Irony

[EVDRIVER]

That said, I have no idea why the Leaf has such a huge battery. Seems like total overkill to "boot" the car.

The reason it has a regular car battery is to run most of the accessories including the LED headlights. It isn't just to boot the car starter.

The size of the battery is specified based on the parasitic loads of the car when off, like the RF transmitter, etc, etc. It is likely a generic medium amp-hour battery with average cold cranking amps, possibly slated to deep cycle but I doubt it since auto makes use cheap batteries.

I'm not sure why there is so much speculation on what is a basic electrical system and so many false statements being made on this forum about how EVs operate. The entire 12V system is very basic and consists of a med sized 12V lead battery (needed to close the contactor) and a high current DC/DC converter which runs the car accessories when on, and charges the 12V battery. The reason the Leaf has a smaller battery than an ICE car is because it has a large battery pack and DC/DC. If the entire pack were low to the point where the car won't drive the DC/DC will likely still run and they have different cut off points to protect the pack. The electronics of a Leaf are similar to any other modern car except it has an inverter and DC/DC converter, the rest is basically the same.


If you removed the 12V battery and had no accessory load and a charged pack, you could likely close the contactor with one or two tiny 9V batteries and then drive the car will everything on. For those people that are truly interested in learning how an EV works there are books available with wiring diagrams, they all are basically the same and have been for years. A basic wiring diagram can be done on a napkin in about 5 minutes that shows the main systems and how they connect.

 

[AndyH]

The lead-acid battery in the Leaf is certainly capable of jump-starting an ICE.

If anyone wants to keep a spare in the glove box, toss in some LiPo or four A123 cells in series.

[youtube]http://www.youtube.com/watch?v=WkKRqaNPIBE[/youtube]
[youtube]http://www.youtube.com/watch?v=qcvmvrmTMMk[/youtube]

 

[Rokeby]

Based on the Prius, I would be reluctant to jump start any ICE with the LEAF. Sure, it
can be done, but small mistkes can be costly. Even if Nissan says it can be done. Extra
caution would most likely be in order.

Those of us who drive Prii have learned, if not through direct experience than through
stories of woe and perdition on our favorite forum, to be very cautious and conservative
when it comes to anything related to the 12V battery.

The 12V battery is considerably smaller than what is typical in ICE cars. It is needed at
start-up to boot the ICUs -- 7? -- and close the circuit to bring the HV battery on-line.
Once the HV battery is on-line, the 12V bus is supplied via a DC-to-DC converter at
~13.8V. If by carelessness or a weak battery the "12V" battery gets discharged to ~11.5V
or less, all sorts of goofy things can happen: the car won't start, the car won't shut off,
random warning lights, random horn toots, wipers coming on, etc.

IIRC, he danger in using a Prius to jump start an ICE is getting the cables switched,
the dreaded reverse polarity. This, along with sparking, is as I understand it the cause
of costly eletrical component damage. Many folks wonder why there aren't the electrical
bits that would prevent this condition. (I forget their name.) At any rate you can buy
jumper cables that have sensing circuitry and apparently adjust to prevent reverse polarity.

Some of us carry a hot start battery so that we can offer a jump start without hazarding
our cars. This so that, should the need or desire to help someone arises, there isn't any
lingering misconceptions that all Prius drivers are smug, stuck-up, tree hugging, pencil-
necked geeks.

 

[Coffee_Slurry]

The size of the battery is specified based on the parasitic loads of the car when off, like the RF transmitter, etc, etc.

That's surprising. A car battery is what, 50Ah? I'll measure the parasitic load (off charger) of a Leaf on Pending date.

 

[garygid]

Most likely, Nissan did not actually use the drawn-on-napkin circuit, but something more complex. But, the napkin would give the general ideas for most EVs, it will not have the actual details of the LEAF.

The questions here are usually how the LEAF actually works, not how EVs in general have been or could be built.

It is likely that the LEAF's DC-to-DC converter is ON while charging the LEAF.

So, the 12v battery probably gets charged, if needed, (from the traction battery, via the DC-to-DC) while the traction battery is being charged.

