Check Prius Battery

Which battery - 12V or traction?
If 12V, you can check the voltage using the jump point under the hood. It's in the manual.

 

If you have random fault codes 12V battery is likely suspect. Best to measure the voltage after it has sat for long time (like overnight). You can check the voltage from the jump start terminal under the hood.

 

Or fit an LED battery status indicator like this one from CTEK to the battery post connectors, leaving the dongle (which also serves as a connection to a CTEK smart battery maintainer) visible at base of rear seat or cargo compartment, around $12 shipped.

http://www.ebay.com/itm/Ctek-Eyelet-Adapter-w-State-of-Charge-Indicator-Status-56-382-US-3300-7002-NEW-/271520673374

 

Does that monitor just voltage or amperage as well? Many batteries have healthy voltage but no CCAs compared to where they should be. That's why battery testing has to test to load to see if the battery fails when taxed.

 

for the hybrid battery, i think a scan gauge will monitor your voltages, temperature and etc.

even better, a laptop and mini vci with tech stream software.

for the 12 volt battery, see rrxing's post #2.

 

Prius doesn’t really require CCA from 12V battery for anything. So just checking the voltage after it has sat is (almost always) enough for Prius.

 

Voltage and predicted decay.

 

the average life of the 12 volt is 4-5 years and costs $2-300. to replace.

the hybrid battery is probably 10-15 years and $2-3000. for a new replacement. less for salvage or rebuilt.
i think in arizona, your hybrid battery warranty is 8/100.

 

Get a digital voltmeter (cheap ones are $20~30, invaluable for many applications), check voltage, by connecting the positive (red) lead at the jump point under-hood:


(Page 543 of Owner's Manual)

And the negative (black) lead to bare metal of the car body.

If you're getting a reading 12.6 volt or higher, the battery is totally fine. If you're reading 12.4~12.5, you've got an older battery, still some life in it, but worth researching replacement battery. If it's reading 12.2~12.3 volts, there's significant deterioration, consider replacing soon.

If you want to be proactive: research smart chargers. Used periodically, and coupled with voltmeter monitoring, you'll stay on top of battery status.

Here's some info on charging. Note the max charge rate of 4.2 amperes. I use a charger around 3 amperes, works fine:


(Page 563 of Owner's Manual)