Superchewie
Posts: 9
Joined: Mon May 01, 2017 9:28 pm
Delivery Date: 29 Apr 2017

Curiosity Only - Near-100% Charging Behaviour

Sat May 06, 2017 6:30 pm

Hi folks,

During a recent ChargePoint charging session (in which I needed a battery level near to 100% at the end), I noticed some interesting behaviour by the EVSE close to the end of the charge. It seems like the EVSE would ramp down to near zero amps, then up for a bit, then back down.

This should be a link to a photo of the charge record on Imgur:
https://imgur.com/gallery/vwHYe

I suppose this is actually controlled by the Leaf?

If anyone cares to "explain like I'm 5" this behaviour to me, I'd appreciate it! I'd like to sound smart to my new-to-EV friends.

Thanks!

ElectricEddy
Posts: 365
Joined: Tue Feb 25, 2014 1:42 pm
Delivery Date: 31 Oct 2016
Leaf Number: 313506
Location: Nanaimo, B.C.

Re: Curiosity Only - Near-100% Charging Behaviour

Sat May 06, 2017 7:21 pm

Superchewie wrote:Hi folks,

During a recent ChargePoint charging session (in which I needed a battery level near to 100% at the end), I noticed some interesting behaviour by the EVSE close to the end of the charge. It seems like the EVSE would ramp down to near zero amps, then up for a bit, then back down.

This should be a link to a photo of the charge record on Imgur:
https://imgur.com/gallery/vwHYe

I suppose this is actually controlled by the Leaf?

If anyone cares to "explain like I'm 5" this behaviour to me, I'd appreciate it! I'd like to sound smart to my new-to-EV friends.

Thanks!

Cells balance at the end in an attempt to equalize (minimize the voltage differential)...routine.
Pearl White Sl
mfd date 09/16

LeftieBiker
Posts: 6788
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Curiosity Only - Near-100% Charging Behaviour

Sat May 06, 2017 7:23 pm

The pack can't be fast-charged as it nears full. Thus the charger tapers the charge. As it gets full, an equalizing charge is applied, which involves the up & down pattern you observed. This gets the cells in balance.
2013 "Brilliant Silver" SV with Premium Package and no QC, and 2009 Vectrix VX-1 with 18 Leaf cells.

The most offensive, tasteless phrase in use here is "Pulled the trigger." I no longer respond to posts that use it.

GerryAZ
Gold Member
Posts: 1367
Joined: Mon Nov 22, 2010 6:47 pm
Delivery Date: 12 Jun 2011
Location: Phoenix, AZ

Re: Curiosity Only - Near-100% Charging Behaviour

Sat May 06, 2017 7:29 pm

The newer Leafs keep trying to get more charge into the battery by ramping up the charge rate after it tapers due to reaching maximum cell voltage. As you can see from the charge profile, they will do this several times. My 2011 would charge at its normal rate until almost the end of the charge cycle and then taper briefly (to keep charging without exceeding maximum cell voltage) before considering the charge complete and shutting down the charge process. At first it seemed strange to have the charge rate taper, but keep charging for nearly an hour after I purchased the 2015.
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015

cwerdna
Gold Member
Posts: 6967
Joined: Fri Jun 03, 2011 4:31 pm
Delivery Date: 28 Jul 2013
Location: SF Bay Area, CA

Re: Curiosity Only - Near-100% Charging Behaviour

Sun May 07, 2017 3:11 am

Yes, it's been speculation that some sort of battery balancing was going on in the '13+ Leafs (which are the first to have this bouncing behavior). Both my current and previous '13 looked just like that when going 100% (most of my charging is on Chargepoint EVSEs at work).
GerryAZ wrote:The newer Leafs keep trying to get more charge into the battery by ramping up the charge rate after it tapers due to reaching maximum cell voltage. As you can see from the charge profile, they will do this several times. My 2011 would charge at its normal rate until almost the end of the charge cycle and then taper briefly (to keep charging without exceeding maximum cell voltage) before considering the charge complete and shutting down the charge process. At first it seemed strange to have the charge rate taper, but keep charging for nearly an hour after I purchased the 2015.

