Need charging circuit diagram and advice

[Lee1111]

I want to put a charging circuit in my device. I've been bugging a few specific people and thought, why not bug everyone! lol I've heard alot about the MAX1811 and it seems the goto one. $15 shipping seems high for only one chip so if you guys know a good supplier LMK please.

I also was wondering where I could find a good schematic for wiring it up.

All help, comments, suggestions, and links are greatly welcome. Thanks.

 

[Java_Az]

Here is a link to the data sheet that explains how to wire it up. http://datasheets.maxim-ic.com/en/ds/MAX1811.pdf. looks like it is a 500ma max charge rate so on a bigger Mah battery it will take quite awhile to charge. leak voltage while not charging is pretty low for that circuit might be why most people choose it. Not sure what battery you plan on using but if it is a higher MAh you can go up in the charge rate which would reduce charge times. So maybe a chip that rated at a higher output would be better depending on your battery choice

Might want to look at mouser or digikey for the chip. Pretty sure you will get a better shipping price.

 

[Lee1111]

I thought a computer could only put out 500mAh regardless?

 

[Lee1111]

I also want the design to have didodes integrated so I can use the PT functionality.

 

[Java_Az]

USB 2.0 specs say that a USB port can go into charge mode of 1.5 amps. If the data wires have a resistance of 200 ohms between them this is supposed to happen. This also relies on the computer maker following the USB 2.0 standard. USB wall adapters and powered USB hubs can be found in 2 amps there are some wall adapters that go up to 3 amps harder to find but out there.

 

[Lee1111]

Do you have a better suggestion for a IC chip? Sorry for all the questions, just starting out.

 

[Java_Az]

Do you have a better suggestion for a IC chip? Sorry for all the questions, just starting out.

That chip might be fine depending on what battery you plan on using. With out knowing what battery i don't know the max charge rate for it. That chip will also work just fine for bigger mah batteries just going to take awhile to charge. Was just pointing out that if you are planing on using a bigger battery you can get a chip that will charge it faster.

 

[Lee1111]

I plan on it being compatible with either a 14500 3.7v or two cr2's for 6v maybe 5 idk yet. If you mean specific manu of a battery then I don't have any certain brand in mind.

 

[Lee1111]

Oh and I ordered a max1811 from one of the vendors you mentioned for at least half the price. Thanks.

 

[Lee1111]

Here are the things I don't understand.

Where does the SELV come from? Same for SELI.

Is the CHG just a line for LED indication of charging?

Also, for the PT function, would I just run a line around the charging circuit to the atty from the mini-USB? I guessing I'm gonna need diodes in there for backflow?

If I have more questions I can ask later. Thanks for reading.

 

[Java_Az]

The MaX1811 is slightly over rated for a 14500 by .050 ma most 14500 are rated @ 450 ma max charge rates. It will not work with CR2's you would have to find a chip made to charge those. Bad thing about adding a diode is that lowest voltage drop ones i have seen are .2 volts. So if you slapped one after the charger it would drop the charge voltage to 4 volts instead of 4.2. That would mean your battery would not get a full 4.2 volt charge. IF using a .2 voltage drop diode you would want a charger chip that delivers 4.4 volts so the resulting voltage to the battery is 4.2 volts. I learned this the hard way but you might want to wait to buy parts till you have a fully designed mod. I started buying parts when i had not fully designed my mod and the more i learned the more my design evolved rendering some of my parts useless. You might want to just copy a few of the mods posted in here first , get a couple of builds under your belt before build one from scratch. Also your best friend is the data sheet. At first i didnt understand much in them. If there is something you dont understand try to find a tutorial on it. Over time they will make more sense. Reading the max1811 data sheet it says no input diode required. The example circuit they show doesnt have a output diode. It just shows one cap. Pretty sure you dont need a diode on this chip.