total discharge of hybrid battery performed, effects?

If they did then they would have to have a special charger from Toyota to recharge it which is very unlikely.

In the stated if a HV battery is discharged, Toyota has to ship a charger to that dealer to charge it.

 

Well, you can bypass my post if you wish.
Because you are asking for "expertise" and instead here I am....something well below expertise.

But what I would ask, is how much do you trust your mechanic?

Because I find it hard to believe what you have been told has happened ( Full Discharge of the Hybrid Battery) would happen, has happened or would be made to happen, by even the most unqualified mechanic.

It sounds more like just the type of statement an unscrupulous mechanic might make, thinking someone might not know better, in order to justify a much larger than needed bill.

Or it could be a misunderstanding of terms. You sure he didn't say or mean "Fully Disconnect"? Which still shouldn't be a big deal.

I just find it hard to believe that any 1/2 way decent or ethical mechanic that even felt they could approach a Prius would also believe you had to fully discharge the Hybrid Battery to replace the aux battery. Why or how even accidentally, could someone come to that conclusion? Even if you were fully ignorant of the operation, as you discovered, a few minutes on the internet...or even just at this site, would reveal that full discharge of the Hybrid Battery is NOT part of the Aux Battery replacement process.

So the scenario you present would mean you would need not only a mechanic with no idea how to replace the aux battery on a Prius, but simultaneously capable of creating a self -delusional fiction as to how to do it, that has no connection to anything I have ever heard anywhere.

Of course none of my concerns here actually help you with the symptoms you say you are now experiencing. My only rudimentary idea, is that perhaps some settings got reset when batteries were disconnected. But I'll leave suggestions as to what or how your suddenly declining mpg performance is manifesting, up to The real expertise.

Good Luck.

 

How much? An official Toyota 12v replacement here is £100 (AU$170) fully fitted and including 20% vat.

One wonders if the dealer lifted your leg as it is the first I heard that the HV battery has to be fully discharged. You sure they don't mean disconnected to carry the work out?

 

Did this ingenious mechanic charge your 12V battery with a charger before you drove off with it.
As others have pointed out, you don't need to do anything to the HV battery to replace the 12V battery.
All 12V batteries need to be properly charged with a battery charger before/after installation.

 

If what you say is accurate, your mechanic is at least an idiot and at worst a crook. Either way you need a new mechanic.

 

Hi Sonjain, and welcome to Prius Chat.

Ah the joys of owning a Prius in Australia, with pretty much no independent prius mechanics, and having to rely exclusively on this type of BS from the dealerships. I'm so glad I do all my own maintenance now, after my first $660 oil change by the dealer 3.5 years ago! (Yes of course they listed that they'd done other work, but they hadn't).

Anyway, as you've already found, no they don't need to discharge (or charge) anything to change out the prius 12v battery. You just remove the old battery and bolt in the new one, the same as you'd do in any other car. The only difference is that the 12V battery is a little harder to access back there in the hatch compared to a normal car. So while the process would typically take 10 minutes maximum in a regular car, it might take 20 minutes in the Prius.

As for the drop in fuel economy, I recommend just driving it for a least a couple of tanks of petrol before worrying too much about trying to "fault find". It's a fairly common occurrence that after disconnecting the 12V battery it takes the computer a while to re-learn some of it's parameters for optimal performance. Also, some of the data collected is merely for calibrating the fuel consumption calculations. Meaning that some of the loss of fuel economy may be only in the reported L/100km, not necessarily in the actual.

 

Unfortunately, this information is incorrect. All replacement 12V batteries need to be properly charge before use.

 

Yep, but they're usually charged before shipping otherwise they'd already be sulphated be the time the user got it. Sure if a battery has been sitting in the store for too long then it's not a bad idea to charge it before installing, but I've installed many car batteries straight off the shelf and just driven, and so have many other users here.

 

And how long do you think they sit on a shelf ? I see batteries less than 4 months from the production date that are 75% to 80% S.O.C. They need to be 100% when put into use. Any good technician will properly charge the battery before installation or at least after. If the shop isn't doing this, it's a halfassed place and you should find another repair facility.

An that makes it the correct way to replace a battery

 

Correct, but the reality is that whether it's 75% charged or a 100% charged at time of install, after 2 or 3 days of typical usage the two would be indistinguishable.

When I'm home I always charge before install, but several times I've swapped out batteries while on the road.

- Stop at parts store.
- Buy battery off the shelf (sure I check the voltage is healthy before I buy).
- Carry to my car.
- Install in car and drive off.
- Two hours of driving later no one would know any difference.

