Although it may look like a small item bolted onto the back of your bike, the 998.4Wh battery on the rear of your bicycle is a large deal. When you consider that the same amount of energy is contained in a 998.4Wh battery (essentially, a full kW), that's the same amount of energy that would be found in a full kW of stored energy, you can begin to understand why many cyclists find the presence of such a battery provides a great sense of flexibility regarding ride-planning. Many cyclists do not feel the need to plan their rides around when they need to recharge their battery. However, they rather simply ride. In fact, one of the larger capacity offerings within the rear-rack battery market segment, the Yose Power 48V 20.8Ah rear rack battery will likely provide the user with sufficient range (i.e., enough energy to allow him/her to ride home after leaving work or school) assuming the cyclist does not exceed the maximum current limit of his/her controller.
Specs and Build Quality
The headline specifications for this battery include:
- Nominal Voltage: 48V
- Maximum Discharge Current: 40A
- Total Energy Storage: 998.4Wh
Inside the battery, the pack consists of thirteen serially connected groups of eight lithium-ion cells. Each group of eight cells is connected in parallel to increase the capacity of that group. Since there are thirteen cells in series, this configuration yields a nominal voltage of 48V. Since each group is comprised of eight cells in parallel, the maximum current capability of the entire pack is increased by the number of parallel connections. As opposed to being mounted underneath the downtube or tucked into the frame triangle, this battery mounts to the rear rack behind the seat tube. Although mounting to a rear rack shifts the center of gravity relative to having a downtube-mounted battery, it affords much greater flexibility since it allows for panniers and other accessories to be added that cannot be easily accommodated when a battery occupies the frame triangle.
Additionally, the Anderson-style output connector utilized on this pack is well-suited for high-current applications and finds its way onto heavy-duty commercial products including power tools and industrial equipment due to its reliability, ease-of-use, and ability to accommodate large currents.
Yose Power reports that their battery will support motors ranging from 250W to 1500W. However, regardless of how powerful the motor, it must also be capable of accepting charges of at least 25A to support operation. Therefore, even though this battery offers ample stored energy for supporting large motors, it is essential to verify that your controller is able to accept 40A discharges prior to purchasing the battery.
BMS and Safety Features
In addition to offering a large quantity of stored energy, Yose Power has incorporated a sophisticated Balancing Management System (BMS) that monitors and controls various aspects of the pack's operation. Specifically, the BMS monitors and controls:
- Over-Charge Protection: prevents excess voltage from damaging the cells.
- Over-Discharge Protection: protects against cell degradation resulting from prolonged exposure to excessively low voltages.
- Over-Temperature Protection: detects overheating and prevents continued operation to prevent damage to the cells.
- Short Circuit Detection: detects a short-circuit condition between two points on the pack and immediately shuts-down operations to prevent damage.
- High-Current Monitoring: continuously monitors pack current levels and will shut-down pack operation upon detecting excessive current flows (in excess of 70A).
As noted earlier, Yose Power utilizes Grade A cells throughout their packs. They claim that these cells will endure more than 1000 charge/discharge cycles. While nobody truly knows if these claims hold true until they are tested via repeated cycling of the pack, selecting reputable manufacturers reduces the likelihood of encountering issues associated with substandard components.
There is also a small 5V USB port located on the front face of this pack. While it might seem nice to be able to utilize this feature to trickle charge smaller devices (e.g., phones), it seems unlikely that this feature would ever be used by a cyclist who mounts a large battery on their rear rack.
The quality control process employed by Yose Power includes testing every pack prior to shipping. Unfortunately, these tests occur at the factory and are therefore not visible during installation or post-installation evaluation.
The pack includes several items that are useful for initial installation, troubleshooting, and maintenance:
- Install and Troubleshooting Information
- Spare Fuses
- Anderson-to-Anderson Adapter Cable
- Two Keys for Locking Pack
- 54.6V DC Input 3A AC/DC Charger
Regarding those two keys provided for locking your pack, while they are marketed as a theft deterrent, they really serve primarily as a method of preventing unauthorized access to your power source when you park your bike and leave. They are not intended as a comprehensive security solution.
Range and Real-World Performance
Amazon currently lists this product with a four-and-one-half star rating based upon eight customer reviews. Given that this represents less than one percent of all Amazon listings for bicycles or bicycle-related products, it is prudent to exercise extreme caution when evaluating ratings based solely upon this limited sample size. Nevertheless, reviewers have offered uniformly favorable commentary regarding performance.
