Description
The battery decides how far the ride goes. Every conversation about electric bikes eventually reduces to one component. Motors are rated, controllers are tuned, frames are painted, and then the battery determines whether the bike is a toy or a vehicle. A rear-rack pack answers the practical question that frame-mounted packs cannot: where does the capacity go when the triangle is already full.
This pack ships in two configurations. The 36V 21Ah version suits commuter and cargo builds that run moderate assist levels over long distances, and the 72V 21Ah LG-cell version feeds high-voltage mid-drive systems where torque delivery matters more than range anxiety. Both mount on a rear rack, which leaves the frame free for a larger triangle bag, a second pack in parallel, or nothing at all.
The cells are grade A sourced from official channels, matched and assembled into a pack with a multi-protection BMS that watches over-current, over-voltage, under-voltage, short circuit and temperature. The case is aluminium rather than plastic, sealed to IP65, and carries a USB port for charging a phone or a Bluetooth speaker plus an LED tail light that runs from the pack itself. That tail light is a small detail with a large consequence on an unlit road.
Service is engineered rather than promised. A CE charger with an inline fuse ships with the pack, the assembly carries CE, UL and RoHS reports, the shipment carries MSDS and UN38.3 documentation for air and sea freight, and an 18-month warranty is backed by service points in Germany, Belgium, the UK, Poland, the US, Canada and Australia. A battery is the one part of an e-bike that cannot be repaired by a local shop, so where it was built and who stands behind it matters as much as the amp hours.
Range is not a specification. It is the shape of your day.
What the Rack Reserve Actually Does
- ✦ Two voltage tiers covering 36V 21Ah commuter builds and 72V 21Ah LG-cell high-torque mid-drive systems.
- ✦ Rear-rack mounting that frees the frame triangle for luggage, a second pack or nothing at all.
- ✦ Grade A matched cells from official channels, never salvaged or re-wrapped stock.
- ✦ Multi-protection BMS guarding over-current, over-voltage, under-voltage, short circuit and temperature.
- ✦ IP65 aluminium enclosure that resists impact and weather far better than a plastic shell.
- ✦ USB charging port and integrated LED tail light running directly from the pack.
- ✦ 18-month warranty with service points in Germany, Belgium, the UK, Poland, the US, Canada and Australia.
Technical Specifications
- Configuration A: 36V 21Ah with rear rack
- Configuration B: 72V 21Ah with rear rack, LG cells
- Cell type: 21700 / 18650 grade A lithium, matched and assembled
- BMS: multi-protection with temperature sensing
- Enclosure: aluminium case, IP65 rated
- Extras: USB charging port, LED tail light, LED power indicator
- Charger: CE charger with inline fuse included
- Certification: CE, UL and RoHS reports, MSDS and UN38.3 shipping documentation
- Warranty: 18 months
- Dispatch: Germany warehouse
Where It Belongs
Cargo bike builders use the rear rack position because the frame triangle is occupied by a reinforced cargo structure. Commuters with long, flat routes choose the 36V 21Ah pack for a day of riding without carrying the charger. Conversion kits running 72V mid-drives need the high-voltage pack for torque delivery on climbs. Rental and fleet operators value the aluminium case and IP65 sealing, since a fleet battery lives outdoors and gets handled by people who did not buy it. Tinkerers who want a second pack in parallel appreciate a rack mount that does not force them to choose between capacity and a frame bag.
Questions Buyers Ask Before Ordering
Q: How do I know which voltage matches my bike?
A: Check the controller and motor rating on the original pack or the motor label. A 36V system will not accept a 72V pack without replacing the controller and motor, and a 72V controller may refuse to start on 36V. Match the pack to the system you already have rather than the other way around.
Q: Is a rear rack pack safe on a bike that carries loads?
A: Yes, provided the rack is rated for the weight. The pack adds mass behind the rear axle, which affects handling more than braking, so keep the total load within the rack rating and check that your rack is bolted to the frame rather than to a seatpost clamp.
Q: What does the IP65 rating actually cover?
A: Dust-tight and protected against water jets from any direction. Rain, puddles and hose spray are fine. Submersion is not, and neither is a pressure washer aimed at the seams, which is how most waterproof claims get tested to failure.
Q: Can I charge a phone from the pack while riding?
A: The USB port runs from the pack, so yes. Draw is small relative to the pack capacity, and the port is useful for a phone running navigation on a long ride. It will not charge a laptop.
Q: How long does a full charge take?
A: The included CE charger brings a 21Ah pack to full in roughly six to eight hours depending on the state of discharge. Overnight charging is the normal pattern. Faster charging shortens cell life, so the standard charger is the better default.
Q: Is there a warranty claim path outside the EU?
A: Yes. Service points cover the US, Canada and Australia as well as Germany, Belgium, the UK and Poland. Claims are handled with return, repair or replacement, and video technical support is available before a return is authorised.







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