I am building a solar lamp/phone charger following this page, with the circuit here below.

I have two 18650 batteries in parallel. The charger module is the usual TP4056 taking 5 V input, and limited to 1 A output. The voltage booster converts the ~3.7 V from the batteries to 5 V, but with a current limited to 600 mA (in practice even less than that).

The problem is that this current seems too low for recent phones, especially iPhones. I found another voltage booster outputting 5 V and 1-1.5 A. However, when I plug the phone in via USB cable, the phone starts charging for around 1 second before the circuit shuts down. Perhaps this is due to the fact that the TP4056 charger module is limited to 1 A?

What would you do to get an output current to charge the phone close to 1 A or more? A phone would take around 1.4 A from a conventional electrical outlet.

I've also heard iPhones might block such DIY charging.

circuit for solar phone charger

  • \$\begingroup\$ The phone controls the amount of current. The phone will take more current if it thinks it can. According to [electronics.stackexchange.com/questions/449593/… if you short-circuit both data wires, the phone will use about 1-1.5A. If the voltage/tension decreases, the phone may decrease the current, so you must be able to keep 5V \$\endgroup\$ Jan 20, 2023 at 22:29
  • \$\begingroup\$ What symptoms are you seeing that make you think the current is too low? You say it "doesn't seem to work well", is the phone charging at all? Charging slowly? \$\endgroup\$
    – vir
    Jan 20, 2023 at 22:39
  • \$\begingroup\$ Thanks for your replies. @vir I have edited my question to described what is problematic with the more powerful voltage booster. \$\endgroup\$
    – mekano
    Jan 21, 2023 at 21:36
  • \$\begingroup\$ @user253751 Interesting, I'll try shorting the data cables. Won't I face the same issues as with the second voltage booster, which can output more than 1A (in terms of compatibility with the TP4056 limited to 1A)? \$\endgroup\$
    – mekano
    Jan 21, 2023 at 21:41
  • \$\begingroup\$ There are also QC3.0 compatible booster boards available, many variants around. It also provides the USB ports and a charger, so all in one board... You could use a step down board to add solar charging. \$\endgroup\$
    – datenheim
    Jan 21, 2023 at 22:26

1 Answer 1


I think you are facing a slow-charging issue (the phone is indicating charging, but it is taking around 5-10 minutes to increase the charging percentage).

Most of today's smartphones need 5 V and 2.0+ A (min. 1.0 A) to charge a phone efficiently. In order to get a 2 A charging current you could change your booster module to something like this "MT3608 DC-DC adjustable boost converter" which can supply 2 A current at its output. You have to set the voltage to 5 V by adjusting the potentiometer on the module.

  • \$\begingroup\$ Thanks for your reply. Yes ideally I'd want an output current between 1 A and 1.5 A. As mentioned in my initial post, I've tried with a voltage booster outputting such current but this seems to shut down the charge shortly after connecting the phone. I suppose that this is due to the TP4056 charger module that is not supposed to handle current larger than 1A, but I'm not sure. \$\endgroup\$
    – mekano
    Jan 21, 2023 at 22:44
  • \$\begingroup\$ Also is there a way to add a female USB port on that circuit? \$\endgroup\$
    – mekano
    Jan 23, 2023 at 20:11
  • \$\begingroup\$ " I've tried with a voltage booster" can you specify which booster. for tp4056 1A and 4.5-5.5 V is the input requirement (of adapter) not output current limit . Output current limit of tp54056 module is >2A which is what its mosfet supports. \$\endgroup\$
    – Chr_arj
    Jan 24, 2023 at 8:53
  • \$\begingroup\$ most of boost converters have their max output current rating above which they dont work , that may b the case for your boost converter you used. \$\endgroup\$
    – Chr_arj
    Jan 24, 2023 at 8:55
  • \$\begingroup\$ Thanks for the clarification regarding TP4056. As mentioned in my initial post, the first booster I used delivers an output current limited to 600 mA, and the second I tried delivers an output current in the range 1-1.5 A (at least that's what is advertised), which would be great to charge a phone. Using this second booster, I measure that the current increases for around 1 s until close to 1 A, and then the circuit shuts down (no more current), which made me think that this could be some sort of control feedback loop from TP4056. Perhaps this control feedback loop comes from the phone? \$\endgroup\$
    – mekano
    Jan 24, 2023 at 15:14

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