My Nissan Leaf Forum

Like many here, I have battery life anxiety to go along with my range anxiety!

Unlike most, I have an incentive to charge during the daytime rather than at night. The reason is that our solar array produces about 8 kW during the sunlight hours. There is a long run back to the meter from the array. While the microinverters produce 240 VAC and I used fairly large wire, I think there may still be a percent or so of voltage drop. So the plan has always been to feed the EV and the array from the same sub panel to eliminate losses in both directions. To my knowledge, our electricity provider does not offer time-of-use metering, so I have no incentive to charge at night from that angle.

But some anecdotal evidence I have read here makes me wonder if perhaps charging at higher ambient temperatures may adversely affect the life of the battery in the Leaf. Of course the charger is temperature compensated, but high temperatures do tend to have the effect of making things wear out more quickly.

So my question is this: Is there any reason to believe that I will get more life out of the battery pack by charging in the cool hours of the middle of the night versus during the heat of the day this summer?

A secondary question would be for winter: It does seem likely that charging during the warmest hours of the day would be more efficient than charging during the cold of the night in winter. Is that correct?

Finally, I'm wondering if I will get better battery life if I charge at a lower power. I understand that There is a fixed 100 W draw, so efficiency drops at lower charging power but will it be better for the battery? I will soon have the options here to charge at 120 V @ 12 A, 240 V @ 12 A or 240 V @ 16 A.

Please provide links to specific data for the Leaf battery or at least Li-ion information if you can.

TIA!

I have no idea. Given that you're in "Northern VA", high day-time temperature is probably not one of your concerns, and also not a concern with battery charging (thought that's pure conjecture on my part). I'd say you have far less to be concerned about than those of us in Arizona or Texas. During the summer here in Austin, it's not unusual for night-time low to be in the mid 80s.

OT- But, are you sure about that, that at no time in the future you will receive a TOU rate option, or that there are no benefits to night charging, beyond a preferred rate?

Virtually all American utilities, and the electric grids they connect to, experience their highest demand in the day, particularly on hot afternoons, due to demand for Air conditioning. They generally meet demand spikes by operating the most costly, least efficient (in terms of energy conversion) plants, typically low efficiency "peaker" natural gas plants.

So, while your rates may not reflect this (yet) you would almost certainly be reducing both the total CO2 output of the grid you connect to, and the total cost of providing electricity to all ratepayers, by charging at night, as it sounds like the marginal reduction in your own efficiency of electricity production and use, by night time charging, would likely be far less.

It's unfortunate that your utility does not have rates that reflect this reality, and provide you a fair return for the premium product you provide, peak demand kWh.

Most all BEV/PHEV drivers now face similar situations, with other failures of market signaling, as is the case when we are given the opportunity to replace paid off-peak charging at night with "free" public opportunity charging.

If you are plugging in during the day, when you could just as easily wait till you got home, to charge overnight, you are almost certainly imposing both short term economic costs on others, and long-term environmental costs, on everyone on the planet, present and future.

I am not trying to suggest what the correct action is to take in any of these situations, I'm just pointing out that your decision, may not always be based exclusively, on immediate cost considerations.

ok I have a side question, how did you manage a 9.87kw system in Northern Va with the limited tax credits
who did the install and is it leased or purchased?

In the summertime the high temperature can get to 105F during the day and 80F during the lowest part of the night. That doesn't happen every year nor will it last longer than a week or so in the years that it does happen. This year we have had the warmest winter that I can remember. If this trend continues into the summer, it will be a very hot year. I haven't measured the temperatures in our garage, but I imagine they are slightly moderated from the outdoor temperatures, although I am not sure.Agreed I have less to be concerned about than those places, but my goal is to have this car for 20 years as our main runaround car with typical round-trip lengths ranging from 15 to 50 miles. Some of those trips require scaling a 1000-foot elevation twice and sometimes the trips will be made at 10F. I seriously doubt the car has the range to make the 50-mile trip with 2 mountain crossings at 10F today. Any reductions in range will eliminate some trips we could make, thus reducing the utility of our purchase.

Since I am a firm believer that charging is the main killer of batteries and we have nearly full control of when we charge, my intention is to charge at whatever times (temperatures) tend to give the best cycle life. Clearly there is a window of temperatures which is optimum for charging the Leaf to ensure the best battery life. I am trying to determine what that window is.

