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LTLFTcomposite
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Re: How is the 12V battery recharged? Max amperage?

Sun Aug 26, 2012 1:59 pm

TonyWilliams wrote:Sounds reasonable. What are you going to power? The refrigerator?

Probably not, these newer fridges are supposedly more energy efficient, "linear compressor" or some such nonsense, but the nameplate claims it draws a max of 5.3A. I think I'd need a bigger inverter for that. Maybe just some lights (LED) and the TV.

There's always the eco-unfriendly Honda generator for heavier loads, but probably not an issue anyway... this time. Looks like Isaac won't amount to much here.
LTL
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ka9q
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Re: How is the 12V battery recharged? Max amperage?

Thu May 15, 2014 3:19 am

I know this is an old thread, but I found it in a Google search for ways to suck lots of DC power out of a Leaf and found it very informative.

I've been thinking of a much more ambitious way. That is, instead of pulling power through the car's DC-DC converter, connect directly to the 400V high voltage battery and use it to run one or more slightly modified PFC corrected switching computer-type power supplies. These will give you multiple voltages, though only 12V is likely to be useful in a radio setup. The big advantages are in being able to pull more power than the Leaf's own DC-DC converter can handle and to save a lot of copper and I^2R losses by running 400V rather than 12V most of the way to several loads, which might have to be 10-20 m away.

I'm VERY well aware of the potential hazards associated with a 400V 24 kWh battery pack that's "always on". I'm an EE with a lot of experince in power circuits and I believe i can do it safely as long as I have enough information about the Leaf's electrical supply system. Naturally I will have cutouts and fuses all over the place. But I do need to know the best place to make the connection to the Leaf's HV supply. I don't want to bypass any battery current shunts that might confuse the car's state-of-charge estimate, i don't want to bypass any safety cutouts that disconnect the pack when a cell in the series string reaches a safe minimum voltage, and I don't want to confuse anything else in the car that might be wondering where all that DC power is going. Basically I want to suck as much 400 V DC as I can out of the pack without damaging the car, confusing its computers or giving Nissan any valid reason to dishonor my battery warranty. And I have to leave enough energy to get home.

My specific application is ham radio''s annual Field Day operation. The theme to Field Day is operation on emergency power, and gasoline generators have long been the workhorses. But I detest generators. They're loud, unreliable, inefficient and dangerous. They invariably run out of gas just as you're having a great run in the contest. And then you have to fuel a hot generator (because nobody wants to wait) in the dark with a toxic, volatile and highly flammable liquid made from dwindling natural resources, the payments for which maintain some of the most medieval cultures in the world.

Batteries and solar panels are often used for a single low power Field Day station, but there's rarely enough capacity to run an entire multi-transmitter operation for the full 24 hours. The 24 kWh in a Leaf battery pack is obviously much more capable.

There's a high power ChaDeMo DC charger almost on my way to the site where I could top off before arriving, and after the contest I could return there to get enough to return home.

Any reason I can't do this?

BrockWI
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Re: How is the 12V battery recharged? Max amperage?

Thu May 15, 2014 6:39 am

A bit sideways on this topic, but did you check out this thread

viewtopic.php?f=37&t=13097

I am not sure what kinds of loads you have bit it seems to me to be easier and safer to just let the internal high voltage to 12vdc converter do it's thing. I understand there are losses going from 400vdc to 12vdc to 120vac (and back to 12vdc?), but again you can do it with off the shelf parts and again the Leaf's dc-dc converter is rated for 1700 watts. And yes if you are trying to run 12vdc 20 meters you need either beefy wires or step up and down. With a good sine wave inverter you should be able to run just about any item you could plug in to a normal 120vac outlet.


No matter which way you go, it will be a LOT less noise than even a good Honda eu2000i :)
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ka9q
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Re: How is the 12V battery recharged? Max amperage?

Thu May 15, 2014 7:14 am

Many thanks for the pointer to the other thread. I now see how to do the mechanics of the 12-volt approach. Using a 12V DC -> 120V AC inverter is certainly one way to reduce line loss, and it also provides what the radio equipment and accessories in the trailers already expect to see.

