Can the Leaf DC power port export power?

[smkettner]

What would the economics look like for lower cost lead acid batteries?
If it made economic sense why are people not doing this already?
Especially if you already have a solar grid tie inverter.

 

[EVDRIVER]

What would the economics look like for lower cost lead acid batteries?
If it made economic sense why are people not doing this already?
Especially if you already have a solar grid tie inverter.

Lead is expensive and has low cycle capacity, regardless the entire point is using a pack one already has in case of emergency or very infrequent use, not as a primary power source.

 

[thimel]

I suspect using your solar inverter to turn the DC voltage of the LEAF into AC for the grid may be more complicated than you think. A solar inverter has something called Maximum Power Point Tracking (MPPT) built in. This is an algorithm to set the effective resistance of the inverter to draw the current from the photovoltaic system that maximizes the power. The voltage as a function of current drawn for the LEAF battery is probably quite different from that of a PV system and there is no reason to believe the MPPT will do what you want. It may work, but there is no guarantee.

 

[garygid]

The typical 7kW PV inverter, when fed with an essentially "constant" 350 volts (LEAF battery), would probably draw more current until its outout was the limiting factor (7kW). At 350 volts, that might be about 20 amps, plus a small bit for losses (which are typically only around 5%).

 

[Coffee_Slurry]

That's what I'd expect -- current draw increasing under MPPT until either the inverter (4kW) or Leaf (?? kW) reaches a maximum.

Again, before everyone gets their panties in a bunch here, I'm not talking about sticking some paper clips in the leaf DC port and seeing if it hurts. I'm talking about maximizing the Leaf battery to move power from $0.07/kWh super-off-peak to daytime peak $0.37/kWh. That could be a profitable exercise.

 

[tps]

I'm talking about maximizing the Leaf battery to move power from $0.07/kWh super-off-peak to daytime peak $0.37/kWh. That could be a profitable exercise.

If it really is profitable, why isn't the power company already doing it? I suspect that when you figure in the cost of the battery, which is degraded slightly by each charge/discharge cycle, it turns out not to be so profitable. Maybe in a few years, you can get some "recycled" LEAF batteries which you can dedicate to such a project, so you don't have to tie up a car in the process.

 

[garygid]

Power companies are already storing energy at night and using during peak demand. However, battery storage is still a small part of it.

1. Potential Energy: Pumping water uphill, done several places, one a fair way south/east of Gilroy, CA, I believe.
2. Kenetic Energy: Stored in Rotating flywheels, a large plant near Albany NY.
3. Chemical Energy: Battrey storage, a whole town in Texas, as I recall. Ask AndyH.
4. Thermal Energy: Stored as hot, liquid sulfur.

 

[tps]

Power companies are already storing energy at night and using during peak demand. However, battery storage is still a small part of it.

1. Potential Energy: Pumping water uphill, done several places, one a fair way south/east of Gilroy, CA, I believe.

This is also called "pumped storage". I believe it's currently the way most grid "electricity" is stored. There's a big pumped storage plant a ways southwest of Philadelphia; they use plentiful nighttime electricity to pump water from a resevoir on the Susquehana River up to a higher resevoir at night and then release it though generators in the day to recover some of the energy they "banked" at night.

Nissan's plans for recycling Li Ion car batteries to other uses may bring battery storage a bit further toward the economic viability of pumped storage. Likely it will help battery storage make further inroads in smaller-scale storage electric requirements.

At one point, before our company found an office building with a backup generator, I was considering building a server room with enough batteries on the UPS to give us a six-hour run-time. Turns out I'd have needed to dedicate a few racks to APC UPS lead-acid batteries. Maybe in a few years, after Nissan starts recycling Li Ion, I would be able to do this more realistically.

 

[abasile]

I have a much more modest goal than V2G. I like to be able to use a LEAF's battery as an emergency power supply instead of a gasoline generator, for those rare occasions when our mountain neighborhood loses power. In an extended outage, I'd want to be able to run our refrigerator and forced air heater every few hours or so. Operating just one appliance at a time would be fine.

I'm thinking this might be possible with a standard inverter plugged into the cigarette lighter, assuming the power draw isn't too great. What I don't know is whether I would be limited to the capacity of the 12 V "accessory" battery, or whether the car would at some point replenish the 12 V battery from the main batteries. Or maybe it would make sense to use the DC port, given an easy and safe way of doing so.

Eventually, I'd like to install solar panels with an option to disconnect from the grid and provide "emergency" power when the sun is shining, but that will have to wait.

Any thoughts?

 

[Coffee_Slurry]

I'm talking about maximizing the Leaf battery to move power from $0.07/kWh super-off-peak to daytime peak $0.37/kWh. That could be a profitable exercise.

If it really is profitable, why isn't the power company already doing it? I suspect that when you figure in the cost of the battery, which is degraded slightly by each charge/discharge cycle, it turns out not to be so profitable. Maybe in a few years, you can get some "recycled" LEAF batteries which you can dedicate to such a project, so you don't have to tie up a car in the process.

I don't have any illusion that what the power company charges me is at all related to what power costs them, or what makes the most sense from an engineering perspective.

It's arbitrage on a very domestic scale. Taking advantage of inequities in the market, and unnatural pricing.

Consider for a moment the same exercise *without* the battery: Taking power from the $0.07 nightly meter and pumping it into your residential meter for five hours every night. Your monthly DR bill would be.. zero. All your power would be billed at $0.07. You win.

 

[garygid]

I like that, no storage, just use the less expensive 7 cent power
to run the full house meter backwards.

Let's see, how could that be done safely? Hum...