 

[johnr]

Why all this talk of reverse polarity? Jumper cables and batteries are simple - the black cable connects to the black terminal with the minus sign; the red cable connects to the red terminal with the plus sign. Simple. Only idiots would have trouble with that :lol:

 

[AndyH]

Why all this talk of reverse polarity? Jumper cables and batteries are simple - the black cable connects to the black terminal with the minus sign; the red cable connects to the red terminal with the plus sign. Simple. Only idiots would have trouble with that :lol:

Too many engineers and engineer-wannabees here, John - some have to overthink everything just for the sport of it.

Hell, most ICE cars on the road have multiple computers that need to be powered - and computers built for vehicles use different components and build practices to stay alive in the hazardous electrical environment of an alternator and the brown-outs and spikes caused by the starter motor. The computers in a car are not like our Dell laptops...

Anyone not comfortable connecting jumper cables absolutely should not jump start a car - whether they do it from a Prius, a Leaf, or a Plymouth Duster.

 

[taztaz]

If you are too afraid to jumpstart a ICE car there is alternatives. Buy a cigarett lighter cable that is made for connecting two cars together. That cable wont use more than 5-10A i think. That way you don't have to mess around with jumpstart cables and its a lot safer. There is also indicators on that cigarett-plug device that shows when ICE driver can start his car...

Problem solved! No more need for discussion .. Just ask Nissan about the jump start thing.. If they say ok its ok!

Here is an example of such device..
http://www.amazon.com/Wagan-EL9796-Quick-Jumper-Jumpstarter/dp/B00005OWK2

 

[Spies]

How did you do it? The only way that I know is on the battery in back..

From http://www.toyota.com/prius-hybrid/faq.html

12. Can Prius be jump-started?
Yes. Should you need it, Prius can be jump-started with any standard 12-volt DC power source, and it actually requires less power than a conventional car. Simply connect the cable clamps to access points under the hood (which are connected to the auxiliary battery near the cargo area) and energize the computer. Then press the Start button to turn the car on. Please see your Owner's Manual for further instructions.

 

[EVDRIVER]

If you are too afraid to jumpstart a ICE car there is alternatives. Buy a cigarett lighter cable that is made for connecting two cars together. That cable wont use more than 5-10A i think. That way you don't have to mess around with jumpstart cables and its a lot safer. There is also indicators on that cigarett-plug device that shows when ICE driver can start his car...

Problem solved! No more need for discussion .. Just ask Nissan about the jump start thing.. If they say ok its ok!

Here is an example of such device..
http://www.amazon.com/Wagan-EL9796-Quick-Jumper-Jumpstarter/dp/B00005OWK2

ANd then sit there for hours to equalize the charge. You can't jump a dead battery via a cig plug. All this jump start discussion is silly. If one wants to jump another car so be it if not call AAA. A leaf could easily charge the hell out of another car battery when on.

 

[LEAFfan]

A couple of things.. you guys are assuming that because the LEAFs battery looks like a normal battery that it is, perhaps its not designed to deliver the hundreds of cold cranking amps that normal cars need.. the battery may have been optimized for high capacity and low self discharge (similar to the battery used in a UPS or an alarm). Such a battery may be able to jump start a car (one that starts easily, and does not need to be cranked for 30 secs, and not in winter) but will probably suffer a reduction in its life.

Some Priuses have suffered several thousand $$ damage from improper jumping.. probably a spark at the wrong time fried some electronic box in the Prius. I have seen some people "test" the polarity of a jump connection by briefly dragging the clamp over the battery terminal, if they see a shower of sparks then they switch the polarity.. I just cringe since many batteries explode when this happens, spewing acid all over.. that momentary shower of sparks is enough to damage or destroy some expensive components.

So I would recommend you NEVER jump start another car with a LEAF. I would do it, but not a real jump start.. I would carefully connect both batteries in parallel, turn the LEAF on and let it recharge the dead car's battery (with everything off, and make sure the driver is out of the car so he does not try to "help" you out by attempting a start), let it charge for about 5 minutes, disconnect the cables and try to start the car.. it usually works, assuming the battery is not so far gone and corroded that it cant take a brief charge.

