Trickle Charger for 12V

Yup, dog with a bone.

 

Right, the recommended way to measure the voltage of your battery is to let it sit overnight with the hood unlatched. Then approach the car without the Smart Key in your possession to make sure it doesn't go through its start-up routine before you take the reading. There are several systems on the car that come to life when you open the door or even just approach the car with the Smart Key. To get a true reading, you don't want any of those systems running when you measure the voltage.

 

60 messages into the thread, I forgot the exact conditions under which you were taking measurements......or you didn't say.
It is important to track the voltage under known conditions, with no load or only a tiny one.
That means NOT opening the doors or using the remote; best to leave the hood ajar and not touch anything else.
IF it holds 12.6 for several days, your battery may very well be healthier than you think.

 

The real issue is to avoid opening the driver door and thus triggering the power brake accumulator pump, which sucks down a lot of electrical juice for a short time. Compared to that, the simple smartkey proximity detection is tiny.

 

I found even opening the passenger door dropped voltage by 0.1 volt. @bisco had mentioned the popped hatch trick so I tried that, got 12.9 volt. Opened/closed passenger door: it was down to 12.8.

 

In any case, these measurements are insignificant compared to the 10.5 V or less criterium that is quite often used in the repair manual.

In my book, while that battery is not in prime condition, it is more than good enough for the time being. People need to drop this fixation with the 12 V battery. It is not really rocket science.

Now that the OP has a battery charger and is going to use it on a regular basis, it is time to move on. For that matter, in these times, if you plan on not using your car for 2 or more days, just put it on charge. With these automatic multi-stage chargers, when the charge is complete it will continue with a trickle charge to keep the battery at full charge until required for use.

 

It has been proven by the experience of MANY owners, reported here, that problems start appearing WELL before the battery gets anywhere near 10.5 volts. I just looked at my "battery charge" chart and it shows 0% SOC at 11.8 with no load.

In MY opinion, his battery likely is marginal, not "more than good enough" and will just continue to get worse.......tender or not.

A tender will not necessarily "keep the battery at full charge" because one common characteristic of a worn out batter is that it won't TAKE a real full charge no matter what you do.

All the evidence says that it is YOU who should "drop" giving out bad advice.
It is pretty obvious that you don't have any real training in this field.

Good basic electronic troubleshooting says to always check the power supply FIRST.
And then if other discovered symptoms don't add up.......go back and check it AGAIN.

 

This might be snake oil but I've been doing it for years and my batteries always seem to last well past their lifespans.

I read somewhere long ago that when a battery dies it's because the sulfates (if that's right) flake off the plates, pile up on the bottom of the case, and once they build up high enough to touch the plates the battery shorts out. So what I do is tap the battery firmly with a rubber mallet and then charge it back up. The idea is that you're knocking down this piling up of flaky material. Like I said, maybe snake oil but hell what's there to lose except maybe some self respect if you do it in front of someone who actually knows what's going on LOL.

I mainly have the problem with my Suburban which almost never gets driven. The stereo unit in it kills the battery as it sits all the time and if I don't routinely start it up I have to deal with the dead battery. I used to have to buy a new battery every 2-3 years because it wouldn't hold a charge any longer. I've had the current battery for about 7 years now. I give it a good rap at least once a year.

 

Sounds plausible, and it can't hurt, a little tap.

 

AGM batteries do NOT suffer from sulfation to the degree that conventional wet cell ones do.

Your "method" might help.
It would help MUCH more if you used a good tender type charger to keep the battery fully charged all the time.

 

Sorry, but it's not my copyright.

CTEK 4.3 hooked up for the last six days.

 

Given what you said about how your charger works............
It very likely is NOT a dumb "trickle charger" and there is a significant and important difference.
Calling it a trickle charger tends to confuse people.
Smart charger or battery tender are much better terms.

Note: Until you do get it replaced, you should leave your charger connected to it all the time that it is not in use, if possible. Certainly overnight. A couple of hours won't be enough.

 

Wow, really pays to comparison shop. Maybe post on yelp?

 

Ignorant Prius new guy here. Is there something special about the Prius 12V battery or can I just go get one at Walmart like I always do?

 

You can NOT put any stock in the difference reported by the onboard system over a short number of miles like that.
Maybe it is mostly downhill from that dealer to home.