12-Volt battery replaced; 2 months later, car is dead again

It should sit ok for two months with a new battery. Perhaps the battery wasn't fully charged when you installed it.

Other than that the only advice is to double check that all lights etc are off and no doors ajar. When leaving it that long without driving it's also a good idea to turn your sks (smart key system) off if you have it.

 

You could try a jump start with leads from another car - there are instructions how to do this on this site or consult the hand book. Be very very careful how you do this. Give the car a good run to get some charge into the battery. If you still intend to leave it for months at a time with driving it, you should invest in a good trickle charger CTEK for example.

 

1. You needed to fully-charge the 12V battery prior to leaving the car for such an extended period.

2. 60 days x 24 hours/day x 0.02A quiescent current drain = 28.8Ah

3. The capacity of the 12V battery, fully-charged is around 40 Ah. It is not considered helpful to allow the battery to get below 50% if you are interested in a long battery life.

Therefore, I suggest that a) you fully-charge the 12V battery now, and b) you should either disconnect the 12V battery when storing the car for one month or longer; or should use a battery minder to keep the 12V battery charged.

 

A battery maintainer is the way to go. Self discharge rates of 12V batteries vary, but sulfation will commence with that long a period of inactivity. Lead acid batteries need activity to stay healthy.

 

Toyota recommends that you turn off the SKS system if the car is not going to be driven for two weeks or more.

You should fully recharge the battery and test it. You may have some parasitic drain on the battery, or you may have a defective battery. If you jump start the car and use the car to charge the battery, be aware that it might take a couple of days in READY mode to fully charge the 12v battery. I'd recommend using a charger.

You might be able to get all of this done at no cost to you at the place you bought the battery, if it's local to you.

 

Doesn't matter. The very first time the battery is discharged to death, it is dead. It will never have the same capacity as a new battery. In a Prius if the battery does not turn the relays on, it is in the 9v range which is beyond dead. In a normal car, a "dead" battery could still be pretty well charged but not enough to crank a hard engine. Nothing like that in a Prius.

If you are routinely leaving your car for months, you definitely need a battery tender.

 

2k1Toaster pretty much spelled it out and hit the nail on the head. You will probably get lucky and be able to recharge your battery, BUT you DEFINITELY shortened the life of the battery AND its ability to hold a charge.

As everyone is saying, you definitely need to either unhook the battery or get a battery tender/maintainer if you are not driving the Prius regularly.