What if Nissan had engineered the LEAF BMS like the Volt?

[DaveinOlyWA]

Agreed because it provides peace of mind like the engine on a Volt but battery capacity restricted to only be used when real dead weight of a degraded batery pack happens is never as good as breakeven

 

[RegGuheert]

I've started following the GM-Volt forum for the last 3 months and I get the impression that nobody over there knows whether GM made plan to eat into the extra capacity over the long run or not to preserve the advertised range of about 40 miles.

Yes, it is sort of a myth that likes to gets repeated here on MNL. There was a comment made in an interview to that affect as I recall but nothing remotely official.

You claim this idea is a "myth"? We can all read about it in a feature article written by Lyle at GM-Volt.com which he begins by writing:

At the recent Chevrolet Volt launch GM finally let the skeletons out of the closets and exposed all of the Volt’s closely guarded secrets.

Hmm, the article is from the Chevrolet Volt launch event. That sounds official to me.

In his report, Lyle writes the following:

As the battery ages and energy storage capacity of the lithium-ion cells degrades, control units will widen the percent state of charge band to continue to deliver the range goal.

So, what do you think, did Lyle imagine that someone at GM said this, or did someone at GM imagine that this is really how the Chevy Volt works? Both of those possibilities seem pretty remote to me considering I cannot think of any other EV BMS which does this.

After 21K EV miles in my 2011 it has not appeared to lose any range. 30 winter, 45 summer (2011/12-EPA 35, 2013-EPA 38).

That statement seems to confirm exactly the operation of the Volt that Lyle reported.

The ~22% to ~87% SOC has been shown in DASHDAQs and it will be interesting to see what the ELR shows.

It seems that DashDAQ used to report total battery capacity, but that parameter was removed back in 2011. I wonder why.

Multiple GM comments indicate they are using more of the battery. That bodes well for thier confidence.

That's good they are confident in their battery system. IMO, they should be. It seems very well-engineered.

Do you have something remotely official that indicates that Lyle's report is incorrect? If not, do you have some compelling evidence that this is NOT actually how the Chevy Volt operates. If so, please post it. If not, I will continue to believe that the battery in the Chevy VOlt does, in fact, degrade with time and use in spite of the fact that your available energy and miles do not go down.

 

[CarZin]

I would have been very pissed off if Nissan had required us to haul around dead weight which is the reason I did not purchase the Volt because that is what the Volt is doing.

You mean the dead weight in about really expensive 12 extra kWhs of battery capacity I'd have to haul around every day that I didnt need with a Leaf? We can play this game all day.

 

[Volusiano]

I've started following the GM-Volt forum for the last 3 months and I get the impression that nobody over there knows whether GM made plan to eat into the extra capacity over the long run or not to preserve the advertised range of about 40 miles.

Yes, it is sort of a myth that likes to gets repeated here on MNL. There was a comment made in an interview to that affect as I recall but nothing remotely official.

You claim this idea is a "myth"? We can all read about it in a feature article written by Lyle at GM-Volt.com which he begins by writing:

At the recent Chevrolet Volt launch GM finally let the skeletons out of the closets and exposed all of the Volt’s closely guarded secrets.

Hmm, the article is from the Chevrolet Volt launch event. That sounds official to me.

In his report, Lyle writes the following:

As the battery ages and energy storage capacity of the lithium-ion cells degrades, control units will widen the percent state of charge band to continue to deliver the range goal.

So, what do you think, did Lyle imagine that someone at GM said this, or did someone at GM imagine that this is really how the Chevy Volt works? Both of those possibilities seem pretty remote to me considering I cannot think of any other EV BMS which does this.

After 21K EV miles in my 2011 it has not appeared to lose any range. 30 winter, 45 summer (2011/12-EPA 35, 2013-EPA 38).

That statement seems to confirm exactly the operation of the Volt that Lyle reported.

The ~22% to ~87% SOC has been shown in DASHDAQs and it will be interesting to see what the ELR shows.

It seems that DashDAQ used to report total battery capacity, but that parameter was removed back in 2011. I wonder why.

Multiple GM comments indicate they are using more of the battery. That bodes well for thier confidence.

