Battery Standby Losses

Does anyone know if there has been any announcement regarding what the self discharge standby losses on the battery pack are likely to be? Alternately does anyone know what one might expect since I'm assuming the Leaf's battery pack is not going to be materially different from existing air cooled batteries of the same size and type?

I know that Telsa has miserable numbers but its not clear how much of the loss is from the batteries vs the battery management system.

There are actually two issues I'm trying to figure out. The first is the classic airport problem. If you have to park the car someplace for a couple of weeks and there isn't a charging station to maintain the battery, how much capacity do you lose each day the car sits unused?

The second is how much power the car consumes just sitting there when it is hooked to a charger but after the battery has reached full charge. Its easy to dismiss this as incidental to the overall operating cost of the vehicle but without numbers one can't be sure. And as I said apparently it was anything but true with the Telsa.

http://www.mynissanleaf.com/viewtopic.php?f=16&t=382

Thanks. Of course I found that right after I posted. Sorry.

Anybody know about the second case. The number I remember for the Tesla was that a quarter (26% actually) of the power at the wall was being lost getting to full charge (68kWh to charge the battery to 54 kWh) but that just keeping the battery at full charge continued to use significant energy due to the power consumption of the battery management system.

I'm not sure why this would be true given the low self discharge rate but I remember reading an article somewhere that due to this just over 50% of what was coming out of the wall was being lost. I'll see if I can find the piece online.

Found it...

Tesla co-founder Martin Eberhard has never been one to mince words about the company or car he helped create, and it doesn't look like that's about to change, with him now taking advantage of his blog to spread the word about "one little thing wrong" with the car. Apparently, like some other Tesla drivers, he noticed that the ESS coolant pump seemed to be running all the time, even when it had been parked and left off for a long time. After a bit more investigation, Eberhard determined that the coolant pump and support electronics drew a hefty 14 kilowatt-hours in four days just sitting in his garage, which translates to 1,278 kWh per year, or the rough equivalent of two large refridgerators. As Eberhard points out, that could also have some pretty severe implications for the life of the pump and battery, and even the car's stated watt-hours per mile. For Tesla's part, it says the pump will shut off, but only when the battery is half-way discharged, which is a state that some with a short commute, like Eberhard, may rarely see.

Also...

Martin Eberhard was along for the Tesla Motors ride for quite some time before unceremoniously leaving the company and starting his own blog. As one of the chief architects behind the current Tesla Roadster, he knows more than a thing or two about how it works, but even he is caught off-guard from time to time with how the vehicle works now that there is a shiny Roadster sitting in his garage. The latest interesting bit of information comes by way of Eberhard's blog and involves how much energy the car uses -- get this -- when parked. Astonishingly, the car's battery constantly has coolant run through it, just so long as it's at least half-charged. Because his car is nearly always fully charged, Eberhard's pump is always running. To track its power usage, a meter was installed and Martin was very surprised to find that 22-percent of his car's energy usage was being used while the car sat!

I know the Leaf isn't liquid cooled but I wonder if it might also draw any power even when not in use for cooling.

http://en.wikipedia.org/wiki/Tesla_Roadster

The Tesla used 146Watts to run the coolant pump, that runs most of the time, if the pack is charged at %90 or more.
We don't know about this for the Leaf, but the Leaf probably uses very little while "off", it has no active coolant system.

Battery system

Connected power supply.Tesla Motors refers to the Roadster's battery pack as the Energy Storage System or ESS. The ESS contains 6,831 lithium ion cells arranged into 11 "sheets" connected in series; each sheet contains 9 "bricks" connected in series; each "brick" contains 69 cells connected in parallel (11S 9S 69P). The cells are 18 mm (0.71 in) in diameter and 65 mm (2.6 in) long (18650 form-factor); this type of lithium-ion cell is also found in most laptop computer batteries. The pack is designed to prevent catastrophic cell failures from propagating to adjacent cells, even when the cooling system is off. Coolant is pumped continuously through the ESS both when the car is running and when the car is turned off if the pack retains more than a 90% charge. The coolant pump draws 146 watts.[85][86][87][27][88]

