How to Safely Discharge and Store Your E-Bike / Surron Battery (Using a Buck Converter)

10FoldMoto
Nov 30, 2025
4 min read

The Ultimate Guide to Storing, Discharging, and Maintaining Surron & E-Bike Batteries (2025 Edition).

How to Choose the Right Buck Converter, Build a Discharge Station, and Extend Battery Lifespan.

Proper lithium-ion battery storage is one of the most misunderstood topics among Surron, Talaria, and e-bike riders. Some riders recommend keeping your battery at 100% all the time. Others say store it empty. Some swear by 80%. Others say the battery should always be stored “as low as possible.”

This guide clarifies everything, based on real engineering principles — not rumors — and shows you how to safely discharge your Surron battery using a DC-DC buck converter so you can reliably reach the ideal storage level.

It also includes a link to the EV Motorcycle DC Power Calculator so you can estimate power draw, discharge times, and load calculations:👉 https://www.10foldmoto.ca/tools/evmotorcycledcpowercalculator

Why Proper Battery Storage Matters for Surron & E-Moto Riders.

Your Surron or e-bike battery uses lithium-ion cells, usually 18650 or 21700 from Samsung, LG, Molicel, or Sony. These cells age primarily due to:

Time spent at high voltage
Heat
Deep discharge stress
Calendar aging

Research is clear:

The lowest battery aging happens when stored at 30%–60% State of Charge (SoC).

Very high voltages (near 100%) and very low voltages (near 0%) accelerate cell degradation.

Why Should You Never Store Your Surron Battery at 100%?

Storing a lithium battery at full charge (84V on a 72V system) causes:

Faster internal oxidation
Accelerated capacity loss
Higher long-term resistance
Increased heat sensitivity
Potential swelling

Full charge is great for riding — but terrible for long-term storage.

Why Should You Never Store a Surron Battery Near Empty?

Some hobbyists say, “Store it as low as possible.”

This is dangerous with EV-sized packs because:

The BMS still consumes power
Low-voltage self-discharge continues
Cells can drop below safe levels
The pack can become unrecoverable

Anything under 20% for long periods risks irreversible under-voltage damage.

The Ideal Surron Battery Storage Level: 40–60%.

This is the scientifically recommended range for lithium-ion packs.

✔ Long-term storage (winter): 40–50%

✔ Short-term storage: 50–60%

✔ Daily riding: Charge to 80–90%

✔ Before a long ride: Charge to 100% right before using it

How to Safely Discharge Your Battery to Storage Level.

The common question riders ask:

“I know I can ride the bike to discharge, but can I use my BMS or charger to discharge it?”

Short answer:

Riding: ✔ safest
BMS: ❌ only balances, cannot discharge the whole pack
Charger: ❌ cannot discharge
Random loads: ⚠ vary risky
Buck converter: ✔ best controlled method

The safest, most controlled way to discharge a Surron battery without riding is by using a DC-DC buck converter.

Using a Buck Converter to Discharge a 60V or 72V E-Bike Battery.

A buck converter steps high pack voltage (60V / 72V) down to 12V so you can run:

Halogen car bulbs
12V fans
Power resistors
LED loads
Small heaters

This creates a stable, controlled discharge environment.

CRITICAL WARNING: Your Buck MUST Support the Battery's Full Voltage.

This is where many riders get misled.

A “72V” lithium battery actually charges to:

84.0V

So your buck converter MUST support:

≥ 90V max input

Safe input ratings include:

20–90V
18–95V
10–120V
72–120V

If your buck says:

“48–72V”
“60–72V”
“Max 72V”

…it is NOT safe for a 72V lithium battery. Even if the product photo shows a “72V battery.”

Most sellers assume lead-acid voltages, which are not the same as 72-84V lithium.

Buck Converter SAFE for 72V Lithium Example.

A safe bet would be a buck converter like this one:

“20–90V to 12V 10A 120W”

This IS safe because:

90V max input
Covers 84V max charge
Works with 60V and 72V lithium packs

Perfect for:

Bike accessories
Discharge station
Bench testing
12V lighting

Buck Converter SAFE for 60V Lithium.

A 60V lithium battery charges to 67.2V, so any buck supporting at least 70V is safe.

So a buck labeled “60–72V input” is perfect for a 60V Surron battery — but NOT safe for a 72V battery.

How to Build a Surron Battery Discharge Station.

Required Parts.

20–90V buck converter
XT90 or QS8 connectors
10A–20A fuse (on the battery input and the load side to protect from random spikes)
12V halogen bulbs (55W or 100W)
Optional: 12V car or PC fans
Mounting system or some zipties if you want to get fancy
Voltmeter or multi-meter

⚙ Wiring Diagram

[ Battery ] → [ XT90/QS8 ] → [ Fuse ] → [ Buck Converter ] → [ Fuse ] → [ 12V Load ]

Recommended 12V Loads.

55W halogen bulb = slow discharge
2 × 55W bulbs (110W) = medium discharge
120W max load = fastest for this converter

How Long Will It Take to Discharge?

Example:72V 40Ah battery ≈ 2,880 Wh

If your buck + load is pulling:

120W → ~24 hours from 100% to 0%
For storage level (40% energy removed):
- 2,880Wh × 0.4 ≈ 1,152Wh
- 1,152Wh ÷ 120W ≈ 9.6 hours

You can calculate this easily using the 👉 EV Motorcycle DC Power Calculator https://www.10foldmoto.ca/tools/evmotorcycledcpowercalculator

Safe Voltage Targets for Storage.

✔ 60V Surron Battery

Stop discharge at 58–60V
Never drop below 54–56V

✔ 72V Surron Battery

Stop discharge at 70–72V
Never drop below 60–64V

These numbers ensure safe storage without risking under-voltage.

Should You Get TWO Buck Converters?

Some riders do. Here's why:

Buck #:1 — On the bike

For lights
Horn
GPS
Fans
USB chargers

Buck #:2 — Dedicated discharge station

Allows precise bench discharging
Safer winter storage

This setup is highly recommended.

Why a Buck Converter Is Better Than Random Loads.

Some riders use:

Old motors
Random heaters
Power tools
Big resistors

These can cause:

Voltage spikes
Uneven discharge
Overheating
Cell imbalance

A buck converter:

Regulates voltage
Limits current
Protects the battery
Protects the load
Allows predictable discharge rates

10FoldMoto.