From being completely clueless to becoming aware, the Service Advisor has been somewhat educated on 12 Volt batteries in the Gen 5 Prius going bad… being drained… and pissing off new owners. I took delivery on my car in February and lost the original battery relatively soon in my “getting to know you” Gen 5 learning curve. As the dealer is close by, I made a habit of stopping by once a month and grilling one particular Service Advisor on any word of an official fix via à TSB. My guy went from clueless, to curious, to a believer. Today I had my 10,000 mile service and inquired about à formal response from Toyota on what was causing the widespread issue with the 12 volt battery. Their research indicated it happens mostly to the Prime and it was the ECU that need a modification which I got today under warranty. The charge control ECU was one of many issues put forward as thé possible culprit… the other popular speculation was a bug in the software remote app. As I had to ask (again) my service advisor it was clear Toyota chooses not to communicate this issue and their proposed fix with its customers. Instead, I guess, we have to ask for it to be fixed. I asked that they provide me with a copy of the Technical Service Bulletin and after much back office dickering, decided that I could get only page one. I have attached that here for your review and action (ask for a free fix).
I posted the whole thing back in June, but I guess it got buried pretty quick in one of the threads. Parasitic battery drain? | Page 4 | PriusChat
Flooded-cell batteries aren’t charged well in Gen 4 and Gen 5 Priuses and Prius Primes by the car's battery-management system (BMS). Get an AGM battery and your problems will be solved. Spending $130 on an AGM battery costs less than your time spent at the dealer getting a warranty flooded-cell replacement again and again—only until your warranty expires. Gen 2 and Gen 3 Priuses came with an AGM battery and didn’t have problems, and the lack of a BMS helped there, too. AGM battery for Gen 4/Gen 5 Prius/Prius Prime and observations on the 12-V charging system | PriusChat
