Storage / Long Term Parking

I left my car for about three weeks, and it had the same 61 miles on it when I got back.

I left the car unplugged, but the 12 volt lead acid was on a tender / trickle charger plugged into 120v.

I'm planning on parking my Rav4 EV for a week @ the airport... so no way to keep it plugged in.

While I'm encouraged that others have not had the dreaded "dead 12V battery" problem for such a duration, I was hoping someone might chime in about trickle charging.

I guess TonyWilliams had a trickle charger attached directly to the 12V battery. I won't have that option obviously.

But what if I could obtain, say, a small solar panel and leave it on the dash plugged into the 12V "cigarette lighter"... I recall somewhere somebody saying that would do it.

Thoughts?

Power to the cigarette lighter is cut off when the car is turned off so that would not work.

You could probably make an adapter to plug into the fuse panel and provide a lighter socket so you could use the solar panel. My quick scan of the manual shows Fuse #21 (Stop Lights) or Fuse #22 (Charge Indicator) would probably have constant +12V under the dashboard.

I think I would just run two conductors to the battery with the appropriate inline fuse. Make sure it has a diode to prevent discharging the 12v battery through the solar panel at night when it's dark.

Just leave it on the dash while parked at the airport.

This looks like a really good one:

http://www.batterymart.com/p-12v-15w-batteryminder-solar-battery-charger.html

I left mine in the driveway for 10 days while I was away on vacation and learned the hard way that the cig adapter is unpowered while the car is off (otherwise my solar charger would have prevented me from finding a dead 12v battery on my return). I'll have to look into running some wires from the fuse box next time as well since the solar panels have battery clips but are only rated for interior usage.

I killed the 12v today the old fashioned way... I left the car on. I think this is my first time in 50,000 total EV miles. Naturally, the car didn't charge either, since the car was left on READY.

Honestly, the horn should blow if the car is plugged in while the car is in READY (or powered ON or ACC).

The funny thing is that it didn't drain the traction battery. In other words, the 12v was not getting charged, even though power was available to do so.

I jump started it today, and pushed the POWER button to OFF as the car came to life. Naturally, the clock set to default 12:00 and eastern time zone (even though the car isn't even sold there).

I lost all the radio presets, of course, and all the charge timers. The address book remained, thankfully.

It seems silly to me that the car can't detect that the 12V battery is getting low and turn on the DC/DC charger while an EVSE is connected. It doesn't have to start charging the traction battery, just pull enough from the EVSE to charge the 12V battery.

Edit: Now that I re-read what I said above, I guess it's not really possible to pull energy from the EVSE without charging the battery. That's the only path the energy can take - through the on-board charger into the traction battery. The DC/DC converter is taking energy from the traction battery to power the 12V accessories and charge the 12V battery. I don't know if the on-board charger can dial down the current low enough to run the DC/DC converter and not do a significant charge.

yblaser said:

Power to the cigarette lighter is cut off when the car is turned off so that would not work.

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This is, unfortunately, true of all three of the "cigarette lighter" 12V receptacles (one in the dash, another in the center console, a third just inside the rear door). Disappointing...

Wonder of wonders, however, the USB jack on the outside of the center console is always hot.

Of course this is probably just spec'd with USB-2 power... meaning something like only 2.5W at 5V. USB-3 would be only a bit more at 4.5W.

So the two questions would be:
1) How much wattage would be needed to keep the 12V battery charged?
2) Given the 5V regulation on the USB receptable's power, can the 12V battery get charge through this port?

What about disconnecting the 12v terminal for 2-3 weeks? Would this suffice? What's the 12v battery self discharge rate when unconnected?

occ said:

What about disconnecting the 12v terminal for 2-3 weeks? Would this suffice? What's the 12v battery self discharge rate when unconnected?

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Of course that works. You just get to setup everything again.

TonyWilliams said:

occ said:

What about disconnecting the 12v terminal for 2-3 weeks? Would this suffice? What's the 12v battery self discharge rate when unconnected?

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Of course that works. You just get to setup everything again.

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Yeah, that's a pain.

So did anyone gone on extended 2+ weeks, and left the rav4ev, as-is, w/ no battery tender, or plugged in, or anything like that, and parked outside yet?

I'm planning a summer vacation, and wonder if 1, 2 or 3 weeks parking in the sun without anything would be doable.

occ said:

What about disconnecting the 12v terminal for 2-3 weeks? Would this suffice? What's the 12v battery self discharge rate when unconnected?

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I very much doubt the issues folks are having concern the self-discharge of the 12V battery. Plenty of ICE cars do quite well in long term parking lots for very extended periods.

The issue for our Rav4 EV is two-fold:

1) It appears the 12V battery is used to keep the traction battery "comfortable"... even when not charging or even connected to a J1772 live plug.
2) The 12V battery is not "recharged" while driving... and is only charged during J1772 charging sessions (unlike ICE cars that have alternators charging the 12V battery).

The first problem is what I'm most concerned about.
The second problem concerns what happens when your 12V battery is dead. Unlike in an ICE car, a "jump start" is not sufficient. You need to get enough of a charge into the 12V battery to make it to a J1772 charging station.

Side story: I was at a Livermore, CA auto shipper this past week. Surprisingly, there was a quite new Tesla Model S hooked up to their 120VAC service (they didn't have the default 14-50P on the lot). I asked about the situation and was told the Tesla had arrived (from where, I do not know - surprising since it had less than 150 miles on it and surely came from Fremont at some point). The shipper had quite a problem just getting the Tesla off his truck.

