Toyota Highlander Hybrid (2006), battery power from 288 V to 12 V battery

Have you Read The Fine Manual? If your HH is anything like the Prius, there will be a point where you connect normal 12v jump- start cables. A Prius keeps this in the engine compartment.

The car should take care of that, once you supply it with power through the jump-start point. Again, RTFM.

This topic came up a few days ago. At the time, everyone agreed it probably could be done. Since then I have found a discussion on the PriusChat.com web site, about connecting a full sine-wave inverter rated up to 1250W to the 12v battery, letting the car's system recharge the battery when needed. (You have to leave the car turned on but can lock the driver's door with the mechanical key stored in the fob. Obviously the car must be left in a well ventilated place to disperse fumes when it runs the engine. And there must be a fat fuse to guard the battery.)

They have an output relay for safety, you can't get any power out of the 288V Hybrid Pack until after the computer boots up and deems it safe. I seriously wouldn't try tapping into it unless you REALLY know what you're doing.

Without Toyota's express blessing in advance, I wouldn't even try tapping off the 288V feed after the safety contactor. The computer is liable to see that added voltage drop/current load, freak out that something's shorting out and shut down the car.

Besides, that's a Catch-22 - if you don't have 12V left you can't boot the computer, so you can't close the contactor to get power past it to run your 12V converter and jump the 12V battery... The safest solution would be to get a bigger and better battery for the 12V Accessory Battery, and then you don't have to worry about it. If you have room in the 12V battery tray - or you can /make/ room - I'd install either a deep-cycle wet battery $70-ish for Group 24, or $80-ish for Group 27. No car starting, so deep cycle is perfect.

Or a Starved Electrolyte 'Optima" battery (Yellow-top Deep-cycle). They will have enough excess capacity to get the car booted and running till you get way down in the -50F range. And if you run around in ultra cold climes regularly, battery heating blankets work on them, too.

Or keep one of those "Jump Pack" batteries inside the house where it's nice and warm - they don't care if they're starting up a Hybrid or Regular car, just clip it on and get 12V out.

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The Toyota dealer did something like this for my mom's Prius, which operates in upstate NY where temperatures are cold, although not as cold as they become in North Dakota or the Yukon. I think they used a regular lead-acid 12V battery with lots of cold cranking amps.

But I'm puzzled by your phrase "No car starting" above -- doesn't the

Also what's the point of using a deep cycle battery in this application? All that's needed is a battery with better cold-weather performance than NiMH, and lead-acid qualifies. You don't need a battery than can lose 80% of its capacity and still recharge without ill effects.

They 12V battery's main job is to run the dome lights and burglar alarm, and to boot up the car computer. The computer closes the 288V contactor, and the Hybrid System inverter spins the engine to start with the 288V Alternator/Starter coupled to the engine.

The heavy lifting is all on the 288V side, the 12V battery doesn't have to supply any cranking current.

They should use Deep Cycle batteries more often - cars have 10ma to

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First, cover yourself with the kind of padding Bomb Squads wear, then buy a fireproof suit, the kind the guys at the military airport Rescue teams wear, you know, those siver things.

Get a good welder's helmet with 3 inch thick glass in the eyepiece. Gloves are in order, Lineman's should suffice. Have your last Will and Testament brought up to date. Lastly, move the car away from anything...anything at all. Neighbor's fences, other cars, your garage. An abandoned airposrt runway would be good.

The rest of us will be watching the evening news...or the Darwin Awards page...

This system is NOT to be meesed with unless you are trained. The Toyota techs go to a two week training session before they even start working on these things. See the big orange connector? If you don't GOOD! DON'T go looking for it.

If you do, RUN AWAY!!!! Disconnecting this thing out of sequence can kill you and possibly start a fire that will engulf the car, and eventually anuthing around it, since you'll at the least be knocked on your ass out cold, and unable to respond.

Aha, no wonder the charge on the 288V battery pack can't fall below 3/8.

I see what you mean! A hybrid-synergy vehicle could be parked (e.g. airport long-term parking) a lot longer with a Deep Cycle battery than otherwise. The only downside is that Deep Cycle lead-acid batteries are heavier than regular lead-acid batteries, and much heavier than NiMH.

Yes, but you need that density in the plates to get the deep-cycling ability without lead wool shedding on a conventional wet D-C battery.

And the heavier plate web sections on an Optima to deliver the massive Cold Cranking Amps.

Toyota was shaving every excess ounce of weight off the car they could find, to get every hundredth of a MPG they could across the entire fleet - make a million cars, and every hundredth counts. Ergo, they used that Garden Tractor sized U1 battery in the car.

Hell, my burglar alarm system has a bigger battery... ;-)

You, the end user, can easily sacrifice a few hundredths of a MPG on your one car carrying a slightly larger and heavier battery, to get a much more reliable battery system.

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Your best bet is to get a drop in replacement lithium battery It's available on ebay find the store selling it and contact them for your size.