Bosch Dual Battery Systems

 
The Riese & Müller Load featuring a Bosch Dual Battery setup.

The Riese & Müller Load featuring a Bosch Dual Battery setup.

 

These questions about vehicle range are common considerations for electric-assist bicycle riders and prospective riders.:

“How much range can I expect from my e-bike?”

and

 “How can I get more?” 

The range of the bicycle depends on a variety of factors, including the assist level used, the weight of the bicycle and cargo, the difficulty of the conditions, and importantly, the power capacity of the battery, usually measured in Wh (short for and read as “watt hours”). A higher capacity battery (more Wh) translates to longer range for the same riding conditions. Bosch offers a pretty handy Range Assistant Calculator to estimate range for your particular setup.
As Li-Ion (“Lithium-Ion”) battery technology improves, batteries are available at higher power capacities without significant increase in weight and size. Riders can gain more range by getting batteries with a high power capacity, and/or by getting a second battery.

Bosch presently makes e-bike batteries for four different mounts:

  • PowerPack Rack (mounted to a rear rack) in 400 and 500 Wh 

  • PowerPack (mounted on frame) in 400 and 500 Wh

  • PowerTube (inside the frame, 349mm) in 400 and 500 Wh

  • PowerTube (inside the frame, 416mm) in 625 Wh

(See Bosch’s website for more about their battery offerings, size, weight, and charge time.)

As batteries get older, the capacity that their power cells store per charge declines (something many of us may have experienced with our aging cell phones). In this case, Bosch predicts after 500 charge cycles, as in 500 times the equivalent power of 100% of the battery’s full charge, the battery power capacity will be around 60-70% of what it was when it was new. Replacing an older battery can increase the power capacity just by getting a fresh start, but it also gives an opportunity to upgrade that old 400 Wh to a 500 Wh.

Dual Battery

Another popular strategy to increase range, and a big selling point for Bosch systems, is running two batteries wired into the system, potentially doubling the capacity and range of the bike.
When setting up a dual battery bicycle, a Y-cable replaces the battery cable from the drive unit to the battery harness, with each branch connecting to a battery harness for each battery. The battery harness screws into special mounts in or on the frame or rack, so that the batteries are secured. The Bosch system also needs a software update with all the components attached. The system only draws from one battery at a time while in use, but alternates between the two such that the charge level of each battery is within 5% of the other, reducing the frequency with which either is drained too low.

Bosch launched OEM dual battery setups in 2017. Today, there are options where the bicycle comes stock with:

  1. Dual Battery: two batteries (for example, the R&M Supercharger and the Tern GSD R14), 

  2. Dual Battery Capable: the second harness is wired up, but battery is purchased separately (all other Tern GSDs)

  3. Frame Designed for Dual Battery: has the mounting braze-ons for a second battery, but wiring kit and battery sold separately, and the mechanic has to do the wiring and setup labor

  4. Single Battery Only: only one battery and no option to mount a second

Benefits of Dual Battery

There are many advantages of a Dual Battery setup, above the extended range of carrying a second battery with you:

  • Extends lifespan: The Bosch system alternates which battery it draws from in use, helping to reduce the likelihood of overdraining either battery. Li-Ion batteries have longer lifespans if operated between 30 to 60% charge, so this extends the lifespan of each pack.

  • On-bike charging: An integrated dual battery setup also allows for on-bike charging with the same user experience as in a single battery setup. A single charger plugs into a single port, and the system alternately charges the batteries so each battery charge level stays within 5% of the other.

  • Safer transport: Li-Ion batteries pose a fire hazard if damaged, dropped, or exposed to too much heat or friction. An integrated dual battery system provides a safe place to mount the second battery on your trip which reduces any danger of transporting a loose battery.

  • Less worry: Less worry about range, but also with the battery installed on the bicycle, less worry about remembering keys, packing the second battery, or making sure to charge both. On many cargo bikes, the second battery is “out of sight, out of mind” under the box or hidden in the frame of the bicycle.

Dual Battery Capable

There are a few Bosch bikes that come all set up, ready to take a second battery even when they are purchased with only one. This makes upgrading to a dual battery setup as easy as purchasing the battery, updating the system software, and rolling out the door! These setups are also great if you want to borrow or rent a battery only occasionally for extending your range on a long weekend trip. One of the things we love about the Tern GSD is that all bikes come as dual battery capable, and that capability is included in the cost of the bike.

Many other dual battery capable bicycles have this as a new bike option at the time the bicycle is manufactured, but unfortunately if not selected at time of purchase, they do not provide the mounts for it to be added later.

Dual Battery Kit Available

Available both as aftermarket and with the initial purchase, for these bikes there is an available dual battery wiring and harness kit that can be added. The frame has the braze-ons, so you can decide when you purchase, or at another time when you are in for service.

These options are very specific to specific bikes and model years, and even the size of the bicycle (smaller-frame bicycles often don’t have the physical space for a second battery to fit), so inquire about the options for your specific bike.

Single Battery Only

For these bicycles, the answer unfortunately is that you cannot run two batteries simultaneously. The only option here is you can still buy a second battery and manually switch the two batteries between the one harness in your system. This gives both the extended range and battery lifetime without buying a new bike. The downside is having to manually switch the batteries, and carrying a large heavy battery not securely mounted to the bike is both cumbersome and more dangerous if not done carefully. 

If going this option, we still recommend a software update on the whole system, once with each battery installed. And we are happy to help discuss how to most safely carry a spare battery on your bicycle.

Can I upgrade to two batteries on my existing e-bike that only has a single battery?

Presently, among the bikes we specialise in at G&O, only Bosch e-bikes offer dual battery systems. While there is some indication that dual battery functionality is coming at some point, Shimano STePS system does not yet offer dual battery solutions in North America. 

Within Bosch, all 2014-later bikes can handle owning two batteries and switching between them, as long as the firmware is up to date. But beyond that, for many bikes, it depends on the frame mounting options. A summary of the availability for bikes we carry or have recently carried:

Dual Battery possible:

Dual Battery possible on some sizes:

  • Gazelle Ultimate C8, C380, and T10

Dual Battery not possible:

  • Gazelle Medeo T9 and Gazelle Medeo Classic

  • Tern HSD

  • Tern Vektron

  • Urban Arrow Family LTD

  • Xtracycle Stoker (2019-2020)

  • Xtracycle (all Shimano models 2021- present)

  • R&M Multicharge Mixte

  • R&M Tinker

More questions on getting more power capacity on your next e-bike? Let us know! Happy riding!

Davey OilComment