Can a Gen III Prius jump-start another car?

Now I understand your username...

 

Yes you can - switch off both cars, connect the two batteries with jump leads + to + and -ve to -ve (it is critical you get this right!!!!!!) and turn on the Prius to 'Ready' with the selector in 'P' and wait, this will safely charge the flat battery of the other car from your 12v converter, you may notice the charge level of the hybrid battery drop and/or the Prius engine start - this is good news as this means the flat battery on the car to be started is sucking power from the Prius and is taking a charge, wait 20 minites or so (go make a cuppa tea), then remove the jump leads THEN start the engine in the other car - this is important, it prevents any possibillity of the starter on the other car overloading the Prius 12 electrics. Note, there is no need to rev the Prius engine, the Prius converter is an intellegent unit and will operate in boost mode to quickly charge any 12v battery connected to it, before switching to maintan mode (a slightly lower voltage) - this makes the Prius an ideal car to jump start another - I've done this many times with out problem. I've not only started other cars, but once topped up a huge bank of 12v batteries at an eco fair after a short in the solar panel controller feeding them drained them all flat - the car was left in 'P' and the engine cut in and out as necessary to keep the hybrid battery topped up, the hybrid battery in turn feedimg the converter that charged up the 12v 200AH bank of batteries - I left it on for about 2 hours. in to a 12v load the converter will only supply its rated power without danger of overload. I always carry a set of jump leads in my Prius.

 

I've started a diesel Volvo with my Prius, Left the two cars connected for 20 ish minutes with the Prius in 'P', turned the Volvo to 'ignition' with the Prius still connected to power the diesel glow plugs from the Prius to preserve the charge in the Volvo battery, then removed a jump lead to protect the Prius 12V system just before turning the engine over in the Volvo to start - vrooooommm! Happy Volvo owner : )

 

Goood! We've a mobile battery charger on the road.

 

Strictly speaking Clivey partly charged another car's battery using a Prius; not what one would normally call a jump-start.

 

If I offered to jump someone and told them it would take 20 min, they would probably be on their cell phone calling another friend.

Most jumper cables I've seen lately in those emergency packs are to small of gauge to properly jump a car anyway. I think the biggest advantage something like my old jeep has is a 60 amp charging capacity.

Does anyone know the maximum charge rate on the Prius 12 volt battery?

 

It says on the battery - 4 Amps, but that is a max so stay below it.

JeffD

 

Having diagnosed a few failed switching power supply circuits (which are at the core of DC/DC converters), I agree this is my biggest fear. We know the Prius DC/DC is pretty robust under load, given the crazy stuff people do with 12v inverters and household appliances, but its behavior when fed a higher voltage from some external source is probably undefined and likely bad.

(I say 'likely' because the number of horror-stories must come from somewhere, and the other potential failure modes just don't strike me as that hazardous. So, this must be it.)

Raise your hand if your bottles of emergency drinking water have ever ended up in someone's cooling system...

I've had a very similar idea myself: Mount a jumpstart pack into the cargo area somewhere, and add a connector to your vehicle's 12v system so it remains in parallel with the main battery and remains charged. When you need to offer a jump, simply unplug it, unstrap it, carry it to the other vehicle, and do the needful.

While this is good because it keeps the jump pack charged all the time, it doesn't protect you from your own dome light... :frusty:

So, consider adding an automatic battery isolator. Only difference from a typical installation would be that the "second battery" happens to live in a portable jumpstart pack, with a connector between it and the isolator. If you need to jump yourself after a dome-light incident, simply put the isolator into "combine" mode.

Also, if you need to perform a "live" jump, with the Prius DC-DC supplying power directly, the isolator (whose job is to keep one battery from feeding the other battery's loads, after all) will prevent the other vehicle's alternator from feeding power back into the Prius's 12-volt bus once it starts. I consider this worth the price of admission alone.

Only problem with this scheme is that, after returning from a jump, the battery in the pack might produce small amounts of hydrogen while recharging itself. If the charge rate is modest, much of this may recombine within the VRLA cells themselves, and whatever gets released is probably trivial, especially if the HVAC blower is keeping things fresh. Since recharging will only happen when the Prius is in [ready] mode, I'm not worried at all.

 

Reving the ICE does nothing for the 12v battery. The car has no engine driven alternator, like a regular car.


NEVER NEVER NEVER jump another car from your Prius.

It can be done but its risky at the least and really bad for the tiny 12v battery

 

lol ha ha ha

You'd better believe it.

 

This may be the case in the US but in Europe there are a number of vehicles that use the same size battery with the same terminals, and need no modifications. Most of these vehicles have normal petrol engine with normal starter motors. These batteries are made by many manufacturers, and are available off the shelf at motorist supply shops and garages.

 

Thanks for explaining the above procedure. It is the safe way to do it for all cars, not just hybrids. Conversely, when the charging vehicle is running and connected to the charged vehicle while the charged vehicle is started, there is often damage to the charging system or other electronics on the charging vehicle. The damage may show up immediately or months later when you have completely forgotten about jump starting the other vehicle.