Battery Knowledge

Ok, first of all, the 12 vdc battery is located at the right rear of the car, not in the front



The thing I outlined in blue is the battery vent tube provision.

Yes, 3-5 is a reasonable life expectancy. The NiMH traction battery should last much longer, in taxi service the traction battery will go beyond 300,000 and still work ok

A popular aftermarket choice with the correct vent tube provision uses the Optima sealed battery intended for a Mazda Miata

12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008 and 2009 with installation kit and free shipping

Its possible to make any other 12 vdc battery fit, but I do not recommend that. A regular battery isn't sealed and doesn't have a vent tube provision

 

The 12V side of the system is much like that of any car, and the 12V battery needs replacing at the same or shorter interval. It's very small for a car battery (looks like one for a big motorcycle) so is taxed a bit more, although it doesn't have to start the car.

When the 12V battery is dieing, there have been a lot of different observed, strange effects. Your charge indicator is a good example. Note that the charge indicator is for the other battery, the traction battery, not the 12V. It's the traction battery that has been showing a much better than predicted lifespan (and the predictions were over 100,000 miles).

Just like with other cars, you don't have to go to the dealer to buy a 12V battery. You can go to Sears or wherever. However, many on the board are using premium 12V batteries to get longer life and better battery performance, such as the Optima.

As for a drain from your aftermarket stereo, it is impossible to diagnose from a post, but if you have a remote amp that remains on after the car is turned off it will be hard on the battery. Due to the small size, any drain has a bigger effect than it would on a larger car battery. Note that most modern amps have sensing technology that, when it sees no signal coming in will shut itself down. Or they're wired to a circuit from the head unit that is used specifically to tell the amp when the head unit is on.

I'd for sure replace the 12V battery first. That should cure your issues. If the new battery goes dead, then start looking for a drain.

 

Toyota provides a "tap" to the 12V circuit under the hood to allow you to jump the system (since there is no way to get into the hatch without voltage, this is a Good Thing - had it been a British car, you would have had to disassemble the hatch to get in ).

 

Lucas, "Prince of Darkness"!

 

Why do the Brits drink warm beer? They all own Lucas refridgerators.

Why didn't the Germans bomb a Lucas factory during WW II? They considered them allies.

Why did all Brit cars have intermittent windshield wipers? They were made by Lucas.

But it could be worse. If you've owned old Italian iron, you come to despise Marelli. In the Alfa club we used to say that people fired from Lucas for incompetence went to Marelli as managers.

 

By whom? No battery lasts forever. For that matter, neither do mechanical parts. When you buy a conventional car, does the salesman point out that eventually the transmission will fail?

Tom

 

3-5 years is what the industry says, but in reality it's typically longer. They want to scare people into buying replacement batteries early...pretty soon the pre-winter commercials to that effect will start up again. (Kind of like oil changes every 3K miles when the auto manufacturer says differently). My 12V batteries typically have lasted 7 years in previous cars. The 12V aux battery in the Prius is a little smaller and used a bit differently, so can't really say for sure on this.

OTOH, the HV (high-voltage) battery, AKA traction battery, has a warranty for 8 years or 96,000 miles (slightly more in California I think), so for most car owner's point of view, that is "forever", since it's longer than they'll keep the car. Several Prius owners have documented going more than 250K miles on the original HV batteries (provided you never try to run the car past the purple bars on electric only when it runs out of gas - that will drastically shorten the HV battery life).

All that said, you have a problem with your system, and it could be radio related. If it was the battery, it should be getting worse with time, after short drives, and in cold weather (you don't have your location in your profile, so I'm not sure if that's a factor for you). But if the aux battery goes, it can throw a bunch of warnings, including the triangle of doom on the front dash.

 

Trans fat. It's bad for you.

Tom

 

I think I see the problem here, at least when referring to aftermarket lights. It looks like there is a misperception that the aftermarket lights were intended to be functional. Easy mistake to make, but in England at the time I remember it was pretty common knowledge that the aftermarket Lucas lights were purely aesthetic, and should under no circumstances have their original opaque plastic covers removed. The whole purpose of the lights was to impress the masses with the fact that you had attached extra lighting to your vehicle and were therefore cooler than them. Functionality as lights was entirely beside the point and so was never really a feature. I guess when these lights were exported to North America this bit of rather important folk knowledge did not make the transition and people actually tried to use the things as lights?

 

I'd agree, except that I have to admit the Lucas Square 8 was a fantastic driving light. I still have a pair of Square 8 fog lights in a box, and have been threatening to put them behind the lower grill in my non-fog-light equipped 2006 Prius. If I could find a pair of driving light lenses I'd prefer that to the fogs. Never had a bit of trouble with either the Square 8's or the Flamethrowers.

 

I don't know if this applies, but I've had to replace the batteries in pretty much every car I've owned since I moved to Southern California at about 3.5 years. I live in the SoCal desert where it's common for temps to be over 100 during the day for six months out of the year.

I was told at one point, and this may be hooey... that a sealed battery fails earlier in extreme temperatures because there's still some evaporation even if it's fully sealed and there's no way to add water back in.

I'm still not sure why the Prius needs a second battery... couldn't there just be a transformer to step down the voltage from the traction battery to run the accessories? I'm sure that's been asked and answered a million times already.

 

Depends on the vehicle, climate, and how it is used. My Tundra V8 goes through batteries about every 2 years...haven't paid for one in a long time as they are still under full warranty when I exchange them. F-150 V8 had a similar appetite and a really awful ignition system--I nicknamed it the crossfire and made an elaborate loom to keep the plug wires well away from one another.

My 240 battery lasted at least 7 years...it took next to nothing to turn that engine over and it fired instantly. I was having trouble with the seat belt glides before the battery ever failed. The Honda took about 3-5 years per battery. About 5 on the first, and progressively shorter after that until I changed out the ignition switch.

The K-car batteries did okay.

Had an old AMC V8 as a kid that ate batteries for breakfast. Apparently Lucas must have designed their ignition system which had some sort of weird nice person random short that I never could track down. I kept two fully charged spares on the floorboard of the back seat. It's the only vehicle I've ever had that tried to start on me while I was standing in front of it. I was staring at some damage to the loose fan cowling under the hood...I wasn't touching anything and had the only extant ignition key in my pocket. Fortunately I had not yet reached into the fan to readjust/reattach the cowling. When this happened I felt for the key in my pocket (check), then lowered the hood to see if someone was in the driver's seat--this on a farm with the nearest neighbor over 1/4 mile away. To make it stop I yanked off one of the battery terminals.

 

Technically easy, but that would be one more way in which a failure could expose people to dangerous voltages. It's safer to have the systems more nearly separate.