12 V battery Voltage

[V8Cobrakid]

i've already posted this question on This thread... then again there are probably several dozen 12v battery threads...

my battery clearly stats to never exceed 4.3amps ( i think it's .3) while charging. it's on a yellow sticker under the +terminal.. under all that plastic.

anyone else?

[Blue Nimhrod]

You guys are making me nervous.

14.1 Volts running powered up

11.9 Volts after 12 hours parked not powered up

I have never had any problems even after parking 5 days at the airport

[frosh]

Originally Posted by Blue Nimhrod

You guys are making me nervous.

no worry for you! I never had a problem other than inside my garage, car unlocked. Thanks for your contribution.

frosh

[V8Cobrakid]

Can anyone read that? "never add water nor charge quickly. when you charge battery, charging current should not be higher than 4.2amps and charging time should be within 10 hours"... etc...

[jayman]

Originally Posted by V8Cobrakid

Can anyone read that? "never add water nor charge quickly. when you charge battery, charging current should not be higher than 4.2amps and charging time should be within 10 hours"... etc...

Yep, I can read it. My buggered up cover has the same label. Yet the Prius PDI states to use the Toyota AUtomatic Battery Charger - made by Associated - set at 10 amps

They warn that a setting of 2 amps will result in very long charging times. For those with a completely dead 12 vdc battery, a 2-5 amp setting will probably not do much.

For a normal battery, the VDC Battery Minder puts out around 1 amp max. The VDC manual cautions that the Battery Minder will only condition and maintain a float charge on a fully charged battery. A dead battery still requires charging with a regular battery charger

I'm in agreement with David Beale that given the huge assortment of battery chargers out there - especially the cheaper ones that put out too much voltage - Toyota had to make a blanket suggestion on the side of caution

[jayman]

Originally Posted by Blue Nimhrod

11.9 Volts after 12 hours parked not powered up

I have never had any problems even after parking 5 days at the airport

You probably won't experience any issues unless there is a cold snap and the car is parked outside

[satwood]

Originally Posted by Blue Nimhrod

You guys are making me nervous.

14.1 Volts running powered up

11.9 Volts after 12 hours parked not powered up

I have never had any problems even after parking 5 days at the airport

It is also important to note where you are making the measurement from. If you are measuring the voltage from the ACC plug, you could be getting a voltage drop dure to the long wiring and other loads on the circuit when the car is in ACCY mode. If you are measuring directly on the battery terminal, then I would expect to see more like 12 - 12.4. However, if we're quibbling over 1/10th of a volt with commercial meters then we don't really have a problem to solve. I'm worried about the numerous posts that look like dead battery issues.

[jayman]

Originally Posted by satwood

However, if we're quibbling over 1/10th of a volt with commercial meters then we don't really have a problem to solve. I'm worried about the numerous posts that look like dead battery issues.

I agree. However, if using a quality DMM directly on the battery indicates voltage lower than it should be, and the car has been going dead, there is either a parasitic drain or the battery is chronically undercharged.

If the battery is going low or dead in bitter cold temps, it needs proper charging. When I had trouble with my Prius in winter of 2004, the dealer couldn't find any parasitic drain and the resting current was around 30 mA. I checked and also couldn't find any unusual current draw

I think a combination of the constant voltage source, bitter cold temps down to -40, headlights always on, Max Heat, and constant electric rear window defrost all took their toll. It should be noted that since I started using the Battery Minder, no more problems

If there was excess parasitic draw, or a shorted cell, the Battery Minder would be unable to charge. My model is current limited to 1 amp, and voltage limited to 14.2 vdc

[N3FOL]

Originally Posted by miscrms

Pretty sure this is a no go, Prius disconnects aux outlets from battery when power is off.

FYI, '05 owners manual states the following:

Open Voltage at 20C (68F):
12.6-12.8V Fully Charged
12.2-12.4V Half Charged
11.5-11.9V Discharged

Rob

I think you are right. I've never thought about that in the 1st place. The plug has no power, when the Prius is powered down. So I guess if I really want to charge my 12V batt in the future, my best bet is to just open the rear compartment and go directly to the batt leads. What is your take on this?

[jayman]

Originally Posted by N3FOL

So I guess if I really want to charge my 12V batt in the future, my best bet is to just open the rear compartment and go directly to the batt leads. What is your take on this?

Unfortunately, if the battery is dead the hatch won't open. Could always use the underhood jump point