Question re: 12-volt battery, please?

Try '4A battery charger ratings'?

 

Hi Julia,

Something like this would work but there is no metering. See what else you can find with those basic specs.
Amazon.com: Peak PKC0CS 2/4/6 Amp Intelligent Battery Charger: Automotive

I personally use a lab power supply set to 13.8VDC and 3A output as my Prius 12V AGM battery charger since that works very well and basically mirrors the charging that the battery would receive if the Prius were left READY overnight. The power supply has digital readouts for voltage and current so I can see when the charging changes from constant current to constant voltage. However that would be overkill for your purposes and a new lab power supply of this design will cost $200-$300 or so.

The 10 mm tools specified in a prior reply are not sufficient as you really should remove the brake power supply for easier access to the 12V battery, and I believe you need a 12 mm socket for that. Might not need 14 mm tools.

 

Hi Julia. I'm not sure this problem is quite as bad as you are imagining. Your Prius is about 5 years old right, and it's most likely the original battery. So sure it doesn't have a lot of life left in it, that's to be expected in most cars.

As you've already discovered the Prius "secret" service menu makes it dead easy to test the battery any time you like (without even opening the hood or getting your hands dirty). And your battery is still working fine, it's just that you wont have a lot of reserve capacity if you leave any lights on or whatever. The truth is that you're unlikely to get any significant change in fuel economy with a new battery anyway (not at this stage). It's the short trips that hurt your fuel economy, not the weakish battery. My battery is in the same condition as yours and I'm still getting 55 MPG tank average! (I drive mostly longer trips though).

A new battery is just for peace of mind that you don't get stranded in need of a jump start. If you buy a new battery and don't do anything other than drive it (given your mileage I estimate you're driving 2.5 to 3 hours per week right) it will still probably still last another 4 to 5 years anyway. I don't think the Prius 12V battery is really as problematic as some people make it out to be. It's just not as powerful as that in some other cars and so doesn't have quite so much reserve capacity. As long as you're a bit careful about not leaving lights turned on etc, then it can last pretty well without any special attention.

If I were you I'd go to Harbor Freight and just get a cheap 2A charger to give your present battery a bit of a boost. This will serve a dual purpose.
1. It will give your present battery a chance to stay in service a bit longer and,
2. It will get you nice and familiar with the jump terminal if you ever do need a jump start, so you will have the confidence to take control and hook it up yourself. (and so avoid having to take the risk of someone of unknown competence stuffing up your car).

 

double post

 

Julia2001,

5 years is borrowed time on any 12 volt battery in any car. The car hates winters and demands more power, the battery hates summers and has less power, sooner or later the battery lacks the power needed.

Buying a battery now means YOU decide when to replace it. Daylight , when it is dry, with a friend reading instructions, beats when the battery decides to die.

 

I would make sure I had it installed so the hidden (female) lead was positive and the exposed (male) lead was negative. That should prevent accidental discharge, although I would prefer a cap of some sort.

Some person on Amazon hated it
Amazon.com: Customer Reviews: Energizer 84028 12V 4 Amp Battery Charger and Maintainer
these folks weren't thrilled either
Amazon.com: Customer Reviews: Universal Power Group, Inc 84028 Energizer 12 Volt 4 Amp Battery Charger and Maintainer
Over 600 folks thought this one was peachy
Amazon.com: Customer Reviews: Battery Tender 021-0123 Battery Tender Junior 12V Battery Charger

 

And I was good and did not play any gender jokes....

 

Actually, it has LEDs that light up depending upon what % of charge (25%, 50%, 75%, 100%) has been achieved. Either that one or the Schumacher would be OK; the Diehard costs less and has a 4A charging position which is exactly what the Prius 12V battery needs.