Is it better to keep the 500e battery topped off of run it to near zero % charge before plugging it in?


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The batteries are actually happiest around 70% charge. I would suggest recharging at around 50% where possible. This also minimises the risk of a weak cell causing problems.

All lithium batteries give a "longer charge life", i.e. most KWH over their life if charged/topped off... the deeper a lithium battery is discharged, the more it wears the battery.

i.e. for the same total watt hours consumed, the battery will have more "life" if it is discharged 1/2 way 1000 times (and charged of course) as compared to discharged fully 500 times.

You can find this info on any manufacturer's site that makes lithium ion batteries...

Greg

Greg Elmassian said:

All lithium batteries give a "longer charge life", i.e. most KWH over their life if charged/topped off... the deeper a lithium battery is discharged, the more it wears the battery.

i.e. for the same total watt hours consumed, the battery will have more "life" if it is discharged 1/2 way 1000 times (and charged of course) as compared to discharged fully 500 times.

You can find this info on any manufacturer's site that makes lithium ion batteries...

Greg

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Complicated somewhat by the battery management software - what it reports as a percentage charge may not be the same as the actual charge state of the cells.

Laptops, mobile phones etc are designed to switch off before they discharge to a level which will seriously harm the battery; what they usually are programmed to display as a percentage charge is the percentage to cutoff, not percentage to true discharge.

Charging over 80% will also shorten battery life, so keeping them fully charged is not the best policy if you want maximum life. As UFI says, the sweet spot is around 70-75%.

Totally NOT connected to cars .........

Lithium Ion batteries are in many things these days. We have a couple of laptops and a Garmin device using them here at home, let alone the iPad, the iPod and the three mobile phones.

The laptops spend most of their lives connected to the charger via the mains, and the Garmin get charged as soon as I get home, the others get charged when they complain, but it's always to 100%.

What you are saying seems to go against the instruction manuals. This also seems to go against accepted wisdom with electric vehicles generally.

A bit mystified,
Mick.

Mick F said:

The laptops spend most of their lives connected to the charger via the mains, and the Garmin get charged as soon as I get home, the others get charged when they complain, but it's always to 100%.

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You are shortening the life of their batteries by doing this. If using a laptop connected to the mains for any length of time, it is better to remove the battery pack completely.

Read the full story here.

Note in particular:

"Let’s look at real-life situations and examine what stresses lithium-ion batteries encounter. Most packs last three to five years. Environmental conditions, and not cycling alone, are a key ingredient to longevity, and the worst situation is keeping a fully charged battery at elevated temperatures. This is the case when running a laptop off the power grid. Under these conditions, a battery will typically last for about two years, whether cycled or not. The pack does not die suddenly but will give lower runtimes with aging."

Thanks for that JR, very interesting.
I have never been told this before.

Question:
Why don't laptops cycle the charging/discharging whilst still physically connected to the mains? It would be a simple process via firmware. Same could be said for mobile phones and other devices.

Going back to electric vehicles, surely the whole idea of an EV is to get maximum range between recharges? Therefore, you charge when you can, and go as far as you can, so 100% is the aim at each recharge.

By doing this, you are shortening the battery life, and therefore you'd be better only doing short journeys and charging up at home, but turning the charger off at 80%? Can the switching off at 80% not be done automatically at the expense of range per charge, but with the dividend of longer battery life?

Still puzzled,
Mick.

JR is correct. The Prius for example keeps it's battery at 40-80% this is a good example because the car has a long battery warranty (in the US at least) and is not range limited by not fully charging.

Electric vehicles would look a bit silly if the manufactures limited their range to only the small fraction of LiFe capacity that resulted in maximum life. The same goes for a phone or laptop, it can't charge to 80% because it doesn't know whether you'll be charging again in an hour or if you need the battery to last all day.

Besides, there's money to be made in replacement batteries (and not just for cars). Compare the cost of a genuine phone/ laptop battery to just replacing the phone..

Hi guys, and good morning.
Yeah, ok, it's a poor day if you don't learn something!

Back to the OP.
He asked if it was BETTER to top it up and run it down.
It's the "better" part of this question that we're discussing.

It's better to use as much battery capacity as you can at the expense of longevity IMHO. To keep it at the optimum 80% ish, would seriously risk the EV convenience and range.

Regards,
Mick.

Mick F said:

It's better to use as much battery capacity as you can at the expense of longevity IMHO. To keep it at the optimum 80% ish, would seriously risk the EV convenience and range.

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For all you know the OP could drive no further than the local shops. If that was the case I'd do my best to keep it in the 40-80% window. In fact I was going to do an EV conversion on an old Suzuki I have just for short trip use (less than 10km a day) with a total range of 20km, would have kept in that maximum battery life window perfectly.

I've done the sums too and really looked at the Nissan Leaf, the money saved in petrol in my case would likely be equaled by battery replacement.

Yep.
I've looked at the figures too, and the high purchase cost, plus the battery replacement is equal to or greater than a comparable petrol car, let alone the electricity cost.

Even looked at the Renault offerings, but you have to pay a monthly charge to lease the battery.

