If you're looking for a compact and popular ebike battery form factor that mounts along the seat tube, the VODIPOWER 48V 20Ah is a solid option. At 960 watt-hours with a 40A BMS, a key lock, and an LED charge level indicator, it checks off many of the boxes for a good replacement or upgrade battery. It weighs in at 9.5 pounds and has been built to pair with motors up to 1000 watts, which comfortably puts it into the sweet spot for most 48V hub motor and mid-drive setups.
VODIPOWER make a range of ebike batteries at many voltages and form factors. This silver fish is their seat tube offering, and it's obviously targeting riders who are in need of something that's basically a direct replacement for a factory battery, or those who want something that looks clean and unobtrusive on a conversion build. The key lock integrated into the design means you can secure the battery to the frame, while also removing it for charging or when you want to store it. Not every aftermarket battery has that.
Specs and Value
The numbers: 48V, 20Ah, which translates to 960Wh of total capacity. That's enough gas in the tank on a 48V system that it should ignore your weekend rides while plowing through your daily commutes without complaining too loudly about getting recharged. The BMS has a rating of 40A as opposed to the 30A boards you see on many competing packs, giving you a little more wiggle room for higher-draw motors.
Physical specs
The battery isn't very compact measured at 15.35 x 2.95 x 4.37 inches, which is common for a silver fish pack. It mounts to the bike frame along the seat tube using a base plate and locking mechanism. The 4-pin discharge port is something to be aware of, as you'll need to verify that you have a compatible port for your controller, or be prepared to switch connectors.
At 9.5 pounds the weight is reasonable for a 20Ah lithium-ion pack. Some of the cheaper batteries in this capacity class come in at 12 or 13 pounds, so this lighter weight indicates their cell quality is decent. You have an LED indicator on the battery for a helpful quick glance at your remaining charge, without the need to power on your display each time.
BMS and motor range
You get overcharge protection, over-discharge protection, short circuit protection, and temperature monitoring courtesy of the 40A BMS. At 40 amps continuous on a 48V system, you're looking at about 1920 watts of theoretical peak output. VODIPOWER rates it for motors up to 1000W in the feature bullets, though the title says compatible up to 1500W. In practice 40 amps is enough for any single motor setup up to the 250W to 1000W range, such as popular mid-drives like the Bafang BBS02.
A higher amp rating than the normal 30A BMS boards, so this battery is able to handle sustained high-draw situations a little better. There are lots of circumstances where a BMS rated at 40A is going to prove its worth over a lower-rated BMS. The most frequent ones are doing long climbs on throttle pulling a load, or even bigger, if riding a cargo bike with a passenger on board. The BMS itself is less likely to prematurely cut out when under such loading stress.
Form Factor and Compatibility
This classic silver fish design is the most popular size and shape for seat tube mounted batteries in the ebike world. They mount vertically down the seat tube that locks it into a base plate with a key. Fitting is just a matter of mounting the base to your seat tube first, sliding the battery into position and locking it with the included key. Removal is equally easy for indoor charging and if you want to take the battery with you.
You'll need to measure your seat tube before ordering to confirm that the battery dimensions of 15.35 x 2.95 x 4.37 inches can fit between it and the rear wheel, some frame geometries may not have enough space. Also confirm that the mounting points of the base plate line up with your frame, and that the 4-pin discharge connector fits your controller or is adaptable.
Your controller voltage should be 48V and rated current 40 amps or less. This will work with the vast majority of 48V ebike systems. If you are carrying out a battery swap with an identical silver fish battery on a preowned ebike that you already have, there's a good chance this will fit as there is often a fair bit of standardization with the size and type of various connectors, but check first that the connector type and base plate sizes are compatible.
Real-World Range
With 960Wh of capacity, you are looking at solid range for most riding use cases. On a 500W motor with reasonable pedal assist and flat terrain, 35 to 50 miles per charge is realistic. With the faster 750W or 1000W motor and using a lot of throttle on hilly terrain, expect closer to 20 to 35 miles. Heavy use of the throttle with lots of steep climbing will drop that further, but even with high demands, the 960Wh gives you a decent cushion.
