Jump-starting from Prius 12v battery--wimpy?

Do not jump any car with the Prius, you are taking a good chance of doing damage to any of it's many computers. The battery is really small because it does not do to much, just throws some relays and starts the dash lights, radio these kind of small things.

 

I encourage folks to have a jump pack, to start their prius, to save the $4000 when you reverse the jumper cables.

It is also the only safe way to jump your neighbor, as the Prius 12 volt battery is not up for the job.

Amazon.com: jump pack - Jump Starters, Battery Chargers & Portable Power / Tools & Equipment: Automotive

 

i think t would have helped if you ran the engine

 

If the prius ice wasn't running I bet it's 12v is now toast.

If you were 500 miles from now where, just running the ice and hooking up to the other car would slowly charge it to the point of success, but, hopefully your not 500 miles from no where

 

In this scenario, unhook the Prius before actually attempting to start the other car.

 

The rule is: NEVER. jump start another car with any Prius. The Prius only needs about 32 Amperes (uses far less). Car with starter motors can draw several hundred amperes thru their starting motors. In parallel this can and will ruin your 12 Volt Battery. Cold weather multiplies this. Running the engine on a Prius does not help, it is still rated at 12V and ~ 32 amps. If you want to try and draw 250 amperes from a 32 ampere battery, have fun. Be prepared to spend $150.00 on a new battery AND in the process other devices can be ruined, computers inverters, etc. all expensive stuff. Don't believe me, search Gen II records on PC.

 

The key point here is that the motorcycle-sized 12 v battery in the Prius (PiP or standard) only needs to operate the computer that controls the hybrid system. The ICE, when needed, is started using power from the hybrid battery via one of the motor-generators. OTOH, the battery in a conventional car has to power a starter to turn over the ICE, which takes a heck of a lot more power. And the power drain of trying to crank a conventional car can easily destroy expensive components (multiple thousands of dollars) on a Prius. Thus the recommendation "just don't do it", even though it won't always blow something up.

 

Why? The Prius doesn't have an alternator and the amount of power the DC to DC converter supplies (only while in READY mode) to the 12 volt bus doesn't vary w/whether or not the ICE is running.

 

The Prius battery is probably also a different *type* from a typical car battery. It should be "deep cycle" as opposed to "starting" type. This kind of lead-acid battery can be drained further than is safe for a starting battery, but it also doesn't provide nearly as much amperage under full drain. ("Marine" batteries are a compromise between the two.)

I carry a 'jump trickle charger' that connects the two cars' accessory/lighter sockets instead of the batteries. You have to leave it connected for at least 10 minutes before trying to start the other vehicle, but at least it's safer. It will not, however, start a Prius with a dead battery, as the accessory socket would be dead in that case.

 

For my PIP I keep one of those oblong, brick alarm batteries in the car. It works fine, I have had it since 2005. It is rated at 12V 7.2 Amperes.

 

I believe the Prius accessory battery is rated to draw only a few amps. Compare that to the CCC required to crack a conventional car!!

However, all to their own! If you want to give a jump with your Prius, just make sure its not a F250 Diesel! Those engines require LOTS of AMPS!!!

 

There is a lot of misinformation mixed into this thread.

The first rule of thumb is correct. Do not jump start with the Prius as in trying to have the other car turn over their starter motor while connected. It is perfectly safe assuming correct connections to charge another battery. The Prius can output 100A on the 12v bus direct from the DC-DC. It does not require the engine to be running, and it can provide the full 100A stopped, idling, or anything else. It is just there because the traction pack is used to supply the current and the car takes care of itself. This is more than enough to charge a mostly dead lead acid battery in a dead car.

The Prius, along with many other modern cars have lots of computers inside. When you reverse the polarity of the jumper cables you can either short them to ground or apply 24volts to a system both of which are major no-no's. In the Prius you will almost certainly blow the 100A fusible link. It is a cheap part, just stamped copper (the bit you are supposed to clamp onto for jump starts) but it is not an easy item to just find apart from a well stocked Toyota dealership (generic auto parts stores do not carry it), and once you blow it the car is now dead until replaced. Worst case is you blow the inverter as well, which new installed from the dealer is about $4K. Used installed would be closer to $1K.

