how to cutoff charger when the battery is fully charge

[mprower]

mn13811-g

I've spent the better part of this morning looking for the Panasonic transistor mentioned in the title for this project, and I found that it was discontinued in 2005. Unfortunately, I've already orded all the other parts. Does anyone know where I can this part or a suitable replacement?

 

[flypcb]

mn13811

I can offer this part in China. How many do you want? Kindly let me know.

Ken(sales@flypcb.com)

 

[mister_rf]

panasonic mn13811-g

''The MN1380 series are elements that monitor the power
supply voltage supplied to microcomputers and other LSI
systems and issue reset signals for initializing the system
after the power is first applied or for preventing runaway
operation when the supply voltage fluctuates.''

And so depending on the application needed it’s possible to replace it with other circuits, some examples: LTC1440/LTC1442, or LMP7300

**broken link removed**
http://www.ortodoxism.ro/datasheets/lineartechnology/144012fa.pdf

See also here
**broken link removed**
http://www.analog.com/UploadedFiles/Application_Notes/783694550AN139.pdf
http://www.icbase.com/pdf/MRP/MRP02680501.pdf

 

[mprower]

panasonic mn13811 g

I can offer this part in China. How many do you want? Kindly let me know.

Ken(sales(at)flypcb.com)

I only need one.

As for the substitutes, I don't know enough to make them work. Any suggestions in that area?

 

[mister_rf]

mn13811-2

To choose a substitute you need to know the application for...

 

[mprower]

mn13811 g

oh, sorry. I had a link in my first post, but I guess you missed it.

http://www.discovercircuits.com/H-Corner/under-volt.htm

 

[mister_rf]

Re: Panasonic MN13811-G

In the schematics, MN13811 compare the supply voltage to an internal reference. The output low level signal will trigger the flash circuit.
There are some solutions to replace the circuit, see for example a possible replacement using LTC1440 or even some bipolar transistors...

 

[mprower]

Re: Panasonic MN13811-G

thanks. I think I'll be going with the LTC1440 option.

 

[mister_rf]

Re: Panasonic MN13811-G

If you want to consider to change the under voltage level, actually it’s 2.4V, you need to recalculate resistors Ra and Rb.

 

[mprower]

Re: Panasonic MN13811-G

That really helps. Now I could use 1.2v rechargeable batteries. What would be a good cutoff point if the system is normally at 2.4v, then? 1.8?

 

[mister_rf]

Re: Panasonic MN13811-G

As you can see, for a single NiMH cell
**broken link removed**

The charging voltage is in the range of 1.4-1.6 V/cell. A fully charged cell measures 1.35-1.4 V (unloaded), and supplies a nominal average 1.2 V/cell during discharge, down to about 1.0-1.1 V/cell (further discharge may cause permanent damage).

That's why for two cells you may consider cuttoff point at 2-2.1V.

 

[mprower]

Re: Panasonic MN13811-G

Right. So if I leave Rb as a 4.7M, I can make Ra a 3.3M and it will work?

 

[mister_rf]

Re: Panasonic MN13811-G

For a 2V cutoff voltage yes, this is the right value. Anyway in my opinion a 2.1-2.2V it’s more suitable in the case you want to have enough power in the batteries to make this circuit work. So maybe a 3.9M resistor for Ra will do the trick…

 

[mprower]

Re: Panasonic MN13811-G

Ok. Thanks for all the help.

 

[stereo]

Panasonic MN13811-G

so mprower, have you tried the circuit and does it works? does the led blink when the voltage is below 2.1v?

 

[stereo]

Panasonic MN13811-G

ltc1440 only works when 2v input is there. so what if the preset voltage is 1.2v. are there any better subtitute?