That's good they are confident in their battery system. IMO, they should be. It seems very well-engineered.

Do you have something remotely official that indicates that Lyle's report is incorrect? If not, do you have some compelling evidence that this is NOT actually how the Chevy Volt operates. If so, please post it. If not, I will continue to believe that the battery in the Chevy VOlt does, in fact, degrade with time and use in spite of the fact that your available energy and miles do not go down.

Do you believe everything every Jack and Jill or Lyle post on a forum as "gospel"? Is Lyle an official GM spokesman? Or just a poster on a forum who wrote a feature article? Did Lyle quote any GM official for saying that they do expand the band if capacity is lost?

Nobody needs to prove that Lyle's report is incorrect. I only need to read through that to see that he didn't quote any GM official when he made that statement. The fact that many OTHER things he said in there are correct doesn't mean that his statement about expanding the capacity band is also correct. GM never officially say anything about it, except maybe for Lyle here who's not GM. So that's why it's a myth until officially confirmed by GM.

 

[TomT]

It's very simple for me: My next EV will have a TMS. Period. End of discussion.

 

[planet4ever]

Do you believe everything every Jack and Jill or Lyle post on a forum as "gospel"? Is Lyle an official GM spokesman? Or just a poster on a forum who wrote a feature article? Did Lyle quote any GM official for saying that they do expand the band if capacity is lost?

I haven't kept up with gm-volt.com, but Lyle was the original creator of that forum. He got (I think) the very first Volt. He was never employed by GM, but did have many interactions with Volt designers and implementers, and was given a good deal of inside information. Lyle is no "Jack or Jill".

Ray

 

[Volusiano]

Do you believe everything every Jack and Jill or Lyle post on a forum as "gospel"? Is Lyle an official GM spokesman? Or just a poster on a forum who wrote a feature article? Did Lyle quote any GM official for saying that they do expand the band if capacity is lost?

I haven't kept up with gm-volt.com, but Lyle was the original creator of that forum. He got (I think) the very first Volt. He was never employed by GM, but did have many interactions with Volt designers and implementers, and was given a good deal of inside information. Lyle is no "Jack or Jill".

Ray

Lyle may be no Jack or Jill, but Lyle is no GM official either.

How many other credible non-GM sources have confirmed this same thing beside Lyle?

There's nothing wrong with calling it a myth because GM never officially confirms this and only 1 non-GM source said this.

 

[RegGuheert]

There's nothing wrong with calling it a myth because GM never officially confirms this and only 1 non-GM source said this.

Sorry, that does not make it a myth. It still stands as the very best explanation of how the Chevy Volt manages its battery.

The myth is the idea that Chevy Volt batteries do not lose capacity with time and use.

 

[Volusiano]

There's nothing wrong with calling it a myth because GM never officially confirms this and only 1 non-GM source said this.

Sorry, that does not make it a myth. It still stands as the very best explanation of how the Chevy Volt manages its battery.

The myth is the idea that Chevy Volt batteries do not lose capacity with time and use.

Wow, even GM said on their own warranty statement that users should expect 10-30% capacity loss during the 8 years 100K miles warranty. So who said anything about Volt batteries not losing any capacity with time and use???

Only Volt owners of barely 2 years old Volts said that they have not seen any noticeable capacity loss SO FAR. But the oldest Volts are barely 2 years old so far, so it's logical that noticeable capacity loss has not occurred YET. This also makes sense in light of the Volt having TMS and the ICE to protect owners from taking the Volt battery to its extreme limits. Heck, even 2-year old LEAF owners in cooler climate say they still have 12 capacity bars remaining on their display with no noticeable loss so far. So it's premature and far reaching to translate this into "Volt batteries don't lose capacity with time and use".

Just the fact that GM said to expect 10-30% capacity loss over 8 years 100K miles already implies that they don't go all out with the BMS trick to keep the range constant, even if they did any which they're not admitting.

If Nissan and GM are telling customers the same thing, to expect up to 30% capacity loss in about 10 years, how does that translate to GM programming their BMS differently to expand the range?

