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Only charging in Hilltop Reserve, Cons?

9503 Views 12 Replies 9 Participants Last post by jostafew, Nov 9, 2017

npgeorgeuw

Discussion Starter · Nov 6, 2017

Another user suggested that Hilltop Reserve charging my somehow skew or lead to mis-estimated battery range calculations... Any evidence anyone has noticed with this? I have had cell phones that needed full discharging to re-calibrate their battery meters but I can't fathom that our cars would use such a primitive estimate system...

As I live on a good size hill (but apparently not good enough to fill the battery when descending) it becomes truly annoying and sad to lose the recouped capacity and any ability to regen the full 7 miles back to work. Basically, this means my car has never been fully charged (ever) and also that I wish the car was a bit smarter and would adjust the Hill Top Reserve over time.

I was under the impression that over the years, Hill Top Reserve charging would only ever help overall battery capacity since you never charge the pack fully and will be in the sweet spot for more time in the pack's life.

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LectricBill

· #2 · Nov 6, 2017

I too use Hilltop Reserve almost all of the time, for the last 5000 miles.

Haven't noticed it skewing anything. The variation that the previous trip's driving experience factors into the GOM seems to far outweigh any variations that might arise from not charging fully.

When I DO charge fully, the estimated range seems to me consistent with when the battery was new.

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surgeonFWW

· #3 · Nov 6, 2017 (Edited)

Most people (90%) find their daily driving to be under 60 miles. Even more (95%?) find it less than 120 miles. The 24 range miles you lose with Hilltop Reserve (10% of 240 miles) is of no consequence to 99% of drivers. HR is not designed “to fill the battery when descending”. Rather, it it exactly what you stated: ability to have regenerative “ braking” every time you drive, and, “minimize” battery degradation over the life of the battery. {As a bonus, why throw away those 7-10 range miles you spent climbing by not being able to recoup them on the way back down.}

Sure, you always have the chance of an unexpected trip erasing 60-90 miles of range. This would suggest nightly charging, not 100% charging. {You don’t want to drift down to 70 range miles on Wed. night, planning to charge after your 20 mile commute on Thur., then remember that meeting at a town 40 miles away when you awake.} Charging to 90% (216 miles instead of 240 miles) will virtually never put you in a bind.

Welcome aboard and happy (safe) driving!

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npgeorgeuw

Discussion Starter · #4 · Nov 6, 2017

surgeonFWW said:
Most people (90%) find their daily driving to be under 60 miles. Even more (95%?) find it less than 120 miles. The 24 range miles you lose with Hilltop Reserve (10% of 240 miles) is of no consequence to 99% of drivers. HR is not designed “to fill the battery when descending”. Rather, it it exactly what you stated: ability to have regenerative “ braking” every time you drive, and, “minimize” battery degradation over the life of the battery. {As a bonus, why throw away those 7-10 range miles you spent climbing by not being able to recoup them on the way back down.}

Sure, you always have the chance of an unexpected trip erasing 60-90 miles of range. This would suggest nightly charging, not 100% charging. {You don’t want to drift down to 70 range miles on Wed. night, planning to charge after your 20 mile commute on Thur., then remember that meeting at a town 40 miles away when you awake.} Charging to 90% (216 miles instead of 240 miles) will virtually never put you in a bind.

Welcome aboard and happy (safe) driving!

Agree completely. Perhaps, since everything is always a compromise for demographics, an adjustable or learning Hill Top Reserve is in the future for gen 2 Bolt? On a semi-related note, I will say that that extra 8-10% might have saved me the ulcer I nearly developed and forgone the night my car spent not charging at home on the mountain but rather charging near my work in the lowlands since the battery was spent.

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Dimitrij

· #5 · Nov 6, 2017

npgeorgeuw said:
Agree completely. Perhaps, since everything is always a compromise for demographics, an adjustable or learning Hill Top Reserve is in the future for gen 2 Bolt?.

This idea crossed my mind the other day, because I could benefit from a 2% hilltop reserve. Should be a simple software patch. That is, if Chevrolet cares enough.

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surgeonFWW

· #6 · Nov 6, 2017

Dimitrij said:
This idea crossed my mind the other day, because I could benefit from a 2% hilltop reserve. Should be a simple software patch. That is, if Chevrolet cares enough.

But does charging to 98% reduce battery degradation enough? I’m sure this is an exponential curve and not a dropoff. Why 10% and not 15%? Did GM already pick the optimum balance... the 45 degree tangent line?

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· #7 · Nov 6, 2017

npgeorgeuw said:
...I was under the impression that over the years, Hill Top Reserve charging would only ever help overall battery capacity since you never charge the pack fully and will be in the sweet spot for more time in the pack's life.

:nerd:I've achieved actual 260 miles plus EV range on every 100% charge (once below 60 miles remaining) in four month. I chose the Bolt was many reasons, but especially the range. With a EPA rated 238 miles EV, and more depending on driving style, why settle for less. I could care less for the possible small regen when using Hill Top Reserve. Save my Bolt's battery for what, who, and when. Sound like a "safe space" for "sensitive" lithium batteries. I submit the following:

"The Bolt EV battery is covered by the electric-car propulsion warranty (8 years, 100,000 miles and higher for CARB states) and Bolt EV customers shouldn’t expect to pay parts costs for warrantied repairs.

In [almost seven] years of Volt sales we have yet to replace a single battery pack under warranty for general capacity degradation, and many owners are still reporting they enjoy the same range capability they had when they purchased the car".

My Bolt is a lease and I won't have it in eight years, the same for many here, and definitely won't achieve 100,000 miles. I'll continue to charge to 100% on every charge to ensure I have max range available. Hill Top Reserve might benefit some, but for saving the battery is over stated. I'm a consumer, and I'm going to consume.

