How do I avoid a dead battery while camping?

Number one, no car should have a problem being parked for a week. If it does, your battery or alternator is dying and needs to be replaced anyway.

You can always unplug the battery terminal and reconnect when you return. Keep a wrench with you. And lock the car the old fashion way, key into lock.

 

Hi Laura. Sitting for 5 days or one week should be no problems if that is all there is to it, as in if the Prius is simply locked up and left alone. So I suspect the issue is that the car is being accessed frequently, doors opened and closed, interior lights used etc, during that time. Is that correct?

Unfortunately even just opening the doors "wakes up" the ECUs on the Prius and significantly increases the battery drain. Also having the smart key in close proximity probably does this as well. I'm not sure if having the tailgate open also counts here, but I suspect that it does.

I see that you're using a Tail Veil (I had to google it, cool idea btw ). Does that mean that you're kind of camping in the back and accessing the car all the time? If so then I think the only option would be to give it a start every couple of days. Maybe you could choose a time when the nearest neighbours are away from their tent or when there's a nice breeze blowing. TBH the prius engine doesn't seem to make as much fumes and most cars.

 

Assuming you're periodically in and out of the car:

Turn the interior roof light completely off, so it doesn't go on when you open a door. Do the same thing for the hatch light. (If applicable, I'm assuming gen 2 has a light in the hatch area and it's switchable.)

MINIMIZE the time you leave doors/hatch open. There's likely "courtesy" lights still coming on, they all contribute to draining the battery.

Never, never, never just sit in the car listening to the radio.

I concur regarding battery age/condition: it could be the battery's just getting on, seen better days. If it's been dead enough to need a jumpstart, and that's all it got, was never hooked up to a charger, and that was a year back, it might be close to gone.

 

The Prius doesn't have an alternator.

But I agree that a healthy aux battery without a parasitic drain should be fine for 5 days inactivity.

My guess is that we have an older aux battery coupled with perhaps some interior accessory lights coming on or being left on with the use of a tail veil or simply opening and closing doors.

I'd probably replace the battery as a matter of course, when camping pay attention to any accessory lights that may be on. And if it was me? I'd invest into one of those portable jump start power stations, and bring it with me fully charged. That way if you miss anything 5 days later you don't have to depend on others to get a jump start.

Just a question.
Would the active pinging of the fob for 5-7 days be enough to drain a healthy aux battery? Assuming of course 5-7 days of inactivity?

 

Yup. A flat one will fit in the hatch sub-floor tray.



On our 3rd gen, even if the hatch area light is switched off, if the hatch is open there's a couple of (tiny) lights under the dash, illuminating the front foot wells.

What about those tents that attach to the hatch. This sort of issue must be tough on their rep, stock value.

 

My suggestions since you must leave the car hatch open for a seven-day period, are

1) to fully-charge the 12V battery before you embark on your trip using a battery charger intended for AGM batteries, set to the 4A charging position, and

2) to disconnect the 12V battery after you've parked the car at the campsite.

Then you should have no concerns about the battery discharging. If a door or the hatch remains open, the battery will definitely discharge because some of the ECUs will remain powered up.

It is not helpful to leave the battery connected and to try starting it "every couple of days" unless you leave the car READY for an extended period such as a few hours. If you turn the car off after a few minutes, all you are doing is draining the battery further than if you had left the car alone.

 

Things I'd suggest:

• Turn off the smart key system.
• Look around the hatch opening area for the hatch-open switch (or look it up in the wiring diagram manual) and fashion some way to clamp the switch down while your hatch is open.
• If you have an ammeter (or a friend who does), now measure the current going out of the 12 V battery when everything is off, smart key system turned off, hatch switch clamped off.
• Multiply that number by 12 to find the watts needed to keep your battery constantly topped.
• Check available solar battery tenders to see if you find one with adequate wattage. Ideally, look for 2 or 3 times what you measured for steady power drain (because the steady power drain continues 24 hours a day, and you have to make it up during sun hours).
• Once set up at your site, strap your panel to the roof or something convenient, attach it to the battery, point it at the sun, and enjoy your worry-free camping!

If you have adequate charge going in, you also won't be worried about occasionally going into the car, using the cabin lights to read by, charging your phones from the power port, etc.

You could also pick up a short length of flexible metal hose to point your exhaust away from the Tail Veil. With the solar tender, you won't be needing to make the car READY just to keep the 12 V battery topped, but now your options multiply. I have a small (not quite 1000 watt) inverter in the back of my Prius, which I confirmed one time is enough to run my bread machine. Or if you get too hot, you can have the only airconditioned Tail Veil in sight. Those options require leaving the car READY while you're using them, but it will only run the engine for short periods as needed to keep the battery charged.

-Chap

 

listen to pat. unlock all your doors and then disconnect the aux battery, I believe a 10mm wrench will disconnect the ground wire from the body. put a baggy or rubber glove over the cable end so it can't accidentally contact the body.
I think if you make a 5 hour drive to the campsite, the battery should be fully charged or close enough.
if it was me I'd skip the tail veil and bring 10 extra gallons of gas. I'd need to run the a/c in ready mode all night and day in Georgia in the summer.

 

Unless recent models changed this, the positive battery cable plugs in at the battery clamp/fuse assembly. Unplugging it there is faster than wrenching on the ground wire, and the free end is already an insulated plug so no baggie or glove is needed.

You'll want to make notes of your radio presets, etc., before unplugging ... probably also how to repeat the window motor self-calibration.

-Chap

 

No, it hasn't changed.

It's what I do, its quick, easy and best of all no tools required.

 

good to know.

 

In the case of the smart key button, OUT = ON