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Tp4056 reverse voltage protection
Hi Vincent.. I got confused on the mosfet to order and have ended up with the 540 not the others.

As these were choice #2 hopefully they will do the job. If not let me know. only 8 bux for 30

I have also drawn the layout on a piece of vero board, the circuit is too simple to waste time and money etching a PCB for these.
If they dont have any radiant heat to speak of, and I doubt they will. I will 3D print some rectangular holders for them and fill them with potting resin to give a measure of protection.

Below is a rough picture of the Vero layout. I have stared at it until I went cross-eyed and can find no wayward routing or connections. If you find fault with it please let me know before I make 26 of these little things...

Thank you yet again for your exceptional help with this..

YOLO is wrong, You live every day. You only Die once so it should be YODO. Angel
Hi Mike,

Though I only took a quick glance, it looks OK to me.
The IRL540(*) should do the trick, and indeed at P = RI², with I=1A and R=0.044Ohm, the MOSFET should dissipate only 0.044W when the charger is at its max, so don't worry about heat.
When soldering, just take care of the orientation of the components. The MOSFET in particular is drawn "from behind", which first made me think the schematic was incorrect. Be careful when assembling...

Now I urge you not to build 26 of them before testing.
Contrary to other technologies, most electronic circuits are cheap to prototype. So please build one complete circuit, connect a power source, connect a battery in the correct direction, measure currents and voltages (and check that they match what you expect), then reverse the battery and measure again, make sure components don't overheat (the TP4056 does become very hot when it's charging an empty battery. It's scary but "normal" for that chip) or blow, and only then consider building more circuits.
Architects cannot afford a skyscraper coming down. We can afford some magic smoke.

Kind regards,


(*) Just noticed your schematic shows a IRF540N, not a IRL540N. The IRL is required for its low VGS(th) = 1-2V, as indicated in a previous post. The IRF has a VGS(th) = 2-4V which means you have no guarantee that a 3.7V cell will fully turn it on. So please make sure you have the IRL version first.
AgentPothead likes this post
Yup just double checked definately IRL540N.s ordered.

I realise the mosfet is back to front, thats because I followed your schematic from Right to left LOL.
Although it looks a bit strange I dont think it will care that much. I tried to keep the track runs as short as possible so I can 
flow some soldier between points to build up the track a little.

I agree to assemble one and test it for functionality before starting a production line.
I will post a few pictures when done and before and after potting, just for curiosity sake. See you created a monster Smile

Stay tuned..

Wolf likes this post
YOLO is wrong, You live every day. You only Die once so it should be YODO. Angel
OK here is the new layout with the 540 around the right way, I am doing them in strips of 4 because that seems to be the industry norm, so 4 x 5 it is.

Built on strip board, supposed to be able to take 2-3amp , but the system only runs 1 amp, will solder coat the main in out strips just to be sure.

Any glaring faults anyone??  There was one yesterday, I forgot to cut the track between the LED and the Transistor. Would have made life fun.


Click on picture for larger version.
Wolf likes this post
YOLO is wrong, You live every day. You only Die once so it should be YODO. Angel
(Yesterday, 07:43 AM)Gremlin Wrote: Any glaring faults anyone??

I don't have the time to check, but I really think it's time to make one as a first prototype and test it.
The rule is :
- Smoke => bad.
- No smoke => good.

Thumbs Up 
I registered just to say thank you for this thread. It helped me choose the correct mosfets. I almost bought ones with a VGS(th) rating that was too high till I saw this thread.

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