---
product_id: 436345015
title: "DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement"
brand: "hxjnldc"
price: "4087 kr"
currency: ISK
in_stock: true
reviews_count: 8
category: "Hxjnldc"
url: https://www.desertcart.is/products/436345015-dc-3-7v-800mah-603040-rechargeable-lithium-polymer-replacement-battery
store_origin: IS
region: Iceland
---

# 3.7V nominal voltage, 4.2V full charge 800mAh high capacity Built-in multi-protection IC DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement

**Brand:** hxjnldc
**Price:** 4087 kr
**Availability:** ✅ In Stock

## Summary

> 🔋 Power your passion with precision and protection!

## Quick Answers

- **What is this?** DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement by hxjnldc
- **How much does it cost?** 4087 kr with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.is](https://www.desertcart.is/products/436345015-dc-3-7v-800mah-603040-rechargeable-lithium-polymer-replacement-battery)

## Best For

- hxjnldc enthusiasts

## Why This Product

- Trusted hxjnldc brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Advanced Safety Tech:** Japanese Seiko IC protects against overcharge, overcurrent & short circuits
- • **Precision Voltage Range:** Optimized 3.7V nominal with 4.2V max charge for consistent performance
- • **Universal DIY Compatibility:** Easily solder or swap connectors with included heat shrink sleeve for seamless integration
- • **Compact & Lightweight Design:** Slim 6×30×41mm size and just 16g—perfect for sleek, portable projects
- • **Power-packed 800mAh Capacity:** Reliable energy to keep your DIY gadgets running longer

## Overview

This 3.7V 800mAh rechargeable lithium polymer battery delivers 2.96Wh of reliable power in a compact 6×30×41mm form factor. Featuring a built-in Japanese Seiko IC for overcharge, overcurrent, and short circuit protection, it ensures safe and stable operation for DIY electronic projects within 3.7-5V range. Lightweight at 16g and equipped with a 2-wire JST connector, it’s designed for easy installation and long-lasting performance.

## Description

Product description DC 3.7V Model Table of Square Rechargeable Polymer Lithium Battery (applicable to 3.7V-5V electronic products) Please note that connector specifications and polarity are based on the product display image., the red wire is the positive "+" and the black wire is the negative "-"The yellow ( white) lead is a 'thermistor'，Do not reverse-charge or reverse-connectreverse. 3 -wi r e batteries retain red and black wires, which can replace 2 -wi r e batteries. Some products' original batteries may lack plugs, have incompatible plugs, or exhibit mismatched polarity. No worries—you can simply cut the wires and use the included heat-shrink tubing to connect the wires of the same color from the old plug.

Review: Nice fit to Anki Cosmo - I have used this battery to update Anki Cosmo robot as described various guides which used 503040 600 mAh. 603040 fits perfect and 800 mAh is much better for endurance - kids tests Cosmo for 2 hours and still very well changed, so I may assume resulting runtime will be 2.5 - 3 hours.
Review: Stuff - Worked fine. Exactly what I needed. Thank you.

## Features

- This battery is applicable to electronic products with DIY 3.7-5V less than 2.96Wh 800mAh.（★Not suitable for power tools and model aircraft）
- Please compare the connector specifications and polarity according to the display diagram before purchasing,★the red wire is the positive "+" and the black wire is the negative "-"，Do not reverse-charge or reverse-connectreverse. The primary battery of some products has no plug or mismatched plug or mismatched polarity. It doesn't matter, you can cut and solder the plug directly or use our heat shrinkable insulating sleeve to connect the same color wire.
- 603040 rechargeable lithium ion polymer battery, nominal voltage 3.7V, full charge voltage 4.2V, capacity 800mAh, power 2.96Wh, ★size 6×30×41mm(0.236×1.181×1.614inch）(T*W*L), Weight:16g(0.564oz)，Maximum current:0.8A。 It can prevent overcharge, overdischarge, overcurrent, and short circuit.
- It‘s consists of of large-capacity A+ lithium battery, Japanese Seiko IC overcharge and overcurrent short circuit protection board, 3302-26 high temperature resistant silicone cable, and genuine JST Pitch1.25mm ★2 wire connector module.
- If there are any quality issues within a year,★ please feel free to contact us via email for replacement.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B09YQ2C1KR |
| Amperage | 0.8 Amps |
| Antenna Location | GPS, Power Tool, Watch |
| Battery Capacity | 800 Milliamp Hours |
| Battery Cell Composition | Lithium Polymer |
| Battery Cell Type | Lithium Polymer |
| Battery Weight | 13.7 Grams |
| Best Sellers Rank | #249,411 in Health & Household ( See Top 100 in Health & Household ) #352 in 3.7V Batteries |
| Brand | HXJNLDC |
| Customer Reviews | 4.3 out of 5 stars 209 Reviews |
| Item Dimensions | 1.61 x 1.18 x 0.24 inches |
| Item Weight | 18.7 Grams |
| Manufacturer | HXJN |
| Model Name | 603040 |
| Model Number | 603040 |
| Number of Batteries | 1 C batteries required. (included) |
| Recommended Uses For Product | GPS, Power Tool, Watch |
| Reusability | Rechargeable |
| UPC | 754525114512 |
| Unit Count | 1 Count |
| Voltage | 3.7 Volts (DC) |
| Warranty Description | 1 |

## Product Details

- **Number of Batteries:** 1 C batteries required. (included)
- **Brand:** HXJNLDC
- **Battery Cell Composition:** Lithium Polymer
- **Battery Capacity:** 800 Milliamp Hours
- **Recommended Uses For Product:** Power Tool, Watch, GPS

## Images

![DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement - Image 1](https://m.media-amazon.com/images/I/61OCFCtcXgL.jpg)
![DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement - Image 2](https://m.media-amazon.com/images/I/61-CfYigTPL.jpg)
![DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement - Image 3](https://m.media-amazon.com/images/I/81jSmvePDIL.jpg)
![DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement - Image 4](https://m.media-amazon.com/images/I/81ygEeonPJL.jpg)
![DC 3.7V 800mAh 603040 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Products with Built-in 2-Wire Battery Replacement - Image 5](https://m.media-amazon.com/images/I/61DxcVn5-ML.jpg)

## Customer Reviews

### ⭐⭐⭐⭐⭐ Nice fit to Anki Cosmo
*by L***M on May 11, 2025*

I have used this battery to update Anki Cosmo robot as described various guides which used 503040 600 mAh. 603040 fits perfect and 800 mAh is much better for endurance - kids tests Cosmo for 2 hours and still very well changed, so I may assume resulting runtime will be 2.5 - 3 hours.

### ⭐⭐⭐⭐⭐ Stuff
*by Z***S on October 24, 2025*

Worked fine. Exactly what I needed. Thank you.

### ⭐⭐⭐⭐⭐ 100% satisfied
*by J***D on October 28, 2022*

I ordered this for my daughters magic mixies cauldron and it works perfect!

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*Product available on Desertcart Iceland*
*Store origin: IS*
*Last updated: 2026-06-07*