How to Use a TP5100 2A 8.4/4.2V 1S and 2S Lithium Battery Charger

How to Use a TP5100 2A 8.4/4.2V 1S and 2S Lithium Battery Charger

TP5100 Charger Module Review: 1S/2S Lithium Battery Charging (And Protection Tests)

In this review, we look at the popular TP5100 lithium battery charger module that can charge either one cell (1S) or two cells in series (2S). You’ll see what the module is, how it’s configured for 1S vs 2S, how to wire it, and real tests: charging current/voltage behavior, thermal hot spots using a thermal camera, short-circuit protection, and a reverse-polarity test. :contentReference[oaicite:0]{index=0}

What This TP5100 Module Does (And What It Does NOT Do)

This board is built around the TP5100 charging IC and is commonly sold as a compact charger for:

1S lithium battery (full charge around 4.2V)
2S lithium pack (two cells in series) (full charge around 8.4V)

Important: This module is not a cell balancer. If you charge two cells in series, the charger charges the pack as a whole and does not monitor each cell individually. If your 2S pack needs balancing (recommended), you need a proper 2S BMS/balancer board. :contentReference[oaicite:1]{index=1}

Main Parts on the Board

Depending on the seller, the PCB color may vary (red/green/black), but the layout is typically the same. Key parts you’ll see:

TP5100 IC (the charger controller)
Inductor (the switching converter inductor; often the warmest part during 1S charging tests)
Schottky diode (part of the power conversion path)
Input pads labeled for approximately 5–15V on the module
Output pads for battery connection
Charge/Standby LEDs (module examples may use red/blue color)

Many versions are sold as 2A chargers by default. Some boards use two resistors in parallel to set the charge current; changing these can reduce the charge current if needed. :contentReference[oaicite:2]{index=2}

Key Specifications (From the Datasheet Info Discussed)

Charge current: up to about 2A (common preset on modules)
Output voltage: 4.2V for 1S, 8.4V for 2S
Input voltage (IC rating): about 5–18V (module marking commonly 5–15V)
Switching frequency: around 400kHz
Inductor on the module: around 20µH (as shown in the review)
Thermal protection: chip reduces/shuts down if overheated
Protection features mentioned: over-current, under-voltage, short-circuit (and “reverse connection shutdown” at the IC level)
Max junction temperature (noted): about 120°C

Note: Real-world behavior depends on your input voltage, battery state of charge, wiring, and the specific module build quality. :contentReference[oaicite:3]{index=3}

How 1S vs 2S Mode Is Selected

The board includes two pads (often near the output area) that act as the 2S select option:

Open (not shorted) = 1S mode (targets ~4.2V charge)
Shorted together = 2S mode (targets ~8.4V charge)

In the review, a temporary wire link is used so the pads can be connected/disconnected easily during testing. :contentReference[oaicite:4]{index=4}

Wiring (1S and 2S)

Input wiring: Connect your DC supply to the module input terminals (the board is labeled around 5–15V).

Output wiring (battery):

1S (single cell): Battery + to module OUT+, battery − to module OUT−
2S (two cells in series): First connect the cells in series (positive of one cell to negative of the other). The pack ends go to OUT+ and OUT−. Then short the 2S select pads so the charger targets ~8.4V.

LED behavior (as demonstrated): When powered with no battery attached, the standby LED may be on. When charging begins, the charge LED turns on. :contentReference[oaicite:5]{index=5}

Charging Test Results (What You Should Expect)

Charge current changes with battery voltage: At the beginning (lower battery voltage), the module can draw higher charge current. As the battery voltage rises toward full charge, the charge current gradually decreases, and eventually charging stops (or transitions to standby). :contentReference[oaicite:6]{index=6}

In the 1S test, a near-empty cell showed a strong charge current close to the module’s rated capability, then it reduced as the cell voltage increased. In the 2S test, current values around ~2A were observed depending on pack condition, and the input current was also measured during operation. :contentReference[oaicite:7]{index=7}

Thermal Camera Findings: What Gets Hot?

Thermal behavior can differ between 1S and 2S setups:

1S test: The inductor was the hottest component in the demonstration. This is common in switching converters because the inductor handles pulsed current.
2S test: The charger IC became the hottest point in the demonstration (around the 80+ °C range shown). This was still described as not immediately critical, but it highlights why airflow and sensible input voltage matter.

If you plan to run near 2A continuously, consider airflow and avoid enclosing the module in a tight box without ventilation. :contentReference[oaicite:8]{index=8}

Short-Circuit Protection Test

The output was intentionally shorted during the review. The module responded by pushing current briefly and then shutting down, demonstrating that short-circuit protection was working as expected on that unit. :contentReference[oaicite:9]{index=9}

Reverse Polarity Test (Important Warning)

A reverse connection test was performed by swapping the battery polarity (connecting + to − and − to +). In the review, this caused visible smoke, indicating that reverse polarity protection did not protect the module in practice (or protection was insufficient for that mistake). After reconnecting correctly, the module appeared to charge again, but any smoke event can permanently weaken components.

Takeaway: Do not rely on “reverse protection” claims. Always double-check polarity before connecting a battery, and consider adding your own external protection (fuse/ideal diode/BMS) for real projects. :contentReference[oaicite:10]{index=10}

Practical Tips Before Using This in a Project

Use the correct mode: 1S (no short) vs 2S (pads shorted)
Use an appropriate input supply: Provide stable voltage/current capability; avoid pushing the module beyond its ratings
For 2S packs: Remember this board is not a balancer; consider a proper 2S BMS for safety and cell health
Watch heat: High current charging creates heat; provide airflow if needed
Polarity matters: Reverse connection can damage the board

Conclusion

The TP5100 module is a convenient low-cost solution for charging 1S or 2S lithium packs with up to around 2A (depending on conditions). The review showed solid behavior for current tapering, clear thermal hot spots to be aware of, and effective short-circuit shutdown on the tested unit. However, the reverse-polarity test produced smoke, so polarity checking and external protection are strongly recommended for real builds. :contentReference[oaicite:11]{index=11}

Parts and datasheet links: Please see the affiliate links below this article for the exact module and related components used in the review. :contentReference[oaicite:12]{index=12}