Low voltage battery

[Florida Prius]

Interesting that my dealer advises disconnecting the 12v battery if the car is to sit for 7 days or longer. It's claimed that the Hybred batteries suck the life outta the battery. I find this difficult to believe, but m wondering what the ramifications are if I do disconnect the battery (or if it does drain down in 7 days).......

[tochatihu]

Originally posted by Florida Prius@Jan 9 2006, 04:59 PM
Interesting that my dealer advises disconnecting the 12v battery if the car is to sit for 7 days or longer.  It's claimed that the Hybred batteries suck the life outta the battery.  I find this difficult to believe, but m wondering what the ramifications are if I do disconnect the battery (or if it does drain down in 7 days).......

[snapback]186638[/snapback]

It is not at all true that the hybrid battery sucks the life out of the 12v. It is true that Prius has a smaller 12v battery than almost all other cars. There is a small drain (on the order of 30 milliamps in the new model), which will eventually discharge the 12v battery to a level where the starting procedure will fail. In addition, a small light left on or the JBL audio power drain problem (both mentioned already in this thread) will accelerate the discharge.

Once a battery has been drained to a nonfunctioning level (especially in temperatures below freezing) it will not recover its originaly capacity, even after being recharged.

Disconnecting it for a non-driving period will eliminate all of the "parasitic loads", but the radio presets and clock will need to be reset afterwards.

[narf]

Another point is that once the READY light appears, the car isn't using the 12V battery, but is providing 12V from the DC to DC converter (and charging the 12V battery). I don't think you need to keep the radio and fan turned off to save the battery once the car is running.

[jsutherl]

"Once a battery has been drained to a nonfunctioning level (especially in temperatures below freezing) it will not recover its originaly capacity, even after being recharged."

Couldn't resist adding my note of affirmation here.
Have had similar problems with our little Gen 1 from our local fleet. Like you say esp. in cold weather. I doubt this will help the Gen 1 owners much on warranty but here is All Data's info on the Aux BATT. capacity situation. There is also info in there advising suppliers not to leave Priuses 'dead on the docks' for too long also.

2001-2003 Toyota Prius L4-1.5L (1NZ-FXE) (Hybrid)
Vehicle Level Starting and Charging Battery Technical Service Bulletins All Technical Service Bulletins Auxiliary Battery - Hard Staring/Low/Dead Battery


Auxiliary Battery - Hard Staring/Low/Dead Battery
Notes

ELECTRICAL
EL014-03

October 2, 2003

Title:
BATTERY CAPACITY IMPROVEMENT

Models:
'01 - '03 Prius

Introduction

Some customers may complain of not being able to start their vehicles after extended parking times and/or repeated short driving times. The purpose of this TSB is to inform you of a new battery and mounting hardware available to improve the storage capacity performance of the Prius.

Applicable Vehicles^ 2001 - 2003 model year Prius vehicles.

Parts Information
28800-21190 Replacement Battery 04003-23147 Kit (includes oversize tray, new + terminal)

Warranty Information

Applicable Warranty*:

This repair is covered under the Toyota Comprehensive Warranty. This warranty is in effect for 36 months or 36,000 miles, whichever occurs first, from the vehicle's in-service date.

* Warranty application is limited to correction of a problem based upon a customer's specific complaint.

Repair Procedure

1. Remove battery ground wire from vehicle. (The new battery ground wire is included with the battery installation kit.)

2. Remove positive terminal/block assembly from wire harness.

3. Place terminal/block assembly in a vice as shown and remove nut attaching terminal end to the block.

4. Attach new positive terminal to the terminal/block assembly.

5. Remove battery hold down, auxiliary battery, and battery tray from vehicle.

6. Install new battery tray and battery.

7. Reattach wire harness to positive block and attach positive terminal/block to new battery.

8. Install new ground wire.

9. Route vent hose from battery to rubber grommet in trunk floor.

10. Double check that the battery and battery wires are secure and install battery cover.


Sorry the pic's didn't paste but you get the general idea. Our 2005 had no trouble this winter despite the cold and in fairness to the 2002 it IS now about 4 years old with 48,000 mi.
Like you all say they boot right back up after battery replacement except for the radio presets.
BTW using an external 'keep alive' was not recommended during changeover.
I still can't help wondering if something doesn't come on periodically during the coldest temps because my old Batt was not THAT bad on the bench. Probably would have made it another summer.
Hey anyway there IS at least one thing that a Prius owner can DYI besides the oil.

[suomi]

Here is an update of what happened with the battery later on.

After initial problems, the battery worked OK for about a month, and then it went dead again. I made a new claim to Toyota service, and they replaced the battery under warranty. I have now had the new 12V battery in for some 2 months, without any problems whatsoever. So, it is safe to conclude that it was just a bad battery after all.

Suomi

[KTPhil]

...or that the seat heaters haven't (yet) killed the new battery.