Jump starting other vehicles with Prius

A few weeks ago, my wife's Sienna's battery gave up the ghost on a really cold day (not surprising since it was almost 4 years old). I was tempted to find out if the Prius could jump it, but I figured since it was not intended to crank a starter motor, I reasoned that the current capacity ("cold cranking amps") probably wouldn't be high enough for an effective jump start. I definitely didn't want to have two dead cars that day. Fortunately, I have a Xantrex backup power supply (essentially a big lead-acid battery packaged with an inverter on wheels with a handle) which worked perfectly on the first try.

Nevertheless, I am also interested in the answer to this question. Mine is a 2006 as well.

- Doug

I have a 10/30/50 amp Schumacher charger. Has served me well over the years. I learned a long time ago there's a fifty-fifty chance the vehicle that could have jumped the other vehicle left the driveway and was half way across town.

A Prius' 12v battery shouldn't be jumpstarting another car's battery. (Too easy to blow the fuse on your donor Prius.)

The Prius' 12v battery is smaller than an average car's 12v battery, because it never has to start an engine. So, if you do a traditional jumpstart/boost, you can overpower the Prius' 12v battery, and potentially blow the 100 amp fuse that charges it (from the hybrid battery).

The preferred method of jumpstarting another vehicle, using a Prius is:

Turn off both cars.

Take the keys of the car to be jumped, so that the owner doesn't try to start their car on your donor Prius' battery.

Connect up the jumper cables per the owner's manual of the car that needs to be jumped. It's probably best to go direct with the Prius'

12v battery terminals, found in the trunk/boot, but if you have a NHW20 (2004 and newer) Prius you can probably use the under-hood jump points in the fuse box. Watch that polarity!

Turn on the Prius to READY, so that the gasoline engine can charge the hybrid battery, the hybrid battery can charge the 12v battery, and the

12v battery can charge the dead car's battery. Leave like this for at least 15 minutes to recharge the dead car's battery.

Turn off the Prius, and disconnect all the jumper cables.

Try starting the dead car using its own somewhat charged battery.

Drive this car around for a while to let it recharge its own battery more.

This'll only work if the dead car's battery is merely too weak to start the car. If it has any damage or an internal short, it won't work (and could be dangerous to charge it).

The real preferred method, other than having an auto club come out, is to have a portable jumpstart kit for your car. Less than US$50, you can get a jumpstart kit that also has other neat stuff in it, like a compressor for tire inflation, or hazard lights. Something worth having in your car toolkit.

Jump start procedure if needing to jump your own Prius is in the "in case of emergency" section of the owner's manual.

In a traditional car, you'd have to drive around for a while after a jumpstart to get your 12v recharged, because the alternator is run off of the gasoline engine. In a Prius, which doesn't have an alternator, you just have to leave the car in READY to charge the 12v battery off of the big hybrid traction battery. (But, if your car is on, you might as well drive it somewhere...) A good 30min drive somewhere should do the trick.

(Don't forget that US 2001-2005 (and maybe 2006 if you have the right paperwork) Prius come with 3 years/36,000 miles of Toyota Roadside Assistance, which includes jumpstarts. If you have the Toyota Extra Mile package (Southeast or Gulf States Toyota region) or if you bought the Prepaid Maintenance package, you may also have the Toyota Roadside Assistance.)

Many times disabled vehicles aren't parked in such a way that running kits to one another is a solution. Furthermore, if someone can't maintain their own car battery chances are they can't maintain another lead-acid battery backup.

One caveat - modern alternators put out an awful lot of current into a discharged battery. Back in the '60s alternators could run all day at full output (often 35 amps) without overheating, but no longer.

It should be safe enough to drive for 15 minutes while charging a depleted battery, but I'd hesitate to go longer than that. The battery would also be happier with a low current charger.

Mike

Yes - it can be driven farther in a pinch, but the alternator gets awfully hot and gradually cooks itself. This has been kicked around in alt.autos.honda for a few years. What we noticed is that alternators failed either because the brushes wore out or because the car was driven a lot after being jump started. It's really obvious when dying batteries were nursed along - the two complaints appeared together frequently. There are those who feel the alternators killed the batteries, but the causality is hard to pin down if that is happening.

Personally, back in the '80s I stopped charging dead batteries by driving. Living in Phoenix, I noticed none of the batteries lasted a month after I did that. Too much heat, I presume.

Mike

Last year, just some month after receiving a new Prius, I left it for some days parked without actioning the automatic door closing system. The light on the trunk was switched on and the 12 V battery went out. I had problems in restarting the car, but then I realized it was a stupid think: the secondary battery is needed only to start the computer, so also a normal torch with 12 V DC is sufficient. The motion battery is very well protected and it is improbably fully discharged. In the engine bay of the car, in the fuzes box, there is a +12V DC with a red cover: you can use this and the vehicle ground, applying

12V DC to restart the computer (less than 1 Amp. is required). For this reason you cannot use the Prius to start another car, but, of course, you can use another car to Jump Start the Prius.