Time to replace the aux battery?

Actually you would have to do the opposite, you would need to fit a battery in poor condition (with say high internal resistance) and drive around with it for three or 4 tanks. Then do the same again with a good battery. Which is essentially what I have already done on two separate occasions in two separate Prii.

 

I guess over 50 years of life experience will do that.

I don't see why someone shouldn't do that. It may not affect performance, but it may void my warranty, so I won't. Anyone who has run an empirical test on this is welcome to present their results.

Want to take bets on the outcome?

That would be incredibly reckless. To put a bad battery, shorting internally, venting gases, into the interior of your car, which could start a fire, is really stupid. Your insurance company would probably agree.

Anecdotal evidence is not empirical evidence. I've explained that already. The truth isn't decided by voting.

 

Good luck with that. You are REALLY gonna need it.

Or to paraphrase Dirty Harry: "A man needs to know his own limitations."

Experts in the field are telling you that you are WRONG but you aren't listening.
This happens over and over. This is a problem.......with YOU.

Do you still believe that the world is flat ??
That the sun revolves around the earth ??

 

How the slug-fest going?

You know: ambulance and fire truck drivers just slam in a fresh battery, every couple of years I've heard.

Why not just look at it like an oil change, or going to the dentist for teeth cleaning? Just one of lifes rituals: maybe 2 years is a bit extreme, but pick a number: 4 years? 5 years? And replace it, don't think about it, just do it.

 

Of course I meant "fix" facetiously. It makes your car seem to run OK, but the problem reappears when the battery runs down. It's a symptom band-aid, not a real fix.

Maybe I haven't yet been fully indoctrinated into the consumerist, throw-away society.

 

most folks who own these cars haven't been "fully indoctrinated into the consumerist, throw-away society" either. they may be brainwashed with some liberal nonsense, but that's a separate issue.

so we wait until something causes us to feel the need to test the 12v, and finding it weak or dead, we replace it, and whatever the symptoms were, they're gone after the battery has been replaced. that's not a Band-Aid.

also, by the time your battery is 6-7 years old, do you think its gonna be in excellent condition? I know a lot of batteries are sold to folks that don't need it, and I've always cleaned terminals before I shot down the battery. but I've also seen many dead batteries that were < 2 years old. on a normal car, a weak battery is pretty obvious, on the prius not so much since it doesn't need to start the ice. so there are other symptoms, such as mpg decreasing, and apparently other odd seeming faults and dash lights. just cause you don't understand it doesn't mean it ain't true. (I use that line all the time on 1/2 wits that think climate change is a hoax.)

 

-

There are other defects than just a shorting cell.

There are ways to do this perfectly safely, as we all know that people drive around (unaware) at sometime with bad batteries.

As I said in another post, this would be pointless. Taking a good battery out of service and running without it will not yield any measurable difference. It is not what I am talking about, which is that a battery that IS failing will have an impact on MPG.

I have asked you specifically to answer why you think there is no impact on MPG, as you are the one that has set yourself up on a pedestal as the expert--a position which I am happy to let you have, and I accord you all the respect that that entails.

However, where I find my respect wavering, is that you have entirely avoided answering my question. So you either don't know, or you are unwilling to make the effort to put together a reasoned response that directly addresses my question. Either way, in my book it makes your contributions to this discussion a waste of everyone's time.

You do not need to have conducted an experiment and collected empirical data in order to offer your knowledge at a theoretical level.

I have to wonder why it is you refuse to address the theoretical premise behind what you believe is to be the truth.

I am leaning towards the idea that you do not know, and you just prefer to be argumentative and like to wind people up.

You're right it is getting repetitive, I ask the same question, you refuse to answer. Yes, you are right, that is pointless.

So either put up or shut up.

 

Well, since you were the one making the claim, maybe you should be one the putting up.

 

Out of all I said, you comment on that.

Why do you refuse to answer the actual question? If you can't or don't want to, just say so. But, please, enough of the inane comments.

