12v battery

With a load tester (like the Solar BA5, BA9 etecetera), you can't hook up like the pic above. I've tried it and it gives me a hard time.

The tester instructions say to connect directly to the posts. I try to do that. With the battery installed it can get a little tricky, the tester clamp jaws will sometimes just be grabbing the cable clamp, which also seems to work. But I try to get so the jaws to actually contact the lead post.

 

Maybe not......for that given test.
I am sorry that I did not pay closer attention to the test screens that he posted.
It is known that those "tests" can be VERY confusing and misleading.

It looks like "we" have inadvertently talked him into buying a battery that he did not need.
So far, I don't think we have seen a voltage reading while the car is actually running.....in the READY mode......and that is important too.

Was it in this thread that I mentioned being sure that a new battery is fully changed BEFORE being installed ??
If not, I just did.

 

Thank you. I’ll buy a digital multimeter. Maybe save me from buying the next battery too early

 

Well, I guess having the new battery installed would have been necessary at some point anyway, so I’m just a bit early and cautious. No worries.

 

Many of us are used to the older cars where the alternator charges the battery (generally at ~14 volts on another brand I'm familiar with) and the battery feeds the starter and actually starts the engine.

But in the Prius isn't it the hybrid battery that charges the 12volt? And the 12volt merely boots up the on-board computer which talks to the the hybrid battery that starts the ICE? The 12volt thereafter runs some of the auxiliaries? And there is no 12volt starter which is why the 12volt battery can be so much smaller physically and in terms of load capacity.

 

I’d like to know the answer to this interesting question too.

 

Yes what he said is mostly right.
And he has been around here long enough to know that it is right.

 

I thought he asked it as a question, didn’t mean to question his knowledge. Good stuff to know, thanks again.

 

The "12 volt" battery (which produces anywhere from 12.7ish volts when well charged down to maybe 10.5 when "considered" fully discharged, though nothing stops it going below that) is connected to the wiring that powers all the "12 volt" stuff in the car. Which is most of the electrical stuff in the car, including the computers, just not the hybrid powertrain.

When you push the power button, and the "12 volt" computers agree to put the car in READY, they send ("12 volt") power to the system main relays, which bring the traction battery online, connecting it to the same big orange wires as the power inverter atop the transaxle.

Those wires carry current from the traction battery to the transaxle when you are driving on battery power, and from the transaxle to the battery when you are charging from the engine, or from downhill or braking regeneration. Also inside the inverter is the "DC/DC converter", which steps some of that power down to "12 volts" and puts it on all the exact same wiring that the "12 volt" battery is connected to.

Now it happens that the "12 volts" coming out of the DC/DC converter are more like 13.8 to 14.7, that is, always above the voltage from the "12 volt" battery. So whenever the converter is operating, power is flowing into the "12 volt" battery, not out of it. All of the "12 volt" electronics in the car are still connected to the same wires and still getting power, but the power they're getting is coming from the converter, and the battery is getting charged.