I made up four of these boards for my 18650’s and have tried several methods of connecting the boards to the battery.
First of all , I tried double !8650 holders with the charger board mounted (glued) in one side and the battery would fit in the other side … Great if you only ever use unprotected cells … Panasonic 3100mAh are too long and don’t fit.
Second method was to cut the ends off the battery side of the double holder … Any length of 18650 fits now … Flying leads (short) soldered onto charger board with magnets soldered on their ends to connect to the battery … Soldering the wire onto the magnets heated them and reduced the power of the magnets but putting an extra magnet on (as well) worked OK.
So I then sent for some “Double ended 15 inch test leads with croc-clips fitted” http://www.ebay.co.uk/itm/110911083614?ssPageName=STRK:MEWNX:IT&\_trksid=p3984.m1497.l2649
These seemed a good idea as they were only £2-14 including delivery … After all they had 20 croc clips and the nice flexible cable for that price … Well , when I measured the resistance of the leads , it varied from 0.2 Ohms to 0.9 Ohms … The croc-clips are crimped on … I had to uncrimp the leads and solder the wire straight onto the croc-clips … The leads are reduced to about four inches long and soldered to the charger board at one end and with the croc-clips soldered to the other end … Finally I am happy with my cheap chargers … I will now be able to clip the 18650 into the double holder , put a magnet on each end of the battery and clip the croc-clips to the magnets … The four chargers are now working perfectly … They may not be as pretty as some other chargers , but they are proper CC/CV chargers.
At last I’m happy with them … But I’m going to try a couple of different types of magnets just to be certain … Type one will be 6mm diameter X 10mm long and type two will be 10mm Diameter X 5mm long with a 3mm Countersunk hole in the middle … Both types will be easy to clip onto.
The good thing about using magnets is that my voltmeter leads will “stick” to them as I have put paper-clips onto the ends of the meter leads … I just switch the meter on when I need to note the voltage of the battery … When the LED changes colour , you can see the voltage drop slightly … If you leave the battery still on charge , the voltage will drop a few millivolts to its resting voltage … These are proper CC/CV chargers.
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I am not able to put pictures on the forum … Seems to be such a hassle to use an intermediate site instead of just sending pictures directly … I can email pictures easily though … I tried to put pictures directly on the forums but they just vanish.
The latest picture would show a black two-slot 18650 battery holder with a charger board glued into one slot and a battery held in the second slot … All springs are removed from the battery holder because the longer protected cells wouldn’t fit … A mini-USB lead would be plugged into the charger board and fed from a 5V PSU … A 4” red lead and a 4” black lead comes out through holes in the ends of the charger slot and each lead is fitted with a croc-clip … Magnets are attatched to each end of the battery and the croc-clips are clipped onto the magnets … Basically that’s the latest (and possibly final) mod … I can take some pictures and email them to you if you want.
Works well though and at about £1-25 (or less) per charger board it makes a great (cheap) CC/CV charger … I can plug up to four of these individual chargers into my five volt (four amp) switch-mode PSU.
These charger boards would be ideal to use in defective Li-Ion chargers to replace a faulty board … I even considered getting some ultra-cheap ebay Li-Ion chargers just so I could use their battery holder part … Take the insides out and fit one of these boards in … Ideally a cheap or defective charger with a USB (5V) input socket already fitted would be perfect … I think I might have a look for some ; the “home-made” one would then look more professionally made.
I only use these for my 18650’s and they are ideal as they charge at one amp (during the CC) … As the LED changes colour , the charging stops properly … If you leave the battery on charge the voltage drops slightly , as it does when resting … I can’t see why I would ever need a better Li-Ion charger … A resistor on the charger board can be changed if other charging rates were needed , but I don’t need this mod.
Hope you can visualise the cheap charger better now.
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Thanks! Available Datasheet too.
There are also boards on ebay (w/ this same chip) that might be easier for some to program for a lower charge current.
These ones still need a resistor change to alter the charge current … They also need a two-colour (common anode) LED indicator to be fitted … I wanted boards with a mini-USB socket already fitted for ease of plugging a power supply in … The boards that I used had the LED’s already fitted and were a bit cheaper … I also only needed one amp chargers for my 18650’s.
I noticed that there are boards that provide a higher charge current … Still , I’m happy with one amp for my 3100mAh batteries at the moment.
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I will stick (pun intended) with the croc-clips and magnets … No problem with any length of batteries.
In actual fact , just the charger board on its own with the short leads , clips and magnets would make a very portable charger … A 1 Amp USB charger plus the short lead (USB to mini USB) is all that is needed and the USB charger will charge any other MP3’s , mobile phones etc that you take on holiday as long as you have the relevant USB cables.
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