Li-ion Li-Po Battery Capacity Indicator 1S–5S LED Tester

LOTHYE Li-ion / Li-Po Battery Capacity Indicator Board — 1S to 5S (3.7V–21V)

Never get caught off-guard by a dead battery again. This ultra-slim LED battery capacity indicator board from LOTHYE lets you check the charge level of your lithium-ion or lithium-polymer packs in seconds — simply press the button, read the lights, and go. Compatible with 1S through 5S configurations (3.7V to 21V), it works with Li-ion, Li-Po, Li-Fe (lithium iron phosphate), lead-acid, and e-bike / electric vehicle batteries.

Made in Mainland China.

Key Features

• 5-LED visual display — 1 red power indicator + 4 colour charge-level LEDs give an instant, intuitive readout at a glance
• Wide voltage range — supports 1S (3.7V / 4.2V full), 2S (7.4V / 8.4V), 3S (11.1V / 12.6V), 4S (14.8V / 16.8V), and 5S (18.5V / 21V) battery packs
• Reverse-connection protection — even if positive and negative leads are accidentally swapped, the board will NOT burn out; simply correct the connection and continue
• Zero idle consumption — LEDs auto-shut-off after 3–10 seconds of releasing the button, drawing absolutely no standby power
• Broad compatibility — Li-ion, Li-Po, LiFePO₄ (lithium iron phosphate), lead-acid, e-bike, and electric vehicle battery packs
• Durable, high-quality construction — ultra-thin module built for long-lasting everyday use

Specifications

LED Indicator Logic

• 1st LED (Red) — Power indicator, always lights when button is pressed
• 2nd LED (Blue/Green) — On when voltage > N × 3.3V (≈25% charge)
• 3rd LED (Blue/Green) — On when voltage > N × 3.5V (≈50% charge)
• 4th LED (Blue/Green) — On when voltage > N × 3.7V (≈75% charge)
• 5th LED (Blue/Green) — On when voltage > N × 3.9V (≈100% charge)

Note: For 1S (3.7V) Li-ion batteries the indicator uses 1 red + 4 green LEDs. All other voltage ranges use 1 red + 4 blue LEDs. N = number of cells in series.

How to Use

1. Connect the board's positive (+) and negative (−) leads to the matching terminals of the battery under test.
2. Lightly press the red button — the LED lights will illuminate to show the real-time charge level.
3. Release the button; LEDs will automatically turn off after a 3–10 second delay.
4. If leads are accidentally reversed, the reverse-connection protection prevents damage — simply swap the leads and try again.

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Frequently Asked Questions

Q: Which battery types are compatible with this LED capacity indicator board?

A: This indicator board is compatible with a wide range of battery chemistries, including lithium-ion (Li-ion), lithium polymer (Li-Po), lithium iron phosphate (LiFePO₄), lead-acid batteries, and electric vehicle / e-bike battery packs — as long as the pack voltage falls within the 3.7V–21V range (1S to 5S configurations).

Q: Will the board be damaged if I connect the leads the wrong way?

A: No. The LOTHYE indicator board features built-in reverse-connection protection. If you accidentally connect the positive lead to the negative terminal (or vice versa), the board will not burn out or be damaged. Simply disconnect, correct the polarity, and reconnect.

Q: Does the indicator drain my battery when it is not in use?

A: No. The display only activates when you press the button. After you release it, the LEDs automatically switch off after a 3–10 second delay. When idle, the board draws zero current, so it will not drain your battery pack over time.

Q: How accurate is the battery level reading?

A: The board has an allowable measurement error of ±2%. This makes it ideal for quick, practical charge-level checks. If your application requires very high precision measurements, a dedicated laboratory-grade voltmeter is recommended instead.