Battery drained in mornings

You need to replace your 12V auxilary battery now. There are many, many threads on here about the life of a Prius battery.

 

It is unclear as to which batteryyou are talking about? The HV or the 12V?

 

Hi findjl. Do you know if the battery SOC (state of charge) has already dropped immediately when you make it ready, or if it just drops rapidly in the first few seconds after starting or when you start driving. If you're not sure then try watching the SOC monitor very carefully from the moment you start up and let us know.

BTW. What sort of drop in SOC are we looking at? One or two bars, or even more? Give us an indication of the typical before and after SOC levels.

 

After 100,000 miles I am assuming you know how to drive the car, BUT, try putting your foot on the brake pedal early when slowing for a stop. Do not depress the brake, just slightlly press. Keep your city and suburbia speed to around 40. When starting out, go ahead and accelerate rapidly to warm the engine up. I use this procedure and have a green battery almost every day. Experiment with stealth after car is warmed up. On the freeway, use CC and let the car conserve gasoline. Should you like to drive 65-85 on a flat terrain, all my comments are out the window. When coming home I drive at the speed limits, with use of brake, as described, so in the morning, sometimes my battery is green upon starting! At that point I do everything I can to preserve that State Of Charge.

 

maybe the colder conditions this time of year?

 

This happened to me in my Gen I. It got to the point that it could not hold a charge overnight, then to the point it couldn't hold a charge longer than a few hours (battery drained when I came out of work).

I was usually able to get it started without a problem, and after a few minutes the system would bring it to a normal operating band so everything worked fine while driving around, but if I parked for a significant amount of time it would be back to square one.

I learned to live with it for a while then really felt a need to replace the car. Even with the warning lights and alarms it was a pretty reliable little car running that way for about 6 months.

 

Thanks for the info gwmort. I think this is the worst case scenario for the OP, a fully cooked battery pack. High leakage current and self discharge is a characterize of a cooked NiMH battery. All of my rechargeable drills ultimately end up like this due to overly aggressive chargers. Fortunately the Prius is a lot kinder to batteries than is my drill charger.

In the case of the OP, it might still be some high initial loads that are rapidly draining the traction battery after starting. We need more info to know for sure.

 

This is an interesting thread as I've often wondered if there is a slow drain on the traction battery when the vehicle is not being used for a few days. I make it a habit to observe the SOC prior to turning the car off. I make a mental note and I have to say I'm quite impressed with the battery's ability to maintain a charge. Last week I had not used the car over the weekend and on Monday morning, it was still green (1 bar short of full). I wish there was some diagnostic tool to determine the health of the traction battery. It is very hard for me to tell, but after 160,000 miles and 8 years, the battery seems quite healthy. Heck, I still can't believe I've had this car for 8 years. This is the longest I've ever kept a car.

 

There is no drain on the HV battery when the vehicle is powered down. A set of relays opens up and completely disconnects the HV battery from the outside world.

NiMh batteries self-discharge, and it gets worse with older or cooked batteries.

Tom