Has anyone built their own Li-Ion chargers?

I imagine it's not very difficult to build the proper circuitry and put it into an enclosure, so has anyone built their own chargers before?

Someday I want to go Li-Ion but I don't feel comfortable with all these cheap chargers that don't have automatic shutdowns when proper voltage is reached. And I don't want to pay for a PILA charger and double the cost of supporting my light. It shouldn't be that difficult to just build a charger with an auto shutdown when 4.2v is reached, is it?

Thanks.

This worked great for me:

http://cds.linear.com/docs/Datasheet/405442xf.pdf

It's linear so you want to minimize input voltage to keep power dissipation in the part down to a manageable level. I use a 5V wal-wart and set charge current to 500mA. I'm still using cells from 5 years ago so this really takes good care of cells with proper charge termination.

I personally used an MCP73861 from Microchip:

http://ww1.microchip.com/downloads/en/devicedoc/21893c.pdf

Same warning and recommendation as CM, it's also linear so use a power supply around 5V (4.5V is ideal).

I personally set mine up so that I could change the charge current, and it's been working quite well so far. Bit more complex than CM's, but I'm very happy with it.

I built the one in this thread a couple of years ago. Hobby chargers have come a long way since then. If I were in the position of needing a charger now, I would look to one of the versatile hobby chargers that can be had for what the parts cost me to build mine. Building it was a learning experience to be sure, but also frustrating at times.

CM said:

This worked great for me:

http://cds.linear.com/docs/Datasheet/405442xf.pdf

It's linear so you want to minimize input voltage to keep power dissipation in the part down to a manageable level. I use a 5V wal-wart and set charge current to 500mA. I'm still using cells from 5 years ago so this really takes good care of cells with proper charge termination.

Click to expand...

Hi CM. Does your charger force a LiIon cell to 4.2 volts and hold it there, or does it recognize internal resistance that might be present in older LiIon's that would not allow them to reach 4.2 volts during a charge. Much discussion here on CPF about CC/CV being the best way to charge LiIon's, which would not necessarily force a cell to 4.2 volts.

Bill

Ok, I just read some of the specs for your charger. It is CC/CV.

i have built 4 so far, only one did i fail miserably at.

when using a voltage regulator to control the max voltage, and the Max Current was the ability of the whole thing. Meaning max voltage , Default max current just because it couldnt do more than that.

the regulator heated up so hot the gate leg came undone, and Bam i suddenly had a 12V charger instead of a 4.2v one :shakehead oops.
mabey they should mention that when the leg lifts on the regulator the voltage goes to the HIGHEST , not the lowest as would seem to be a smarter thing to do
It even was heatsynced so stuff like that wouldnt happen, now i know why those heat syncs were on sale back to the drawing board.

same thing happend with one of them (cheap%#$) Mastech power supplies, which regulates current and voltage, was pumping some juice through something, and out of the blue it jumped to 30V and Stayed there. Grrrrr.