A full recharge of the battery system requires 3½ hours using the High Power Connector which supplies 70 amp, 240 volt electricity; in practice, recharge cycles usually start from a partially charged state and require less time. A fully charged ESS stores approximately 53 kWh of electrical energy at a nominal 375 volts and weighs 992 lb (450 kg). [89]

Tesla Motors stated in February 2009 that the current replacement cost of the ESS is slightly under USD$36,000, with an expected life span of 7 years/100,000 mi (160,000 km), and began offering owners an option to pre-purchase a battery replacement for USD$12,000 today with the replacement to be delivered after seven years. The ESS is expected to retain 70% capacity after 5 years and 50,000 miles (80,000 km) of driving (10,000 miles (16,000 km) driven each year). Tesla Motors provides a 3 year/36,000 mile warranty on the Roadster with an optional 4 year/50,000 mile extended warranty available at an "additional cost" (2008 Roadster buyers received the 4/50 extension at no cost while later purchasers need to pay). A non-ESS warranty extension is available for USD$5,000 and adds another 3/36 to the coverage of components, excluding the ESS, for a total of 6 years/72,000 mi (120,000 km).[90][91]

Tesla Motors announced plans to sell the battery system to TH!NK and possibly others through its Tesla Energy Group division. The TH!NK plans were put on hold by interim CEO Michael Marks in September, 2007.[92][93][94] Think now obtains their Lithium-Ion batteries from Enerdel

So all in counting the wall to battery losses for the Tesla are about 32%. That's 26% from the charger and another 6% loss to the circulation pump. A third of the energy lost, but still not material in light of the cost of the battery pack.

I wonder how bad the derating is going to be for the Leaf as a function of ambient temperature. When you preheat the car does that preheat the battery too or just the passenger compartment?

I'm very curious about this myself; I own a Vectrix scooter that consumes roughly 100W to power its charge controller board even when the battery does not need any charging. Since the fan cooling this controller board only runs when actively charging, this leads to a rather warm board in addition to the wasted energy so the general consensus has been to unplug the Vectrix once the charging cycle is complete (or even before so as to avoid the extra heat and energy consumption used during the final "topping off" phase of the charging cycle).

I do recall mention that the Leaf will be "smart" enough to fully stop its power draw once topped off, but I have to imagine there will be some level of vampire load, even if only 5W...

OK, I think I'm confused - Does this mean that if the Leaf is plugged in, the traction battery pack is charged, but the 12V is not? The 12V only gets recharge when the Leaf is moving (or via solar panel on the SL)?

For example - suppose I fly to Florida for two months in the winter. I leave my Leaf in the garage plugged in with the L1 EVSE.

When I come back, the traction battery pack is fully charged, but the 12V is dead because of cold and no re-charging, so I won't be able to start the car?

charlie1300 said:

OK, I think I'm confused - Does this mean that if the Leaf is plugged in, the traction battery pack is charged, but the 12V is not? The 12V only gets recharge when the Leaf is moving (or via solar panel on the SL)?

For example - suppose I fly to Florida for two months in the winter. I leave my Leaf in the garage plugged in with the L1 EVSE.

When I come back, the traction battery pack is fully charged, but the 12V is dead because of cold and no re-charging, so I won't be able to start the car?

Click to expand...

For most EVs, the inverter system isn't connected until the car is powered on. I'm pretty sure it is the same on the Leaf, which is one of the reasons why I reserved the SL version with the solar panel for maintaining the 12 volt battery.

DarkStar said:

charlie1300 said:

OK, I think I'm confused - Does this mean that if the Leaf is plugged in, the traction battery pack is charged, but the 12V is not? The 12V only gets recharge when the Leaf is moving (or via solar panel on the SL)?

For example - suppose I fly to Florida for two months in the winter. I leave my Leaf in the garage plugged in with the L1 EVSE.

When I come back, the traction battery pack is fully charged, but the 12V is dead because of cold and no re-charging, so I won't be able to start the car?

Click to expand...

For most EVs, the inverter system isn't connected until the car is powered on. I'm pretty sure it is the same on the Leaf, which is one of the reasons why I reserved the SL version with the solar panel for maintaining the 12 volt battery.

Click to expand...