So I still think it's speculation and a myth at this point to assume that GM goes all out with the BMS trick. If they did, why wouldn't they advertise that fact to their advantage as a marketing point, instead of still cautioning users to expect up to 30% loss?

 

[RegGuheert]

If they did, why wouldn't they advertise that fact to their advantage as a marketing point, instead of still cautioning users to expect up to 30% loss?

Because they are in a competitive marketplace and they consider this fact to be a trade secret. The fact that owners like you believe that the TMS prevents battery degradation is good marketing, as well.

Sorry, the idea that Volt owners are not seeing degradation because the batteries haven't degraded enough to notice is really too much for me to believe. There are many Volts which receive an 80% DOD each day in a hot climate and are charged to 85% SOC and left there, some in hot climates.

Don't expect Volt owners to see and degradation in kWh or miles within the next couple of years because it is being hidden from them. Eventually, it the batteries will start to go beyond the point where the BMS can hide it and we will start to have an idea how they are doing. As mentioned previously, GM is only guaranteeing 70% of 65% or 45.5% of the battery's capacity. I think they will achieve that in most cases.

 

[Volusiano]

The fact that owners like you believe that the TMS prevents battery degradation is good marketing, as well.

It's not just good marketing when just about every other manufacturers except for Nissan chose to do TMS even though it raises their cost of manufacturing. It's not good marketing but actually good engineering. Mitsubishi is the only other company that doesn't do TMS, but due to the same reason that Nissan doesn't do it, to keep the cost down.

As far as what owners choose to believe, we have seen plenty of LEAF owners, even not in hot climate like in CA (like TomT) who publicly said that they'll never ever buy another EV without TMS anymore. Tony Williams (who lives in CA, too) abandoned the LEAF for a RAV4 EV which has TMS.

On the other hand, we have not seen a single owner of the Volt or Tesla or Rav4 EV say that they wish their car didn't come with TMS after all. And this is not just new buyers, but owners who have lived with their TMS EVs for at least 2 years so far.

So you can call these owners naive and being duped by good marketing all you want. I call them sensible owners who learned through their own experience (of having a TMS or not having a TMS on their EV) the value of TMS.

 

[RegGuheert]

The fact that owners like you believe that the TMS prevents battery degradation is good marketing, as well.

It's not just good marketing when just about every other manufacturers except for Nissan chose to do TMS even though it raises their cost of manufacturing. It's not good marketing but actually good engineering. Mitsubishi is the only other company that doesn't do TMS, but due to the same reason that Nissan doesn't do it, to keep the cost down.

Trading off cost for capability is a very reasonable design decision.

As far as what owners choose to believe, we have seen plenty of LEAF owners, even not in hot climate like in CA (like TomT) who publicly said that they'll never ever buy another EV without TMS anymore. Tony Williams (who lives in CA, too) abandoned the LEAF for a RAV4 EV which has TMS.

Yes, but I don't think they believe a TMS can prevent battery degradation, only that it reduces it in hot climates. So far, the Chevy Volt has shown NO reduction in available capacity or range regardless of age or miles even though it has the smallest battery of the lot. You seem to believe this is due solely to the TMS. I contend that the BMS is what makes this possible. And don't get me wrong: I think this is a very clever approach for the BMS.

On the other hand, we have not seen a single owner of the Volt or Tesla or Rav4 EV say that they wish their car didn't come with TMS after all. And this is not just new buyers, but owners who have lived with their TMS EVs for at least 2 years so far.

Note that the battery in the Volt is 1/3 the size of the battery in the RAV4EV and 1/5 the size of the battery in the Model S. Also note that the battery in the Volt uses a chemistry very similar to the chemistry in the LEAF which is much less capable of handling heat than that used in the RAV4EV and Model S. In those vehicles the combination of a big battery, a better battery chemistry and TMS reduce battery degradation to very low levels. The Volt has the TMS, which can help it in hot climates, but it has the drawback of a small battery and a less robust chemistry. So GM chose to use a BMS technique to both reduce battery degradation earlier in life AND hide degradation from their owners.

