Bosch DualBattery: Compatibility and Installation

Are you riding a relatively new ebike, i.e. built in 2014 or later, with a Bosch motor? Then you can almost certainly install a second battery. Bosch’s DualBattery system increases the range of the ebike up to twice. You can cover more kilometres without an unscheduled stop. Above all, you save the second battery in your backpack for charging.

1. Possible combinations with Bosch DualBattery
2. Does not fit every bike
3. The crucial question of space
4. What you need to switch to Bosch DualBattery
5. Appropriate cables for the conversion
6. Complete sets ease the work
7. Comfortably reaching the motor
8. Special tools for precision all the way through

1. Possible combinations with Bosch DualBattery

With DualBattery, a Y-cable splits the connection between motor and battery. In this way, both batteries are recognized by the energy management system and their capacity is combined. This now works with all current Bosch motors and batteries. Due to the numerous potential configurations, you have a lot of options. Depending on which batteries you combine with each other, you can achieve a total capacity of up to 1,250 Wh. You can choose from the Powerpacks with 400 and 500 Wh, as well as from the new Powertubes with 400, 500 and 625 Wh.

All variants at a glance

PowerTube + PowerTube

PowerTube + PowerPack

PowerTube + PowerRack

PowerPack + PowerPack

PowerPack + PowerRack

2. Not suitable for all bikes

Not all e-bikes are equipped with DualBattery from the start. In addition, not all manufacturers offer a suitable kit to modernize it; However, the upgrade can also be installed quite easily on your own. You just need a little creativity to tackle the challenge of properly attaching the extra battery to the frame.

In theory, DualBattery works with all Bosch motors. However, in practice, it is possible that the manufacturer of your electric bike has prevented this option for various reasons. In most cases, the frame design simply doesn’t provide enough space to accommodate a second battery. Those who still want to try this are responsible for this and in any case risk the bicycle warranty. Usually a short message to the manufacturer is enough to find out what is feasible and what is not. Unfortunately, there is no list, database or similar, to help you safely clarify this for yourself.

3. The crucial question of space

If you have the green light, you can start. You will soon know which spare parts and cables you need. First of all, you need to check one basic requirement: how much free space you actually have.

Measure the available space in your e-bike frame. There is usually room for the second battery on a frame tube, on the luggage rack or in the down tube. The last option is usually the best. Depending on the type of bike, you will quickly know how to best implement your project. Electric cargo bikes generally offer several options. With a fully electric mountain bike, or generally an e-bike with a rather small frame, the risk of giving up already at this point is significantly higher.

4. What you need to switch to Bosch DualBattery

Each ebike manufacturer is responsible for fitting and attaching the batteries to the bike’s frame or rack. Battery suppliers like Bosch merely provide their solutions. Therefore, there is no universal mounting for a second battery. With a bit of luck, the manufacturer of your ebike has a kit, a mounting plate or an adapter in its range of products. Today, some brands are already offering appropriate solutions, such as the Haibike MRS Range Extender or the Scott Range Booster.

If there is nothing readily suitable on the market, you can order all the necessary components individually. These include: brackets, screws, cables, lock cylinders and cover-caps. All these are common spare parts for ebikes with Bosch batteries. It’s the collection of all the things you need to upgrade to DualBattery. What and how much you need depends on the location of the additional battery. You have to budget about 100 Euro to 200 Euro for these accessories. We have already calculated this for you using two examples. In case 1, a second Bosch PowerTube 625 is needed, in case 2 a Bosch PowerPack 500:

5. Appropriate cables for the conversion

The Bosch DualBattery Y-Adapter Kit ensures a smooth power supply between the motor and both batteries. This kit is available in our store with the item number 1228. This Y-cable replaces the original power supply cable and splits the connection that leads from the Bosch motor to both batteries. One connector socket is used to connect the battery that is already installed in the ebike. The other socket is used to connect the second battery.

6. Complete sets ease the work

DualBattery is a worthwhile option that makes it relatively easy to increase capacity and enable longer tours. This has not only become common knowledge among cyclists. In the meantime, individual manufacturers are also offering complete sets for expansion. One of these manufacturers is the Focus brand. Its adapter kit is designed for the Focus Jarifa2 model from the 2020 and 2021 model years. This ebike is a hardtail e-mountain bike in which the bottle cage mounts on the down tube are used to mount an additional frame battery. The charging socket is located at the bottom of the seat tube and points towards the down tube.

However, thanks to its carefully selected components, you can also use the set on other ebikes. It contains the following parts:

• base plate
• DualBat 515/430mm adapter incl. dummy plug charging socket and pin cover
• PowerPack Frame 220 mm cable
• plastic housing lock, incl. upper and lower shells
• battery holder, incl. holding shells
• mounting bracket, mounting frame and threaded pins
• Trelock frame lock

Double check

If you want to use the set on a different model, there are two details you should pay particular attention to. Firstly, the base plate features three holes for screws, as the Focus Jarifa2 mentioned above has three mounts on the down tube. In all likelihood, your ebike will only have two mounts where a standard bottle cage can be attached. The distance between the screw points is standardised and is usually 65 millimetres. This also applies to the distance between the screw points on the base plate of the Focus set. This means that you can still attach the plate to two of the three points.

The second special feature concerns the cable that leads from the Bosch PowerPack to the charging socket. It is not completely encased in black full insulation. A few centimetres are missing towards the plug that goes into the charging socket. This is because on the Focus Jarifa2, the charging socket in the seat tube is replaced with a dummy plug charging socket. The charging port disappears into the inside of the frame. And the cable passes through the dummy plug charging socket with the thinner section with the lower insulation. On your ebike, you can plug the cable directly into the respective charging socket. It is best to wrap the aforementioned few centimetres with additional insulating tape. In the end, it just looks better too. You won’t need to replace the charging socket with the dummy plug charging socket because it probably won’t fit anyway.

7. Comfortably reaching the motor

It may make your work easier having direct access to the motor. To do this, it’s best to remove the crank on the drive side and the chainring beforehand. The necessary tools for this are: torx wrench or screwdriver, torque wrench, ratchet 1/2″, crank puller, lock ring puller and Bosch SpiderTool (suitable for the correspondent Bosch Drive motor model) for removing the lock ring.

8. Special tools for precision all the way through

In the end, the conversion succeeds when the battery’s fixation points on the battery holder are the correct distance apart. This adjustment can be quite tricky. Bosch offers special assembly gauges for this, which are very helpful. However, as a special tool for specialist workshops, they also have a “special price”. In return, Bosch guarantees 100% fitting accuracy. Please note that not all gauges are compatible with all current Bosch model series.

Of course, you may always assemble it all without such a gauge. It just takes a little longer.