Specifically, customers report that this pack meets their estimated capacities for producing electrical energy for their bicycles. Several owners report that they have been able to extend afternoon rides across varying terrain types due to the abundance of stored energy in this pack. None of these reviews suggest dissatisfaction among buyers regarding performance.
The primary drawback identified by reviewers relates directly to price. The cost per watt-hour represented by this pack is significantly higher than what consumers typically encounter when purchasing from vendors utilizing unknown branding.
It appears that consumers are willing to expend additional funds for a proven name-brand, warrantied product containing a robust 40A BMS and employing rigorous quality control processes prior to shipment as part of an overall bundle that includes all necessary accessories.
While it would be possible to purchase similar packs from unknown vendors at substantially reduced prices, ultimately consumers must weigh perceived value derived from premium features against costs incurred.
When using the charger supplied with this pack (a 54.6V DC input at 3A), complete recharge times are approximately seven hours. While this is acceptable for overnight recharging purposes, charging times could potentially become quite lengthy if attempting rapid recharging between shorter trips. Consumers seeking faster recharging capabilities would require acquisition of chargers delivering more than three amps.
Who Is This Battery For?
For cyclists who tend to invest in premium products and prefer not to risk money on inexpensive unknown branded products (with potential to fail early), this is an attractive option for building high-powered ebikes. While there certainly exist less expensive alternatives available, consumers receive a recognized brand name (and thus warranty), quality components (including Grade A cells), a robust BMS, and rigorous quality control processes as part of this premium product. Some consumers choose to acquire budget-priced products simply as a means to save money. Although others may eventually learn that lesson firsthand.
Mounting this battery onto most racks is relatively straightforward, essentially bolt-on. Of course, rack configurations vary depending upon the specific design used, so ensure adequate clearance prior to ordering.
As previously mentioned, range will depend upon multiple factors including:
- Your motor power output
- Your body weight
- Terrain characteristics
- Throttle vs Pedal usage patterns
Upon average power outputs below 750W, customers often report extended ranges attributable largely to this pack's massive 998.4Wh capacity. Therefore, view this pack as an alternative for extended-range applications as opposed to merely an accessory for quick local commutes. If you want to see how it stacks up against downtube and frame options from other brands, our blog has more battery breakdowns worth a read.
Frequently Asked Questions
Will this battery work with my 48V motor?
If your motor and controller run on 48V, the battery is electrically compatible across the 250W to 1500W range. The catch is matching the 40A discharge to your controller's limits. Check your controller's max amp rating before you buy so the BMS isn't tripping on you mid-ride.
How long does a full charge take?
The included 54.6V 3A charger takes around 7 hours to go from empty to full. It's not fast, but for overnight charging it's perfectly workable. If you want quicker top-ups you'd be looking at a higher amperage charger.
Is the rear rack mount easy to install?
Generally yes, especially if your bike already has a rack. The battery sits on a holder base and locks with the included keys. The exact mounting depends on your rack design, so double check the measurements against your setup before ordering.
How much range can I actually expect?
That depends a lot on your motor power, your weight, terrain, and how much you pedal. On a typical 750W setup, users report very long rides thanks to the 998Wh capacity. It's safe to say this is a battery built for big range, not a quick hop around town.
What does the 40A BMS actually protect against?
The BMS is designed to prevent damage caused by excessive charge levels, excessive discharge levels, excessive current flow through the cells themselves, and short circuit conditions. It prevents overcharging, over-discharging, exceeding maximum allowable sustained current, and short-circuits, with a 40A sustained discharge limit and a trip threshold around 70A for surges.
Is the extra cost worth it over cheaper batteries?
That's the real question, and it comes down to what you value. You're paying more per watt hour here than for some budget packs, but you're getting a known brand, a proper 40A BMS, QC testing, and the full accessory bundle. For a high-power build where you don't want to gamble on a mystery pack, a lot of riders find it worth it. You can check the current price and details on Amazon to see if it fits your budget.
The rear rack battery segment has a few strong options, and the Yose Power 48V 20.8Ah is one of the bigger capacity plays in it. If you want to see how it stacks up against downtube and frame options from other brands, our blog has more battery breakdowns worth a read before you pull the trigger.