Counterfeit versions of most products merely disappoint. Counterfeit lithium batteries can burn. Inside a genuine branded pack sit matched cells, a protection circuit, and a housing built to survive a building site. Inside the fake, whatever cells were cheapest that week, sometimes with the protection electronics left out entirely.
Prices make the trap attractive, since genuine batteries are expensive and wear out. This guide explains what differs inside, the external checks that reveal a fake, and how to buy replacements without gambling on the component most likely to hurt you.
Genuine packs use cells from known manufacturers, matched for capacity, with a management board that balances charging, cuts off shorts and overheating, and talks to the tool and charger. Counterfeits save money exactly where you cannot see: lower grade or recycled cells with overstated capacity, and boards that mimic the connector while omitting real protection. The result is a pack that may work acceptably for a month, then fade fast, swell, or, in the worst cases, vent and ignite during charging. Runtime claims on the listing are fiction written from the genuine product's specification. When a fake claims the same amp hours as the original at half the weight, physics has already told you the truth.
Weight is the hardest property to fake cheaply: look up the genuine battery's specified weight and compare it with scales at home; significant lightness means fewer or smaller cells than claimed. Moulding quality shows next: seams, latch fit on the tool, and the crispness of embossed markings are all poorer on copies, and labels carry spelling slips, wrong fonts, missing regulatory marks, or serial numbers that repeat across multiple packs. Contacts should be clean, correctly shaped metal, not thin plated substitutes that run hot. Test fit and first charge in a supervised hour, never overnight, and treat swelling, excess heat, or a charger error as a stop signal, not a quirk.
Marketplace third party sellers and auction sites carry the bulk of counterfeit batteries, dressed in the genuine brand's imagery and vocabulary like OEM and original that, read carefully, often says compatible or for followed by the brand name in smaller print. Genuine stock does go on sale, but through authorised dealers whose names the tool brand lists on its own site. A seller with hundreds of every brand's batteries, no physical business identity, and prices a third under every dealer is describing their supply chain accurately: it is not the brand's. Save the modest difference on a charger or a case if you must; the battery is the worst component in the system to economise on.
Do not bin a suspect lithium battery with household waste and do not keep charging it to see what happens. If it is swollen, hot, or damaged, isolate it away from flammables and use your local hazardous waste or battery recycling route promptly, following their instructions for damaged cells. For a merely disappointing fake, report the listing, pursue the refund with your comparison photos and weight evidence, and recycle the pack rather than selling it on, which just moves the risk to someone else's garage. Going forward, register genuine batteries where the brand offers it, keep purchase records, and replace like with like from dealers. Your tools, charger, and house are all worth more than the saving.
No. Honest compatibles sold under their own name by real manufacturers are a legitimate category. Counterfeits pretend to be the genuine brand. The deception, not the compatibility, is the offence, though quality still varies widely.
It varies, but a pack claiming equal capacity while weighing noticeably less than the genuine specification is a strong fake signal, because lithium capacity and weight are physically linked.
Yes. Poor protection circuits and badly shaped contacts can overheat, trigger charger errors, and in serious cases damage the tool's electronics or start a fire during charging.
Authorised dealers listed by the tool brand, or the brand's own store. Keep the receipt; genuine batteries carry warranties that marketplace fakes will never honour.