rkiyer
Posts: 15
Joined: Sun Sep 10, 2017 8:18 pm
Location: South Bay Area, California

Charging frequently to full vs dropping to 30%

Fri Oct 20, 2017 5:14 pm

Is it better to "top up" frequently to 100% or is it better to wait until <30-40% charge before charging back to full. Many days, I only use about 10-20% of the battery and wonder if there's any harm in charging back overnight to full each night? I know some Nissan Leaf owners typically "baby" their battery this way.

I am curious if anyone has seen anything in the manual or heard anything from a Chevy dealership about this. Any opinions? What do you typically do?
White 2014 Spark EV w/ FC

Taxman
Posts: 107
Joined: Thu Sep 01, 2016 4:51 pm
Location: Michigan

Re: Charging frequently to full vs dropping to 30%

Fri Oct 20, 2017 6:25 pm

I would think keeping it between 30% and 70% would maximize the life. Most lithium batteries prefer to be half charged.

MrDRMorgan
Posts: 1132
Joined: Wed Oct 30, 2013 7:27 am
Location: Manteca in Central California

Re: Charging frequently to full vs dropping to 30%

Sat Oct 21, 2017 3:48 pm

I have yet to see a posting that really answers this question. I have a 2014 Spark EV and a 2015 Spark EV and my wife and I have been driving both for 2.5 years. For L1 and L2 charging, I usually let the battery in both cars drop below 50% before re-charging and then I re-charge to 100% in the IMMEDIATE charging mode.

Only my 2015 Spark EV has the quick-charge option which I only use if I am driving outside of the "comfortable" round-trip range of the car. I found I can quick-charge from 30% to 90% in about 15 minutes at EVgo DCFC locations.

So far, how I am charging my vehicles does not seem to have had any impact on either vehicle. However, range changes due to weather [AC and heater use] and road speed can drive you nuts. New tires can have an impact on range too. My 2014 Spark is giving me full-charge range mileage as good as or slightly better than 2 years ago. The 2015 is about the same as 2 years ago too.

When my garage air temperature gets above 90 deg. F in the summer, I usually leave both vehicles plugged in at night to allow each car to keep the battery temp controlled if necessary. I use the IMMEDIATE charging mode so power is applied all night.

So far, what I am doing seems to be working fine and both cars continue to give me great full-charge ranges.

rkiyer
Posts: 15
Joined: Sun Sep 10, 2017 8:18 pm
Location: South Bay Area, California

Re: Charging frequently to full vs dropping to 30%

Wed Nov 29, 2017 4:58 pm

Your experience, especially with the regular summer charging, is reassuring, MrDRMorgan. I am hoping that I can charge frequently without impacting the long term battery capacity too much.
White 2014 Spark EV w/ FC

MrDRMorgan
Posts: 1132
Joined: Wed Oct 30, 2013 7:27 am
Location: Manteca in Central California

Re: Charging frequently to full vs dropping to 30%

Wed Nov 29, 2017 5:49 pm

rkiyer wrote:Your experience, especially with the regular summer charging, is reassuring, MrDRMorgan. I am hoping that I can charge frequently without impacting the long term battery capacity too much.
Two days after I posted my October 21 remarks, I purchased a 2016 Spark EV 2LT with 6700 miles on the ODO. Today, approximately 1000 miles later, the full-charge range on my 2015 Spark EV [24,000 miles on the ODO] is about 5 miles lower than my 2016 Spark EV [7700 miles on the ODO]. There are a lot of variables that affect the range so I figure it is just about a wash between the 2015 and the 2016. However, my 2014 Spark EV w/o the quick-charge option [ 12,200 miles on the ODO] continues to outperform both the 2015 and the 2016. I expect to see some battery degradation on all three cars. How much remains to be seen but, so far, I am quite happy with all three.

Recently, the SERVICE VEHICLE SOON light went on in my 2015. I took the car to the dealer and they said the error code was related to a defect in the DC charging module. I was told I could slow charge the car but the quick-charge option would not work. A part was ordered. But.... when I picked up the car at the dealer, the SERVICE VEHICLE light was off and my mi/kWh numbers were going all over the map. I took the car to my local DCFC station and proceeded to quick-charge with no problems. Today, after a few hundred miles of driving and a number of quick-charge visits, the SERVICE VEHICLE light remains off and the mi/kWh number are returning to near normal. It looks like some memory section got erased and reset and that fixed the problem. I still plan to have the new part installed when it arrives.

I continue to try not to let the HV battery capacity drop below 30% and, when I quick-charge, I disconnect at 90-95%. At home I use both a L1 and L2 EVSE and I usually charge overnight to 100%.

All three Spark EVs continue to be a trouble-free joy to drive. It will be very hard to part with my 2015 Spark EV when the lease ends in May. But, I still have the 2014 and 2016 Spark EVs which I own.

SparkE
Posts: 392
Joined: Tue Sep 06, 2016 1:18 am
Location: SF Bay Area (San Jose, CA)

Re: Charging frequently to full vs dropping to 30%

Wed Nov 29, 2017 8:29 pm

The battery chemistry is very important for properties of Li-Ion batteries - even a small change in % of "other metal" in the mix can change properties greatly. I have seen no specific studies on the batteries in the Spark. I have seen studies on other types of Li_ion (for example, those used in computers, and the one in the LEAF).

In general (but maybe not for the Spark in particular), Li_Ion batteries :
- do not like being fully charged on a regular basis
- do not like being fully discharged on a regular basis
- do not like being charged when it is really hot
- do not like sitting fully charged for long periods, especially if hot
- heat up when quick charged (the Spark DCFC @ 50 kW charges at about 2.7C)
- last longest when the charge is (generally) maintained between 30-70% SoC

(In this context "does not like" equates to "impacts long-term capacity".) Now, GM built in a certain "buffer", in that a small % at both the top & bottom is reserved (you can't use it) so that the battery can't be FULLY charged or discharged. Nobody really knows how much, but it can't be oodles and oddles (like on PHEVs, which often reserve 35-45% of battery capacity).

So, what I have been doing with my Spark is :
- rarely charging it past 80-85%. (Except once every 4-6 weeks to make sure the cells in the battery are balanced.) I don't often need 80 miles of range on any given day, so I charge up to 65-70 miles range.

- I use DCFC fairly often (once a week or more) just because it is convenient. When I do use DCFC, I rarely charge past 70% (unless I need the range). That way I minimize the heat generated in the battery pack (the fuller the battery gets, the hotter it gets at the same charge rate). I'll stop by for 10 minutes when I have (say) 30 miles range, to get an additional 30-35 miles, then I'm off to the highway (about a 60-65% SoC). (There are 2 DCFCs on my way to the freeway - very convenient.)

- If I'm not in a hurry, I'll use the 24 kW DCFC instead of the 50 kW charger. It heats the battery less.

- Basically, if I need the range then I charge it up - otherwise I don't. If I need the range, I don't sweat it - I just do it. But that's maybe once every 2-3 months.

- I don't let the car sit with a really high SoC overnight. If I need the range tomorrow, I'll charge up to maybe 80-85% the night before, then plug the car in the next morning when I get up. It'll be at 100% when it's time to leave, and it's only been at that SoC for a little while.


I figure it's better to be safe than sorry, and since (1) there are 3 DCFCs within 2 miles of the house, and (2) it's a second family car, and (3) most of our driving is 30 miles or less per day (often under 20) - it's no real hardship for me to only charge it up to 80% most of the time.

If you need the range, charge it up. If you don't, then only charge it up to 80-85%.

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