But it does involve several lossy conversions: the Leaf's 400V DC -> 12V DC converter; the 12V DC -> 120V AC inverter, and finally the radio power supply that usually does 120V AC -> 12V DC. That's three distinct conversions, plus the car's overhead power in that ON-ON state. (Anybody know?) My approach would involve just a single conversion, 400V DC -> 12V DC (or whatever), and it would (or should) allow the car to be essentially OFF to minimize its own overhead draw. There'd be additional savings in the use of the higher voltage for transmission, but that's probably much less than the savings from having only one DC-DC conversion.

BrockWI
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Re: How is the 12V battery recharged? Max amperage?

Thu May 15, 2014 8:23 am

You are correct about all the conversion losses. If you can make it work safely, I say go for it. As for idle power draw see below. I am not sure if the main contactor has to be energized to pull/push power from the dc port or how it "turns on".

snipped from this thread

viewtopic.php?f=31&t=8583

Ingineer wrote:While I'm at it, someone asked me recently what the idle draw of the Leaf is. It bounces around a lot, but it's as low as 140w, typically around 160w with all accessories, lights, and CC off, and 230 watts for headlights and 360w with High-Beams on. (My Leaf will be slightly lower, as I've changed most of the incandescent bulbs to LED.) Again, these power measurements were derived by recording amperage at the cell interconnect level using a high-accuracy kelvin-connected current shunt.
-Phil
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TimLee
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Re: How is the 12V battery recharged? Max amperage?

Thu May 15, 2014 9:32 am

But the contactor is INSIDE the battery pack.
The only straihtforward way to get the high voltage is by having the LEAF in On or Ready.
Could you reverse engineer making the contactor close and maintain all the safeguards, possibly, but your equipment to do this will probably have losses similar to what the LEAF does.
With the contactor closed and high voltage available I have no idea whether you can then safely take power from the high voltage buss.
There has been mention by Ingineer that cover removal for some tests does leave high voltage exposed.
But whether you can just hook to it and draw power and the LEAF software will tolerate this I have no idea.

Tim Lee
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Levenkay
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Re: How is the 12V battery recharged? Max amperage?

Wed Jul 16, 2014 6:40 pm

TimLee wrote:But the contactor is INSIDE the battery pack.
The only straihtforward way to get the high voltage is by having the LEAF in On or Ready.
Could you reverse engineer making the contactor close and maintain all the safeguards, possibly, but your equipment to do this will probably have losses similar to what the LEAF does.
With the contactor closed and high voltage available I have no idea whether you can then safely take power from the high voltage buss.
There has been mention by Ingineer that cover removal for some tests does leave high voltage exposed.
But whether you can just hook to it and draw power and the LEAF software will tolerate this I have no idea.

This *has* to be what Nissan's "Vehicle to home" solution does, so it sounds possible to me. Shoot; never mind the down-converter; fetch along a vacuum-tube transmitter, and use the LEAF's battery directly as B+!

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JeremyW
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Re: How is the 12V battery recharged? Max amperage?

Wed Jul 16, 2014 8:11 pm

The leaf to home uses the CHAdeMO port along with "special" CAN bus commands over the port and a firmware update in the leaf to allow power to be drawn from the pack via the CHAdeMO port. The contactor used to connect the battery to the port is powered by the leaf to home over 12v. In a normal charging session via CHAdeMO the contactor is also powered from the external charger.
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Bob
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Re: How is the 12V battery recharged? Max amperage?

Thu Jul 17, 2014 6:42 am

If you tap directly into the big battery pack, you will be bypassing a lot of safety devices. So if someone has a radio that draws too much energy, it could overheat your big battery pack and do real damage. I don't want to over-react, but in rare cases, Lithium-Ion batteries are known to catch fire when abused.

The nice thing about using an inverter on the 12V system is that you have the inverter's inherent power limiting AND the Leaf's DC/DC converter power limiting to protect you from damaging the big battery.

Bob

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JeremyW
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Re: How is the 12V battery recharged? Max amperage?

Thu Jul 17, 2014 8:15 pm

The leaf's HV systems are not live if the leaf is powered down. There are two contactors in the battery pack for the HV rails to the rest of the leaf systems and two contactors for CHAdeMO. All are more-or-less controlled through the battery controller or VCM (main controller).
Former 2012 SL leasee 6/23/12 - 9/23/15
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