ESP8266 Community Forum

- Wed Sep 14, 2016 1:53 am #55073 Hi guys,

I've designed this circuit which includes a TP4056 lithium charging board. The idea is to use this circuit to power the ESP12 by solar panel through the TP4056. At the same time I'd like this setup to still work to power the device if there's no solar power available (cloudy).

When testing this circuit with a solar panel connected or alternatively an external psu connected, the ESP12 boots fine but the problem I have at the moment is I don't seem to be able to get the ESP12 to boot from battery power alone. The lithium cell I'm using is a single 18650 cell which I believe is in decent shape / is holding a charge and is charged to around 3.9v.

This is all setup and being tested on a pcb at the moment but having gone back to my stripboard prototype I've now realized the problem exists there too so it seems I might have something wrong in the circuit. There's something common between the pcb design and the prototype setup causing this problem at least.

Can anyone see anything obviously bad with my schematic?

Thanks for any help
Joe

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Last edited by anotherjoe on Wed Sep 14, 2016 7:40 am, edited 1 time in total.

- Wed Sep 14, 2016 4:24 am #55080 Hi, which TP4056 board are you using? There are two kicking about, one has two terminals at the battery end and no low voltage protection, the other has 4 terminals at the battery end and does have low voltage protection. From your schematic I'm guessing your using the second, if so you might need some capacitors on the battery and possably output side (but output side may make thing worse). The way that TP4056 works is when the voltage drops below the minimum it disconnects the battery from the output until its voltage rises above a preset. It is possible that when the ESP powers on (or transmits) the sudden increase in current causes the voltage to momentarily drop and the battery is disconnected, however as soon as this happens the voltage rises above the preset and the battery is reconnected. If it boots correctly with a different power supply I would add some capacitors to help the battery with the sudden changes in demand.

- Wed Sep 14, 2016 7:37 am #55088 Hi thanks for that. Yes you're right, I'm using the 4 pole version of TP4056 board where the 2 inner poles are the B+ / B- battery terminals and the outer pins are the TP4056 OUT+ / OUT- supply terminals.

It's probably not very clear from the schematic but what it's trying to show is that the TP4056 (shown bottom left) output is connected to the LF33AB voltage regulator input (top left). That means with the way things are connected at the moment I have a 47uF cap on the TP4056 output supply to the LF33AB and the 3.3v output from the LF33AB regulator (which is the ESP12 VCC) has a couple more 47uF caps in parallel.

I thought this would have been enough capacitance in the circuit because the only other device I have onboard at the moment is a TMP36 temp sensor and most people seem to get by with a 100uF cap and an ESP8266 board.

That said I do agree with your thinking - I was thinking myself that this could be a capacitor / volt drop related problem. I'll try a cap or 2 directly across the battery to see if that helps.

Cheers

- Wed Sep 14, 2016 10:34 am #55097 Interested to know how you get on. The esp can apparently be quite demanding at times, and i'd like to try something similar to your setup....