You can see in my crumby schematic that I am using a Non-latching relay to turn on a 3A circuit (one of them arc lighters), which is powered by a 25C (supposedly) lipo battery. That same battery also powers an Arduino through a TP4056. This works fine when I first turn it all on, but once the relay is activated by the Arduino, the lighter + Relay only turn on for a split second before stopping (when the Arduino is powered via USB, it works fine). I am thinking that the Arduino+Relay+Lighter is too much for the battery, even though it claims to be 25C. It is just strange because the Arduino+Activated Relay consume what, like 200 mA?

Notes: When I manually turn on the lighter, the light on the Arduino dims a fair bit, but stays on. The Arduino is running at logic level of 3.3V so that I didn't need a booster. enter image description here As for fixes, I was thinking about trying to use a transistor or SSR instead of the chunky relay I have now (which would be good, I need this to be compact). Or maybe the TP4056 is failing to provide enough output despite a decent input?

I am FAR from an electrical engineer so if anyone has any pro tips for improving this it would be much appreciated.

  • what is the voltage output of the battery when the lighter is energized?
    – jsotola
    Aug 3, 2020 at 3:08
  • When you put power to the LED lighters the current is high for a short time. You can't compare this value to the continuous current that you can detect with a multimeter. The best way is to use another power supply for the Arduino. The relais I used hat two different circuits: logic and power.
    – harper
    Aug 3, 2020 at 6:41
  • 1
    The TP4056 is a battery charger not a power supply.
    – Majenko
    Aug 3, 2020 at 7:15

1 Answer 1


The TP4056 is a battery charger, not a voltage regulator. It cannot be used to supply power to a device like an Arduino. It is designed for charging the Lithium Ion battery from a 5V (e.g., USB) source.

By trying to use it as a power supply you're asking for trouble. It thinks it's trying to charge a battery (from a 3.7V nominal source) and will be doing things like:

  • Running constant current making the voltage fluctuate wildly as current demands change
  • Running constant voltage with limited current causing starving of power
  • Shutting off when it thinks it sees the non-existent battery being fully charged.

The TP4056 should be connected to a 5V USB power source and to the battery for charging it. The battery should be then through a (very) low-dropout regulator (ideally a switching regulator with zero dropout bypass ability) to power the Arduino at 3.3V.

Alternatively, if you don't need a (reasonably) precise 3.3V then you can power the Arduino directly from the battery.

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