Standard charge topping off?

[Bunnak]

I've noticed that after a standard charge my battery icon is completely full (100%) with 175-176 miles. Shouldn't the car stop charging much sooner? Isn't it supposed to only go to 100% if I choose "top off"? Then I notice within an hour or two I lose several miles and it settles at 169. Is this normal charging behavior?

 

[Bunnak]

To clarify when I charge my car I notice in ovms it charges to 100% in standard mode to 175-176m. I have seen other users have mentioned their ovms battery percentage automatically stops charging at 96-97% in ovms whereas mine charges to 100%

After charge within an hour or two I lose several miles and it settles at 169. Is this normal charging behavior?; is this battery bleed? Is the standard charge topping off my battery to 100% instead of 80%; just curious to why my charge in ovms goes to 100. My CAC is currently 138.44.

 

[gregd]

The Roadster re-scales the reported battery state of charge depending on which mode you're in. If you were to charge fully in Standard mode, it says 100%. Then switch to Range mode, and you're at, um, a bunch less (80% I think). I forget the number. The actual SoC percentages are shown in the logs. On my car, standard mode stops at about 83%, range mode at about 94%. There's a similar re-scaling that occurs on the discharge end of the curve, with standard mode hiding (or range mode unlocking) the bottom about 10% or so.

The range reduction that occurs after things settle is normal. I presume it's a result of the cell balancing that goes on, though yours seems a bit more dramatic than mine. Right now I'm charging to 163, and it settles out to about 161. CAC is 136.8. I had one episode after driving a long distance for the first time in a number of years, and was range charging from a 120v outlet for the drive home. The car stopped charging with a severely LOW Ideal range estimate, something in the 180's. Then, after balancing, and while I was trying to figure out how I was going to limp home, the number crawled back up the expected value of 212. So, it can work both ways.

 

[Bunnak]

The Roadster re-scales the reported battery state of charge depending on which mode you're in. If you were to charge fully in Standard mode, it says 100%. Then switch to Range mode, and you're at, um, a bunch less (80% I think). I forget the number. The actual SoC percentages are shown in the logs. On my car, standard mode stops at about 83%, range mode at about 94%. There's a similar re-scaling that occurs on the discharge end of the curve, with standard mode hiding (or range mode unlocking) the bottom about 10% or so.

The range reduction that occurs after things settle is normal. I presume it's a result of the cell balancing that goes on, though yours seems a bit more dramatic than mine. Right now I'm charging to 163, and it settles out to about 161. CAC is 136.8. I had one episode after driving a long distance for the first time in a number of years, and was range charging from a 120v outlet for the drive home. The car stopped charging with a severely LOW Ideal range estimate, something in the 180's. Then, after balancing, and while I was trying to figure out how I was going to limp home, the number crawled back up the expected value of 212. So, it can work both ways.

Shouldn't there be space left in the battery icon on the VDS if you're charging at standard mode; it should not be full. Also my OVMS says it's at 100%. Shouldn't our cars stop charging around high 90% while in standard mode?

 

[ML Auto]

The car looks completely normal from your pics. Your issue is with whatever you are expecting from OVMS.

 

[Bunnak]

The car looks completely normal from your pics. Your issue is with whatever you are expecting from OVMS.

It's not just the OVMS. Shouldn't the VDS have the battery icon not completely full? That is, shouldn't there be some grayed out areas as seen in the picture below?

 

[Bunnak]

Instead mine looks like this (notice battery icon is at 100%).

 

[gregd]

The car runs two sets of "books". One aimed at the driver, one internal. It fakes the driver-oriented metrics to have 100% full at an internal SoC at about 83%, and fully discharged at abut 10%. Range mode unlocks an additional 10%-ish on both the top and bottom (*), and re-adjusts what the driver sees. This leads to some interesting metrics when modes are switched, for example if one is charging on one, and driving on another.

I don't know what exactly the OVMS is quoting, but the design intent is for OVMS to reflect what the driver sees. Mine seems to do just that, at least in the modes I've tried.


(*) There's still a little (very little) anti-bricking reserve at the bottom, when the car hits a driver's view range mode zero, but highly unwise to test this. The car does not prevent draining to a real zero SoC, at which point the pack is likely unrecoverable by a customer.

 

[drewski]

It's not just the OVMS. Shouldn't the VDS have the battery icon not completely full? That is, shouldn't there be some grayed out areas as seen in the picture below?
View attachment 560926

as GregD says, the Roadster re-scales standard vs. range so 100% Standard Charge = XX% (80%??) Range Charge

 

[markwj]

OVMS will just display the same as the normal (user) VDS display. By design.

The car will by default use two different ranges to display SOC. One for standard mode, and the other for range mode. Both are designed to read 100% when the battery is full in that specific mode. If you charge the car to full in standard mode, you will see 100% SOC (or close to it). Switch to range mode, as the VDS will show somewhere around 80%. Charge to 100% in range mode, and switch to standard mode, it will still show 100% and will continue to show 100% (capped at 100%) until about 1/5 of the pack has been drained.

As to why your car is showing 100% on a standard mode charge with a CAC of 138, that is strange, but I wouldn't worry too much about it. Neither the CAC nor SOC are exact - both are just estimates of energy storage (which can't be directly measured like a petrol tank can). Are you sure you didn't do a range charge, then switch back to standard (so standard mode SOC was above 100%)?

 

[DeedWest]

Nak,

I understand what you’re pointing out. For example, I charge on 32A. If you watch the VDS towards the end of a charge, you’ll notice the amps drop below the full 32A as it nears completion. It is my understanding that the firmware does this to avoid overcharging in its current mode. It will show something like “17/32A”

Similarly, when an ESS cooling cycle activates, you’ll notice the amperage increases. However, at the end of a charge, this amperage increase forces the charge to stop. 90% of the time I’ve observed the car charging, it stops due to this. You’ll hear the fans kick in, and as soon as they start blowing, the charge stops.

The few times I’ve experienced the same thing as you, it’s due to the ESS being at or below the desired target temperature (for Standard Mode, it’s 27C) that it doesn’t activate as many cooling cycles. This usually prevents the charge from stopping a little earlier due to the amperage increase from the cooling cycle.

Otherwise, I’ve observed that it’s just an occasional random occurrence in which the car decides to go to 100% of a Standard Mode charge. The firmware is strange and I don’t think I’ll ever understand it. There’s no harm in it finishing at 85% versus 83% as normal. If anything, it’ll just balance itself.

 

[im4uttx]

Mine almost always stops at 97% reported...standard charge.

 

[einhalv]

Mine almost always stops at 97% reported...standard charge.

Mine too. OVMS reports 97%, sometimes 98%, at end of charging.

 

[jason.tv]

same; 97% sometimes 98%

 

[drewski]

if I charge on 120V, it regularly goes to 100%.

on 240V it usually goes to 97%, as others have mentioned.

 

[markwj]

if I charge on 120V, it regularly goes to 100%.

on 240V it usually goes to 97%, as others have mentioned.

Think of it as a game to get as close to a finishing line, but not cross it. One contestant runs, the other walks. Guess who will get closer?

 

[Bunnak]

same; 97% sometimes 98%

Looks like I'm fine. It was at 99% when done charging last night. I don't think it really ever goes to 100%. Thanks for all your feedback and reassurance everyone! Best car community in the world!