12 volt battery loose connection

What kind of voltage did you measure at the jump points under the hood ?

Recheck all of the cabled connections in and around the 12v battery again, are the 3 wired connections also clipped in and secure?

Disconnect and or look for rust where the negative ground cable connects to the body of the vehicle, sand and reattach if needed.

Since you didn't list a location in your profile, we will assume that you might be in the Puget sound area. Maybe @PriusCamper can help.

 

THIS. It is also possible that there is a failed connection INSIDE the battery itself.
Some simple voltage testing is needed.

 

If it is an Optima battery its extremely likely the battery post has cracked. Poor quality.

 

Hmmm - by far no expert on cars whatsoever, however sounds similar to the problem I was having with our V 2 months back. Sometimes it wouldn't have any power when I attempted to start it, my wife's remote always worked when I went in and got it. Changed the battery in my remote and no problems. Have no idea why or if that was the problem, but so far so good!!

 

measure the voltage across the 2 battery terminals. Write that down. Then measure the voltage at the front jump point.

It should only be .5 volts lower at the front jump point.

If it was me I would unbolt the negative wire where it bolts to the cars chassis. Sand down the mating area where the lug attaches.
Sand down the lug mating area. Put some grease on that sanded area. Bolt it back up.

Make sure the 2 black wires plugged into the terminal assy on top of the battery are plugged into there sockets. Push them in..

Then do my test above.

A healthy 12 volt battery in a Prius G2 should live at 12.6 volts at the front jump point. if lower than that test it.
With car off turn off turn on the headlights in high beam. While the lights are on and car off measure the front jump point. It should not sag more than .3 volts with the highs on. I bet your battery tanks under this test like 11.5 volts.

 

Wrong order.
That kind of a flat, smooth conductive surface should NEVER have plain or dielectric grease put on it BEFORE tightening it down.
The grease is applied AFTER.

 

I noticed that too. Dialectric grease is non conductive and serves as a vapor barrier to moisture/battery-fumes, which cause corrosion. Put it on first before assembly and the result is an insulated union ... "Dielectric, sometimes referred to as tune-up grease, is a viscous non-conductive waterproof substance used to protect electrical connections "

 

We circle around this mulberry bush every so often. Most comprehensively, perhaps (with numerous references and also direct testing) back in May of 2021, for anybody interested.

TL;DR don't assume that because "dielectric grease is non conductive" you know what will happen when it's used on electrical contacts. What happens is more complicated than that, and engineers often do specify it for that use.

 

Dielectric grease will prevent electrical flow if trapped between electrical connections. Which is possible if the connection is loose. Normally people get away with it as most of it is displaced by tight connections. Good practice is to use it sparingly after making a clean and tight connection.

But we know all Prius problems originate with clogged egrs and it is best to measure flow

 

There's more to it than "normally people get away with it", and the details can be read in many industry documents that specify it for the use. This all has been covered before, including fairly extensively in the thread linked in #9.

 

It seems that there are a lot of folks on here who fall into the category of:
Don't confuse us with facts; our "mind" is already made up.
This is one of those subjects where that applies.

I recently had a dialog with a motorcycle owner who's bike wasn't running good.
He had just replaced the plugs.
About 4 messages into the discussion, he finally mentioned that he thought dielectric grease would be just as good as anti-seize on the plug threads. He also mentioned that he felt a slight shock anytime he touched bare metal anywhere on the bike.
You have to know the design of metric bike ignition systems to understand why that was happening.

 

Say... you LIKE doing this don't you? Unable to resist pushing the big, red candy-like button?

(I must say that I'm not quite sure what a "metric" bike ignition is- does it have different electrons than what's on a SAE or imperial bike?)

Posted via the PriusChat mobile app.

 

As a kid crossing into Canada, I had to remember how many electrons were in an imperial coulomb.

 

Assuming that comment was directed towards ME..............
4 cylinder metric bikes fire the plugs in two "sets" with two plugs in series in each set.
One plug of the set is connected to the + side of a coil; the other of the set is connected to the - side of the same coil.

When the coil fires, the electrons go out one side of the coil to one plug, to the cylinder block then to the other plug of the set IN from the block through the plug and back to the other side of the coil. One of those plugs actually uses the spark to fire and the other just passes it along on a "dead" stroke.

This arrangement is elegant in it's simplicity.