So that's the story? When I come back from my hypothetical Florida trip, I will need to jump the 12V to get the Leaf started, then run it 20-30 miles to recharge the 12V? (solar panels won't help me in the garage).

charlie1300 said:

So that's the story? When I come back from my hypothetical Florida trip, I will need to jump the 12V to get the Leaf started, then run it 20-30 miles to recharge the 12V? (solar panels won't help me in the garage).

Click to expand...

You might need to jump the 12v before you can power the LEAF up, but after that I would think you could just let it sit in the garage powered up for a while to fully recharge the 12v.

The amount of energy needed from the 12V battery for starting the LEAF is a very small fraction of what is needed to crank an ICE.

All you need is enough power to power up the systems (when you turn the key) and then the contactor will connect the traction batteries, and will charge the 12V battery rapidly.

I would just install a battery disconnect for the 12 volt battery. Sounds like it would be $10 well spent!

charlie1300 said:

So that's the story? When I come back from my hypothetical Florida trip, I will need to jump the 12V to get the Leaf started, then run it 20-30 miles to recharge the 12V? (solar panels won't help me in the garage).

Click to expand...

Would an LED lightfixture above the solar panel, while the car is parked in the garage, be sufficient to keep the 12V charged ?

I don't like the idea of the battery disconnect switch ... we're not sure at this point what all settings might be lost. So, instead use a 7-day timer to run the LEDs for a few hours per day (or even week) at very little energy cost, to keep the 12V charged ?

LEDs don't tend to excite solar panels very much. (They are, after all, low power)

Once someone willing takes delivery, maybe they can park the Leaf, and disconnect the 12v battery to go through a multimeter shunt -- measuring the static current draw over a few hours. This would give us an idea of how long that massive 12v lead acid battery can power the parked car.

I wouldn't expect this to be any different from a typical ICE car, though. Same stuff is powered while the car is off, and it hasn't been a problem in other compact cars, right?

I wouldn't worry yourself with illuminating the solar panel.. that's about the most inefficient thing imaginable. If long-term parking is a concern, I'd get a Battery Tender Jr or similar 12v float charger. Pretty typical for seasonal vehicles.

charlie1300 said:

So that's the story? When I come back from my hypothetical Florida trip, I will need to jump the 12V to get the Leaf started, then run it 20-30 miles to recharge the 12V? (solar panels won't help me in the garage).

Click to expand...

If it were me, and I wanted the 12V aux battery to stay charged, I would use a very inexpensive 'trickle' battery charger. It puts the very minimal juice into the battery and would keep it topped off. I used to do it with some older cars and it worked great. It can be left on indefinitely if you use a small enough trickle charger.

I leave a solar cell panel to keep the 12v for my outboard boat charged up and it seems to work fine. Even produces enough power that if it rains and the bilge pump kicks in the battery is plenty strong to start the engine. Of course that's in full sunlight at the height of summer.

Does the Leaf have a cigarette lighter that allows charging the battery? Alternately running a pair of wires into the cabin with a quick disconnect would be pretty easy although I would have thought that Nissan would have handled this themselves.

OK, I got the idea - if I'm away for an extended time and want the Leaf ready to roll when I get back, I need to use the L1 EVSE to trickle charge the traction battery pack, and use a separate trickle charger for the 12V battery.

Not exactly elegant, but doable.

charlie1300 said:

OK, I got the idea - if I'm away for an extended time and want the Leaf ready to roll when I get back, I need to use the L1 EVSE to trickle charge the traction battery pack, and use a separate trickle charger for the 12V battery.

Not exactly elegant, but doable.

Click to expand...

And totally unnecessary, but suit yourself.

GroundLoop said:

charlie1300 said:

OK, I got the idea - if I'm away for an extended time and want the Leaf ready to roll when I get back, I need to use the L1 EVSE to trickle charge the traction battery pack, and use a separate trickle charger for the 12V battery.

Not exactly elegant, but doable.

Click to expand...

And totally unnecessary, but suit yourself.

Click to expand...

Hold on, didn't you recommend a battery tender Jr trickle charger for the 12V just 4 posts back? (looks like a good product)

I realize that I could just do nothing, see how the pack and the 12V are when I get back, maybe have to devote a few hours to getting things back in shape on the first day home, but I would like to consider a more pro-active approach.