Custom battery pack process: from cell selection to BMS matching
A custom battery pack is not ordered; it is developed. This article follows that development from the first decision to the first production batch, in the order a buyer will actually experience it.
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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Step one: the device specification
Every custom pack starts with a device specification, and the specification is five facts: the device type, the space available, the nominal voltage, the capacity or runtime target, and the peak current. Those facts are the design brief. A buyer who writes them down before contacting a manufacturer gets a faster, more accurate reply than a buyer who starts with a price target, because the manufacturer can immediately test chemistries, series counts and outlines against the brief instead of asking for the same facts again.
The space fact deserves emphasis, because it is the most often underestimated. Length, width and maximum thickness must all be stated, with room for the protection board, the wiring and the connector, because a pack is a system, not just cells. A cavity drawing, where one exists, is worth more than a paragraph of description: it lets the manufacturer see the outline, the fixing points and the cable exit in one view, and it prevents the most common custom-pack failure, which is a pack that is electrically right and mechanically too large.
Step two: cell and chemistry selection
With the brief fixed, the manufacturer proposes a chemistry and a cell. LiFePO4 suits storage and long cycle life; Li-ion suits energy density; Li-polymer suits thin and shaped outlines; NiMH suits legacy voltages and simple charging. The cell choice follows from the brief's voltage, capacity, space and peak current together, not from any single figure: a cell with the right capacity but the wrong discharge current fails under load, and a cell with the right current but the wrong size fails in the cavity.
Cell selection also fixes the series and parallel arrangement. Series adds voltage; parallel adds capacity. A 12V-class pack, a 24V pack and a 48V pack are different series counts, and each implies a different charger voltage, a different protection board and a different wiring plan. A buyer should check the series count against the device's voltage window early, because changing it later means changing the charger and the protection as well.
Step three: protection and BMS matching
The protection board is matched to the pack, not chosen independently. Its series rating must equal the pack's series count, its current rating must cover the pack's peak discharge current with margin, and its features — balancing, temperature sensing, communication — must match the application's needs. The BMS guide on this site explains the board levels in general terms, and the custom BMS solution page describes how a board requirement is written for a specific pack. The key point for a buyer is that the board and the pack are one design: a board proven with one pack does not automatically suit another, even at the same voltage.
Charger matching belongs in the same step. The charger must match the pack's chemistry, series count and charge rate, and it must be confirmed against the exact pack, not chosen on voltage alone. A pack, a board and a charger specified together form a system; the same three items specified separately often disagree on at least one point, and the disagreement usually appears after samples, when it is expensive to fix.
Step four: samples, testing and production
The sample step is where a custom pack is proven. An engineering sample is built to the agreed specification, and the buyer tests it against the real device: fit in the enclosure, runtime under real load, behaviour at peak current, and charging with the intended charger. The company profile on this site states free samples as part of its service, which makes the sample step cheap; skipping it makes it expensive, because a bulk order built on an unproven design carries the whole design risk at volume.
Testing should be planned before the sample arrives, not improvised after it. Decide what fit means — which dimensions, which fixing points, which cable exit — what runtime means — which load, which duty, which reserve — and what peak-current behaviour means — which surge, for how long, with what voltage sag allowed. A sample that passes an undefined test proves nothing, while a sample that fails a defined test teaches exactly what to change.
Production follows the sample, and the principle is simple: the production pack is the sample pack, built at volume with the same construction, the same board and the same charger match. Scalable mass production, as the company profile states it, means the design proven in samples is the design produced in bulk, not a different construction at volume. A buyer should confirm that principle in writing — same cells, same board, same outline — before the first bulk order, because a production change that looks minor can change fit, protection or runtime.
What to send to start
A custom pack inquiry needs the five brief facts, plus the quantity band in general terms — sample, trial order or volume order — and the documents needed, noting that certificates are available upon request. It does not need a price target, and a price target without a brief cannot be answered accurately in any case. Send the brief, the cavity drawing if one exists, and the test plan for the sample, and the reply can be a design conversation rather than a request for the same facts again. Order quantities, in general industry terms, are discussed as bands rather than as a single figure, because the right band depends on the design's maturity and the buyer's market, and this site does not present a general quantity figure as this company's policy for any particular pack.
Common custom-pack mistakes
The most common custom-pack mistake is ordering from a price target rather than a specification. A price without a brief — without voltage, capacity, space and peak current — cannot be quoted accurately, and the reply will either be a guess or a request for the same facts again. A buyer who starts with the brief gets a design conversation; a buyer who starts with a price gets a delay. The brief costs an hour to write and saves weeks of revision, because every later decision — chemistry, series count, board, charger — refers back to it.
The second common mistake is skipping the sample test plan. A sample that arrives without a defined test — which dimensions, which load, which runtime, which peak current — can pass or fail without teaching anything, and the bulk order then carries the same uncertainty at volume. A test plan need not be long: fit in the enclosure, runtime under the real load, behaviour at peak current, and charging with the intended charger, each with a pass mark written before the sample arrives. A sample that fails a defined test is useful, because it says exactly what to change; a sample that passes an undefined test proves nothing.
The third common mistake is changing the design between sample and production. A different cell, a different board, a different outline or a different connector may each look minor, but together they make the production pack a different product from the proven sample. Confirm in writing that production uses the same cells, board, outline and charger match as the sample, and treat any proposed change as a new sample step rather than a production detail. That discipline is what scalable production means in practice, and it is the cheapest insurance a custom-pack buyer can buy.
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.