What to look out for when buying a used e-bike (part 8)

Buying a used e-bike often involves expensive risks. Hidden defects in costly components like the battery, motor, or frame can quickly turn a bargain into a bad investment. When purchasing used e-bikes, motor damage proves to be the most common weak point. An unusually severe impairment in motor performance constitutes a clear material defect.

Therefore, look for clear reference values. The battery should still have a residual capacity of at least 70 to 80 percent. Regarding charge cycles, 500 to 1,000 cycles serve as a benchmark.

Tip: Protect yourself from expensive surprises with four simple steps:

• Perform a thorough electronics check.

• Carefully inspect all mechanical components.

• Complete a structured test ride.

• Protect yourself legally with a purchase agreement.

Key Takeaways

• Inspect the battery and motor carefully before buying. A dealer can test the remaining battery capacity for you.

• Pay close attention to the frame and brakes. Cracks in the material and worn brakes significantly jeopardize your safety while riding.

• Always take a thorough test ride of at least 15 minutes. Test all motor assistance levels and brake hard at least once.

• Only buy the e-bike with a written purchase agreement. Directly compare the printed frame number in the contract with the bike itself.

Checking the E-Bike Battery and Motor

The drive system is the heart of every pedelec. Faults in these components quickly lead to high repair costs. You should therefore examine the battery and motor closely before purchasing.

Battery Capacity and Charge Cycles

The battery loses performance over time. With average usage, modern energy storage units typically start to gradually lose total capacity—and thus range—after about 400 to 500 full charge and discharge cycles. Ideally, you should ensure that the battery still has a residual capacity of at least 70 to 80 percent.

You can rarely detect the actual performance of the battery with the naked eye. Sellers often only estimate the range roughly. The actual remaining capacity can be professionally determined by requesting a professional diagnostic report from a specialist dealer. This service is usually inexpensive (approx. 20 to 30 euros) and provides precise data on the exact condition and real residual capacity of the battery. Therefore, always demand a measurement or arrange for a check at a workshop.

Motor Performance and Diagnostic Log

The motor must support pedaling force evenly. Before buying, you need clear information on the condition and performance of the motor via a service diagnostic log. This document shows stored system errors and the total mileage to date.

Mechanical damage is often announced by noticeable symptoms. Watch for the following warning signs during your test:

Additionally, internal damage can be caused by improper use:

• Thermal winding damage: Persistent overload leads to heavily darkened, black, or melted windings.

• Gear damage: High starting torque or overvolting can lead to broken teeth on the gears of geared motors.

• Accelerated wear: Heat exposure and high torque massively shorten the lifespan of individual components.

A thorough check protects you from undiscovered defects. Test ride the motor extensively in all support levels.

Charger and Connections

The charger must be included in the sale. Check the original power supply for visible damage to the housing and the cable. A defective cable poses a safety risk.

Additionally, examine the plug contacts on the battery and frame. The metal contacts must be clean and free of corrosion. Discoloration on the contacts indicates intense heat development. Plug the connector in and out several times. The connection must click firmly into place and should not have a loose contact. Only intact connections guarantee a safe charging process and a trouble-free power supply during the ride.

Inspecting the Frame and Wear Parts

In addition to the battery and motor, the chassis determines your safety. High forces act on the material. You must therefore thoroughly examine the frame and all wear parts before purchasing.

Frame Inspection for Cracks and Rust

The frame carries the entire weight of the rider and the technology. Thoroughly examine all tubes for visible damage such as cracks, scratches, dents, paint damage, or rust. Pay special attention to weld seams on the head tube and bottom bracket.

You can identify hidden material damage on aluminum or carbon frames using various testing methods:

Specialized testing institutes also use modern diagnostic procedures for expensive frames:

• Computed Tomography & Radioscopy: X-ray-based methods used by specialized institutes for the precise localization of internal weak points.

• Electronic Microscopy: Fine mechanical examination for the detection of microscopic laminate and material damage.

• Professional tap test: Acoustic diagnosis to identify defective laminate through dull-sounding areas.

Braking System and Brake Discs

The brakes guarantee your safety in traffic. Check the condition of the brake pads and brake discs precisely.

You can identify glazed brake pads by the following signs:

• Decreasing and reduced braking performance

• Pronounced squeaking when applying the brakes

• Strong vibrations during the braking process

• Visual features after removal: A smooth, shiny, or slightly shimmering surface that looks polished (unlike a normal, rough, and matte structure)

Worn brake pads show these clear indicators:

• The pad thickness is below the minimum threshold of approximately 1 mm.

• Audible metallic scratching when the spreader spring rubs against the brake disc.

• Significant metallic grinding noises as well as a massive loss of braking power as soon as the metallic backing plate rubs directly against the brake disc.