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npgeorgeuw

Discussion Starter · #8 · Nov 6, 2017

-1- said:
:nerd:I've achieved actual 260 miles plus EV range on every 100% charge (once below 60 miles remaining) in four month. I chose the Bolt was many reasons, but especially the range. With a EPA rated 238 miles EV, and more depending on driving style, why settle for less. I could care less for the possible small regen when using Hill Top Reserve. Save my Bolt's battery for what, who, and when. Sound like a "safe space" for "sensitive" lithium batteries. I submit the following:

"The Bolt EV battery is covered by the electric-car propulsion warranty (8 years, 100,000 miles and higher for CARB states) and Bolt EV customers shouldn’t expect to pay parts costs for warrantied repairs.

In [almost seven] years of Volt sales we have yet to replace a single battery pack under warranty for general capacity degradation, and many owners are still reporting they enjoy the same range capability they had when they purchased the car".

My Bolt is a lease and I won't have it in eight years, the same for many here, and definitely won't achieve 100,000 miles. I'll continue to charge to 100% on every charge to ensure I have max range available. Hill Top Reserve might benefit some, but for saving the battery is over stated. I'm a consumer, and I'm going to consume.

I don't think I am too worried about batter pack longevity with HTR. I think it was just a part of the possible benefits as the OP was asking about. Regardless, it is a benefit. I'd hope someone isn't losing sleep about that benefit though.

The regen behavior on the other hand, I might disagree. Not sure if you do or don't, but if you live on a mountain and have been used to hundreds of trips going down the mountain every morning with even normal D-mode regen, not having it at all (IMHO) is kind of annoying but depends most on your driving habits. I think it is safe to say that if you have significant decline in grade, then HTR will save you brake pad life possibly quite significantly depending on the grade change to your daily commute, as well. I know it took over 8 miles to get anything resembling normal regen back the first time I charged the car before I changed the HTR setting.

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frenchfry

· #9 · Nov 6, 2017

Range not skewed with HTR on.

I drive 162 mile commute each day with HTR on. I use it 6 days a week.

I agree that unless you need the extra mileage, there is no use in putting the battery through its paces 100% of the time.

I have seen absolutely no range decrease in the overall capacity when HTR is off occasionally on the weekend. On the one day I fully charge, my range increases back to the amount of the battery when new.

Driving 45,000 miles per year, battery longevity is a major issue for me. I really want to see what kind of degradation there is with this pack over the long haul.

Volt/LG Chem. battery packs have excellent longevity however their pack never sees 90 or 100% charging as only 60% or so of the Volt pack is actually used.

HTR kind of helps the Bolt stay closer to those parameters since it is made by the same company.

Same goes with Tesla. Tesla has the ability to monitor their packs and remotely decrease the full charge percentage based on various factors including too much supercharging which as we all know, degrades the pack faster. Some Tesla enthusiasts have reported this happening to them.

It was great that GM included this feature in the Bolt. My suggestion is to use it if you can to preserve battery longevity.

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jostafew

· #10 · Nov 6, 2017

LectricBill said:
I too use Hilltop Reserve almost all of the time, for the last 5000 miles.

Haven't noticed it skewing anything. The variation that the previous trip's driving experience factors into the GOM seems to far outweigh any variations that might arise from not charging fully.

When I DO charge fully, the estimated range seems to me consistent with when the battery was new.

Agreed. I've charged to 100% maybe four times in the last 20,000kms when I thought I would need the extra range (turns out I didn't). On those occasions the expected range was as accurate as it usually is when I charge in Hilltop mode. From watching the graphs on my JuiceBox EVSE I see that the car is balancing cells at the end of a Hilltop charge just as it would on a regular charge, so everything is good there. Long story short I'd recommend using Hilltop mode to help conserve battery capacity over time, and if you actually live on a hill top then all the better!

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Rick CH

· #11 · Nov 6, 2017

jostafew said:
From watching the graphs on my JuiceBox EVSE I see that the car is balancing cells at the end of a Hilltop charge just as it would on a regular charge, so everything is good there.

That's really valuable info; any way you could post those graphs? I'm just really curious to see the balancing at work.

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rgmichel

· #12 · Nov 6, 2017

I find hilltop reserve to be invaluable. I go down hill from my house, and it is most disconcerting when you find you don't have regen barking and you actually need to move your foot to the friction brakes! Hilltop reserve solves this problem.

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jostafew

· #13 · Nov 9, 2017 (Edited)

Rick CH said:
That's really valuable info; any way you could post those graphs? I'm just really curious to see the balancing at work.

Here's a screenshot from the JuiceNet app on my phone from last night's charge. You can see a pretty steady 7ish KW charge, then tapers off to about 2kw where it gets kinda spikey. I'm interpreting this as the primary charge ending and a transition to a balance / cell maintenance finish. You can see a brief drop followed by a little spike, this to me is the system pausing the charge while it burns off a bit of potential from some cells, then take a bit of charge, and so on until all cells are happy. Finally it drops to zero for a short while when the charge / balance cycle is complete, followed by a big spike when I was preconditioning the cabin before heading out.

This is pretty typical for my charges to hilltop reserve capacity. Next time I think about it I'll try a full 100% charge from a similar starting state and compare the graph.

Edit: Added a 2nd graph for comparison (still charging to hilltop reserve)

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Only charging in Hilltop Reserve, Cons?

npgeorgeuw

LectricBill

surgeonFWW

npgeorgeuw

Dimitrij

surgeonFWW

-1-

npgeorgeuw

frenchfry

jostafew

Rick CH

rgmichel

jostafew

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