Driving in diagnosis mode to check hybrid battery, mine reads 12.3? Is my hybrid good or bad?

No it means your normal 12v battery is fairly well charged up.

 

that's not the hybrid battery, it is the 12 volt battery, and that is the inverter voltage maintainng the 12 volt (like an altenator in a non hybrid)
the only way to check the hybrid battery is with toyota tech stream diagnostic software, or a phone app like dr. prius

 

Not exactly. If you were reading 14.3v on the 12v system, it means the 12v battery is low on charge. If you read 13.2v it means the 12v battery is almost fully charged, which is a good thing. Charging systems increase the voltage to charge more, reduce the voltage to charge less.

But 12v battery charge has almost no relationship to the health of your hv battery. A totally bad 12v battery may cost you some mpg but your 12v battery seems to be ok.

 

exactly

 

Have you put a charger on the 12v battery and given it a full charge??? Or attempt too anyway.
If so, wait 30 minutes, after removing the charger, then load test it. Since you probably don't have a load tester, you can turn on
the head lamps, high beams, then measure the battery, at the battery. If you are getting 10.3 volts,
the battery is more than likely bad. Hold old is the battery?
If the 12v battery is bad, it could be constantly drawing more amperage/voltage from the hybrid battery
because it's trying to charge it up and keep it charged, which will cause the hybrid battery to drain faster
which will cause the engine to run more to charge the hybrid battery.

 

you needa new 12v battery. how old is it?

 

I agree. Have the 12v battery checked very soon. It is costing you mpg and is likely to strand you.

 

If you drive to any car parts store, they will give you a free 12-volt battery health check if you ask them.

 

Ah…., forget it.