Find the likely cause of battery problems in 3 steps: reduced range, charging issues, sudden shutdowns, and more.
What are the most common e-bike battery problems? Reduced range (capacity loss), failure to charge, sudden power cutoff, and swollen casing are the four most common e-bike battery issues. Most can be narrowed down at home, only swelling and BMS failures require a dealer. Enter your symptoms below for a likely cause.
Covers all major drive systems: Bosch, Shimano STEPS, Yamaha, Brose, Giant SyncDrive, Fazua, and Bafang.
Estimate your battery State of Health
Enter what you know about the pack and how you use it. The result is a band, not a single figure, because cycle life varies between packs.
Amp hours times volts gives watt hours. More on how to convert Ah to Wh.
Count charge events, not full cycles. The next field converts them: two half charges make one full cycle. Not sure how many? Yearly distance divided by your typical range gives a usable figure. Work it out with the e-bike range calculator.
Storing the pack in a cold, unheated garage also speeds up ageing, even at the right charge level. That effect is not quantified here.
Estimated State of Health
79 to 88percent
Healthy
At or above 80 percent of nominal capacity.
That is 150 full charge cycles at the depth of discharge you selected.
Usable capacity today: 395 to 440 Wh out of 500 Wh nominal. Expect rides to come up 12 to 21 percent shorter than when new. Check what that means for a route with the e-bike range calculator.
This is an estimate from usage patterns, not a measurement. A real State of Health figure comes from the manufacturer app, such as Bosch eBike Flow or Shimano E-TUBE Project, or from a dealer diagnostic.
Source: none for the 80 percent line. No standard sets a State of Health at which an e-bike battery stops being healthy, so the bands on this page are this site's own. The makers publish something different and lower. The Limited Warranty Bosch eBike Systems says each Bosch North American battery will maintain at least 60 percent of nominal capacity for 400 to 800 Wh packs and 70 percent for a 300 Wh pack, within 500 full charge cycles. That is a warranty floor, the point below which Bosch owes you a battery, not a health verdict, and it sits well under the 80 percent used here.
This tool provides general diagnostic guidance only. E-bike battery systems are proprietary and brand-specific. For safety-critical issues (swelling, overheating, fire risk), stop using the battery immediately and contact a certified dealer. Always follow your manufacturer's service guidelines.
If your display shows a specific code, the E-bike Error Code Troubleshooter covers 37+ codes across Bosch, Shimano STEPS, Brose, Yamaha, and Giant. Once you know which code you have, the E-bike Battery Life Estimator estimates remaining capacity and replacement timing based on your charge cycles and age. For tyre pressure on your e-MTB, see the eMTB Tyre Pressure Calculator, it accounts for the extra weight of the motor and battery.
How to check your e-bike battery health at home
Most battery problems can be narrowed down without tools. The key signals are how long charging takes compared to when the battery was new, whether range loss happened gradually or suddenly, and whether problems correlate with temperature or load. Bosch, Shimano, Yamaha, and Giant all offer smartphone apps that display the State of Health (SoH) percentage, this is the most reliable home check available. A healthy battery reads above 80% SoH. Below 70%, range loss and cutoffs become noticeable; below 60%, replacement is typically recommended.
Buying a used e-bike: how to check the battery
Before buying a used e-bike, read the battery State of Health (SoH) from the system app or ask the seller for a dealer diagnostic printout. For a purchase decision, treat SoH below 80% as a battery that is already past the easy half of its life, because a replacement costs 300 to 700 EUR (330 to 770 USD) and is often close to a third of what the used bike itself is worth. That 80% mark is deliberately stricter than the 60% replace-now threshold further down this page: when you already own the bike you ride it down to 60%, but when you are paying for it you are also paying for the years it has left.
Where to read SoH
Bosch Smart System: the eBike Flow app shows battery status, the full SoH readout comes from a dealer diagnostic report.
