Storage - what happens!

That's good news.
The HV battery doesn't seem to suffer from long layoffs, IIRC there was one young man here that had his dad's Prius (after his dad had passed) in storage for a year? and when he finally charged the 12v battery enough to start up found the HV batt still had 70% charge. The big issue always seems to be the anemic 12v AGM battery used in the Prius and the PIP.

 

My car sits in the garage more than driven. The ScanGauge always shows 12.xx volts when I check it. I need to put my homebrew tender on it next week as it will not see the outside until May.

Mike

Mobile on my SGH-i717

 

Ahh you Yankees. Our cars are happier in the winter. No bugs, 50 degree temperature.

 

This is the expected result.


Strictly speaking, the lifespan for Lead-Acid batteries depends on the depth-of-discharge.

Of course, this curve can be tweaked higher (more lifespan) by adjusting the design of the battery (giving up current output, as with the Optima-brand Prius replacement battery), but the fundamental shape stays the same.


For your standard car-starter battery, the curve is like this:



Of course, with a standard car, it's only using 5-10 percent of the battery to start the car until your engine/alternator comes on.



I'd imagine with a Prius the lifespan is so short because people abuse the "Accessory" mode.

On normal cars you can turn the key a little bit to get the radio, but most people probably just turn the car all the way on.

On the Prius it's easy to hit the Power button without the brake pedal pressed and you get the radio. I bet a lot of people do this to listen to the radio without realizing it harms the battery.

Combine radio with head lights on, and you can put a good 20-30% dent in the 300Wh lead-acid battery in 10 minutes. Maybe more with the fan and everything else.

 

As a new Prius owner, what,if any, is the best way to listen to the radio while parked in the car? I do lots of stakeouts when working, just sitting in the car for sometimes hours, watching a house. Will just the radio really run down the battery?

 

Leave the car in "Ready", i.e. when you stop just put the transmission in P. The 12 DC-DC converter stays active, powering your radio. once the tractrion battery gets low (with just the draw of the radio this should take a long time, maybe around 30 minutes or so) the engine will fire up for 2-3 minutes, charge the traction battery back up, and then turn off again. Once the traction battery is low again the engine will fire up for a few minutes again. Simple!

 

Yeah, what he said.

As long as you're not running heat or air conditioning, just leave the car on. The Prius will steal energy from the 1700Wh traction battery to top off the 12V 300Wh battery. (strictly speaking for longevity the Prius computer limits the power you can extract from the traction battery to about 600-700Wh).

When the traction battery gets low enough, the engine will turn on to charge both.


Or, if you don't care, you could just keep running the 12V battery down and pay the $200 to replace it in 1-2 years. Turning the car on every 20-30 minutes.

 

I told my wife we need a house down south but she said I have to wait 5 years

Mike

Mobile on my SGH-i717

 

I drive my wife to meetings and some trips I have to sit 1-3 hours. I leave the car in Ready mode and it takes care of itself

Mike

Mobile on my SGH-i717

 

The OP had his 12V battery on a battery minder, so discharge was not an issue.

Btw, as a side note, this is my 18,000 post, not including Fred's.

Tom

 

Yup. That was the point I was making (and the point he was proving).

 

Heh, unfortunately it doesn't work that way. The 12V battery is being "cycled" every time the car is off.

Also, all batteries have internal resistance, and a degree of self-discharge, so it's always draining.

It's a fact of chemistry. As long as there's heat, chemical reactions occur. Short of storing the battery in the freezer, there's no way to avoid this.


Which brings up a point. NiMH longevity is directly tied to storage temperature. I'm curious if one "benefit" of the solar prius is reducing cabin temperature in hot climates, thereby extending the life of the traction battery.

One article I read suggested NiMH longevity decreases 20% for every 20 degrees you go over 80F.

Of course, this isn't all-or-nothing. It's an average, so one hot sunny day isn't going to ruin your battery. But if you regularly live in Arizona, it could be an issue.

 

If you keep it on a battery minder the chemical reactions are mostly kept in check. I suspect you meant your comment to apply to a battery not being held on a float charge, but it wasn't clearly stated.

Tom

 

Some chemical reactions like electrode corrosion are temp dependent and not related to charge. This is why batteries eventually fail, even when in float charge service. This is also why car batteries fail sooner in hot climate.

On the other hand, sulfation will be inhibited by float charge.

 

True. Another reason that batteries fail sooner in hot climates is that many charging systems do not adjust the charging curve for temperature. Few things kill a battery faster than overcharging.

Tom