I’ve owned my new Sienna since Feb 03 and it’s on its 5th battery. The dealer finds everything ok. 2 were Toyota Batt and 3 were Walmart. I live in Phoenix Az, where batt. & tires don’t last as long as cooler climates, but an average of 1 yr per battery seems too short. Lots of local driving.
Are you paying for these batteries? How are they failing? Do they suddenly fail, or do they get weak? Has anyone checked the charging system? I suspect they are being over-charged. What is the voltage at the battery when the engine is running? That may show up OK, but if the voltage regulation is going high on occasion, it can cook a otherwise good battery.
The batteries are not the problem. Someone is overlooking something; either the charging system, battery drain, etc.
You did not get 5 straight bad batteries.
Thx, I only paid for 1 Walmart battery so far. The Toy dealer wanted twice as much for less warranty coverage. 13.6 volts on battery while idling.
This is a tough one without details as noted. Some things that kill lead-acid batteries are excessive heat, overcharging, repeated deep cycling and vibration. Do you know that you have an accurate voltmeter? 13.5 to 14.8 volts at fast idle and battery charged is OK.
Along with the other posters I sustpect the battery is being overcharged also. Overcharging is a good way to kill a perfectly good battery real quick. If you don’t have a voltmeter built into the dash you might consider getting one that could be plugged into the cigarette lighter socket so you can monitor the voltage and see if there is a intermittent problem there.