12volt battery discarged on Prius

Yes. Odds are you didn't close the rear hatch completely. Always lock the car; if anything is ajar it will beep at you.

 

<div class='quotetop'>QUOTE(richard schumacher @ Jun 25 2007, 09:02 PM) [snapback]468065[/snapback]</div>

Agree. For additional protection I keep the hatch light switch in the off position. Switch it on when I need it; switch it off when I don't.

 

Sure, I am having this problem regularly on my 2007 model Prius.
It takes about 12-16 hours for the 12volt battery to discharge when a door is left open and some 40-48 hours when doors are closed, but not locked.
Dealer had it now 3 times, never found anything. I have told them that occasionally I left drivers door open. Dealer found a 25mA draw which was below limit of 35mA. They replaced the battery.
I never lock the car in the garage, but most times I close the door.
Dealer said, the doorlight should not cause the battery go empty in one day, so I suspect, when the drivers door is open, some other drain occurs temporarily. The doorlight takes about 150mA. That still would run 80 hours ...
Also Dealer said, there is a battery protection circuit that prevents the car from starting when 12volt battery is running low. He says, just touch the 12volt terminals with a jumpstart cable. That works, though you got to have a jumpstart available.
I take fault for when the car door was left open, but I would be very curious what exactly causes that much drain, that an 12AMP/hr battery goes dead this quick.
I am loosing the radio stations every time, too ...

Could somebody make any sense to me? Our VW switches off all electrical consumers after 30 minutes, maybe I'm just spoiled?

frosh

 

This is only true if you have and use the SKS.

 

Uhh, good point. Owners without SKS just have to be more careful.

Frosh, do you have any after market or dealer installed electronics? These have sometimes been at fault, either because of poor design or incorrect installation.

Keep in mind it's just a measly little motorcycle-sized 12V battery, not a marine battery. Dealer (mis-)representations aside the dome light is sufficient to drain the poor thing overnight, as you and others have discovered.

 

Richard, I didn't have anything modified, it's standard as it was delivered. I kind of recall reading in the manual, that 5-6 hours after parking some pump comes on and that customers shouldn't be worried about.
Aside from that, maybe I should just lock it, even inside the garage.
It just surprises me that the dealership claims, there was a battery protection circuit which is supposed to protect the battery from exceed drain. If that circuit indeed exists, it doesn't come on when the doors aren't locked.

The first time I experienced battery outage, I have connected a little charger trying to recharge the battery, but its 2Amps were not enough to pull the battery up to 12V in order to start. The dashboard lights would come on dimly and some relays started clicking, just like there was too low voltage. Electronics go all kind of crazy when too low a voltage is supplied, we know that.
Also, it looked like the power switch relay was stuck in "on" status, because I couldn't switch off the dim clavilux on the dashboard (which explains that a 2Amps charger wasn't enough).

Thanks,
frosh

 

The brake booster may be trying to fire. It draws a 1/2 sec 40 Amp pulse. It can fire at any time, and also does so when you place your foot on the brake pedal to start the car. Starting causes another 1/2 sec. 40 Amp pulse. At that time the relays in the main battery box are closed and the 12V system is then supplied by the main battery via the inverter (charger circuit in it).

If you are leaving the headlamps on (or have a Canadian car with auto headlamps), and don't open the drivers side door when you leave the car, the headlamps will stay on for awhile. Perhaps until the battery dies. Many say to turn off the SKS. This isn't really necessary, as it will turn itself off after a predetermined time of non-use.

I just started Pearl after she sat for just over a week at -5C. No problems whatsoever.

 

you are spoiled!
so was I with every previous car

Why they dont fit a timer cutoff especially as it's a smaller than normal battery
It happend to me while cleaning it with the doors open

There is a workaround
leave the key in its slot - press start, then park

 

The Toyota PDI clearly states to use a 10 amp 12 vdc automatic battery charger. If a 12 vdc battery is dead, a 2 amp trickle charger is not going to cut it

I was having problems with my teeny 12 vdc battery the first winter I had my Prius. I solved the problem by hooking up a VDC Battery Minder and plugging it in whenever I didn't use the car

The nice thing about the VDC is that you can leave it plugged in all the time with no worry about overcharging the battery. Say you're gone 1 month on vacation or 6 months at a winter home, no worries

The better units will also desulfate the battery to improve performance and battery life. Before I started using my VDC, the auto headlights would badly dim once the brake boost and coolant transfer pumps ran. After a couple months of using the VDC, the auto headlights barely flickered

I used to park in secure underground heated parking when I had my condo. I recently purchased a home with a heated attached garage. Either way I hook up the VDC. I use one on the FJ as well, since I don't drive it during the week. It cranks much faster than new

 

Agreed, but what I'd like to say is the effect that one can't switch off the equipments, as soon the battery is below voltage. That will drain the battery even quicker after you pushed the power button and before you realize the battery needs recharge. It would have been more clever that the power relay does not stick to the "ON" position under this condition.
Without this additional load the smallest charger would have helped and I wouldn't have been stuck calling the tow truck.

frosh

 

Yep, like a lot of electronic equipment, once the voltage dips below minimum threshold or gate values, odd behavior can result. A boost with a conventional vehicle would have overcome that, same as using one of those jump start boxes.

It wasn't soon after I bought my Prius that I started lurking this forum, and after the tales of dead Prii, picked up a 700 amp Canadian Tire jump start box.