Yes, it seems likely that it is to cram more charge in. We learned of it via the articles that viewtopic.php?f=31&t=21628 references. That might be responsible for a small part of the higher EPA range rating of the '13 to '15 24 kWh Leafs (84 miles at 100% instead of 73).

'13 blue Leaf SV w/premium package (owned)
'13 blue Leaf SV w/QC + LED & premium packages (lease over, car returned)
'06 Prius

LeftieBiker
Posts: 6788
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Curiosity Only - Near-100% Charging Behaviour

Sun May 07, 2017 3:31 am

I don't know about the extent of the voltage fluctuations, but my '13 also does some balancing at 80%. I know because all three charging lights glow steadily for about 5 minutes as it reaches 80%. (Then my car, for some unknown reason, maybe a cell with different capacity, drops back to 79% like clockwork.)
2013 "Brilliant Silver" SV with Premium Package and no QC, and 2009 Vectrix VX-1 with 18 Leaf cells.

The most offensive, tasteless phrase in use here is "Pulled the trigger." I no longer respond to posts that use it.

cwerdna
Gold Member
Posts: 6967
Joined: Fri Jun 03, 2011 4:31 pm
Delivery Date: 28 Jul 2013
Location: SF Bay Area, CA

Re: Curiosity Only - Near-100% Charging Behaviour

Sun May 07, 2017 4:50 am

LeftieBiker wrote:I don't know about the extent of the voltage fluctuations, but my '13 also does some balancing at 80%. I know because all three charging lights glow steadily for about 5 minutes as it reaches 80%.

I don't know that the all 3 lights on for 5 minutes necessarily means anything (balancing or otherwise). It's in the manual that they'll stay on for 5 minutes.

The '13 Leaf manual says
When fully charged
All of the indicator lights1 to3 illuminate when
the Li-ion battery is fully charged to the selected
charging mode level.
The indicator lights turn off after approximately 5
minutes or when the charge connector is removed.

Oddly, from the '11 Leaf manual
When fully charged
All of the indicator lights *1 to *3 illuminate
when:
. The Li-ion battery is fully charged
. 80% of a charging timer is completed
. When 90% of a quick charge is completed
The indicator lights turn off after approximately
15 minutes or when the charge connector is
removed.

'13 blue Leaf SV w/premium package (owned)
'13 blue Leaf SV w/QC + LED & premium packages (lease over, car returned)
'06 Prius

BenTheRighteous
Posts: 59
Joined: Tue Feb 14, 2017 5:36 am
Delivery Date: 14 Feb 2017
Location: Raleigh, NC

Re: Curiosity Only - Near-100% Charging Behaviour

Sun May 07, 2017 6:12 am

My OpenEVSE logs something that's even more pronounced:

Image
2017 Leaf S
OpenEVSE P50-D WiFi Kit
Raleigh, NC
USA

cwerdna
Gold Member
Posts: 6967
Joined: Fri Jun 03, 2011 4:31 pm
Delivery Date: 28 Jul 2013
Location: SF Bay Area, CA

Re: Curiosity Only - Near-100% Charging Behaviour

Sun May 07, 2017 11:51 am

^^^
Interesting. On Chargepoint, we only can see the graph in 5 minute intervals.

'13 blue Leaf SV w/premium package (owned)
'13 blue Leaf SV w/QC + LED & premium packages (lease over, car returned)
'06 Prius

User avatar
OrientExpress
Forum Supporter
Posts: 1028
Joined: Sun Aug 08, 2010 12:22 pm
Delivery Date: 10 May 2011
Leaf Number: 2331
Location: San Jose, Ca

Re: Curiosity Only - Near-100% Charging Behaviour

Sun May 07, 2017 12:58 pm

Yes, it seems likely that it is to cram more charge in. We learned of it via the articles that viewtopic.php?f=31&t=21628 references. That might be responsible for a small part of the higher EPA range rating of the '13 to '15 24 kWh Leafs (84 miles at 100% instead of 73).


On the MY 11 and 12 cars a factor in the lower EPA rating was because for the test they had to show the 80% charge range result and not the 100% rate. With the 80% rate removed in 2013, then they could now list the higher range rate.
2014 LEAF SV
Ocean Blue
Delivery May 23 2014
46,000+ miles - all 12 bars - Same range as new - No warranty issues ever!

Return to “Range / Efficiency / Carwings”