 

[Coffee_Slurry]

What I don't know is whether I would be limited to the capacity of the 12 V "accessory" battery, or whether the car would at some point replenish the 12 V battery from the main batteries.

I don't know the answer to this. How/when does the 12v lead-acid battery get charged? Is it only while the car is running, or also while off? The Prius will actually start the engine if the 12v battery runs low. If you leave it parked with the headlights on, the engine will cycle.

If I had to guess, I'd say that they most likely shut down the high voltage inverter and associated stuff when the car is off, and don't recharge the 12v battery unless the car is on. The accessory port is probably switched off when the car is off, like most cars do today. If the car is on, it has to charge the 12v battery, since the headlights and other things depend on it.

The 12v battery in the Leaf is surprisingly large, considering how important weight is. It has to be for more than just the key transponder, alarm, charge timer and such. It's not like there's a 500 cold-cranking-amps starter motor anywhere.

 

[Coffee_Slurry]

I like that, no storage, just use the less expensive 7 cent power
to run the full house meter backwards.

Let's see, how could that be done safely? Hum...

I wonder if both the L2/AC and L3/DC ports can be used at once.
Turn the car into a big AC-to-DC power supply, and drive a DC-input grid-tie inverter.

You'd have safeties in the EVSE, the car, and the inverter.

 

[motornature]

Has anyone thought of a warranty issue?
I doubt Nissan doesn't mind that its cars are used as back-up generators, and would not be surprised to learn that any V2G application voids the warranty. I understand it's not much, but if it increases the strain on the battery, Nissan will not like it.

 

[EVDRIVER]

What I don't know is whether I would be limited to the capacity of the 12 V "accessory" battery, or whether the car would at some point replenish the 12 V battery from the main batteries.

I don't know the answer to this. How/when does the 12v lead-acid battery get charged? Is it only while the car is running, or also while off? The Prius will actually start the engine if the 12v battery runs low. If you leave it parked with the headlights on, the engine will cycle.

If I had to guess, I'd say that they most likely shut down the high voltage inverter and associated stuff when the car is off, and don't recharge the 12v battery unless the car is on. The accessory port is probably switched off when the car is off, like most cars do today. If the car is on, it has to charge the 12v battery, since the headlights and other things depend on it.

The 12v battery in the Leaf is surprisingly large, considering how important weight is. It has to be for more than just the key transponder, alarm, charge timer and such. It's not like there's a 500 cold-cranking-amps starter motor anywhere.

It's smaller than a normal car battery and does only run the items you mention. It's likely bigger than normal, I would have liked to see a lithium battery here but too expensive.

 

[EVDRIVER]

Has anyone thought of a warranty issue?
I doubt Nissan doesn't mind that its cars are used as back-up generators, and would not be surprised to learn that any V2G application voids the warranty. I understand it's not much, but if it increases the strain on the battery, Nissan will not like it.

They need to prove what one did damaged the pack and if you can't do this without damaging it you should not be doing mods like this. Warranties can no longer be voided just because the car was modified, the law here has changed quite a bit in the past years.

 

[Coffee_Slurry]

It's smaller than a normal car battery and does only run the items you mention. It's likely bigger than normal, I would have liked to see a lithium battery here but too expensive.

Lithium isn't the right fit, but it seems like an Odyssey PC545 could drop in and save some significant weight. Really, what high-current demand is there? Maybe the standby (off) state of the car draws a lot of power from the 12v? Something worth measuring when deliveries start.

 

[EVDRIVER]

It's smaller than a normal car battery and does only run the items you mention. It's likely bigger than normal, I would have liked to see a lithium battery here but too expensive.

Lithium isn't the right fit, but it seems like an Odyssey PC545 could drop in and save some significant weight. Really, what high-current demand is there? Maybe the standby (off) state of the car draws a lot of power from the 12v? Something worth measuring when deliveries start.

It has nothing to do with high power is has to do with AH. Lithium replacements are used in performance cars to reduce the weight and size. Once the car is turned on the DC/DC is on and the 12V system likely has 100A. The contactor likely draws no more than 2-3A There is no need for a high amp battery, just a AH rating that makes sense for the parasitic loads.

 

[mitch672]

you could probably adapt a standard PV Grid Tied Inverter, to run off the HV battery on the Leaf, the voltage is similar (350-400VDC?), the issue is, you would need to find a way to draw the DC off the L3 connector, and also to have the Grid Tied inverter startup, without an actual grid load present (if you want to use the Leaf as a backup generator). Of course that could be done with a small self-exciting UPS to get the grid tied inverter working. You would also need an autmatic or manual transfer switch to disconnect the actual grid, so you don't backfeed it.

could it be done? sure, but I'm not sure anyone will bother.

 

[EVDRIVER]

you could probably adapt a standard PV Grid Tied Inverter, to run off the HV battery on the Leaf, the voltage is similar (350-400VDC?), the issue is, you would need to find a way to draw the DC off the L3 connector, and also to have the Grid Tied inverter startup, without an actual grid load present (if you want to use the Leaf as a backup generator). Of course that could be done with a small self-exciting UPS to get the grid tied inverter working. You would also need an autmatic or manual transfer switch to disconnect the actual grid, so you don't backfeed it.

could it be done? sure, but I'm not sure anyone will bother.

There are plenty of inverters out there and one can easily trick a solar inverter to come on. There are two power connections off the L3 port and once a proper signal is sent to the car the contactor will close, this happens on the Prius pack when this is done. Should not be very difficult. There will be issues with how the energy removed is monitored and how the Leaf keeps track of capacity and how the car will then function once charged. If the same shunt/system connection location is used to monitor consumption from the car then it should be ok.