No such thing as a free lunch.

Best wishes,
Mick.

So where does the Tesla fit in?

Servicing will be cheap though which isn't to be scoffed at.

Sweetsixteen said:

So where does the Tesla fit in?

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It's an expensive toy. The base model is around eight grand down, then over £1000/mo on a 4yr contract.

I can't see many of the folks who buy one being all that concerned about this sort of cost/benefit analysis. You're not going to finance this sort of purchase out of the fuel savings.

Manshms said:

Is it better to keep the 500e battery topped off of run it to near zero % charge before plugging it in?

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Have a read of this and you will realise that the answer to your question is much more complicated than you may perhaps have first thought.

Much of this information is new to me and I was surprised to discover that the mean temperature of the place where the car is kept and used may be more significant in determining battery life that the number of times the battery is cycled. That said, I have for some time stored Li-ion batteries not in regular use in the 'fridge, charged to about 50% of capacity.

The key point to take away is that you might want to reconsider purchasing an electric vehicle if you live in a hot climate - most premature EV battery failures reported in the US have been in Arizona.

jrkitching said:

Have a read of this and you will realise that the answer to your question is much more complicated than you may perhaps have first thought.

Much of this information is new to me and I was surprised to discover that the mean temperature of the place where the car is kept and used may be more significant in determining battery life that the number of times the battery is cycled. That said, I have for some time stored Li-ion batteries not in regular use in the 'fridge, charged to about 50% of capacity.

The key point to take away is that you might want to reconsider purchasing an electric vehicle if you live in a hot climate - most premature EV battery failures reported in the US have been in Arizona.

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It is true that the temperature during use (charging/discharging) is important, but a large amount of EVs (including the 500e) have active cooling and heating to maintain the battery at an appropriate temperature.

An EV that has suffered in climates such as Arizona is the Nissan Leaf most publicly as that only has passive temperature control of the battery.. i.e. the battery gets rather warm in those conditions!

The UK is pretty much an ideal climate for a battery powered vehicles, nothing too hot or cold

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As far as the OPs question I would say that as much as I know the ideal situation is (as mentioned) using say the 40-80% range of the battery regularly.

I don't know if the 500e has a "charge to 80%" mode or equivalent but if it did I would plug it in at the end of the day on that setting. If it doesn't, to be honest I would still plug it in every day, the convenience is better than any potential battery life lost, which as the 500e is thermally managed should be minimal. If you are leasing the car this is even less of an issue.

I say plug the car in every day and enjoy it

jrkitching said:

It's an expensive toy. The base model is around eight grand down, then over £1000/mo on a 4yr contract.

I can't see many of the folks who buy one being all that concerned about this sort of cost/benefit analysis. You're not going to finance this sort of purchase out of the fuel savings.

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I have to disagree with that statement, premium/luxury cars these days cost well in excess of £30-40k the cheapest tesla is £50k and has luxury kit that puts many £60-70k cars to shame, in addition to that the technology that's gone into the electric motors and battery not only puts many sports cars to shame with a 0-60 of something around 4seconds in destroys most other electric vehicles on rage at 300miles in normal use for the bigger battery version. Yeah it's expensive and out of the range of many people, but it's ground breaking and setting new standard in the ev industry.

By comparison the Nissan Leaf which is getting more and more popular will get you a maximum 124miles, without going past 38mph and with no heating or aircon, and that's going to cost at least £22k

You can do deals to rent the leaf battery which can cost nearly £100 a month so you don't have to worry about battery problems, mean while the tesla gives you an 8 year battery and motor warrantee.

When you talk of cost benefit analysis, the sort of person buying a tesla will be swapping it for something a bit more fuel thirsty than a 1.2 500

So yes it's expensive but you certainly can't call it a toy, it's a proper car in its own right

I read the battery university site... it's well known... not the be all end all of knowledge, but few mistakes on the site.

The first page says partial discharges (and thus partial recharges) increase battery life.

Where is this statement by the battery manufacturer that says do not charge over 80%?

Also, it seems that many people are using old knowledge that applies to nicad battery charging in their statements, LiIon chargers cut off completely when the battery is full..

I stand by my previous statements, and this is not my first time with rechargeable batteries.

Greg

306maxi said:

Servicing will be cheap though which isn't to be scoffed at.

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You'd think so but apparently a service on a Leaf costs $400

Greg Elmassian said:

Where is this statement by the battery manufacturer that says do not charge over 80%?

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http://powerelectronics.com/portabl...y_charger_ics/804PET22li-ion-battery-life.pdf

Like I said earlier, it would simply be bad publicity to advertise 'don't use this product to it's maximium capacity', especially since so many batteries are over rated. The manufacturers really don't want you to get maximum life out of a battery either.

Figure 2 plainly demonstrates that charging a 4.2v cell to 4.0v can more than triple it's life, this happens to be the 70% figure of my first post

The 40-80% figure was quoted by Toyota in relation to the Prius. Nicads and Nihms did best when fully charged and discharged, I don't think anyone's got confused there?