12V Battery

Of course it is going to be lower with it connected, otherwise you wouldn’t ever be able to start the car. And then he is going to have to go through the hassle of resetting systems that need to be, because he disconnected the battery. Your solution will create more headaches than are necessary at this point.

The dealership test has already shown the battery is bad.

 

How do propose to replace the battery without disconnecting it?

 

But it hasn’t shown if the car is bad

 

I’m using a Solar BA5 for this. Current version is BA9.

 

Removing all parasitic draw including the normal -25ma by disconnecting the battery proves very little.

 

The testing you are discussing is attempting to read impedance, with other electronics connected.?

I would prefer to err on the side of 'best practices'

 

It would easily show if you have a large draw

 

You don't need to limit charging to 4 amps. That is one of many myths floating out there just because two or more people said it on a forum.

The manual is concerned with an old school 5 amp or larger charger that will not stage itself.

Not true on almost vehicle charging system. The inverter's dc to dc is quite sophisticated when charging a 12v battery and can and will supply 15vdc at 80 amps or more for a controlled and monitored period. In most cases the battery will quickly accept that charge for a couple of minutes when the dc to dc will stage down many times reducing the charging voltage and current. It usually gets to somewhere around 13.5v as a float voltage while simultaneous carrying all vehicle 12v current loads.

 

I can't address all of the myths, but I can take a picture of the OEM battery where it clearly states "Do Not Exceed 4.2 Amps"
This was a surprise to me when I had to recharge it on a cold night in the body shop parking lot after a deer committed suicide on the drivers side door, and it wouldn't latch - leaving several 12v systems activated.

The issue is when that tiny battery is deeply discharged, it will accept much higher currents for a long time, leading to overheating (not much mass to save it) - I am not worried about the initial spike of 6 amps or so while I am watching the meter.

I tend not to argue with manufacturers instructions, nor do I derive my knowledge of batteries from the Interwebs (though I am always learning

 

Where on earth did you get that idea! Come on man! I’m talking about disconnecting the battery to prove something that is already known! Why am I even responding to this? Just proves that I can be just as much of a fool!

 

I just disconnected the Aux battery to service the brakes, and the only thing I had to reset was the clock afterwards.
If you want the most accurate test results and/or charging of a battery, it should be disconnected from anything else.

Is connecting a properly working smart charger to the Aux battery 'good enough' without disconnecting from the car?
In my opinion, yes. I do it about once a month, despite all of the dire warnings. My charger has reasonable charge parameters for the application.

But while I had it disconnected for the brake service, I charged whether it needed it or not. It did accept a charge.

YMMV

 

I just installed a new Toyota battery today with the 84 month waranty. I didn't know it costs only $186! I remember many years ago the Toyota dealers were already selling them for over $200+ and that was the time I switched over to the Optima batteries. Costco was selling their Interstate batteries for $250 with only a 3 year warranty.

 

Thanks for the report!
I have paid the premium price for Optima batteries (in other applications) in exchange for the reliability that the spiral-wound construction brings. Being able to install one in an occupied space was a plus.
It was a gamble, because I could have bought a couple of replacement flooded Starter, Lights, Ignition (SLI) batteries for the same price - or less.

I did get one of them to last ten years.
I think another can accept a charge after 15 yrs, but it has been retired.

2 yr free replacement and 60 month pro-rated following - that is pretty good!
7 yrs is a long time!

Although there seems to be an odd exclusion:

What is not covered:

• Recharging of discharged batteries.

 

Hopefully, that was not on your new 2023!

That's a pretty good price. Last time I bought one was about 18 months ago for my wife's 2017 to replace her 4-year old original that was getting wimpy here in the Florida heat. With coupon, I paid $176. Installed it myself. (Gen 4 uses a wet battery, so I think it's a little cheaper.)

 

Haha It was for my 2012 Prius Plug-in. Finally replaced the original battery after 11 years. Glad to see my EV miles reset back to 12 EV miles and then subsequent full charge of 13.9 EV miles.

 

You've been here for a while, so I assume you know that that doesn't mean you get that many miles. The car just forgot how many miles you were getting before so it's displaying the numbers as if it's a new car. Once it learns how much energy the battery holds and how fast you use it, the display will reflect that range. It has nothing to do with how far you can go, just how far you've been going.

And PiPs do take better care of their 12V batteries as they maintain voltage while the traction battery charges.

 

I was just happy to see a double digit number again and just reminiscing the good old days.

 

My 12 v battery on 2020 Prime doesn't seem to be rapid charging during use or charging, not at all. Where is the reference to this capability?

 

My understanding is that on the '12v Auxilliary' side of the DC/DC converter, it is a steady 14.2 volt supply capable of delivery around 2 kW.
It is not a smart charger, otherwise your lights and accessories would be varying in voltage as the 'charger' tended to the battery.

I believe it is what it's name says - a DC converter.

I have no reference for that either, but I will be inquiring.
I will also be testing real-time.

 

This only applies to non-staged chargers used for hours. In fact the inverter's dc to dc often applies 60 or more amps to a partially discharged 45ah 12v battery. Toyota won't void the warranty unless you burn it up with an old school charger.

In most driving situations the 12v battery is floated at essentially zero amps with a 13.36 vdc "charge" voltage. That charging voltage varies up to 14.9 v in an advanced staged manner. Which provides 8 years of aux battery life in many cases. When in Park, the charge voltage goes to 14.4v. All of this is quite easy to observe with a scanner and even a diagnostic menu on the mfd.