12 V Battery -to the moon!!!

How old is the 12 volt battery

 

You seem to know what you are doing, what you can also do is get ahold of a voltmeter and check the battery voltage before you leave from work to come home. that way the car has had a charge from the inverter, but what I want to see is where the voltage from that battery rests after sitting for a couple hours.
Ideal thing to do would be to get the car home and completely disconnect the 12v battery from the car (leave the battery sit in the car, just no wires connected to it). you will lose your stations and all that but do that and then check the voltage in the morning or after 4 hours. let us know what the voltage is. that will give us a tell tale sign if its the battery or something in the car draining it.

 

Are you talking about the battery reading of the bar display? And the dealer said your "batteries" are fine? Are they talking about the HV battery, the 12v battery, or both, and based on what? Sounds like either the 12v needs replacing (most likely) or there is a disagreeable drain on the 12v that may have weakened it enough to need replacing. It's not uncommon for the 12v to need replacing in 4-5 years, regardless of what the dealer says.

 

I agree. with replacing in 4-5 years. Regarding the bar on the dash, that is your hybrid battery level, mine is an 01 prius and mine stays at 3/4 all the time but thats normal, the 07 im not sure, yours might go up to full. but im not sure about that. that dash indicator will not show your 12v battery level. As I said above, get home from work or whatnot and disconnect your 12v battery and let it sit for a couple hours and check the voltage on it with a voltmeter. let us know what the voltage is.

 

True. That's why I was asking the question. At best the 12v probably needs a significant amount of time recharging. At worst it needs replacing. The rear hatch light has been a culprit for some caused by leaving it on or not closing the hatch all the way. Just a thought.

 

Steve, a good charge overnight would not hurt at all. When I bought my prius 4 months ago, I did a charge for about 8-14 hours and it now sits at 12.5v all the time. granted its an optima battery. but it was sitting at 12v when I got it. so this individuals battery may need a nice reasonable charge from a battery charger. I dont have the hatch as mine is a trunk since its an 01 but thats not to say it could become an issue.

 

If you do end up replacing the battery, go with the Optima upgrade, they are not as sensitive to drain as the stock toyota battery. I have read that the toyota 12v battery if drained like what you did can kill it easily whereas the optima can take it alot easier.

 

Rhonda the Prius only charges the battery at a maximum of 4 amps. This is the maximum charge rate that the OEM battery can take, so it follows that if the battery is fully discharged it would take about 8 hrs of the car being in ready mode to recharge it fully as the battery has a capacity of 36 amp/hrs.

The car does not need to be driven to recharge the battery (as with a normal car) as it does not have an alternator, it is charged from a converter from the HV battery. However charging with a charger at 4 amps for 8hrs is the best way.

Having said all that I agree that it is time to fit a new battery, be it OEM, Optima, or Exide Edge.

The important thing is that the new battery should be supplied with a minimum voltage of 13.8 volts "measured with a voltmeter" the reason for this is batteries often sit on the suppliers shelf in a discharged state "they naturally slowly discharge without load" and this damages the battery reducing it's service life and capacity.

John (Britprius)

 

You have doubt about the 12v battery, it can be the driving style/temperatures/distances or the charging system or just simply the battery. The last is the most easily tested by asking any place that sells batteries to do a load test after the battery is fully charged. My bet is, if you haven't replaced the battery before..it is the original battery, then going into winter it is a good bet the battery just needs to be replaced. A load test will tell.