So you can call these owners naive and being duped by good marketing all you want. I call them sensible owners who learned through their own experience (of having a TMS or not having a TMS on their EV) the value of TMS.

They have only been duped if they believe TMS prevents battery degradation. I doubt they believe that. But I think they feel it is the best option for their application.

It still remains to be seen if TMS provides much benefit in other locations. It certainly has drawbacks. Cost is one of them. The other big one is e effect it has on battery maintenance. One Volt owner has complained that his Chevy dealer got coolant all I've the electronics in his Volt when they serviced his battery. No, thanks. I'll take a bigger battery instead where I live.

 

[edatoakrun]

="RegGuheert"

...It still remains to be seen if TMS provides much benefit in other locations. It certainly has drawbacks. Cost is one of them...

When the increased cost of active TMS is discussed, usually only the much higher manufacturing cost is taken into account.

Remember, a TMS vehicle will use more energy in heating and cooling the battery, so you will have to pay for the increased kWh use.

When the TMS BEV/PHEV is not plugged in, those kWh come from the battery pack, in itself "degrading" the battery, by increasing cycling from this discharge.

The cooling mode is where the active TMS advantages over a passive TMS BEV/PHEV are greatest, IMO, as it will increase battery pack life in hotter climates.

However, the offsetting maintenance and repair costs that will be imposed by requiring your vehicle's cabin air conditioner to do double duty as a battery pack refrigerator are probably underestimated.

I have no idea how long you can expect the very complex cooling systems on active TMS vehicles as on the Volt to last without maintenance or repair, or how these repair and maintenance costs (ever had pay to replace your ICEV's AC system?) will compare with simply replacing the battery a few years earlier, as you should expect to have to do in hotter climates with BEVs like the LEAF, that do not use ATM.

I do expect that battery costs will continue to decline at a fairly rapid pace in the future, while I expect the cost of kWh, and the cost of both ATM systems and the labor to repair and maintain them will not.

So, if even Nissan's decision to passive ATM was not the more economic choice today, I expect it was the better choice for the future, and that all BEVs will use passive (or semi-passive thermostatically controlled access to ambient temperatures) battery cooling for thermal management, in the fairly near future.

The high cycling rates of the smaller-battery and shorter-EV-range PHEVs, probably mean ATM will continue to be used in them longer, and they may still have ATM, if PHEVs are still being built in large numbers, ten years or twenty years from now.

 

[Volusiano]

TMS only helps reduce battery degradation due to heat, but of course it doesn't prevent battery degradation due to calendar time or cycle counts.

TMS also helps increase range in cold weather by keeping the battery warmer.

Of course TMS doesn't just cost in terms of manufacturing, but will use more energy to heat or cool the battery. But not all of that energy is always from the battery. In fact the majority of it is probably from the wall since the car probably spends more time a day being charged than being driven.

Of course there are trade-offs to having TMS, including higher maintenance cost as well. But obviously all these trade-offs are deemed well worth it at this point by most manufacturers in light of the lack of maturity in battery technology to have a more heat resistant chemistry.

We're not debating the merits of TMS 5 or 10 years down the road. We're only debating the merits of TMS today in face of the current infancy of immature battery technology.

 

[RegGuheert]

But obviously all these trade-offs are deemed well worth it at this point by most manufacturers in light of the lack of maturity in battery technology to have a more heat resistant chemistry.

Agreed. If you are going to sell the car in a wide range of climates with the current battery technology, then TMS makes good sense.

We're not debating the merits of TMS 5 or 10 years down the road. We're only debating the merits of TMS today in face of the current infancy of immature battery technology.

And for me, today, the TMS/smaller battery combination does not look good. Perhaps Nissan is focused on the long-term rather than the short term. The question is whether or not they will create so much bad will that they will not make it to the long term with their approach.

In any case, the topic of the thread is BMS, not TMS.

 

[edatoakrun]

....We're not debating the merits of TMS 5 or 10 years down the road..

Well, I am considering the merits of the TMS in terms of total operating costs for the life of my BEV, which does extend another five to ten years into the future, and quite possibly even longer.

Two years ago, I felt passive TMS was probably superior, for my "warm" climate use, and I still do today.