In any case, the dealers story to the OP that somehow something special had to be done to the Prius battery was completely false. If anything the Prius would be less susceptible to any problems resulting from a less than 100% charged battery at install time, due to the lack of cranking requirement. Also you're way over-estimating Australian Toyota service departments if you think they'd do it correctly.

 

Incorrect. The alternator will know and it can lead to alternator problems. Alternators aren't designed to "CHARGE" batteries. They're designed to replenish what's used by the vehicle. By not charging your battery to 100% capacity, you force your alternator to work harder. I own a new Prius C. After one month of driving it, I checked my 12V S.O.C. It was 75% and took about 2 hours to bring it to 100%. I charge all my 12V batteries every 6 months. My wife's Matrix battery lasted 8 years before it need to be replaced. You can do whatever with your vehicle, but please don't post misinformation for truth. It only adds to the interwebs garbage pit.

I never said anything about a Australian Toyota dealerships work ???

 

I believe The Prius doesn't have an alternator.
It charges the battery via the Hybrid Battery and inverter.

If that makes a difference.

Update:
I stand corrected, evidently...via Hybrid Battery and Converter.

 

True, but it's the same. The MG1 acts as an alternator through the HV systems inverter. It also uses a regulator to maintain the 12V battery. It will not "CHARGE" the battery like an actual charger will. That's why my 2013 C, 12V battery had a 75% SOC after 1 month of use. I would say about 1400 miles the first month.

 

Actually the Prius has a DC/DC Converter that converts the HV batteries' 200+V to about 14 VDC to charge the 12V battery and supply the car's 12V equipment.

 

Yes, I said inverter by mistake. It actually charges at 14.3 volts, per my Scan Gauge II. It still won't CHARGE the battery to full capacity. No alternator/hybrid converter will and that's why it needs to be done with a real charger when replacing a battery. Like I said, I charge my 12V batteries every 6 months. I can't prove it's why the Matrix battery lasted 8 years, but I'm sure it was I've never had a battery last past the 5 year mark that wasn't serviced during it's lifetime.

 

While I agree any battery should be checked and charged if required before fitting .You are totally incorrect about the hybrid system not being able to charge the battery fully.
I have done extensive testing on the Prius gen2 charging system and your statements and assumptions are completely wrong.


The Prius charging system will put out 14.6 volts and more. An AGM battery dependent on manufacturer has typically a fully charged voltage of 14.1 volts to 14.2 volts but can be as high as 14.7 volts.
There is nothing special about a plug in charger compared to the Prius charging system. In fact a large numbers of chargers are cheaply and poorly designed in comparison. The Gen2 has a two stage charger later versions have 3 stage.
If the gen2 Prius does have a fault with the charging system it is the fact that it is not current limited and is capable of continuous high output currents "well in excess of 50 amps" into a discharged battery. This could and I believe does boil or evaporate off some of the water contained within the glass mat drying the battery out. Later versions I believe have temperature monitoring of the battery so this may have been addressed, although it is possible this is just to check the charge voltage level at different temperatures.
Further what would be the point in having a charging system on any car that cannot recharge the battery after a partial discharge. The battery would be destroyed by sulfation in a matter of months if it could not be recharged.
Please stop spreading misinformation on this subject, your statements are so full of holes, for instance:-

Alternators are not designed to charge batteries "Quote". Can you tell me why we have them "the discussion on the Prius not having one is mute at this point"
By not charging the battery to 100% capacity you force the alternator to work harder "Quote". A battery in use on a vehicle is constantly being discharged and recharged. Just opening the drivers door on a Prius partly discharges the battery.
Then you say after one month of driving you Prius C the battery was only at 75% charge. You do not state under what conditions you checked it's state of charge making the statement worthless.
I am afraid the garbage is coming from you.

John (Britprius)

 

the oem battery is expensive here as well. i have seen posts here where people have paid upwards of $300. plus. the battery itself is $200., unless you can find a discount. my mechanic replaced the one in my '04 for $160. so he must have gotten a good price and it only takes a few minutes to change it out. to find an honest mechanic is better than a pearl in an oyster!

 

Since we are all trying to guess what the original mechanic may of meant by "discharge" the battery. I'm wondering if perhaps he wasn't referring to the the battery discharge "vent"?

If I remember right since The Prius battery is in the cabin, it has venting going from it to the outside. Maybe he was saying that making sure that was all hooked up to "discharge" the battery fumes was what he meant. STILL not something that should result in a higher cost to install IMO.

But in any case, whether this is a lost in translation misunderstanding and/or simply an unethical mechanic, I still find it almost impossible to believe the hybrid battery would of been totally discharged. Because as pointed out, even if you somehow found a way to do it (needlessly)...you'd then need the rare Toyota Charger to recharge it.

And I think if it happened, you'd suddenly be having a lot more problems than just a dip in fuel economy.