12V Battery Drain Causes?

I would get a decent smart charger, one that can be kept on indefinitely, just leave it plugged in when the car's going to be idle more than a day. No need to remove the battery to charge, btw. That's assuming it's possible to run an extension cord to it. Also, a block heater would be very beneficial.

 

+1, Plus I recommend you get a Scangauge and monitor your high voltage and 12v battery's status. I find it helpful to know what's going on.
Mine is a 2012 C and still on original 12v battery, but I'm watching it and will replace when it no longer keeps above 13v or so and before it strands me.

X

 

Not sure. Could be some parasitic drain. Still, aren't extreme cold winters hard on 12 volt batteries?

You can check parasitic drain with a multi-meter with milliamps scale. You basically have to wangle a way to put the meter in series with the battery. The simplest way I think, and what I did, is to disconnect the negative cable at the body, then connect a wire lead to the body, and another other to the disconnected battery cable. Run these leads out, under a weatherstrip (rear right door I guess, with the c).

After about 20 minutes, with the fob well away from the car, hook these leads up to your meter, first in an amperage scale, then switch to milliamps.

Doing this I got readings around 16~20 milliamps, with sporadic (every 10~15 seconds) spikes to 40 milliamps. There's a little security light blinking on the dash, but it's more frequent than 10~15 seconds, so not sure what was with the spikes. Still, any sort of reading in that range is ok, say anything under 50. That's not to say it's not taking a slight toll though, compared to a completely disconnected battery.

 

it's a very small battery, and likely just the cold. start monitoring the voltage with a cheap meter.

 

The basic problem is the cold temperature. In dealing with aircraft that used similar small batteries the only effective solution was to remove the battery and keep it indoors in a warm place. Unfortunately, when reinstalling, the problem is compounded in the Prius with the hatchback now having to be manually opened, which, of course, requires crawling back through the rear to the manual hatch release. This probably would be no fun with a parka, boots, and mitts on. So you are probably best off to follow the instructions that Mendel Leisk so thoroughly outlined in a previous message. I kept my old arctic parka and once a year peek into the closet and look at it for about 5 seconds. Then I slam the door and ignore it for another 364 days.

 

How about a battery heater? It's a heating pad for your battery.


http://www.amazon.com/Kats-22400-Watt-Battery-Heater/dp/B000I8XDAS/ref=sr_1_5?ie=UTF8&qid=1518241007&sr=8-5&keywords=battery+heater

 

How on Earth does one apply a tickle charger to a battery under the back seat? I've read it's no good to use the jump points for that. One has to take the whole seat apart to get to the battery.

 

You can hook up a charger at the jump point. If you're going to be doing it regularly (our case, with our garage queen), a lot of chargers come with (or you can order) a quick-connect cable. I did that with ours, so instead of needing to pop the hood and then pry off the fuse box cover, and then fuss with alligator clips, I now just pop the hood, and plug in an adapter. I'm using a smart charger, 4 amp range, the kind you can leave on indefinitely: it charges, then subsides to a sort of maintenance mode, just giving it a little tick of boost every so often.

 

BAD information. It is perfectly fine.

 

the early c didn't have the jump point, but i think they added it by 2014.

 

End of February, early March 2013 had them.

 

gracias.

 

Thank you!

 

And thank you too Sam!

 

Please tell me how this is done since I am not sure what you mean by "plug in an adapter". Plug it in where? I see chargers with cigarette lighter adapters on line but new cars don't have cigarette lighters. If there's a brand of charger you can recommend that comes with complete instructions, please let me know. Thank you!

 

The expression plug-in is a bit misleading. The 12 volt plug-ins in the dash are not on if the car is not on. What I'm talking about is avoiding the need to use alligator clips when connecting a charger, to wire something in that's a quick-connect for the charger.

I'm currently using a CTEK Multi US 4.3 charger, and used a CTEK Multi US 3300 before that (still have it). Never any problems, relatively easy to use. For both there's an wiring adapter CTEK Comfort Connect that you can permanently connect to the car, making connection of the charge a simple plug-in:



With the Prius, with battery away from the engine bay but jump point under the hood, the best option for the adapter is to wire the adapater at that jump point. The c may be a bit different, but here's a video for connection with regular 3rd gen Prius. You basically need to connect the red lead to a 12 volt positive point, and the black lead to a substantial bare-metal component of the car body or engine. Video #23 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

If you google any of the above names you'll find product links. I'm just partial to CTEK, there are a lot of options, but it's one that's worked for me.

 

Here is the charger he is talking about.

http://www.amazon.com/CTEK-56-158-Automatic-Battery-Charger/dp/B000FQBWCY

 

I just had this problem...

I was driving regular roads. Arrived, shut down the car, pulled the key. After about an hour decided to re-park my car. The screen was really dim... Since I've totally forgotten about "under-the-hood disconnect", I disassembled the back seat and removed the negative wire. After a few hours reconnected everything, but the battery (12V) was still "half-dead". Friends helped me to start using jump-start wires. Arrived home (after a 30-minutes drive) - the car was starting OK. Just in case used "smart charger" (which has AGM mode) recarged the battery.

In the morning (with everything connected as it should be), the car didn't start. The battery showed about 6.5V. Used charger again, it read 12.5V after 3 hours of charging. However, the car was not starting (the screen dimmed when I try to start it).

Bought a new AGM battery (bought Optima Yellow Top 750A). It's wider than the original I had (which was 350A), but it fits (had to remove the "arm" on the battery strap holder).

Also, while troubleshooting, I used an Ampermeter to see how much the car drains with the key pulled off. I disconnected the white thick wire and used an amperemeter between the socket and wire. When I first connect, it comes about 250-300 mA. Then, after about 5 seconds it comes down to below 100mA and then alternates between 80mA and 110mA (every second).

On one hand, 80-100 mA seems to be pretty high. From another hand I never bothered to check, how much was it consuming (draining) before. When I "stuck" with a drained battery, I had some kind of weird sound, coming from somewhere under the engine. Something like a small electric motor still running (sound was coming even when keys were pulled off the ignition). So, I'm not sure, if it was something that was kept running, something failed, or it's "just a mystery thing". Right now, after all, I've done, I don't have this sound (I checked the coolant level, suspecting it could be a hybrid system pump, checked other fluids, etc.).

So... I will see tomorrow if the new battery will drain as well. Then I have not many options as to go to the Toyota dealer (last resort). Will try to run Techstream (if find my USB cable), but don't know if any of these things will be reported.

PS. And just in case, I bought a portable jump starter. Don't want to get stuck somewhere...