The short answer

Choose a custom lithium battery pack manufacturer that can prove its safety certifications, name the exact cells and BMS it will use, and show you a working prototype before production. Price matters, but a factory that cannot explain its BMS design, cell sourcing or testing process is a bigger risk than a slightly more expensive partner. In this guide we walk through the qualification checklist B2B buyers use when sourcing custom battery packs.

Why supplier selection matters more than chemistry

A lithium battery pack is the most safety-critical component in an e-bike, power tool, robot or industrial machine. The same 48V 20Ah specification can be built with genuine, grade-A cells and a properly designed BMS — or with downgraded cells and a minimal protection board that quietly shortens life and creates fire risk. Because the difference is invisible from the outside, B2B buyers must verify the process, not just the price.

This matters for compliance too. If your product is sold into the EU or North America, the battery certificate (for example UN38.3 transport testing, CE documentation or UL 2271 for e-bike batteries) is part of your own compliance file. A supplier that cannot produce valid documents will become your problem at customs or at an audit.

Step 1: Verify certifications and documents

Ask for the following before you discuss price. Any serious manufacturer has them ready:

  • UN38.3 test report — required for transporting lithium cells and packs by air, sea and road.
  • MSDS / SDS — material safety data sheet needed for shipping and customs.
  • CE documentation — for selling into the EU (batteries fall under the EU Battery Regulation 2023/1542, which also adds QR-code and battery-passport requirements from February 2027).
  • UL 2271 — the standard for light electric vehicle (e-bike, e-scooter) batteries sold in North America.
  • IEC 62133 — the international safety standard for portable sealed cells and packs.
  • RoHS — restricted-substance compliance for EU markets.

XINYUEGE New Energy’s custom packs are built with CE, RoHS, UN38.3, MSDS and UL 2271 compliance in the documentation set. If you are an importer, read our guide on EU Battery Regulation 2023/1542 to understand the passport deadlines that now apply.

Step 2: Ask about cells and BMS before you ask about price

Two questions reveal more about a factory than any price list:

  1. Which cells will you use, and can you name the brand and model? Genuine cells from major manufacturers (for example Samsung, LG, Panasonic, or established brands such as EVE and CATL) have traceable production lots. Ask for the cell model, its datasheet, and a sample of the batch label. Counterfeit or “white-label” cells are a known problem in spot-market procurement.
  2. What BMS will you use, and what does it protect against? A well-specified BMS protects against overcharge, over-discharge, over-current, short circuit, over-temperature and cell imbalance. For industrial packs you may also need communication (CAN, RS485, UART or Bluetooth) and state-of-health reporting.

If the supplier cannot answer both questions in writing, move on. Our engineers always specify the cell brand, cell model, BMS architecture and protection parameters in the proposal for every custom project — see how we did it for a 41.2V humanoid robot battery with Samsung 50S cells.

Step 3: Check engineering depth and the prototyping path

Custom packs are rarely “off the shelf”. Your battery must fit a physical space, match a voltage and current profile, survive your environment, and talk to your controller. That requires engineering, not just assembly:

  • Electrical design — series/parallel configuration, cell selection, BMS architecture.
  • Mechanical design — enclosure, mounting, connectors, waterproofing (IP rating).
  • Prototype — a functional sample built and tested before mass production.
  • Certification support — helping you get the right tests and documents for your market.

A typical development flow at XINYUEGE follows five phases: requirements analysis, solution design, prototype development, testing & certification, then mass production with QC. We publish the full flow in our article on custom battery development services.

Step 4: Write a real RFQ

The quality of the quote depends on the quality of your specification. Include at least:

  • Nominal voltage and capacity (or energy in Wh).
  • Max continuous current and peak current (this decides the BMS rating and cell choice).
  • Operating environment — temperature range, vibration, indoor/outdoor, IP requirement.
  • Communication protocol if the device needs one (CAN, RS485, UART, Bluetooth).
  • Physical dimensions and mounting constraints, connector type.
  • Target markets, so the supplier can include the right certificates.
  • Expected annual volume — this affects cell sourcing and pricing structure.

You can use our custom battery inquiry form — it collects exactly these parameters (size, voltage, capacity, motor power, BMS current, communication protocol and application) so the engineering reply starts from real numbers.

Step 5: Test the sample, not the brochure

Ask for a functional sample and test it in your real device with production-intent motor, controller and charger. Check: runtime under load, temperature rise, charge behaviour, vibration resistance, and how the pack behaves at low state of charge. The sample is the cheapest insurance you can buy — problems found at this stage cost days, problems found after mass production cost quarters.

Red flags to avoid

  • A price list with no engineering questions about your application.
  • Vague cell sourcing (“we use good cells” without a brand and model).
  • No UN38.3 report, or only a generic one not tied to your cells.
  • Commitments on cycle life with no test data behind them.
  • Offering to swap cells after the sample stage “to save cost” without your approval — insist on a cell-brand lock clause in the agreement.

Frequently asked questions

How long does a custom battery pack take to develop?

Typical projects run from a few weeks for standard configurations to several months when new tooling, testing or certification is involved. The exact timeline depends on the specification and the certificates your market requires. Ask for a dated milestone plan at RFQ stage.

What is the minimum order quantity (MOQ) for custom packs?

Many manufacturers accept small prototype quantities for testing, then require larger volumes for mass production. Discuss both numbers separately: prototype MOQ and production MOQ.

Can you build LiFePO4 packs as well as NMC?

Yes — XINYUEGE designs and manufactures both Li-ion (NMC) and LiFePO4 packs. The chemistry should follow the application: NMC for weight- and size-sensitive devices, LiFePO4 where cycle life and safety matter more. Compare them in our article Li-ion vs LiFePO4: which chemistry.

Do you support BMS communication protocols?

Yes — CAN bus, RS485, UART and Bluetooth are all options, depending on the application. See our guide on customizing voltage, capacity, BMS and communication.

Ready to evaluate a partner?

Send us your application and target specification via the custom battery inquiry form or contact us on WhatsApp. We reply with a real proposal: cell options, BMS architecture, documentation plan and a milestone timeline — no generic price list.