Measuring amount of charge - 2018 Honda Clarity Forum
 3Likes
  • 1 Post By 2002
  • 2 Post By MPG+
 
Thread Tools
post #1 of 10 (permalink) Old 04-04-2020, 10:53 AM Thread Starter
Member
 
Join Date: Oct 2019
Location: CT
Posts: 47
Measuring amount of charge

I would like to keep track of how many kWh I use when charging my Clarity, similar to knowing how many gallons of gas I put in the tank. I can easily track kWh charging at home with a watt meter for 110v, but this wouldn't work at public EV charging stations that are 220v. With all the data that Honda makes available on the info screen, it seems that it would have been an easy thing to measure and make available. I know EV range is displayed, but that is just an estimate which varies and doesn't tell you true cost. Since I'm wishing, it would also be great if they tracked EV miles and ICE miles separately. Does anyone have any suggestions or solutions? Thanks for thinking about it !
MPG+ is offline  
post #2 of 10 (permalink) Old 04-04-2020, 04:13 PM
Senior Member
 
Join Date: May 2019
Location: Atlanta, GA
Posts: 263
Quote:
Originally Posted by MPG+ View Post
I would like to keep track of how many kWh I use when charging my Clarity, similar to knowing how many gallons of gas I put in the tank. I can easily track kWh charging at home with a watt meter for 110v, but this wouldn't work at public EV charging stations that are 220v. With all the data that Honda makes available on the info screen, it seems that it would have been an easy thing to measure and make available. I know EV range is displayed, but that is just an estimate which varies and doesn't tell you true cost. Since I'm wishing, it would also be great if they tracked EV miles and ICE miles separately. Does anyone have any suggestions or solutions? Thanks for thinking about it !
About all you can do with external public chargers is keep track of the SOC change from the beginning and end of each charge session. Presuming you have already figured out for your home charging how many kWh on average it takes for each percent increase in SOC, you can assign that same value to external charging as a way of estimating how much electricity was used. Won't be exact as there could be differences in efficiencies but it should be close enough for estimating purposes.
2002 is offline  
post #3 of 10 (permalink) Old 04-05-2020, 11:49 AM Thread Starter
Member
 
Join Date: Oct 2019
Location: CT
Posts: 47
Thanks for that info 2002. I do recall discussions on SOC so could you restate how to calculate that again so I will try it? Doing some research there are a couple of phone apps that sound promising, called "EVNotify" and "myEV data logger". The first looks like it's only for Hyundai vehicles and I don't think the second is available yet. I've noticed there are many OBD2 scanner tools available and wondering if any would give me the info I'm looking for. Apparently they all plug into the vehicle, but I don't know if they measure EV batteries.
MPG+ is offline  
post #4 of 10 (permalink) Old 04-05-2020, 02:34 PM
Senior Member
 
Join Date: May 2019
Location: Atlanta, GA
Posts: 263
The HondaLink app shows SOC. It's not titled as such but on the screen where it shows EV miles, right above the bar is a percentage which is SOC. It updates the SOC when you shut off the car and also when you start or finish charging. To verify that you are looking at the current SOC you can look in the middle of the screen where in a tiny gray font it shows what time it was last updated.

During charging the SOC updates at 15% intervals. There is a way to get an SOC update between increments but it's a multi-press workaround that isn't worth the trouble. If you needed ongoing SOC level during charging (or driving) then you would need one of the OBDII devices. The one I got is Bafx Products - Wireless Bluetooth, it was $20 on Amazon, it doesn't come with any software but there are free apps that you download like Torque for basic data and you can upgrade to a paid version with more features.

But for this particular exercise that you are doing you just need the starting and ending SOC which the HondaLink app handles with no problem. At least for me, some people have problems with HondaLink but for me it works pretty flawless for what I use it for which is charge scheduling and remote climate.
2002 is offline  
post #5 of 10 (permalink) Old 04-05-2020, 07:49 PM
Senior Member
 
Join Date: May 2019
Location: Atlanta, GA
Posts: 263
One thing you will notice when you start looking at SOC is that 0 EV miles is usually around 10% SOC plus or minus around 2%. A full charge is to 100% SOC. So using an example let's say you charge at home with 0 EV miles and it shows the SOC as 11%. You charge to 100% and your meter shows that you used 14.2 kWh of electricity for that charge session. So 14.2 kWh / (100-11) = 0.16 kWh per SOC percent change. You can do it a couple more times just to make sure you get a similar number, you don't have to have the same starting and ending SOC for each test as it shouldn't matter. What will matter is if the battery cooler runs during charging, which you won't always know is happening thus running the test multiple times should help average that out.

