If you have an electric bike, that means you have pretty big energy storage 🔋, that can give a chance to stay in line in period on mains voltage absence arrow.

Why?

Bike battery have got very large energy storage, for example I have got battery 48V 10Ah with total energy:

E = U · C = 48V ·10Ah = 480 Wh

Typical energy of common use electronics devices required for modern human in city:

• Laptop: 60 Wh – 100 Wh
• Cellphone: 10 Wh – 20 Wh
• Illumination: 10 Wh – 15 Wh

E = (LPT_E·n + CELL_E·n + ILM_E·n)·η= (100Wh·2 + 20Wh·5+ 10h·10Wh)·0.83 ≈ 480 Wh

η – Efficacy; n – Charging times.

So, you can charge you notebook twice, fifth time charge you phone and 15-20 hours have a good light.

So, let's go! 🔦

Structural Block Diagram

The most difficult is find DC-DC with high voltage input 😅

Functional Block Diagram

How the components were selected can be seen below ⤵

Battery overview

Your battery might be with case, like mine, it's more convenient to operate (installation and removal) and better environmental protection, but more expensive than unpackaged.

Charging port

Typically battery with case have a charging port 5.5mm, so for power bank system you should have a charger.

Battery level indicator

Your battery should have a protection (high-current, low-voltage and high-voltage), so try to do't discharge your batteries too much and monitor the level of charge, the optimal level is 50-75% (it is in this range that mobile phone batteries are charged).

Contacts

The difficult question was way to connect electrical circuit to battery, because contacts non-standard .

*NC — Not connected

For make a custom plug I used FR-4 (foil fiberglass) from my unassembled boards.

The thickness is 1.6 mm, but it can be slightly increased by solder:

Solder good wire (recommended 1.5mm²-2.5mm²) to contacts and protect it with shrinkable tube:

Components

Toggle Switch

This is a big toggle switch with high power communication, try to ordinary button switch with high amperage, because first DC-DC have big input capacitance.

Fuse

In my assembly there is no fuse, but STRONGLY RECOMMENDED to use fuse. You can install car fuse with maximum amperage 10A (yes, voltage is higher than 32V) or glass fuse 5x20 mm.

DC-DC 19V

• IC: Undefined
• Type: Synchronous Buck Converter
• Uin: 8V-60V
• Uout: 1V-36V
• Iout(MAX): 15A (10A recommended)
• Pout(MAX): 100W (200W with additional cooling)
• Dimensions: 70×38×31 mm
• Features: screw terminals, input reverse polarity protection, external transistors

Yes, I know there is exist battery converter with high input voltage (around 60V), but it's the best and most available for purchase.

DC-DC CC 3A

• IC: XL4015
• Type: Buck Converter
• Uin: 6V-38V
• Uout: 1.25V-36V
• Iout(MAX): 5A (3A recommended)
• Pout(MAX): 75W (with additional cooling)
• Dimensions: 61.7×26.2×15 mm
• Features: screw terminals, Constant Current (CC), Constant Voltage (CV)

DC-DC 5V

• IC: IP6506
• Type: Synchronous Buck Converter
• Uin: 6V-32V
• Uout: 5V/3.4A, 9V/2.5A, 12V/2A
• Iout(MAX): 3.4A
• η: 90%-97%
• f: 220kHz
• Pout(MAX): 75W (with additional cooling)
• Dimensions: 61.7×26.2×15 mm
• Features: USB-A output connector, TVS on input, QC2.0 and 3.0, MTK PE1.1/PE2.0

LED

• Custom boards with SMD LEDs
• LED: 2835 1W 9V 100MA (3 crystal in one package)
• P(MAX): 10W-15W (limited by heat dissipation)
• Features: no current limit resistors, mounting holes

Wiring

So, now I have to connect all components together:

Try to use 1.5mm²-2.5mm²wire to have enough electrical and mechanical safety .

I use wooden base  to fix all the components, but if you can replace it by fireproof material.

Demonstration

Not ideal, but it works 😄

On the right side you can see small blue LED, that means DC-DC 5V module powered and you can charge phone through USB Type-A port.

In fact light is very bright, 10W-15W enough for emergency illuminance of small room, and, thanks' for two LED panels and long wire this light sources could be convenient located.

Light is bright and could be installed on high place, thank' for long wire.

It turned out a convenient power system that does not change the design of the battery:

Video

Script of the video

Full text of script: 📔 Power Bank Battery 48V Script.docx.pdf

Conclusions

Ebike battery is a huge energy storage device, in comparison to modern battery-powered electronics devices, so it could be used as a power bank with great opportunities.