Chain, Derailleur, and Tire Pressure

The drivetrain wears out quickly due to high torque. Check for chain elongation and the cassette with appropriate tools:

Here is how to use a chain checker step-by-step:

1. For checkers with two sides, select the appropriate side according to the material type of your cogs/chainrings (e.g., S-side for steel, A-side for aluminum/titanium).

2. First, insert the shorter hook (the nose) of the checker with the notch between two chain rollers.

3. Carefully guide the other end with the longer hook down onto the chain.

4. Evaluate the result: If the checker lies flat and completely on the chain, the chain is too stretched and must be replaced. If there is an angle between the checker and the chain, it can still be used.

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Also, look for signs of worn cogs:

• Visible tooth wear: The tooth profiles look pointed, sharp-edged, unevenly worn, or resemble a shark fin.

• Chain skipping under load: The chain no longer finds a firm grip and slips over the teeth of the cogs when pedaling.

• Noticeable noise development: Loud, crunchy, or uneven drive performance due to poor fit.

• Impaired shifting behavior: Gears shift with a delay, jerkily, or the chain gets stuck while shifting.

A faulty drivetrain causes consequential costs for spare parts:

• Chain replacement: The assembly of a new e-bike chain averages 40 to 50 euros, including material.

• Brake discs and other wear parts: Costs for brake discs as well as cogs/cassettes occur in larger intervals, which, together with other service work, can add up to about 200 euros in workshop costs per year.

Finally, check the tire air pressure. The optimal pressure depends on the intended use of your bike:

The ideal air pressure varies significantly depending on the bike type and tire width: while narrow road bike tires (25 mm) require very high pressure of up to 8.0 bar in the rear tire for minimal rolling resistance, wide MTB tires (54 mm) operate at significantly lower pressure (approx. 2.0 to 3.0 bar) to ensure maximum grip and damping on off-road terrain. For city and trekking bikes, about 3.5 to 5.0 bar ensures efficient riding on asphalt.

Documents and Maintenance History

Complete paperwork legally secures your purchase. Good documentation proves the previous owner's honest care of the e-bike. This allows you to avoid future disputes and expensive surprises.

Proof of Ownership and Sales Contract

A written contract protects you from unpleasant surprises. When buying a used e-bike privately, you should strictly pay attention to the following documents:

• Sales contract: A written record clearly proves the legitimate acquisition of the e-bike.

• Original bike documents: Ideally, the seller should provide the original purchase receipt or the initial invoice.

• Important contract details: The document must include the frame number and the seller's name. It is best to also record the seller's ID card number.

You can additionally check the origin of the bike online. Simply enter the specific frame number into the search field of the online database bikefinder.de. The system immediately checks the number against bikes reported stolen in their system. This allows you to identify stolen goods immediately.

Service History and Inspections

A complete service booklet shows you how well the vehicle has been maintained. Specialist shops follow strict guidelines during maintenance:

• Initial inspection: The first check-up should take place after the first 500 to 800 kilometers.

• Regular inspection: Workshops check the bike at least once a year or every 1,000 to 1,500 kilometers.

• Increased stress: Difficult riding conditions require a service every 500 kilometers.

The maintenance schedule differs depending on manufacturer specifications and components. A minor inspection is due every 6 to 12 months or after 2,000 to 4,000 kilometers. A major inspection should occur every 12 to 18 months or after 4,000 to 8,000 kilometers.

StVZO Compliance and Frame Number

The frame number uniquely identifies your e-bike. You can find these digits in different places on the frame:

• Under the bottom bracket: The number is on the underside where the cranks meet.

• On the head tube / handlebar head: The engraving is located directly in the handlebar mounting area.

• On the seat tube: The series of numbers runs along the vertical seat tube.

• Rear wheel area: The manufacturer places the number on the lower side of the frame near the rear wheel suspension.

Tip: Compare the engraved number on the frame directly with the entry in the sales contract. Both numbers must match exactly.

For use on public roads, your e-bike requires complete equipment according to the StVZO (German Road Traffic Licensing Regulations). This includes functional headlights, a taillight, two independent brakes, and spoke reflectors.

Conducting the E-Bike Test Ride

A thorough test ride reveals the true condition of the bike. A ride of at least 15 minutes is usually sufficient for a meaningful assessment. Use this time intensively for practical tests.

Support Levels and Start-up Behavior

Test all motor settings one after the other during the ride. Switch step-by-step from the lowest to the highest support level. The motor must react immediately and without interruption during every change.

Pay special attention to power delivery during acceleration:

• The drive pushes you gently and evenly.

• The system shows no jerky movements while pedaling.

• The sensor stops support immediately when you stop pedaling.

Unsteady start-up behavior often indicates defective sensors or outdated software.