Tesla service was called and they came out, dismantled the front of the car to gain access to the 12V battery (this is a 1st gen car!) to trickle charge it. After a little bit, they were able to get it off the truck and then hooked up the portable EVSE to their 120VAC service.

I also learned an alarming fact about the Tesla that occurs when the battery (presumably the 12V) is very low. Since the door locks have no place to insert a physical key, the safety measure Tesla took was to automatically roll down the drivers window! Just imagine the auto shipper's surprise when they arrived in Livermore only to find a dead Tesla with the driver's window lowered. Having seen the muck that can accumulate on (unenclosed) shipped cars, this could have been disastrous.

Although there seems no reason - other than the common but seemingly unrelated components - that the Rav4 EV would have this horrible behavior. But it would be good to know from any of those that have reported having killed their 12V Rav4 EV batteries...

edmc said:

occ said:

What about disconnecting the 12v terminal for 2-3 weeks? Would this suffice? What's the 12v battery self discharge rate when unconnected?

Click to expand...

I very much doubt the issues folks are having concern the self-discharge of the 12V battery. Plenty of ICE cars do quite well in long term parking lots for very extended periods.

The issue for our Rav4 EV is two-fold:

1) It appears the 12V battery is used to keep the traction battery "comfortable"... even when not charging or even connected to a J1772 live plug.
2) The 12V battery is not "recharged" while driving... and is only charged during J1772 charging sessions (unlike ICE cars that have alternators charging the 12V battery).

Click to expand...

I believe you are wrong on these points. First, I believe the traction battery is used for conditioning. Second, I believe that the 12V battery is only charged when the car is "ON", not while charging from the J-plug. The cars have gone dead on dealer lots when connected to charging stations because nobody turned them on. The problem is the "dark current" required by the car when it is turned off. If you disconnect the 12V battery, it will have exactly as much energy as you left it, many months later, so it's not "self discharge".

TonyWilliams said:

I killed the 12v today the old fashioned way... I left the car on. I think this is my first time in 50,000 total EV miles. Naturally, the car didn't charge either, since the car was left on READY.

Honestly, the horn should blow if the car is plugged in while the car is in READY (or powered ON or ACC).

The funny thing is that it didn't drain the traction battery. In other words, the 12v was not getting charged, even though power was available to do so.

I jump started it today, and pushed the POWER button to OFF as the car came to life. Naturally, the clock set to default 12:00 and eastern time zone (even though the car isn't even sold there).

I lost all the radio presets, of course, and all the charge timers. The address book remained, thankfully.

Click to expand...

Wait a minute. Now I'm confused. The car was left "ON" and it did not drain the traction battery, but instead the 12V died. Was the key in or near the car? If you took the key away, it probably shut down, but left a bunch of accessories on. Does this sound right based on what happened Tony?

miimura said:

Wait a minute. Now I'm confused. The car was left "ON" and it did not drain the traction battery, but instead the 12V died. Was the key in or near the car? If you took the key away, it probably shut down, but left a bunch of accessories on. Does this sound right based on what happened Tony?

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I don't think the car would shut down based on taking the key away. Tony's experience is pretty strange, as one would think that while the car is "READY" the 12v is getting charged. It must be that plugging the car in took it out of "READY" mode and into something like "ACC" mode, where it wouldn't allow charging from the wall and also wouldn't supply power to the 12v system.

Hmm... seems to me we have a lot of conflicting speculation going on... along with conflicting experience. It sure would be nice to have a definitive answer. Anybody have a relationship with a Toyota Service department that could answer?

Here and elsewhere, we've seen postings of 12V going dead when not plugged in... one where "ignition" was left on in fact.
This would seem to support the claim (not mine, I'm just repeating) that the 12V is only charged when plugged in.
As for 12V drainage when not plugged in, we also have conflicting reports alas.

Oh, well... my trip is in four days so my window for a solution is rapidly closing. The PV panel to USB was admittedly a Hail Mary :-(.

The 12v died because that battery is not serviced by the main traction battery through the DC-DC converter while the car is plugged in.

This is common to the Nissan LEAF, which does exactly the same thing. If it's plugged in, and you leave it in READY, or even if it's turned off, the 12v is not being serviced.

edmc said:

Hmm... seems to me we have a lot of conflicting speculation going on... along with conflicting experience. It sure would be nice to have a definitive answer. Anybody have a relationship with a Toyota Service department that could answer?

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Haha, I'd take speculation in here (appropriately filtered, of course) over "official" word from Toyota anytime.

edmc said:

This would seem to support the claim (not mine, I'm just repeating) that the 12V is only charged when plugged in.

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There's absolutely no way this is true. The 12v system must be powered via a DC/DC converter from the traction battery while you're driving, otherwise an hour-long drive with the headlights on would kill the battery.

edmc said:

Oh, well... my trip is in four days so my window for a solution is rapidly closing. The PV panel to USB was admittedly a Hail Mary

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The safest bet is just to disconnect the 12V battery, or connect a battery tender direct to the battery if you have one.

fooljoe said:

miimura said:

Wait a minute. Now I'm confused. The car was left "ON" and it did not drain the traction battery, but instead the 12V died. Was the key in or near the car? If you took the key away, it probably shut down, but left a bunch of accessories on. Does this sound right based on what happened Tony?

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I don't think the car would shut down based on taking the key away. Tony's experience is pretty strange, as one would think that while the car is "READY" the 12v is getting charged....

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No, the car won't shut down if you take away the key. What if the battery to the FOB died while you were driving down the freeway... the car would die, if that were the case.

If you ever find yourself driving off and somebody else had the key (happens to me all the time), DO NOT SHUT THE CAR OFF UNTIL YOU GET HOME !!! It will not restart if you turn it off, or until a key returns.