12 volt battery

Especially for people street parking, I think you could skip the hood-up-overnight bit: a bit overkill. If you're concerned about opening the driver's door "waking" the car, affecting the battery voltage: go in through the front passenger side, reach across to the hood release, pop it, get out, close door.

Wait say 5 minutes if you want before measuring voltage, but I'd suspect if you do an immediate reading, then one say 20 minutes later, you'd see no difference.

Still, while reading at-rest voltage with a digital multi-meter is definitely useful, gives insight into the battery's condition (and is what I usually do), if you've got definite battery problems: for the DIY'r something like the Solar BA5 is the bees knees.

 

Good to know. Enjoy the road trip. Do the resting voltage test the morning after you get there and see what it is, just out of interest. If ever you see a resting voltage 12.3 or less, charge the 12 V battery up using a automatic charger with an AGM setting. Fully charged it should be 12.8-13.2 V.

 

I use a couple. Have CTEK 3300 for over a decade now, a little simpler/cheaper and works fine. Also have a CTEK 4.3, which has slightly more power and complexity, does pretty much the same thing.

Look in the Owner's Manual for max charge rate, but I believe it's 4 ampish is the guidance, for max. It should be "smart", ie: it'll run through a complete cycle, monitoring the battery as it goes, and can be left on indefinitely, if you want. The latter case, it's just giving the battery the slightest amount of boost, acting as a maintainer.

 

Honey...

The 12v battery in a Prius is SMALL, like uber tiny and cannot carry a load for any real length of time, completely opposite of a "normal" sized 12v in a traditional vehicle. Your battery is perfectly ok, would I keep $200 handy, yep.

In a normal vehicle, if you turn the lights on you will read battery voltage in the low 12s to high 11s after 5 minutes and for comparison sake, these can produce HUNDREDS of amps for 30s and 25+ amps for an hour our more. The 12v in a Prius cannot do 25A for even 30 minutes, maybe not even 15 before falling below 10.5v.

 

+1 on the Ctek 4.3.

 

11.9 is getting there. Start saving up for new battery. The accessory test does not reflect the dip the battery takes when you initially boot the car.

The car is very smart when you dip below 11 volts the car throws an instant big red exclamation point in the dash to warn you it's about to leave you, only flashes once but very noticeable as it's not in the turn on bulb check routine on the dash and u never see it till it throws. It does not log a DTC either.

Other very easy test is at night turn on the head lights and then boot the car
And see if they dim in the slightest. Headlights run off the 12 volt battery so it's showing you true load. Best technical test is hook a DVM to the front jump points and position the DVM so you can read at while you boot the car.
Take note of how low the 12 dips upon boot up. Your car at sitting 11.9 is probably right at 11.10 volts upon boot.

 

That is the charging voltage from the inverter after a successful boot. The issue is the battery voltage during the boot process. Too low and the boot fails.

JeffD

 

Try not to over think it. From what you have told us, your battery is in reasonable condition, so one less thing to worry about. Happy road trip.