I purchased a refurbished HV battery in September, 2025 for my 2007 Prius. The battery performed well for 2 months then began charging/discharging more frequently - going down a hill frequently gets the state of charge to 70%. I've had the car for 10 years and fuel economy dropped slowly from 5.0l/100km to 5.4l/100km over that time. After replacing the HV battery fuel economy increased to 4.9l/100k but after 3 months it's down to 5.6l/100km. The vendor says they won't do anything unless I get dashboard warning light. I feel these lights are to avoid catastrophic failure - not to warn of an imbalanced battery. There is a one year warranty for the battery, however, I feel this warranty is useless as the battery is not likely to set off a warning light within the warranty period. The battery is bad not on the verge of completely failing. Do you have any recommendations?
Bingo yes sir that's correct.you have to read between the lines of that nonsense .smells like poop etc . They no rebuild other batteries anywhere in my world . Till a Prius came along . Desulphating etc sure . But all this cottage industry nonsense ! I buy a real battery from a company that procured the original and produced the vehicle. They have a good chance of knowing something about it. Whereas the cottage industry well!
Who would've thought that replacing old weak batteries with other old batteries would last????? While I understand the price point issue and your basically gambling with a 'rebuild' - battery testers/balancers are expensive and time consuming. The end product isn't going to live up to a new set of batteries. This is like going to an auto parts store and asking for 10+ year old used spark plugs that came out of a 'supposedly' low mileage wreak. SORRY - Bottom-line; it isn't going to perform like a new traction pack would; that has already lasted you 15+ years. IMHO; fix it correctly or sell it, while it's still running decently and worth something.
"Oh, my great-grandpa who invented nickel metal hydrate" and other claims. The facts are it costs time and money to "rebuild" a nimh battery to last more than a few months to a couple of years. For the few suppliers that do it to that level (see video) a subset will guarantee them maybe three years. Even those guys still require battery codes, as does Toyota new oem dealers. Some of the better used mix and match rebuilders used to offer "lifetime" replacement but put you on the wait list for weeks or months, often ghosting you if this was the second time. The best rebuilders who have a huge stock of modules and spend time matching, end up costing the same or slightly less than new oem nimh. Buy oem for 10 or more years of reliable service just like the original. The secret is you don't walk up to a dealer's parts counter without a shop account. Most parts at a dealer have close to a 100% markup. Or you time your purchase for the big discounts available from select online Toyota dealers during holiday sales. In the winter, increased engine operation to maintain cabin heat can reduce mpg. For now just drive it but start saving for a new replacement.