Hi every one, im newbie both BLF also flashlight world. I love C8 type but in my country, buy a authentic ultrafire or convoy or sofirn etc…is mission imposible. So i order “really cheap” c8 type from 1688 (about 4usd including ship cost door to door). main cause just i want to mod and want to know how bad they are. And as my imagine, they have plastic reflector cup, semi-hollow pill( its hollow type but attach one small thin alu plate, seem its solid but not), and driver is marked YN-20-5( very popular, 5 mode no memory, include 1 IC named GY05, 1 capacitor, 1 protect resistor and block 4 resistor at 0.25ohm for current limit). I burned maybe 8 LED to findout the last mod and wanna share who have this type.
All of part and step have picture and i will attach it later due to sort them from my mess photo.
Almost 100% cheap C8 type have hollow pill. They have big gap from led and reflector if you thread tighten pill to head, if you guy want to tight to reflector, u must thread up the pill. So, the heat have not good transfer situation to head and your led will burn. Including, the hollow pill and semi hollow have not big transfer surface too, they just can heat conductive through very small surface at the edge. My mod is not buy new one, im casting them. To do it, you will need stove and some accessories to melting aluminium from beer cans or anything else, then fill them to flashlight head. May u need lathe machine, i have not so im saw it. Yes, just hand saw, drill and sandstone or sand paper. The cons is u will not have anything to attach driver, its floating into head. But its good, heat transfer very fast.
The driver is yn 20 5. The IC just can handle max 1.4amps. On the PCB, u will see 3 solder pad. 1 led+ from right, 1 led - from bottom and another led- from the left. If you soldering negative led to bottom led- pad, they will be limit by block resistor beyond, they just give you max around 1.2amps instead of 1.4amp, quite low.
I want it pull up to atleast 2.5amps and the p channel fet is solution. IC from PCB is GY05, it operate as PWM IC which max 520hz frequency. Of this point, u can set up this like any popular switch circuit using fet( google it and u will findout more clue). The ouput signal of IC ( directly connected to right led- pad) will give you NEGATIVE VOLTAGE. So u need use p mosfet instead n channel fet ( gate of p fet use negative voltage). The chosen pfet must be a logic lvl gate fet which have vgs atleast –0.3v ( see it on datasheet), that mean, u will need a gate voltage atleast 0.3v below source voltage. ( more simple, just substract led voltage to 0.3v then you will have gate voltage). After u have your chosen fet. Buy more resistor for pull up network, value from 4k7 to 20k up to your fet. Done. Solder it.
See your IC, it have 3 terminal, the one at top is GND, the right at bottom is signal and last one is VDD. Solder your gate fet to Signal, source fet to VDD and the drain fet for led. Solder resistor between gate and source of fet. Done. But notice this. From now on, the drain of fet is your led positive and the led negative must connect to ground. This reversed.
For example, i used AO3415 pfet. The result i have 2.3amps at full fresh cheap china 18650. If i stack up 2 fet ( same the way with amc7135 method). Then i have 2.5amps at all time if battery voltage still 3.7v.
I will up picture later. Sorry about this. Just want help people mod cheap c8