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E-bike battery cases for cargo bikes

Cargo builds carry the most weight over the longest distance, and that combination is what decides the format — not the frame.

Who this is for: Assemblers building cargo and delivery packs, and brands whose frames expect a rack-mounted enclosure.

What this build actually constrains

Payload beats stealth

A loaded cargo bike already looks like a cargo bike. Hiding the battery inside the frame buys nothing and costs capacity.

The envelope is the whole problem

Cargo routes are long. Every extra cell you can carry is range you do not have to trade for load.

Weight wants to be low and central

Which is the one place a down-tube case and a rack case differ most.

Formats that fit

What we would put on this build

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  • Rear Rack — 17 models, up to 104 cells on 18650 and 78 on 21700.
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  • Downtube — 21 models, up to 200 cells on 18650 and 160 on 21700.
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  • Silver Fish — 27 models, up to 130 cells on 18650 and 160 on 21700.
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Worth knowing — the one to avoid here

Water Bottle

A 30-cell envelope is the least you can carry. On a cargo build it is the wrong tool — the frame has room for a down-tube case, so use it.

Highest capacity in those formats

Models worth starting from

Full range in every format, with the numbers, in the format comparison.

Questions we get about this build

What is the biggest battery case for a cargo bike?
Our largest envelopes take 104 cells on 18650 or 78 on 21700 on a rear rack case, and 200 cells on 18650 on the largest downtube mould. Rack mounting frees the frame triangle, down-tube mounting keeps the weight lower and more central.
Can I use a rack case on a two-wheeled cargo bike?
Yes, but be aware of how it changes handling: the weight sits high and behind the rider. On a trike that is a non-issue. On a two-wheel cargo bike with a light front end it is noticeable when loaded.

Send us the build and we will say which format works

Frame envelope, cell type, series and parallel count is all we need. If the answer is that none of our moulds fit and it needs a new one, we will say that rather than sell you the nearest thing.