Gears and Brakes Under Load

Ideally, find a slight incline for this test. Shift through the gears intentionally while riding uphill. The chain must jump cleanly onto the individual sprockets. If the chain slips under load, the chain and cassette are likely already heavily worn.

Tip: Test the brakes at low speed first. Then, for safety reasons, perform a controlled emergency stop on a clear stretch.

Both brakes must stop the bike quickly and in a controlled manner. The pressure point on the brake lever should feel firm and not spongy.

Ride Stability and Noise Levels

Let go of the handlebars for a brief moment on a clear, straight stretch. The bike should ride cleanly in a straight line. Pulling to one side indicates a warped frame or a crooked fork.

Listen for unusual noises in the handlebar area throughout the entire ride. Clicking noises or noticeable play in the headset often have clear causes:

• Insufficient preload: Too little tension creates noticeable play when braking.

• Dry or worn bearings: Worn roller bearings lead to annoying clicking noises.

• Misalignment of the fork cone: An unevenly seated fork cone causes noise under high load.

• Lack of lubrication: Missing grease and tiny air gaps cause minimal play and grinding noises.

Unsteady steering behavior significantly reduces your riding safety. Therefore, always check this area very carefully before purchasing a used e-bike.

Buying Sources: Dealer vs. Private Sale

You face an important decision when buying an e-bike. Purchase your used pedelec either from a commercial dealer or directly from a private individual. Both paths offer specific advantages and disadvantages.

Warranty When Buying from a Dealer

Buying from a commercial dealer offers you maximum security. A specialist dealer thoroughly checks used e-bikes for technical defects before selling them and refurbishes components.

When buying from a dealer, you benefit from clear legal rights:

• Basic entitlement: When purchasing a used e-bike from a commercial dealer, the statutory warranty applies.

• Duration and reduction: The regular period is two years, though this can be reduced to one year (12 months) through a corresponding agreement in the sales contract.

• Reversal of the burden of proof: Within the first six months after the purchase, the dealer is responsible for proving that the vehicle was free of defects upon handover.

The additional service from a specialist dealer affects the price:

• Price premium: A used e-bike costs on average about 200 to 300 euros more at a specialist dealer than when buying privately (e.g., via eBay).

• Added value of dealer purchase: This price premium acts as protection, as buyers receive tested quality, fixed contacts, and service offerings (such as free replacement of defective components in the event of damage).

Risks and Opportunities in Private Sales

Private sales attract buyers with significantly cheaper offers. You often save several hundred euros compared to specialist dealers. However, you assume the full financial risk for any repair damage occurring after the handover.

Private sellers almost always exclude statutory liability in the sales contract:

• Contract clause: Liability for material defects can be effectively excluded with phrases such as “The sale occurs under exclusion of liability for material defects.”

• Exceptions to liability exclusion: The exclusion of liability does not apply to:

  • Defects maliciously concealed

  • Explicitly given warranty promises

  • Intentional causation of damage

Tip: Always test the e-bike extremely thoroughly during a private purchase. Without a warranty, only your own careful inspection protects you from undiscovered damages and subsequent costs.

You best protect yourself when buying used through a systematic inspection. First, check the electronics, mechanics, and frame thoroughly. A complete service booklet and a printed battery diagnostic report provide the greatest security against expensive bad purchases. These documents prove the precise maintenance and the genuine residual capacity of the energy storage system.

Tip: Always insist on an extensive test ride. Never conclude the purchase without a written contract.

A legally sound sales contract contains the following important points:

• Complete identity details of both parties

• Detailed description of the e-bike including frame number, battery, motor, and charger

• Fixed purchase price, payment method, and handover date

• Clear exclusion of statutory liability for material defects

• Location, date, and both signatures

FAQ

What is the minimum residual capacity a used e-bike battery should have?

Look for a residual capacity of at least 70 to 80 percent. Below this value, your range will noticeably drop. Replacing a battery also entails high costs. It is best to have the actual performance confirmed by an up-to-date diagnostic report from a specialist dealer.

How do I best check the e-bike motor during a test ride?

Switch through all support levels one after another. Test the start-up behavior on an incline. Listen for unusual grinding noises or unfamiliar vibrations. The motor must stop immediately when you stop pedaling. This is how you identify potential defects early.

Is buying from a dealer better than from a private person?

💡 A dealer offers you a statutory warranty and tested components. Buying privately saves money but usually excludes liability for material defects. You bear the full financial risk for later repair damages yourself during a private sale.

What documents do I absolutely need when buying used?

Demand these important documents from the seller:

• Written sales contract with the frame number entered

• Original purchase invoice of the first owner

• Complete service booklet for all inspections

• Current battery diagnostic report from the workshop

These papers effectively protect you from stolen goods.