Bosch legacy (pre-2022): no app readout at all, dealer diagnostic only, so ask the seller for a printout.
Shimano STEPS: E-TUBE Project app, battery health section.
Specialized: Mission Control app, battery health percentage.
DJI Avinox: Avinox Ride app, battery section.
Bafang and generic hub drives: usually no SoH readout, so judge by a real-world range test and by the charge cycle count if the display reports one.
On the test ride, check the real range against what the seller claims, using our e-bike range calculator to work out what that bike should manage with your weight and terrain. Watch the gauge for sudden percentage drops rather than a steady decline, inspect the battery casing for cracks or signs of water ingress, and verify the charger is the original one for the system. Ask when the battery was last replaced and whether it ever sat fully discharged for weeks, because a deep discharge left standing does lasting damage that no app will attribute to the previous owner. Our battery life estimator turns the bike's age and the seller's riding habits into a rough degradation estimate you can sanity-check the asking price against.
What to do with a swollen battery
Stop using it and stop charging it, today. A case that has changed shape means gas has built up inside the cells, and that is the one symptom on this page that does not wait. Do not charge it, do not ride it, and do not try to open, puncture or compress the pack to see what is going on. Do not put it in household waste or a general recycling bin either: a damaged lithium pack in a bin lorry is how battery fires start in waste facilities. Move it somewhere away from anything that burns, ideally outdoors or onto a hard floor clear of furniture and soft furnishings, and leave it there while you arrange collection. Then contact your dealer or a battery collection point and tell them the pack is swollen, so they handle it as damaged rather than as ordinary end-of-life stock. If the swelling appeared after a charge, read the battery safety section before charging anything else with that charger. Whether the pack carries the certification your jurisdiction asks for is a separate question, answered by the e-bike legal checker.
The EU battery passport from 2027
From 18 February 2027, new e-bike batteries sold in the EU must carry a battery passport, a QR code linking to data that includes State of Health. This will make checking a used battery much easier for bikes sold after that date. Existing e-bikes and batteries are not affected and remain fully legal, the requirement only applies to products placed on the market from 2027 onward.
How long do e-bike batteries last?
Most lithium-ion e-bike batteries are rated for 500 to 1,000 full charge cycles. Under typical use of 2 to 4 charges per week, this translates to 3 to 7 years of service life. Bosch rates its PowerTube and PowerPack batteries at 500 full cycles to 60% SoH. Shimano STEPS batteries show similar figures. Yamaha PW batteries tend to retain capacity slightly better in the 300 to 500 cycle range. Actual longevity depends heavily on storage habits, batteries stored at 40 to 80% charge at room temperature degrade significantly slower than those stored fully charged or fully depleted.
Bosch e-bike battery problems
Bosch batteries are among the most reliable on the market, but BMS errors (particularly Error 610, voltage error) can occur after physical impact or deep discharge. Bosch's proprietary architecture means that any BMS-level fault requires the Bosch Diagnostic Tool available only at certified dealers. Common owner-fixable issues include dirty contact pins causing intermittent power, cold weather charge refusal, and range loss from charging to 100% every ride rather than 80%.
Shimano STEPS battery problems
Shimano STEPS batteries (BT-E6000, BT-E8014, BT-E8035) have a higher reported fault rate than Bosch in independent studies, particularly the older BT-E8014. Common issues include charging refusal in cold temperatures and BMS errors following deep discharge. The E-TUBE Project app provides SoH data and error log access, making it one of the more transparent systems for home diagnostics.
When to replace an e-bike battery
Replace your battery when the State of Health drops below 60%, when range loss exceeds 40% of the original figure, or when the battery causes repeated mid-ride cutoffs that worsen over time. Replacement costs in 2025 to 2026 range from 300 to 700 EUR / 330 to 770 USD depending on brand and capacity: Bosch PowerTube 750 costs approximately 600 to 700 EUR / 660 to 770 USD, Shimano BT-E8035 approximately 500 to 600 EUR / 550 to 660 USD, and Yamaha PW series batteries approximately 400 to 550 EUR / 440 to 605 USD. Generic Bafang replacements are available from 150 to 300 EUR / 165 to 330 USD but vary significantly in cell quality.
