Aux Batteries keep dying

What is your reference for this information, or the source of the chart?

 

You need to do a parasitic draw test:

 

That video was already linked to back in post #17 when testing for a parasitic draw was discussed.

 

Did you happen to measure the voltage after it sat and before connecting it up?

In any case, it seems the battery is in a reasonably good state. Are you proceeding to do the next step to confirm the car quiesces to 20 mA as outlined in post #17? (Quoted below.)

 

That's not a parasitic draw test. There's no shortcut for the labor that needs to be done. You also need to apply a load tester to the battery. The lowest cost one at harbor freight is the best one that I've used for over 20 years. The digital one that calculates battery life by measuring internal resistance is woefully inadequate and notoriously wrong. It also cost more to get wrong results. Buy this one and test both the battery and do a parasitic draw test.
There's just no way around doing this correctly...
100A 6/12v Battery Load Tester

 

Who said it was?

How exactly does that load tester also do a parasitic load test?

 

Here is another one

 

I did a parasitic draw test on our 2010. Basically disconnected the neg cable from the body, bolted a long lead to the body, a second to the neg cable, ran both leads out through the hatch threshold, closed the hatch, taped the separate leads to the slab, waited about an hour (fob away, in the house), then measure first amperage (for safety), then milliamperes, with a multi meter. Got 15~20 milliamperes with occasional spikes to 40~50. The spikes might be due to the security icon blinking on the dash, but they didn't seem to sync. Anyway, VERY low. No where near 0.5 amp mentioned earlier.

 

I don't see a problem........unless it continues to fall by a tenth of a volt every day.

 

The Gen 2 Prius only trickle charges the 12 volt battery. If you start with the less than full charge it'll take a long time for the car to catch it up.

If you don't have a smart charger, just take your new battery to an auto place and have it fully charged before you start it in its life cycle

 

I'm new here and cant seem to find a place to start a new thread and ask a question ? help !

 

Sorry, LOAD testing the 12v in a Prius is a fool's errand. These batteries are NOT "starting" batteries in terms of size or capacity so testing it like one will not obtain the desired and accurate results. Would one start a motorcycle or garden tractor? Sure. But that is NOT how it is being used.

Unless the CURRENT DRAW is measured with the B- cable REMOVED from the battery (-) post, you will not know if there is too much "draw" on the battery. One clever trick, since the battery is in back, is to trip the liftgate latch CLOSED, which should keep the dome light off while the measurement is taken.

Normal "key-off" draw is under 0.5A, ANYTHING over that is too much and for a 12v to live, it should be in the 0.2A range, lower is better!

 

Skimming through this thread I have not seen anybody mention the SKS system. Does your Prius have the smart key system? That is always drawing a small amount, unless you physically turn it off with the switch under the steering wheel.

 

Agreed...the 12 volt battery doesn't spin the motor.
The 12-V battery turns on all the switches. without a 12-volt battery the car won't start. The user is reporting that the 12-volt battery is dead. Parasitic draw to the 12-volt battery needs to be tested. Load testing of the 12 volt battery still needs to be performed. It's too late to charge up and load test the old batteries because they're already damaged from a low charge state. But you can test the current battery. Then you can do a parasitic draw test on the system.

 

You still need to perform one. Make no assumptions. You don't know what the voltage drop rate is for a given parasitic draw