How to Charge Electric Bikes with Solar Panels?

How to Charge Electric Bikes with Solar Panels?

How to Charge Electric Bikes with Solar Panels?

Replacing the AC charger

You can use the sun as main source of energy for your electric bike with:
- a flexible solar panel
- a solar MPPT boost charge controller

Solar MPPT Boost charge controller

The solar charge controller has 2 main functions:
- Boost: raise the voltage of the solar panel to reach the charging voltage of the battery, i.e. from 12V to 36V or 48V.
- MPPT: constantly optimizing the sun power conversion, with an efficiency up to 99%

The solar charge controller provides the same voltage as the AC charger for charging the bike battery.
When the battery is full, the solar charge controller stops charging.
You can charge the bike battery when stopped or while driving.

The output charging voltage of the solar charge controller must be the same or a bit lower than the original AC charger.
For instance, in most of cases you will find:
- 54,2-54,6V for 48V Li-ion batteries
- 41,7-42V for 36V Li-ion batteries

Solar panels

The best solar panels for electric bikes are flexible, light and are made of high efficiency mono-crystalline solar cells.
The solar panels can be installed on many ways to provide power to your e-bike: as a roof, on a trailer, on the luggage carrier. The solar panel should be installed ideally flat, this way the angle with the sun is always the same.

A solar panel of 100W installed flat can produce up to 500Wh per day during summer in Europe.
This corresponds to the full charge of a battery of the same capacity in one day.

Compatibility issues

Bafang is one of the few major brands that allow direct solar charging of the battery supplied with their engine.
By default, the brands which are compatible use battery plugs with only 2 contacts (+ and -).

Most major brands (Bosch, Shimano, Yamaha, Brose) use battery plugs with at least 3 contacts (+ and - and data) and do not allow you to charge the battery when the engine is on or with a charger other than the original (electronic locking system). In some cases, it's possible to replace the original battery and charger by a compatible brand that uses only 2 contacts (+ and -) for charging.

In case you have to remove the battery to charge it (input not accessible), you can charge a second battery in the solar  trailer while driving.

The 2 ways of solar charging

1. Charging the battery

The best and easy way is to connect the charge controller to the battery input, replacing the AC charger.
There is no modification to your bike, so you can keep the warranty conditions unchanged.

Works well with: Bafang - With others brands, it needs to be checked case by case.

2. Charging the battery and powering the engine

The second way is to connect the solar charge controller between the battery output and the engine.
The current will flow both way, to charge the battery and/or to power the engine.
This modification requires technical knowledge of electrical circuits and cannot be carried out by everyone.
You will lose the warranty by modifying the original configuration of your electric bike, so this can only be done at your own risk.

Apply to: Bosch, Shimano, Yamaha