I was told by Nissan CS that charging at L2 (240v) is best. It's built for that. I have no idea on the best temperature to charge at, but I think as close to 70F is best (just my opinion); unfortunately that's not always possible as I usually have to charge while sitting outside.

IMO - it's not the charging that is the main killer of batteries (certainly not at at the trickle charge L1/L2 rates) - it's storage of the car in high temperatures and high SOCs that is the killer. The higher the SOC of the battery during that time spent sitting at high temperature, the faster the battery will age.

Avoid charging to more than 80% unless you think you'll need the extra range and if charging to 100% time the charge so that it finishes as close as possible to departure time (it takes right around 90 minutes to go from 80-100% but the last 30 minutes the charge rate ramps down).

No, I am not. In fact, I am asking in this post whether there is benefit in terms of battery life in charging at night.Here is a link to our electricity provider, Rappahannock Electric Cooperative (REC). I do not know what their demand curve looks like, but it seems to me that they have been taking rural customers off the hands of the larger utilities that no longer want to deal with them. If the great majority of REC's customers are rural, I would be not too surprised to see peak wintertime demand occur in the early hours of the morning when all the heat pumps and emergency resistive heaters are on. But I am sure you are correct that the peak demand during most of the year is during the daytime.There are a lot of assumptions in what you say regarding how electricity is generated around here. Most of the base electricity generation comes from coal with some nuclear. While I do not know the exact make-up of peakers in the area, I do know that there is a 600 MW pumped-hydro peaker in VA. I'm pretty sure this peaker is used to allow the utilities time to bring coal power on and off-line. I'm not aware of any natural gas peakers in the region, but there may be some. We do not have natural gas lines in the immediate vicinity, but neither do we have power plants (except for a few solar arrays).

The point is that my electricity is produced by either coal or nuclear with peaking done using hydro. If we can more efficiently use the PV solar that we produce *and* more efficiently charge the EV that we have, then I have *reduced* the amount of electricity that I will consume overall and hence the amount of coal that is burned. And in either case this house will be a net producer during the daylight hours most days.
We *just* got an electronic meter last June which is capable of tracking time of electricity usage, so I am hopeful that they will soon offer more attractive rate plans.I'm not sure whether you are referring to a singular or plural "you", but I am proposing to charge during the day in the wintertime and at night in summertime to try to improve battery life, both of which are possibly off-peak for my utility. I expect any improvements in battery life would have a very positive long-term effect on the environment.I hope you will agree that the essence of the question in this post pits the long-term cost, both to me and to society in general, of the battery against the short-term savings that I could gain by charging when the sun shines. It is all about conservation.

Since you have plentiful free electricity, why not air condition the garage where the Leaf sits while charging?

Since you are in this for the long run, instrument the battery case with a temperature sensor, then you will know how hot it gets.

I suspect many Leaf owners will be updating batteries as they evolve, whether they need to or not.. there will be lots of used batteries for sale. Its like a hobby

You have a high mix of nuclear power in your utility.. 38.6% nuke, 51.1% coal

This site will tell you:
http://www.epa.gov/cleanenergy/energy-a ... clean.html

To be honest, we purchased a kit on eBay and installed it. At the time we purchased, the plan was to sell SRECs to Washington, DC for about $0.25/kWh since they were allowing neighboring states to participate at that time. Between that, the federal tax credit and net metering, we expected the system would have paid for itself in 5 or 6 years and been cash positive after that. Unfortunately the SREC prices in Washington DC collapsed due to oversupply and they closed their borders last August. Oh, well.

We can still sell SRECs into PA, but those prices have also collapsed, so I expect they will also close their borders. If everything stays the same for the next 20 years, then I expect our system will just break even. But I think that is highly unlikely. It seems that the electricity market in VA is about to be deregulated, which will likely greatly increase prices if VA is anything like neighboring states. I also expect to benefit from TOU metering in the future.

Only time will tell, but experience tells me that this type of investment tends to pay off in untold ways. For instance, when we purchased our Honda Civic Hybrid ten years ago, gasoline cost $1.65/gallon. I did a calculation that I would need to drive 100,000 miles on $2/gallon gas to pay back the $4000 extra on the price tag. After 10 years and 90,000 miles, gasoline costs $3.75/gallon and the HCH is still going strong! I suppose the hybrid system has paid for itself at this point and will continue to pay benefits to us and the environment. We will see.