For commuters, this battery can do 20 to 30 mile round trips with ease and plenty of reserve. The 20Ah battery size puts it on the large side of the silver fish batteries available, so you might as well check out the other 48V 20Ah options on our comparison table to see how it measures up on price per watt-hour.
What Amazon Reviewers Are Saying
In the small sample pool, the VODIPOWER 48V 20Ah has a fantastic 5.0 star average across 3 reviews on Amazon.
One purchaser bought it to use as a spare on a Narrak ebike and said the quality was better than the standard ebike battery. A note of caution as they had to change the positive and negative connectors. Everything required for the swap was included, and after making that wiring switch, everything worked great. They also say well-packed and fast shipping. Another reviewer bought this for their folding electric bicycle and says it fits perfectly and is just over half the price of the original battery would have been. After a week of use the battery was still great and hardly needed recharging. A third buyer just confirmed it fitted their electric bicycle and recommended the shop.
The common thread through the three reviews is fit and compatibility. They found that this silver fish worked as a drop-in replacement on bikes that originally used the same battery shape, which is exactly what you want.
Who Should Buy This
The VODIPOWER 48V 20Ah silver fish battery is a great choice for riders looking for a seat tube mounted replacement battery with some decent capacity. The 960Wh gives you a lot of range, the 40A BMS will work for a motor of up to 1000W with some headroom, and the key lock plus LED indicator add useful practical features that cheaper batteries leave out.
It works best as a replacement for an existing silver fish battery on a commuter ebike or as part of a conversion build where you want a neat seat tube mount. The consistently positive reviewer comments suggest a good build quality and reliable fitment on bikes designed for this battery shape. If your bike uses a different form factor (downtube, shark/hailong, rear rack), this won't work without modding. And the 4-pin discharge connector means you'll want to verify compatibility with your specific controller before ordering. But for riders with a 48V seat tube setup that want a high-capacity, well-protected battery with security features, this VODIPOWER pack is worth a look. Check how it compares on our battery comparison table.
Frequently Asked Questions
What is a silver fish battery? Silver fish is just a form factor for ebike batteries that mount along the seat tube of the bike frame. The name derives from the fact that they are an elongated fish type shape, slightly tapered. They attach to a base plate using a locking mechanism, making them easy to take on and off to charge.
How long does the VODIPOWER 48V 20Ah take to charge? Using a standard 2A charger, expect about 10 to 12 hours to go from empty to filled up again. A 3A charger would cut that down to more like 7 to 8 hours. Check what charger is included with the specific listing option you select, as different VODIPOWER configurations may bundle different amperages of charger.
Will this battery fit my ebike? That's a question of the geometry of your frame and what battery mount the rear of this pack attaches to. This battery is 15.35 x 2.95 x 4.37 inches and uses a base plate which mounts to the seat tube. If you already have a silver fish battery of the same dimensions mounted, it probably will. Just make sure you measure your available space and note that the discharge connector type is 4-pin before ordering.
What does the 40A BMS do? The BMS (battery management system) protects the battery from overcharging and also from discharging too much. In the event the pack is accidentally shorted, the BMS also prevents damaging excessive heat build-up. A 40A rating means this system can safely draw up to 40 amps of continuous current at once on a 48V system, for enough power to drive a 1000W max motor and then some. More amps to the BMS means more protection headroom before your system cuts out under heavy load conditions.
Can I use the key lock to prevent theft? Locking this battery to the included base plate keeps them from just yanking it off and running away with it. Not a foolproof plan against determined thieves, though, who might use tools. For greater anti-theft purposes, plan to run a separate cable lock through the battery as well or park it in a more secure location.
Do I need to reverse the wiring like one reviewer mentioned? One Amazon reviewer had to reverse the positive and negative when installing this on a Narrak ebike, meaning that the polarity from the factory is different than some other stock batteries. Definitely double check the positive and negative terminals on any battery you get with your controller wiring to verify. You can damage your other electronics if you connect with those terminals inverted.