Rechargeable battery packs: the basics
A rechargeable pack is bought for its lifetime cost and convenience, not for a single discharge. This guide explains the ideas a first-time buyer needs: chemistries, cycle life, self-discharge, charging and replacement.
Layered pack cross-section — the site's recurring diagram motif. It is a schematic, not a photograph of a product, factory or customer project, and it is not presented as a photograph of this company's factory.
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Chemistries first. Li-ion packs offer high energy density for tools, vehicles and portable devices. LiFePO4 packs offer long cycle life for storage, solar and backup. Li-polymer packs offer thin and shaped outlines for wearables and compact devices. NiMH packs offer simple charging and standard sizes for toys, home devices and legacy equipment. Sodium-ion models appear in this range as a secondary line, with lower energy density in general terms. No chemistry is best for every device; the best chemistry is the one whose strengths match the device's duty and whose weaknesses do not matter for it.
Cycle life second. A cycle-life figure — for example 2000 cycles or more on this site's solar packs, 800 cycles on the 18650 cell, 500 cycles on the e-bike pack and the NiMH pack, 300 cycles on the wearable Li-polymer pack — describes how many full charge and discharge cycles the listing states before capacity fades to a defined level. Cycle life is measured under the listing's conditions, and real service differs: shallow cycles last longer than deep cycles, gentle currents last longer than harsh ones, and temperature matters throughout. Compare cycle-life figures only between listings that state comparable conditions, and treat any figure without conditions as a general indication rather than a guarantee.
Self-discharge third. A rechargeable pack loses charge while sitting unused, and the rate is listed per model — 3% or less per month on the solar packs, 2% or less on the 18650 cell, 1C discharge rate figures on other listings being a different measure entirely, not to be confused with self-discharge. For a device used daily, self-discharge hardly matters; for a backup pack, a sensor or a seasonal device, it decides whether the pack is ready when needed. Ask for the self-discharge figure for the exact model, and compare it on the same monthly basis.
Charging and replacement close the basics. Charge a pack with a charger matched to its chemistry, voltage and current — the charger pages on this site explain the matching for each chemistry — and never improvise a charger across chemistries. Replace a pack by matching the original's voltage, capacity, dimensions, protection and connector, not just its chemistry label, because a pack that matches on one dimension and differs on another is still a mismatch. For a new device, the custom route designs the pack around the device; for an existing device, the original pack's specification is the design.
Questions to ask before you order
- Which chemistry's strengths match the device's duty?
- What cycle life does the exact listing state, and under what conditions?
- What self-discharge rate applies, and does the device sit unused for long periods?
- Does the charger match the pack's chemistry, voltage and current?
- For a replacement, does the new pack match voltage, size, protection and connector?
Related pages
Custom packs · 18650 basics · Chargers · Choosing a custom pack
How to place an inquiry, step by step
- Send the device facts. Tell us the device type, the available space (length, width and maximum thickness), the nominal voltage you need, the capacity or runtime you target, and the peak current if your device has motors, radios or heaters.
- Name the model or the chemistry. If a page on this site matches, quote its model description and listing details. If nothing matches, say so and describe the chemistry and voltage you need, so the conversation starts on the custom route.
- Confirm documents and terms in writing. Ask for the certificate set for that exact model, confirm the minimum order, the price basis and the lead time for that listing, and confirm payment and warranty terms before you pay. Terms stated for one model listing do not transfer to another model.
- Agree the sample step. Confirm whether the next step is a listed sample, an engineering sample for a custom design, or a small trial order, and what test you will run on arrival — fit in the enclosure, runtime, or peak-current behaviour.
Send all of this in one message through the contact page: device type, space, voltage, capacity, peak current, model description if you have one, and the documents you need. That is the whole inquiry — no separate form, no account, no extra step.
What to send us now
Send one message with your device type, the space the pack must fit, the voltage and capacity you need, the peak current if it matters, and the model description if a page on this site already matches. Add the documents you need — certificates are available upon request — and whether you need a listed model or a custom design. Use the contact page or write to [email protected], or call +86-755-25629920. A specific message like that is what turns a range of hundreds of models into a short, answerable question.