Do I Have to replace aux. battery Every 2 years?!

The batteries should have a warranty?

You should use a charger that charges with 4A to 10A with an AGM charging setting. Nothing less, nothing more

 

Prius doesn't seem to do well charging those 12 volts. I trickle charger mine once or twice a week.

Posted via the PriusChat mobile app.

 

2008 = 10 years

3rd battery = 3+ years / battery

there's a lot involved with the 12v. brand, model, warranty, usage, parasitic drain, leaving a lite on, etc

no one buys a new battery every two years. some replace on a four year schedule in hot climes prophylactically
mine last 8-10 years

 

I wonder if Poster #1 & #3, unintentionally drain the 12V down by sitting in the car in ACC mode, listening to the radio repeatedly and for prolonged periods? If so, it will take a long time for the Prius charging system to fully charge the 12V battery.

Poster #1, possibly Poster #3 too, might have aftermarket accessories installed that always remain HOT, thus the continual discharge and weak 12V battery?

It seems clear that both Poster #1 & #3 are not using a smart AGM compatible charger.

A trickle charger is intended to keep a battery that is ALREADY fully charged from discharging. It is not intended to resurrect a a dead or discharged battery.

Read Post #8) State of Charge chart, AGM compatible battery chargers.
Is my inverter coolant pump slowly failing? | PriusChat
Right tool for the right job. Get an AGM compatible smart charger.

 

My CTEK's on your list. I would say most any smart charger would be fine, AGM "compatible"

At least judging from my CTEK's manual. the compatibility is that they recommend charging with the higher voltage setting (snowflake symbol on the charger), with spiral wound AGM's (like the Optima Yellow Top). They also recommend that setting for any battery, is severe cold weather.

For conventional case AGM (like the ones from the factory), they suggest to just use the regular voltage setting, nothing special.

 

i like the looks of the sc1305

 

One I use

Posted via the PriusChat mobile app.

 

One I use.

Posted via the PriusChat mobile app.

 

First you should try to determine WHY you are having so much battery trouble.
MILLIONS of owners totally ignore their 12 V battery and it lasts 5 years or more.

Are you in an extremely HOT climate ?
Have you tested the charging voltage while the car is "running" ?
Have you checked that there is no current flow when everything is supposed to be OFF ??

I think you should STOP buying batteries and spend the money on finding out what is really going on.

Note: I wish people would stop using the term "trickle charger".......because a real cheap trickle charger is virtually worthless and sometimes causes more trouble than it fixes.
If you have a smart tender type automatic battery maintainer (good) please do NOT call it a "trickle charger".

 

The charge profile for an AGM is NOT the same as for a flooded or gel battery, therefore if the charger used does not have the correct profile for the AGM as used in a Prius, it will not correctly charge it.

 

I never use a charger except as a precaution when grid charging the traction battery in case a dome light gets left on too long. It may be that the "trickle charger" is not made for your battery, as has been suggested and is killing your batteries. Under normal circumstances there is no need for a charger.

 

Let's not forget that the inverter is not designed to (re)charge the 12V, but to maintain it.

 

Beg to differ on 12v batteries in hot climates. 2008 lasted nine years and was still functional when proactively changed. 2012 has seven years and counting (delivered nov 2011). Both suffered a couple of discharges. In every case the inverter did a stellar job of charging and especially maintaining them. Cars driven daily helps. Certainly they do go bad but they are in a relatively conditioned space away from engine heat and shock and their normal loading is almost zero. And they are sealed agm batteries which are superior to cheaper batteries. I agree the problem needs to be found. I would start with a verification of the off state current draw. Measure without a key nearby and allow time for the ecms to fully shutdown. Should be less than 20 ma. Then turn on the hatch light (a common issue when the hatch fails to close 100%). Some add on boxes like security or amps may be sucking power. It is a small battery. Finally I agree a trickle charger can ruin a battery especially if its that cheap one from Harbor Freight or most other rebranded equivalents. The only time I use a “battery tender” is when I have a battery in storage.

 

No one said the inverter would not recharge the 12V, only that it is not DESIGNED to. A good multi-stage charger designed for AGM batteries IS designed to recharge them, an inverter is not. Toyota engineers are REALLY smart folks, the inverter does a great job, but a dedicated charger does better.

 

If you have ever changed an alternator on a conventional car the directions say, "This alternator is NOT a battery charger". They tell you to
charge your battery before you start your car with a new alternator.

 

You can "differ" all you want but you will still be wrong.

A vehicle DRIVEN in a hot climate is somewhat different than one just parked out in the sun for months on end.

Heat is HARD on batteries. That is a fact.
Look it up.

 

I don't know how common it is but some batteries are actually made for warm climates. I learned this when I took a battery to Walmart to be tested and the guy told me it was a southern battery. There was a "S" at the end of the group number. I don't know how common this practice is but it was a Walmart battery made by Johnson Controls.