Once you know your average kWh per SOC percent change you can use that to estimate your electric usage at public charging stations. Let's say you are at a charging station and you charge from 33% to 79%. So then to estimate how much electricity was used it would be (79 - 33) x 0.16 = 7.4 kWh
2002 is offline  
post #6 of 10 (permalink) Old 04-05-2020, 08:47 PM Thread Starter
Member
 
Join Date: Oct 2019
Location: CT
Posts: 47
OK thanks 2002, I have a better understanding of it now. I do have the Honda app and I'll use it when I'm charging. So can I assume if the app says 70% for EV Charge, that would be (.7 X 17)= 11.9 kWh of charge? Then if I fully charged the battery, it would take (17-11.9)= 5.1 kWh more to top off?
MPG+ is offline  
post #7 of 10 (permalink) Old 04-06-2020, 09:11 AM Thread Starter
Member
 
Join Date: Oct 2019
Location: CT
Posts: 47
Thanks for all that useful information 2002. Your post actually came while I was composing my last one, so didn't see it until later. So I will track my charging at home a few times which will give me a pretty good indication of my average kWh per SOC % change. Stay healthy!
MPG+ is offline  
post #8 of 10 (permalink) Old 04-06-2020, 02:52 PM
Senior Member
 
Join Date: May 2019
Location: Atlanta, GA
Posts: 263
In your previous post, the one that you wrote before you saw mine, you said,

"70% for EV Charge, that would be (.7 X 17)= 11.9 kWh of charge"

Not really because not all of the 17 kWh is available, a buffer is kept above and below the "usable" amount of charge because battery life would otherwise be shortened if the battery was depleted to nearly empty then charged all the way to 17 kWh. People who have measured indicate that it takes about 14.4 kWh of electricity to charge from 0 miles (approx 10% SOC) to 100%. Including charging losses this means probably between 13 and 14 kWh of the battery is usable.

In other words SOC on the app is more of a virtual SOC not the true SOC which would be 0 kWh to 17 kWh. But in the end it doesn't really matter for these type of calculations as all we really care about is how much electricity do we put in and how far does that electricity take us.
leemell likes this.
2002 is offline  
post #9 of 10 (permalink) Old 04-06-2020, 08:16 PM Thread Starter
Member
 
Join Date: Oct 2019
Location: CT
Posts: 47
Understood!
MPG+ is offline  
post #10 of 10 (permalink) Old 04-09-2020, 01:17 PM Thread Starter
Member
 
Join Date: Oct 2019
Location: CT
Posts: 47
OK, so I measured 4 different at-home charges, over 3 days, and here is the data:

kWh Charge........SOC % Increase........kWh to increase SOC by 1%
3.8,..........................23,................. .........................0.17
4.5,..........................25,................. .........................0.18
4.7,..........................25,................. .........................0.19
3.7,..........................21,................. .........................0.18

I was somewhat surprised by the variance, small as it was; the kWh to increase SOC by the same percentage is not always going to be the same, probably based on ambient battery temperature and other conditions. But the difference is negligible for my purpose, and the test charges are similar to what I do in public, so will go with the average of 0.18 kWh and use that to calculate public charging.
The Gadgeteer and 2002 like this.

Last edited by MPG+; 04-09-2020 at 01:22 PM.
MPG+ is offline  
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Related Threads
Thread Thread Starter Forum Replies Last Post
Ev charge miles in winter jimmyd Honda Clarity Plug-In Hybrid 20 03-30-2019 02:01 PM
Contradicting battery charge indicators acadork Charging and Batteries 10 02-10-2019 11:19 AM
HV charge petpeople Honda Clarity Owners Registry And Check In Area 3 12-10-2018 03:29 AM
HV Charge? longfam18 Honda Clarity Range, MPGE And Economy 7 11-27-2018 05:36 PM
stopping charging before the battery is full semenzato Engine And Technical Discussions 9 11-27-2018 11:33 AM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome