A Safe 18650 LiPo Charger with a 5-12V Boost Converter

Do you need a portable & rechargeable 5-12V solution to power your projects?  Simply add a 28-29mm (1-1/8") hole into your application & insert this carrier design.  The self-retention clips will secure it in place.

Change History

(06-07-25) 18650_lipo_charger_booster_v2.  Added more clearance at PCB mounting locations to facility in-place soldering.  

The following describes a charger circuit for a single-cell 18650 LiPo battery using the popular TP4056 coupled with a ME2108 or MT3608 boost converter.  Understanding how each circuit works is essential when it comes to safety & extending the life of your LiPo's, not to mention saving your electronics from an unexpected failure of your power source.

IMPORTANT NOTICE:  This solution is not suitable for load sharing; i.e. charging and load control at the same time. Therefore, you must disconnect any load before charging the battery when using any TP4056 based boards.  With a load connected, the monitored charge current will be altered such that the current detected by the TP4056 may never terminate the battery charging process!  There is a good article about the problem here:  The TP4056: Lithium Ion/polymer Battery Charger IC

The good news is that you can add a load sharing circuit yourself, or buy a different module based on something like the MCP73871.  There is an excellent article on how to add one to a TP4056 board using only 3 components: TP4056 lithium charger module - modification to add power sharing - Other Hardware / General Electronics - Arduino Forum

Typical TP4056 Based Chargers

A very popular & inexpensive single-cell LiPo charger consists of the following components:

• TP4056 battery charger;
• DW01A one cell LiPo Battery Protection;
• FS8205 Dual N-Channel Enhancement Mode Power MOSFET.

An important function of the DW01A is to provide over-charging & over-discharge protection, along with the use of the FS8205 to disconnect the circuit from any output electronics.

Figure 1:  A typical TP4056 based PCB & Schematic

Charger Circuit Drawbacks

Although readily used, there are a number of drawbacks with respect to using most TR4056 based boards which users need to be made aware of:

1. Over-discharge voltage protection:  The battery over-discharge voltage protection cut-off is set too low for most LiPo batteries; i.e. 2.4V.  The lowest recommended working voltage for typical 18650 batteries should be around 2.75V.  One solution to fix this is to add a 400 ohm resistor to ground at the VDD pin of the DW01A to act as a voltage divider with R4.  This would yield a over-discharge voltage of approximately 3V vs. the 2.4V default.  The disadvantage of this technique is that the resistor would create a constant current draw of approximately 8.4mA at 4.2V or 6mA at 3.0V.  A better solution is to add a rectifier diode is series between R4 & VDD on the DW01A to drop the voltage down by 0.7-1.0 V;
2. Charge current:  The charge current default is set to 1A via R3.  This might be a problem for smaller batteries having lower capacities.  For most LiPo's, the recommended charge rate should not exceed 1C.  For example, a LiPo battery with a capacity of 500mAh should have a charge rate of no more than 500mA.  Therefore, in this circuit, R3 would need to be changed to approximately 2.7K.  However, for a 18650 with a 2500mAh capacity, the default 1A charge value should not be a problem;
3. Load Sharing:  As mentioned previously, there are no load sharing provisions available.  Therefore, any load must be disconnected from the TP4056 output during charging. This is easily accomplished by having a simple switch to turn-off or remove any output circuitry, like a voltage booster, from the TP4056;
4. Voltage booster:  There is no voltage booster circuit at the output to power external electronics.  Most TR4056 based boards don't contain DC to DC Boost Converters that can operate from 2.5-4.2V at the input & 5-12V @ 0.5A at the output.  

IMPORTANT NOTE:  The booster needs to operate down to a minimum of at least 2.5V, or at least down to the programed minimum working voltage of the TP4056, otherwise, your boost converter could output a higher unregulated voltage & damage the output electronics.
 

Table 1:  Programming Charge Current with value of R1

Alternatives to a typical TP4056 Circuit Board

There are a number of TR4056 based LiPo charger boards with integrated DC to DC booster ccts available. They go under product codes J5019, HW-357 & AC01, to name a few. However, the problem with most, if not all, is that they do not contain the DW01A overcharge & over-discharge protection switch OR any load sharing circuit for some odd reason & therefore, not recommend for safe use.

Figure 2:  Example of a TP4056 Board with built-in Voltage Boost Converter but with no overcharge or over-discharge protection or load sharing cct.

A Better Solution

So until someone develops a TP4056 based board with a boost converter AND a proper DW01A protection switch, the best & still cheapest solution is to use a separate voltage boost converter at the output of a typical TP4056 PCB. As mentioned earlier, the converter needs to operate down to the programmed over-discharge voltage protection cut-off.  A good candidate are ME2108 or MT3608 based circuits which are capable of operating at inputs down to 2.5V & therefore, compatible with TP4056 type circuits having a lower over-discharge voltage protection cut-off programed at 2.5V or higher.

Figure 3:  A typical ME2108 5V Boost Converter Schematic & PCB

ME2108 5V Boost Converter Specs

• For input 2-3V:  output 5V 150-380MA
• For input >3V:  output 5V 380-480MA
• Operating frequency 150KHz, typical conversion efficiency of 85%.
• Dimensions: 11mm x 10.5mm x 7.5mm

Figure 4:  A MT3608 5-12V Boost Converter Schematic & PCB with jumper selection vs. potentiometer

MT3608 5-12V Boost Converter Specs

• Input voltage 2.3 to 5V DC
• Output Voltage 5V - 8V - 9V - 12V selectable by solder jumper or potentiometer
• Maximum Output Power 6W - Maximum Output Current 1A
• Operating frequency 1.2MHz, typical conversion efficiency up to 97%.
• Dimensions:  11 x 22 x 4.5mm

Final Parts List

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