Li-ion Battery Capacity Gauge | 1S–8S 3.7V Lithium Tester

Li-ion Battery Capacity Gauge – 1S to 8S Lithium Power Display Module

Keep your lithium battery packs operating at peak efficiency with this compact, easy-to-read Li-ion Battery Capacity Gauge. Designed for 3.7V single-cell and multi-cell packs (1S through 8S), this nixie-tube display module gives you an instant, real-time readout of remaining charge — so you always know when it's time to plug in and never risk damaging your equipment from over-discharge.

Whether you're managing battery packs for RC vehicles, e-bikes, DIY power walls, drones, or portable electronics, this versatile tester handles lithium-ion, lithium lead-acid, and nickel-hydrogen chemistries within its 3–34 V operating range.

Key Features

• Wide voltage range: Operates from 3 V to 34 V, supporting 1S–8S lithium battery configurations
• Simple pad-select setup: Solder-bridge the matching S1–S8 pad to configure for your exact battery string in seconds
• 4-segment LED display: Lights up 1–4 blocks based on real-time voltage; all segments off signals it's time to charge
• High-precision reading: ±2% voltage accuracy at only 5 mA working current — minimal drain on your pack
• Broad temperature tolerance: Operates reliably from –20 °C to +50 °C (–4 °F to 122 °F)
• Compact & portable: Slim form factor makes it easy to embed into battery enclosures or carry in the field
• Universal chemistry compatibility: Works with Li-ion, LiPo, lead-acid, and NiMH packs within the voltage range

How It Works

Connect the positive and negative leads of the display board directly to the corresponding terminals of your battery pack. The nixie tube instantly displays the charge level:

• Voltage > N × 3.9 V → 4 bars (full)
• Voltage > N × 3.7 V → 3 bars
• Voltage > N × 3.5 V → 2 bars
• Voltage > N × 3.3 V → 1 bar
• Voltage < N × 3.3 V → 0 bars — charge immediately

N = number of cells in series (e.g., 3S = 3 cells). Maximum input voltage must not exceed N × 4.3 V.

Specifications

Important Notes

• Not waterproof — if used outdoors, protect from moisture. Electronic components require a dry environment.
• Only one S1–S8 solder pad may be bridged at a time; shorting two or more simultaneously will damage the module.
• Do not exceed the maximum voltage of N × 4.3 V for your selected cell count.

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For more information on lithium battery safety standards and best practices, visit the U.S. Consumer Product Safety Commission – Lithium-Ion Battery Safety.

Learn more: MagSafe (wireless charger)

Frequently Asked Questions

Q: What battery types are compatible with this Li-ion capacity gauge?

A: This battery capacity gauge is compatible with lithium-ion (Li-ion), LiPo, lead-acid, and nickel-hydrogen (NiMH) battery packs, as long as the total pack voltage falls within the 3 V to 34 V operating range. It is most commonly used with 3.7 V lithium cells in 1S through 8S configurations.

Q: How do I select the correct cell count (1S–8S) on the module?

A: The module includes labeled solder pads marked S1 through S8. Simply apply a small solder bridge to the pad that matches your battery string count (e.g., S3 for a 3S pack). Only bridge one pad at a time — bridging two or more simultaneously can damage the module.

Q: What does it mean when all four display segments are off?

A: When all four LED bars go dark, it indicates the battery voltage has dropped below N × 3.3 V (where N is your cell count). This is the module's low-charge alert — you should recharge your battery pack promptly to avoid deep discharge damage.

Q: Can I use this tester outdoors or in wet conditions?

A: This module is not waterproof. If you plan to use it in outdoor environments, you should enclose it in a waterproof housing or apply a conformal coating to protect the electronic components from moisture and humidity.