Symptoms of dead 12V but charger says battery full?

A 3 amp charger just doesn't have enough power to charge a dead battery. Sometimes, people have to trick the charger by connecting a second battery in parrallel with the dead battery, so that the charger can sense that the battery being charged is not below the acceptable voltage for charging. Once the charger starts its charging cycle, it is supposedly OK to disconnect the second battery from the battery being charged.

However, like I mentioned earlier, if you have a 7 year old original battery, it's time to replace it. A lot of batteries have a date of manufacture on it for warranty purposes.

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The sensor circuit in the charger gets "confused" when it tries to charge the battery but no current flows.
That is, the battery will not accept a charge. AND it won't give back whatever charge that it has either.
Typical symptoms of a totally failed battery.

 

HEAT kills batteries.
COLD is actually good for them.......to a point.

 

That really isn't true, in general.

It depends on how "dead" the battery IS and why.

If the battery hasn't failed completely, a 3 amp charger is plenty but many hours will be required.

 

The date of manufacture, might be the one printed in the middle ending in 13.

It's a 2014, so it might be the day of the year (xxx out of 365), or the week, and 13 is the year of manufacture. So maybe the 311th day of the year 2013?

But that's just a guess.

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Did you get a new battery?

 

Be sure that your new battery is fully charged......before it is put into use.
That can be done before install or after, makes no difference.

 

Not necessarily, it sits on the shelf slowly losing charge. It's always a good idea to charge it up, before or after installation.

FYI, I thought my batteries were going bad because my charger would never get to full charge. Turns out that the charger was the one going bad. Bought a new one and it charged up the two batteries in short order.

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You would think so.
But people are lazy and incompetent these days.

And ones you get "mail order" are guaranteed to be flat most of the time.
Unless they can hook a meter to it before you leave the store and SHOW you that it is 12.8 volts or more.......then don't assume anything.

 

I had a battery that I just turned in to Walmart for core credit. My 14 A Schumacher Ship 'n Shore would charge it up to 100% real quick. If I unplugged it and plugged it back in about 1 minute later, it would start off at 1% and continue to charge up to 100% rapidly. Pretty much a dead battery. You can test yours similarly, disconnect your 3 A and then 1 minute later plug it back in. If it starts charging again and takes a while (because yours is 4x as slow), it is likely a dead battery. It should show full after only 1 minute.

(BTW- I have two of those exact same units now. I'm slowly replacing the Automatic voltage sensing 6 V/12 V 1.5 A Schumacher maintainers as they mistaken dead batteries as 6 V and I find them DEAD, like the one I just replaced. Only negative is they come with permanent clamps and no swappable ring terminals).

 

Your new Toyota battery will be fine. The high areas of expertise around here center around 12v batteries and egrs causing all sorts of issues from cancer to illegal immigration. Add in no starts and head gasket failures and you have a perfect storm.

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The EGR can be hard on your poor aching back.

 

And then you go on to spout off a lot of things that while likely true, have NO bearing on whether or not the battery will come from the dealer with a full charge in it or not.

 

When you go to pick it up, just ask them nicely to check the voltage for you, and ask them to show you the date code sticker(s). Mine was 2 months old, and IIRC was at 13.1 volts. I was happy with that.

 

Geez, spring for a cheap multimeter at least, check for yourself?

Again, voltage alone is not a very good indicator of battery health; acquiring something like Solar BA9 ($50~ USD electronic load tester), you’re set.

 

Most will reply nicely, I don’t have a meter here to measure it. Been there asked that.