Pedalwise
Reference

E-bike battery rebuilders and replacement pack builders

When a rebuilt or third-party battery makes sense versus a maker replacement, what to ask a builder, and a neutral list of builders that state they use new name-brand cells.

Last edited Nov 8, 2026 by Pedalwise team Edit History Add a subpage

The Pedalwise team started this page from official manuals, support pages and repair videos. Fixed this yourself, or spotted something wrong? Help improve it.

Battery and electrical safety. Lithium-ion batteries can catch fire if they're damaged or charged wrong. Never open a battery pack, and stop using any battery that's swollen, hot, wet or smells burnt. Every edit to this page is checked by a second person before it goes live.

When an e-bike battery wears out, the first place to look is the company that made the bike. CPSC advises using only a replacement pack that has been tested and approved to work safely with your device and that the device maker confirms is right for it. A third-party new pack or a rebuild (new cells fitted inside your old case) is a fallback for when the maker's pack is no longer sold, or when you accept the tradeoffs below. This page explains how to weigh that choice and lists a few builders, for information only and not as endorsements. See CPSC's micromobility safety page.

A few facts worth knowing before you decide:

  • A third-party or rebuilt pack is not approved by your bike's maker. Electric Bike Report notes that fitting one will likely void the bike's warranty while it is still covered, and builders such as ChiBatterySystems say the same on their own pages. See Electric Bike Report's replacement battery guide.
  • CPSC says never to use a pack that was modified or reworked by unqualified people, and never to use repurposed or used cells. Only consider builders who state they fit new, name-brand cells and a battery management system (BMS).
  • UL 2271 is the safety standard for e-bike battery packs on their own, including aftermarket packs, while UL 2849 tests the whole e-bike electrical system together. Electric Bike Report links many battery fires to low-cost packs and to repairs done without the maker's authorization. See Electric Bike Report on UL certification.
  • Some makers point owners of older models to a rebuilder. Optibike, for example, names a third-party rebuild as a cheaper and faster option for its older bikes. See Optibike's rebuild options page.

Never open a battery pack, swap cells or touch the BMS yourself. A damaged or badly built pack can catch fire. Also avoid cheap packs with no stated cells, no BMS details and no certification. If your battery is failing, start with battery won't charge and e-bike battery care, then get a pro.

How to choose a builder

Ask these questions before you buy or ship anything:

  1. Can the maker still supply a pack? If yes, that is the approved option. Check repair or replace for help weighing the cost.
  2. Which cells will they use, and are they new? Look for a named cell brand. Skip any builder that uses used, reclaimed or unnamed cells, as CPSC warns against used cells.
  3. What BMS goes in the pack? The BMS protects against overcharge, over-discharge and overcurrent. Grin's battery guide describes these protections. See Grin's battery options guide.
  4. Which certifications do they state? Look for UL 2271 on the pack and UN38.3, the testing lithium batteries need for shipping. Electric Bike Report treats a UN38.3 mark as a reassuring sign even where it is not required.
  5. What is the warranty, and what does it exclude? Get it in writing from the builder's own site.
  6. How does shipping work? Lithium batteries ship under hazardous goods rules. Mail-in rebuilders usually send you a label or a special shipping kit, so wait for their instructions.
  7. Will it work with your charger and display? Electric Bike Report advises using the original charger where you can. A rebuilt pack may lose features such as the battery's own charge lights. See check your charger.

Builders and rebuilders

Listed alphabetically. These are listed for information, not endorsements. Details come from each company's own site as read in November 2026, so confirm current terms with the company.

ChiBatterySystems

ChiBatterySystems builds replacement and higher capacity packs for e-bikes, Onewheel boards and other light electric vehicles, and says its batteries are designed and assembled in its Chicago Heights, Illinois facility. It also runs a mail-in rebuild for Juiced 52V G1 and G2 packs, fitting Samsung 50S 21700 cells and a Daly Smart BMS inside the original case, with a stated 1 year warranty. That rebuild page says using its battery voids the vehicle maker's warranty and that the battery's own charge lights and power button no longer work. See ChiBatterySystems and its Juiced rebuild page.

EM3ev

EM3ev builds e-bike battery packs from 36V to 72V, plus custom packs, and says it has built its own packs since 2011. It is based in Changzhou, China, and its site names Samsung, LG and Panasonic as its cell sources, with a smart BMS, and a 1 year warranty on products unless stated otherwise. It does not offer rebuilds. Its shipping policy says most US addresses get battery shipments with duties paid by the seller, some addresses are billed duties on delivery, and delivery usually takes about 2 to 3 weeks after dispatch. See EM3ev's about page and its shipping policy.

FTH Power

FTH Power, in Walnut, California, sells new e-bike packs it says are assembled in the USA and offers mail-in repair and rebuild. A $55 evaluation comes first and is credited toward the repair if you go ahead. It states it uses only Panasonic, LG and Samsung cells for rebuilds, and it does not rebuild packs with proprietary data systems such as Bosch, BionX, Shimano and Yamaha. Its site states a 2 year limited warranty on new batteries and 1 year on rebuilds. See FTH Power's repair page and its warranty page.

Grin Technologies

Grin, based in Vancouver, Canada, sells new e-bike packs rather than rebuilds. Its site says the packs use Panasonic, LG or Samsung cells with a protective BMS, that its triangle packs and 48V 21Ah downtube pack are UL 2271 certified, and that all packs ship with UN38.3 certification. Its warranty is 3 years on its own LiGo packs and 1 year on its downtube packs, and it says batteries cannot simply be sent back for diagnosis and repair. See Grin's battery options guide and its warranty page.

When to go back to the maker

  • Your bike is still under warranty. A third-party pack will likely void it, so contact the maker or your dealer first.
  • Your bike uses a system battery, such as Bosch, Shimano, Yamaha or Brose. These packs talk to the motor, and FTH Power, for one, says it cannot rebuild Bosch, Shimano or Yamaha packs.
  • The battery is built into the frame. Electric Bike Report says swapping a frame-integrated battery is a job for the dealer or an expert shop.
  • There is an open recall. Check CPSC and your maker's site, and follow the official fix.
  • The pack is swollen, hot, smells odd or was in a crash or flood. Stop using it, keep it away from anything flammable, and take it to a shop. Don't ship it until a pro says it is safe to. CPSC advises taking dead lithium batteries to a battery recycler or hazardous waste center, never the trash.

For charging habits that make any pack last longer, see e-bike battery care and store your battery for winter.

Sources

Stuck after these checks? Find a shop near you.

Need a pro?

If these steps didn't fix it, find a shop near you in our partner network. For battery or wiring trouble, look for shops marked Battery and electrical.

Talk

Questions, things that worked for you, or something that looks wrong on this page.

Sign in to join the conversation.

CC BY-NC-SA 4.0Text by Pedalwise and contributors, shared under CC BY-NC-SA 4.0. Linked videos and manuals keep their own terms. How to reuse it