I've used it quite a few times to assist other motorists, and it's nice to know that I have that security blanket in my hatch

One thing you should realize, once the 12 vdc battery in the Prius gets discharged, you really can't count on the Prius recharging it. If you have a garage, I would park in there, open the hatch, and proceed to remove the 12 vdc battery.

Hook the tiny lawn tractor size battery to the charger, and leave it on until fully recharged

 

The most stupidest thing about it is, that the dealer tries to make believe that a battery protection circuit kicks in to protect battery from user...
Which led me to believe, that circuit must be broken and I have to take the car to the shop now for the third time.
Could Toyota not train their personnel at least ?

frosh

 

Oh boy, ain't THAT a joke? Yep, once something deeply discharges that poor little battery, you're SOL. Dealer disinformation never ceases to amaze me

For example, around 2 years ago I thought it would be a good idea to remove the motorcycle battery from my Prius. Just to make sure everything was ok, despite the fact I use a VDC Electronics Battery Minder float charger on it whenever not in use

Got to admit, a bit tricky to get it out. The hardest part is that plastic cover over the pos post, I'm pretty sure I buggered it up. The little vent tube is a PITA too.

So I finally had it out, and as I moved it to the bench, I heard gurgling. So I held it up towards one of the windows and gently shook the battery. I could very clearly see free electrolyte sloshing around inside

Wth? Dealer implied it was some sort of special gel battery. Yeah, BS to that.

Anyway, I have a load tester so I applied a 30 sec load to the battery, then went inside for lunch and to feed the cat, Hour later I checked the battery and it was 13.0 volts, so it's in good shape. I recharged it, cleaned the posts, applied some silicone dielectric grease to the cables and body ground bolt, and put everything back in.

I repeat, you really should take the motorcycle battery out and give it a proper charge with a good automatic battery charger, preferably set for 10 amps. You can't depend on the Prius constant voltage charge circuit to do it for you

 

OK, I understand better now. On the drive home, usually at night, the last stretch I can pretty often drive on battery. That drains not just the hybrid, but also the 12Volt battery with the lights on. The little doorlight (if I forgot to close the door) does its thing to completely drain the 12Volt and there we are!

Thanks buddies, appreciate your help very much!

Just an idea: why could Toyota not activate the hybrid battery to jumpstart without having to jumpstart?
All the converters are there, activating them might be a bit problematic without helper energy if all the electronics are connected to the 12Volt source only... Some extra push button maybe ?


frosh

 

Because Toyota want the prius to be just like a conventional car to drive.

Having the lights on and driving on electric does not drain the 12v battery, it is still charged by the inverter from the traction battery.

 

Actually, with the constant voltage source for the 12 vdc system, it shouldn't drain the 12 vdc any more if running on electric only. The problem is that once the little 12 vdc battery gets undercharged - or even worse, discharged - then it appears the Prius is incapable of returning the battery to full charge

If you suspect your 12 vdc battery is undercharged, or if it has gone dead say due to lights being left on, it really is best to just remove the battery and charge it with an automatic battery charger set at 10 amp setting. This is the suggested PDI from Toyota, 10 amp setting.

It would be nice if the NiMH could be programmed to "boost" the 12 vdc just once, in an emergency. Some hybrids allow boosting in the reverse direction. For example, the Ford Escape Hybrid has a normal size 12 vdc battery. If the traction battery should go dead, you can use the 12 vdc battery to boost it

 

Well well,
I have good news and bad news.
The good news is that now I have taken my own measurements and know better what's going on.
The bad news is, depending if the car is locked or not, the drain on the battery is different. I took a Voltmeter and took the voltage at the battery terminals. The car wasn't locked but doors closed. Display was 12.08 Volt. Then I locked the car, after a while the voltage went up to 12.24 Volt.
This means, that an unlocked car uses more drain on the 12volt battery than a locked car.
Surprise? What is it? I have tried with and without SKS...

frosh

never mind, self caused mistake...
voltage is back to 12.23 Volt with closed but unlocked doors. I guess, some activity causes some electronics to com on for a while.

 

Assuming you are using a decent DMM to measure DC voltage, those readings indicate your battery has no more than about 40% charge on it.

Battery State of Charge Determination

http://www.wind-sun.com/PDF_Files/battvoltandsoc.pdf

OPEN CIRCUIT VOLTAGE Chart

As an example, I use the VDC Battery Minder on all the equipment at my hobby farm, as it can sit for weeks - even months - at a time. If I disconnect the Battery Minder and leave the batttery 24 hours to allow residual charge to go off the plates, my batteries usually read 13.01-13.3 vdc

With my Prius, if I leave it off the Battery Minder 24 hours, then measure the voltage, it is usually 12.9-13.1 vdc. In either case, that is considered a near perfect 100% theoretical battery capacity

I would pull the battery out, and use an automatic charger set at 10 amp setting, to fully charge the battery. Then wait 24 hours and recheck the voltage.

 

My voltmeter is cheap but halfway decent, i.e. my fully charged jumpstart batt shows 12.93V. The Prius just after a 20min. ride shows 12.45 and goes up to 12.69 when connecting the jumpstarter.

What's the charging voltage while on the ride? I believe 14.4V for lead batteries, should I read that on the Prius, too?

Thanks for all the tips,
frosh