Frequently asked questions
What should I do with a swollen e-bike battery?
Stop charging it and stop riding it. A swollen case means gas has built up inside the cells, so do not charge, puncture, open or compress the pack, and do not put it in household waste or general recycling, where a damaged lithium pack can start a fire in the collection lorry. Move it away from anything flammable, ideally outdoors or onto a bare floor, then contact your dealer or a battery collection point and tell them it is swollen so they treat it as damaged.
How long does an e-bike battery last?
500 to 1,000 charge cycles for most lithium-ion e-bike batteries, which is typically 3 to 7 years under normal use. Bosch and Shimano rate their batteries at 500 full cycles to 60% of original capacity.
How do I know if my e-bike battery needs replacing?
Replace when range drops more than 40% from new, when State of Health (SoH) reads below 60% in the manufacturer app, or when mid-ride cutoffs become frequent. All four symptoms together confirm end-of-life.
Why does my e-bike battery drain so fast in winter?
15 to 30% range reduction is normal below 5°C (41°F). Lithium-ion cells temporarily lose capacity in cold temperatures. Store the battery indoors overnight and warm it to room temperature before winter rides to minimise the effect.
Can I repair my e-bike battery myself?
No. E-bike batteries should never be opened by the user. Bosch, Shimano, and Yamaha explicitly prohibit self-repair. Faulty cells and BMS faults require certified dealer tools. Attempting self-repair also voids the warranty.
How much does an e-bike battery replacement cost?
300 to 700 EUR / 330 to 770 USD for branded systems (Bosch, Shimano, Yamaha). Bosch PowerTube 750 is approximately 600 to 700 EUR / 660 to 770 USD. Shimano BT-E8035 approximately 500 to 600 EUR / 550 to 660 USD. Yamaha PW series approximately 400 to 550 EUR / 440 to 605 USD. Generic Bafang replacements cost 150 to 300 EUR / 165 to 330 USD.
Why does my e-bike cut out on hills?
3 main causes: an aged battery with high internal resistance, cold weather reducing cell output, or insufficient charge level (below 20 to 30%). Try reducing assist level on climbs and keep the battery above 30% charge before steep sections.
How do I know if my e-bike battery is bad?
Four signs together confirm a failing pack: range down more than 40% from new, charging that stops early or refuses to start, sudden power cutoffs under load, and a casing that looks swollen. One sign alone is usually a sensor, cable or cold weather issue rather than the cells. Run the State of Health estimator above, then confirm the reading in your manufacturer app before spending money.
What is a good State of Health for an e-bike battery?
90% or above is what a healthy pack in its first seasons reads. Between 80 and 90% is normal wear and nothing to act on. Below 70% is where you should start looking at replacement, and below 60% replacement is due. Bosch rates its PowerTube and PowerPack batteries at 500 full charge cycles to 60% State of Health, which is the end of useful life rather than the end of function.
How do I check e-bike battery health before buying used?
Read the State of Health (SoH) in the system app: eBike Flow for Bosch Smart System, E-TUBE Project for Shimano STEPS, Mission Control for Specialized, Avinox Ride for DJI. Bosch legacy systems from before 2022 have no app readout at all, so ask the seller for a dealer diagnostic printout instead. Back that up with a real-world range test on the viewing, because a battery that reads well but drops percentage in sudden steps is still a problem.
What is a good battery SoH when buying a used e-bike?
90% or above is good, 80 to 90% is acceptable if the price reflects it, and below 80% means you should budget for a replacement soon at 300 to 700 EUR (330 to 770 USD). This buying threshold is stricter than the 60% point at which replacement becomes necessary, because when you buy you are paying for the years the battery has left, not just the ones it has used.