Be very careful when making that connection, avert your face since many lead-acid batteries do explode. Its better if you use modern jump cables, with polarity reversal protection and a way to make a remote connection.

You should NEVER connect the negative cable to the batteries, but to a piece of metal on the block far from the battery on both ICE cars.

 

[EVDRIVER]

"Jump starting provides power to the 12 volt system to allow the electrical systems to operate. The electrical systems must be operat- ing to allow the Li-ion battery to be charged. Jump starting does not charge the Li-ion battery. The Li-ion battery must be charged before the vehicle can be driven.
If jump starting is necessary, see “Jump starting” in the “6. In case of emergency” section. If the power switch does not switch to READY to drive position by jump starting, the 12-volt battery may have to be replaced. Contact a NISSAN certified LEAF dealer."

From the user manual


It says you can jump start a Leaf but you should not use the Leaf to jump another vehicle. This is likely to protect the DC/DC in situations where the other vehicle has a very dead battery causing a high current load to the DC/DC and smaller battery. Even in an ICE vehicle it is necessary at times to "pre-charge" the other cars battery to reduce the load.

 

[Smidge204]

You should NEVER connect the negative cable to the batteries, but to a piece of metal on the block far from the battery on both ICE cars.

I've never heard a reasonable explanation as to why this is that didn't rely on factors that haven't applied since the 1970s. What's the current rationale behind this advice?
=Smidge=

 

[LEAFfan]

You should NEVER connect the negative cable to the batteries, but to a piece of metal on the block far from the battery on both ICE cars.

I've never heard a reasonable explanation as to why this is that didn't rely on factors that haven't applied since the 1970s. What's the current rationale behind this advice?
=Smidge=

It will avoid explosions due to sparks. By using this procedure, the sparks when you connect will not detonate the gases from the battery.

 

[LEAFfan]

A couple of things.. you guys are assuming that because the LEAFs battery looks like a normal battery that it is, perhaps its not designed to deliver the hundreds of cold cranking amps that normal cars need.. the battery may have been optimized for high capacity and low self discharge (similar to the battery used in a UPS or an alarm).

Here is info from the LEAF manual: ...the 12-volt battery is the same as the
battery in vehicles powered by gasoline engines...

 

[turbo2ltr]

From the manual..

If you use LEAF as a booster vehicle, the electricity for jump starting vehicle is not enough due to the amount of electric power at jump starting is larger than the power Li-ion battery charges 12-volt battery. However it is no problem using gasoline engine vehicle to supply battery to LEAF.

Thats clear as mud. lol

 

[LEAFfan]

From the manual..

If you use LEAF as a booster vehicle, the electricity for jump starting vehicle is not enough due to the amount of electric power at jump starting is larger than the power Li-ion battery charges 12-volt battery. However it is no problem using gasoline engine vehicle to supply battery to LEAF.

Thats clear as mud. lol

It sounds simple to me...you shouldn't use your LEAF to jump start an ICE, but an ICE can safely provide a jump for you.

 

[evnow]

From the manual..

If you use LEAF as a booster vehicle, the electricity for jump starting vehicle is not enough due to the amount of electric power at jump starting is larger than the power Li-ion battery charges 12-volt battery. However it is no problem using gasoline engine vehicle to supply battery to LEAF.

Thats clear as mud. lol

Here is the rewrite ...

If you use LEAF as a booster vehicle, the electricity for jump starting ICE vehicle is not enough due to the amount of electric power needed at jump starting is larger than the power available in the Leaf 12-volt battery. However it is no problem using gasoline engine vehicle to supply power to the LEAF battery.

 

[smkettner]

From those blurbs in the manual it would appear there is no problem using LEAF to jump another vehicle.
The only possible trouble will be if the 12v battery itself does not have enough power.
No harm to give it a go.

 

[TRONZ]

So..... both sides are still claiming to be right :?: