Tesla Roadster #570 EU
Status | Your Roadster has over 17000 km on the odometer, 293 km range on standard charge.
That's kind of how I look at it too. I'm sure it's possible to outsmart Tesla's engineers but I'd imagine the savings will be very small as you said. It also takes one of the EV advantages away which is leaving home with a full 'tank' each day, even if you rarely need it.
I didn't mean to imply that the Tesla engineers weren't doing an amazing job. I think the Roadster has been great and the Model S looks to be even better.
Last edited by dsm363; 03-27-2012 at 04:42 AM.
>Can I ask you by taking these precautions after eight years what is the efficiency of the batteries?
hcsharp reported in the battery log thread that he still gets 245 miles in range mode, so I think his charging practice is working for him
>Heat aggravates the microcracking process, so keeping your battery cool contributes to longer battery life.
@hcsharp to contradict that for sake of argument, if you don't need to charge then why charge it? Ignoring the fact of emergency miles... Since heating will result in heating the pack up. So wouldn't be better to not charge it if you don't need to and are over 50%? I think its also key to charge at a lower ambient temperature if possible.
I don't want the SOCs to be sitting higher than 50% with nothing to do (if you know you're not driving the roadster til the morning). So for me I have the Roadster begin its charge so that its completed 1 hour before I leave for work. The one hour gives time for the pack to equalize and cool. Anytime you can allow the pack to cool is a good thing. Then I drive 35 miles to work, for which I pull the SOC down from 185 ideal miles to 150 (81% SOC). The roadster sits unplugged all day, I then commute back home another 35 miles and my ideal miles is at 115 miles (62% SOC). I then plug the roadster, where charge is not initiated until the next morning, in where the cycle starts again where my charge initiates 1hr before I need to depart for work. Over the weekend I don't do too much driving since I live in Santa Cruz and its a resort for me, beaches, bike rides, sun and kayaking in the ocean I leave the roadster unplugged typically over the weekend holding the 60-62% SOC. So my working SOC is between 60% and 81% give or take a few %'s A SOC range the battery pack should like. The one thing I would need to do every so often is to rebalance / equalize the battery pack. The best way to do this is to leave it sitting in Standard Mode for a long duration. If you're going on a trip for a week it is most likely adventurous to use this down time of the EV to equalize. I'd let it sit the week in Std. mode. I was told the battery pack begins this equalization process of the battery pack whenever the SOC is over 80%.
I know the LiPo battery packs tested in consumer electronics favor the 50% SOC in longevity tests I've seen and reviewed with a battery engineer I work with (who's also an EV enthusiast).
Last edited by wiztecy; 09-03-2012 at 11:11 AM.
The thing about leaving the battery at lower SOC is that the cell voltage slumps a bit. That means that the car has to draw more current to maintain the same power level, which would mean more heating and stress on the battery. So storing the car at lower SOC is better for the battery, but operating the car at lower SOC is not.
Thanks Doug and for the background on the battery science technology Henry. Makes sense and very good points to keep in mind. Another thing to consider is AMPs to charge. I believe Tom did an analysis on what Amps are the most efficient to charge at and his curves showed 30Amps ( I need to revisit it if that was the exact Amps, I believe so). Any lower and its inefficient in terms of cost to push the amps across the line. I believe above 30 Amps you start building up heat and heating up the battery packs more than necessary. When I charged at Tesla down in Santa Row they had the 70amp quick charger. I wasn't in a hurry and my charge not too low so I dialed it down to 30Amps in the Roadster.
There's the factor of time that batteries have a constant shelf life. But it does mean your battery should be more reliable and healthier if you understand the battery technology as well as the physical and electrical principals that are tied to it. The battery logs research is a big part of this and I encourage all to participate. I know every time I stop at Tesla to have anything done they pull my logs. I'm sure they're doing the same and much more analysis on this data as we are to understand battery and charging characteristics based on multiple variables.
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