12 volt Battery Issues

Smart Key System
SKS: https://drivingconnective.com/what-is-sks-with-toyota-prius/

 

No diodes. But what you can have is a severely discharged battery that may initially draw 80 amps from a jump source. This will cause a low voltage from the jump pack, at least for a few minutes. Typically this would be a battery with very low voltage.

While not popular, reading the manual suggests you hook up the jump source, turn it on and wait 5 minutes. This covers the initial inrush caused by a "normal" no start discharge, eg perhaps a 10v battery. After 5 minutes the amps you put in are available from the battery to help your Lithium JumpPack.


Story Time

The other day I helped a clueless neighbor who had a one volt battery on a conventional Honda. She had left it for months without driving it. They jumped it from another car and it ran until the jumper cables were disconnected. The Honda's 100 amp alternator (the charging system) could not handle the massive initial charging amps required by the battery and still run the car. Remember this was a one volt battery and it was fairly new. In her case, I put a 10 amp staged charger on it for six hours. It recovered the battery to about 12.2v and all was good.

Solution

Normally a Prius that is driven twice a week for 15 miles would never have a problem. A decent six year or newer AGM battery and normal parasitic draws will start a Prius three or four weeks later.

Finding the excessive parasitic draw is the solution for reliable operation. There are downsides to battery disconnects including loss of some tuning parameters. Plus increased risk of jump damage costing hundreds or thousands. And decreased 12v battery life.

Finally if your properly repaired Prius has to sit longer than three weeks at a time, use a $35 Battery Tender Jr while parked. Don't disconnect. If your not driving it for a year, sell it.

 

It's the system that has sensors that recognizes your key fob approaching and unlocks the door as you reach for the handle, as well as allows you to drive the car without plugging your FOB in, as long as the fob is with you in the car it picks up on the signal. If you have this system you can turn it off using this "key" button:

 

I always recommend the Toyota battery. It's hard to beat an 84 month warranty.

I'm not saying this is you since I doubt that yours is original, but it's amazing to me how many people say something like, "My original, 10-year-old 12V died. What kind should I get to replace it?" Makes me wonder if it's a trick question.

 

12 v is not barely alive. 10.5v overnight with a low draw is barely doing its job. Depends how old the AGM battery is, not how many times it dropped to 12.0v. One of the features of an AGM is its ability to recover from multiple discharges versus a normal wet lead acid battery.

A Battery Tender Jr ($35) has a quick connect adapter which comes with it and it is a multistage charger, safe for the battery. If your battery is three years or less, I would get the charger first and try it for a few weeks.

A led bulb for the hatch, normally switched off, was my solution there.

A Toyota AGM battery is the gold standard if you can find one. Most people get six or more years. Otherwise an Interstate Battery direct equivalent followed by any AGM direct equivalent.

 

Not your problem but ….Very easy and a few dollars to replace all of the interior lamps with LEDs along with many of the other lamps like license plate, etc. much less current draw when using and longer life

 

And better illumination. Made a big difference in my cars.

 

Here's the best battery for the price: 12 Volt (12V) 55 Amp (55Ah) VRLA AGM Sealed Lead Acid Battery 55 AMPS HIGH CAP | eBay I had a battery like this last 9 years in my Prius. Don't listen to auto part stores that sell batteries worse than this for three times the price.

 

Second 12-v Toyota battery since 2008 and it is still going strong. Same experience with all my Toyotas and using genuine Toyota Batteries. I usually get 7-10 years. Great warranty, also.
kris

 

You just buy slightly longer bolts than it comes with and a washer for the top and bottom of each terminal and sandwhich the terminals between the washer and stick the bolt through it and tighten it.

 

Hi Alan,

Yeah, it's all a juggle between time, money, energy, effort, convenience, utility ;-)

Good luck.

 

Did you ever say if your battery is out of warranty after only 1.5 years? If so, that is a crappy battery. If not, take it back for a warranty swap.

If you’re thinking about selling the Prius because of oil a consumption problem, just sell it and don’t put money into a battery or anything else. There’s never been a better time to sell a used Prius. Dealers will buy it in a heartbeat and they’ll figure out what to do with it.

 

same, all the best

 

That changes NOTHING about what I said before.

Then.....you did NOT "charge the battery up to 14.7. That is not possible.

14.7 is the CHARGING voltage and you should expect it to drop fairly quickly down to it's nominal resting voltage of about 12.8 very quickly after the charging is removed.

As for measuring the "phantom drain", first you must be sure that you are reading the meter right.
Then, some systems stay alive for a while after everything is OFF.
Let it sit with everything connected for about 4 hours before you take a current drain reading.

 

thread is finished sam, see post #36. let it go... OMMMMMMMMM

 

Do PriusChatters ever really let a thread go? I mean would @bisco have 96K comments and 43K likes if we just let it go?