12 V battery Voltage

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?

 

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

 

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

 

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

 

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.

 

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

 

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?

 

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

 

There is an inexpensive wiring kit to make the front cig (oops, aux power outlet) active when your Prius is off. You can order it from: Prius Accessories

JeffD

 

Thanks to this forum I switched on maintenance monitor and I saw a horrifying 9.8V in accessory mode. Actually you can see that dashboard and interior lights are dimmed prior to switching the car to "ready" mode.
I am replacing the battery next week. The car is 6 years old and has 75.000 kilometers.

 

Is this true?
How do I know the FOB is too close?

If so I think I found the reason we abused our 12 Volt battery to death this winter.

Bob

 

Hi Frosh. Mine are similar but you really should post the conditions under which you're measuring, because there are lots of factors that will affect it.

Here are some measurement I made a while ago here : http://priuschat.com/forums/gen-ii-...-troubleshooting/72319-tested-my-battery.html

 

oh

 

The battery has been replaced! I wonder if there is any explanation for that I feel the car works a bit smoother and uses more electric motor and keeps the engine on lower revs than before replacement? I noticed fuel economy improvement. I did 40 kms in city traffic today and I got 4.6l/km. Before I would get something around 5l/100km in the same conditions.

 

well of course there is an explanation.

your dead 12 volt battery was exactly that, dead weight!!

run 100 yards while timing it.

then run 100 yards carrying a 2 year old (how bad can it be, they only weigh 20 lbs right??) see the difference in time. should it be that much?? after all the kid only weighs 20 lbs.


well your Pri is the same way. its a mother helping out its child by ensuring the 12 V battery is fully charged, but the battery is dead and can no longer keep what mother is giving it, but ya know how mothers are. they have 100% faith in their children no matter what, so they keep feeding power into that tiny little mouth with total love in their eyes. so, that teeny tiny insignificant drain on the system is significant.

 

So, here are my numbers from that Signal Check screen, on my 2004 Prius with 100750 km on it.

Maintenance mode: 12.0 V
Press power again: 11.8 V, or 11.7 V with the heater fan on low and 3rd party GPS plugged in.
Ready mode: 14.1 V

Temp outside is about 2 degrees C (or about 36F).

Do I need a new battery, or am I still OK for a while? That elearnaid page seems to suggest that it's OK (albeit not great).

BTW, has anyone shipped from them to Canada? If so, which shipping method? Air Mail seems to be the proper one at $71.50, but it's not entirely clear from their website. If $71.50 it'd be $251.50, plus probably a handling fee at the border so about $260 plus tax.

What is the cost in Canada for the OEM battery? If it's only about $150, then maybe I'd just get that, if it's easy to install, and if I actually need one that is.

P.S. I don't know how to turn on the rear windshield heater in Maintenance mode.

P.P.S. No I haven't tried a voltmeter yet. I guess I should do that first.