i found this LM2596 DC-DC StepDown and i wanted to discuss about it so will it work to charge 18650 cells ?
US $20.39
Oh HELL no!
I got 2 of those for $10~
http://www.ebay.com/itm/300853743826?ssPageName=STRK:MEWNX:IT&\_trksid=p3984.m1439.l2649
Yes you can manually charge Li ion cells with it…but you must monitor it CONSTANTLY
Set the constant voltage to 4.2vdc, short the output leads thru an ammeter, dial in the current output to below the safe charge C rating of the cell…then hook the ammeter up in series with the cell and monitor the current flow going into the battery, once it stops pulling current down to approx 3% of rated capacity the battery is full
I actually have two of those small .36” volt meters on the in and output just to ensure I can see the voltage on both ends while charging (I only have charged lead acid batteries) but they have a similar charge pattern as Li Ion…remember…4.2vdc MAX PER CELL thus its really only safe to charge one cell at a time manually
WHy bother? Use one of those mini usb chargers here
charging 18650s is serious business
If you feel a need to build your own charger than I’d make sure you’ve written out your will .
Cheaper just to buy a lighter and some sticks
Yeah, yeah, your house will explode… :weary:
But you need something with constant current (or current limiting) and a maximum voltage of 4.2 Volts.
That makes it a dedicated / suitable charger.
The one you linked to is okay, but WAY to expensive…
The same one from an ebay vendor:
$3.08 
But it’s a bit big for charging a single 18650, and you have to do the proper adjustments yourself.
Personally i like these too:
http://www.ebay.com/itm/281334520522?\_trksid=p2055120.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
$2.15
The USB cable is the charger has 2 colour LED in the USB part, the batt holder is just a holder.
But many flashlights nowadays have the same 3mm connection, that’s why i like these cheapies.
I guess they have a 4.2 Volts regulator with 1 AMC7135 to limit the current or something like that.
I bought me a intellicharger i2 (2 channels, 2 slots) also, which is more reliable and safer i guess, and has good adaptable (sliding) batt holder slots.
So the question would be:
Do you want to charge single 18650 batts or more at the same time, or maybe a parallel pack?
those pcb are the way to go IMO; HKJ’s tests showed good results.
they are almost free, and if the limited charging current is ok for you (i think the max I saw was 1A) they are a perfect solution, much better than those kit chargers we all know
They have the improved version with micro usb which is on almost every phone but i’m too lazy to search for them :bigsmile:
it is US $4.08 / piece not US $20.39
and cant i charge like 4 cells in parallel with it as long as it can give 4 A ?
O, right, it’s a 5 piece lot!
4A is a bit high for that buck converter. 4A is peak power, for short periods.
With the specified maximum 3A you can charge 6 pieces (at 0.5A each, which is ‘normal’)
It will get hot though, as it’s the maximum continuous current.
thank you it is a great idea i can think to buy 6 of them and make housing for them and the batterys and power them with an old computer power supply that can give 5 volts
and sorry for many any questions but while i am waiting for the item we were talking about to arrive i have this LM2596S-ADJ / voltage adjustable switching and i know i cant control its current so can i adjust its voltage to 4.15 and hook it up to 6 cells in parallel so every cell will be taking .5 a ? with monitoring it CONSTANTLY
Yes you could, i think.
Not sure about the charging current when nearly fully charged though…
It’s usually less at the end.
But that’s to be expected when the difference between charger and batt is getting less and less.
[edit]
I wouldn’t ask the full 3A from that buck converter though.
It’s the maximum continuous current it can provide, so it will probably get a bit hot…
Also:
Don’t put cells with more than, say, 0.2 Volts difference in parallel.
It will transfer charge uncontrolled, maybe exceed max charge current.
There are some of These switching modules with 3 pots.
These Are made for charging.
O.o
850mA. Use dual boards in parallel for 1.7A. Can also be modded for other currents.
Just be sure to get boards with chips that have the stylized TP logo. That is the only chip HKJ tested. See my post in the tp4056 thread on the chips. Thread link in my sig.
Ahermm…
I think those were mentioned in the opening post… 
Ding ding ding
That is the kind I have…blue boards but with the 3 pots not red board
And yes you can charge in parallel, but if you have a weak cell in that parallel it can quickly pull more current than the rest, get hot and kablooey (also putting in different charge levels in the ports can cause high current flow between batteries as the try to equalize to the same voltage)
good call Werner
Came across these…built in displays for input and output voltages w/ ammeter 5A
(a little more pricey than the ones without the display)
2PCS - $15.96