To combat this, always use "smart" jumper cables in the Prius. These you connect any way, any terminal to any terminal, and they automatically determine the correct polarity and connect the batteries after the terminals are fully connected, usually a 2-3 second delay at least. This means no sparking either which can be tens of thousands of volts. I bought my "smart cables" on sale for $20 a while ago. Brand new not on sale I see them for about $50 - $60. That is too low of a price to risk inverter damage in your car. And they will work with anything. Even in normal cars connecting to the battery directly if it sparks you risk explosion, that's why the order you are supposed to connect and locations are important. With the smart cables, it no longer matters and you can go directly from battery to battery for the highest current flow, not using the sheet metal as a ground return which is crap in modern welded cars.

And the battery in the Prius is not a deep cycle battery. It is a normal SLA with a vent tube that runs outside of the car. One discharge, and it is toast. It is also sized for the domestic Japanese market. Most batteries over there are of similar size. It is a uniquely american thing to sit in a car with the car off and accessories on waiting for 30minutes or hours. Batteries are usually increased in size to handle this draw in the smaller engine cars that make there way over to the states for resale. This did not happen in the Prius.

 

Thanks, 2k1Toaster for clarifying a number of things I was about to. Here are two additional points on things you can do:
1) It is acceptable to jump start another Prius/hybrid/EV from a Prius. This is because we know the other vehicle "starts" in exactly the same way the Prius does -- all that needs to be done is booting a computer until it kicks on the main battery pack relays. The best part is that unlike traditional jump starting, you don't have to dick around with revving the engine to run the alternator or waiting a few minutes for the 12V system to "recover" -- it'll just work right away. Heck, you don't even have to turn on the car with the good 12V battery! My Prius and Leaf have both jumped each other on various occasions; they don't even bat an eye.
2) It is also acceptable (albeit annoying) to use your Prius to charge up a battery in another car of any type (assuming it can still take a charge). You hook up the jumper cables, turn on only the Prius (so the DC-DC converter is running), and let it sit for a long while (could be 15-30 minutes or more). Then disconnect the jumper cables, and see if the 12V battery in the dead car has charged up enough to let it start on its own. Had a friend do this with his Prius.

 

Assuming this is correct, it's a terrible decision by Toyota, based on price alone. There is no reason at all to have a starting battery in this application, other than cheaper supplier prices. The most popular replacement battery among Prius aficionados is the Optima yellow Top, IIRC, which is a hybrid starting/deep cycle battery. BTW, it's a bit of an inaccuracy to say that one full discharge will kill a SLA battery of any type dead. Typical full discharges are about 95%, and the battery does survive. It just loses substantial capacity afterwards. This applies to deep cycle batteries as well - they just tolerate 90% discharges better, but not happily. They do best with discharges of no more than 50%.

 

It is correct, and it is standard. There is no reason to change it, and a deep cycle has no benefits to people who don't abuse the battery. The Prius battery is barely used. It gets a short burst of up to 30A for priming the brake pump and then a few hundred milliamps to flick relays.

In a Prius, by the time the battery no longer works (i.e. is "dead") the voltage has dropped below around 9v, the minimum coil latch-on voltage for the hybrid relays. A 9v SLA is dead dead. Recharging it leaves you with an extremely small battery with an even further reduced capacity.

 

Yes, the Prius 12V battery is a small deep cycle type battery, not designed for high amp cranking loads.

If you need to help another with a low battery, it is OK to attach the jumper cables to another car and allow the Running Prius to CHARGE the other low battery. Leave it connected for 5-15 or longer minutes to warm and recharge the low battery, but DO NOT attempt to start the other car while the cables are connected to the Prius. disconnect the jumper cables then start the other car with it's now warm and partly recharged battery

 

How about jump-starting a Prius with a bank of 8 1.5V size AA batteries connected in series to give 12V? Would this be enough to do the job when the 12V battery is depleted (but not dead)?