 

Well, every claim has it's doubters, and my doubts are very strong, considering my experience. I could refute your claim with scientific trials if that were my intent, but I have no time or interest in doing so. I'm content to have explained in considerable detail why I doubt your claim. If that fails to satisfy the debate, I'll just consider it finished and move on to other discussions.

 

That's not what I'm after. I have a theory, you must have a theory of why I'm wrong. All I want is to hear is your theory. Is that so hard to do? Where is the post where you "have explained in considerable detail why [you] doubt [my] claim"?

 

I'll do my best, one last time. I've worked with countless machines with all types of charging systems for many years. I have good educational background in the sciences as well. Both my knowledge and experience have shown me absolutely no evidence whatsoever over that entire time, that the operating characteristics of those machines were affected in the slightest way by the condition of the battery, whether it was brand new, or on it's very last legs. The only visible change I ever saw in all that time was in it's ability to start the engine. Nothing more. I've certainly had enough exposure to these things to have detected even the slightest effect of a poor battery on the operation of the rest of the machine.

I left you the benefit of the doubt that it is possible that a battery could have an internal short, serious enough to load down the charging circuit, parasitizing the horsepower output of the engine, but I never saw it once. That's pretty compelling evidence for me, but since you weren't there for those 40+ years, you don't have to believe me if you don't want to

 

Thanks for that, but I think you are hung up on the "affecting the motor to produce power", which I accept. But it is not my question.

The crux of my question is that you will use more fuel with a bad battery (and not necessarily one with a catastrophic short--but thanks for throwing that bone out there). By saying it makes no difference, you say to me that you believe that the energy used to keep the 12V battery on constant charge comes from nowhere. If you don't believe it comes from nowhere, you have to concede it costs you fuel. That's all I'm saying.

I believe, in this instance, all your experience in what is a very specialised field, is actually closing your mind off to accepting something about a different kind of machine, because in a lot of ways it is similar to the machines you are used to. Further, with the kinds of machines you are used to, you would never measure the fuel consumption before and after, so you don't actually know whether they used more fuel before you changed the battery or not. Likely they would be reasonably inefficient so the difference would most probably be immeasurable and therefore not an apple to apple comparison anyway.

Thanks for your input, that at least is a satisfactory answer and if you are happy we can leave it there. At least I can see from where you are coming.

Peace out.

 

I've understood what you've meant throughout, but I was widening the scope of the question to cover all the bases. Just for the record, I strongly doubt that loss of mileage can be due to the condition of the 12V aux battery.

 

on any vehicle with a normal charging system, you are correct. but since the prius does not have a normal charging system, in this one case, you are wrong.

 

Ok, geez.... are we done with the size contest yet?? Btw, you two are both measuring wrong!

I just wanted to comment, in agreement with Patrick Wong, that my first choice for a 12v battery would also not be an Optima. I had many problems with two Optimas. Finally, I bit the bullet and went to the Toyota Dealer to buy a Yuasa, and ever since installing it, its like I have been feeding my Prius a steady diet of unicorn tears. The Yuasa battery is the bees knees.

 

That isn't logical. It works the same way. The power source is regulated to deliver a nominal voltage (usually in the 14.2V range) according to power demands, and the battery charges to that level.

 

Let’s say 12V battery has one cell that empties itself when car sits. Prius can start with that with no problem. Traditional car can barely start. Traditional car uses only bit more fuel since its charging system is losing fuel anyways. Prius uses more fuel because it’s 12V charging system (almost) isn’t using fuel if it doesn’t need to charge 12V battery.

 

Well, I don't think that's how it works. Batteries don't "empty one cell." Internal shorts can cause a battery to become unbalanced, and one cell can be to blame, and the battery can either be re-balanced or it can't, in which case it's replaced.

At any rate, internal shorts are usually a matter of milliamps, and charging rates are usually a matter of amps, (and tens of amps) therefore the two don't really relate to each other. That's why I don't believe battery condition has anything to do with loading down the charging system to the point where it affects fuel economy.