very hard to read the part number on the ic chip

This is helps a lot at
I now understand how this switching power supply is suppose to work

From what I read it might not make a difference but I will have try it and see how it works

Now what I could limit the current more than it is set to now this is just a thought at this point

[sam_sam_sam]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

One note

I would be charging these batteries with a BMS protection board

[R_J]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

If you could not read the numbers clearly, It could also be a KTG3546

[gabiz_ro]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

That 24 volt li-ion battery packs how are made?
In most cases (for tools example) are in multiple of 3.6 or 3.7V
18V ones are formed by 5 elements,
3.6V x 5 elements = 18V
but fully charged
4.2V x 5 elements = 21V
So depending on number of elements voltage may be higher than 24V

[sam_sam_sam]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

It has 4.2 X 6 elements = 25.2 volts —> before the BMS protection board ends the charging cycle which is really 4.1 X 6 elements = 24.6 volts

[sam_sam_sam]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

If you could not read the numbers clearly, It could also be a KTG3546

You have the right part number the second digit was the one that I could not really make out for sure what it is

[sam_sam_sam]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

I would not use it for lithium ion battery charging because it will always have poor regulation and it's not really a 29W power supply. The parts would overheat.

I did run a test on this battery charger controller

On a scale of ONE board does not work at all TEN board works perfectly

I give it a 2.5 and this might be too high of a rating

Here is why

One note the battery voltage was at 3.3 volts per cell

Yes it will charge the batteries however after about five minutes the temperature of the case goes to a temperature of 128*F at this point I stopped the charging of the batteries

You were right about it would over heat but I want to test it myself and see just how bad it could get

[sam_sam_sam]

Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

Now I have found a way to use the secondary side of this power supply based on this reply

The LM358 and all those parts are just for the LED.

I did have to add more resistance to LED lights circuit so the LED lights would not burn up
It only takes 10 milliamperes to active the current sensing circuit LED light and 0 milliamperes
for the other LED to be lighting

( the circuit works at voltage of about 13 volts and higher to about 30 volts I think I read in the data sheet)

I cut the circuit board and separate the primary from the secondary and use that part of this circuit to let know when the battery pack is fully charged

The primary side of the circuit is going to used for a low level LED module but I have to work on this circuit when I have some time for this project