RavCharge, a solution to charge timer and entune woes

[Kohler Controller]

Thanks fooljoe for the time till charged feature (including standard or extended charge settings)!
This will come in handy when charging in the wild, as last week I used a public blink charger which I calculated to be 208V/25A or ~14 miles per hour of charge.


I took Tony's meter suggestion and added it to my AV EVSE. 240VAC and 30A throughput. If I take my EVSE with me to charge at an RV park or a friend's house, I'll now be able to enter the exact info into RavCharge.



The only thing I would recommend is to use 85% instead of 80% efficiency.

 

[Dsinned]

Ditto! RavCharge is turning out to be a very fine webapp for RAV4 EV owners.

I have the same LCD meter as Kohler on my EVSE (with rated output of 240Vac @ 32A), so it is easy to use the new sliders to find out the time to complete charging. Note, that this is only the time to complete "BULK CHARGING". RavCharge has no knowledge of the subsequent, much lower power level, cell balancing and/or topping off charge, and neither does Entunes. That usually happens several hours after the bulk charge completes, and typically lasts ~10 minutes longer than the preset Departure Time on a scheduled charge. Nevertheless, RavCharge does an admirable job!

I will test this new feature this weekend by comparing the estimate to the actual recording of power consumption upon activation of my EVSE with a HEM system.

Thanks again Joe!

 

[fooljoe]

The only thing I would recommend is to use 85% instead of 80% efficiency.

Hmm, as you can see in the screenshot I posted, RavCharge predicted my charge would take 1:40 last night, and it turned out to be 1:43, so I'd certainly hesitate to increase the efficiency after that. Of course my voltage could be a little lower than the 235 I chose, but it would have to be a lot lower (like 215) if I had 85% efficiency instead of 80% in the formula. Did you have a charge that finished significantly faster than RavCharge predicted?

including standard or extended charge settings!

One thing about the extended charge thing - as previously discussed we don't have any SOC information between a full normal charge and a full extended charge, so don't pay attention to the time-to-charge estimate if you have a high SOC under extended charge mode. It'll say you have ~1 hour or so to charge even if your extended charge is already done; unfortunately there's no good way around this for now.

 

[fooljoe]

I have the same LCD meter as Kohler on my EVSE (with rated output of 240Vac @ 32A), so it is easy to use the new sliders to find out the time to complete charging.

Those LCDs are cool - I've gotta get one when I get around to building my open-EVSE. In the meantime, if you guys get a chance can you take note of how the amps taper off as you near charge completion (for both normal and extended modes)? I suspect such tapering will make RavCharge's estimates a little optimistic, so if I could figure out what level of tapering is seen I could add in a "fudge factor" to account for it. In the meantime keeping the efficiency factor conservative and perhaps lowering your voltage a bit below actual can even things out.

 

[miimura]

If @Dsinned or another user that has an energy monitor can capture the data from an extended charge, it would be easy to make an accurate estimate of the charging time including the taper. You could also account for the fact that a 20A EVSE like the Clipper Creek LCS-25 may not taper at all. Actually, now that I think about it, maybe another user with a 40A EVSE needs to capture the taper data as well since @Dsinned has a 32A EVSE.

 

[user 340]

There could be more taper with a 100% charge than an 80% one, and it would be good to see the data.

 

[Kohler Controller]

Here is a log of a standard charge. Notice it has no taper. The ~750W towards the right is pre-cooling the cabin.



Here is a log of an extended charge, with the taper shown lasting about 15 min.



Here is one of the extended charge, with taper, with the equalization charge to which Dsinned has previously referred, and the pre-cooling event.

 

[Kohler Controller]

I have the same LCD meter as Kohler on my EVSE (with rated output of 240Vac @ 32A), so it is easy to use the new sliders to find out the time to complete charging.

Those LCDs are cool - I've gotta get one when I get around to building my open-EVSE. In the meantime, if you guys get a chance can you take note of how the amps taper off as you near charge completion (for both normal and extended modes)? I suspect such tapering will make RavCharge's estimates a little optimistic, so if I could figure out what level of tapering is seen I could add in a "fudge factor" to account for it. In the meantime keeping the efficiency factor conservative and perhaps lowering your voltage a bit below actual can even things out.

For what its worth, I just charged my car up using extended charge. RavCharge estimated it would take an additional 1:18 to complete after it reached 100%, when it actually took 1:03 (hr:min).

 

[miimura]

Kohler - Thanks for the interesting charts. Interesting that it tapers down to about 10A, but only for the last 15 minutes of a nearly 6 hour charge. I would also be interesting to see where the taper starts on a 40A EVSE. I'm assuming the charts are from your AV EVSE. It looks like the different charts have a different draw - one is clearly over 7kW and the other is barely over 6kW. Why is that?

 

[Dsinned]

Kohler, you must be using a HEM system called Enerati to graph your EVSE power consumption. I have the same thing, and see very similar graphs while charging my RAV4 EV. Btw, how do you capture a screenshot of the graph to post here on the forum? I see "Img" as a selection in the toolbar above a post text entry window, but I haven't figured out how to make it work. Please advise. TIA.

Joe, as can be seen from Kohler's first graph, there really isn't much of a taper on a "standard" (bulk) charge. Unfortunately, the sampling of data points using the Enerati HEM system (that apparently both Kohler and I are using) is only once every minute or so. Not enough to get much definition of the true shape and slope of the taper. The taper at the end of charge while charging my Chevy Volt, is much more noticeable. What is also quite noticeable after the bulk charge completes on a RAV4 EV, is a drop to zero of several hours before it resumes charging again but at a much lower charging rate. This is what has been referred to as the balancing charge, topping off charge, or equalization charge. I have found this to typically have a duration of almost exactly 27 minutes after a standard charge.

I will give an extended charge to my RAV4 EV this weekend to obtain some additional feedback on the end of charge taper and the equalization charge characteristics. I just need to figure out how to post a graph here, otherwise I can put a link to Enerati which will expire after 24 hours.

 

[miimura]

Exporting the data to a spreadsheet would be much more useful for real calculations. I suspect that Kohler just did a screen shot and cropped and uploaded to PhotoBucket.

 

[fooljoe]

Thanks for all the cool plots and other info guys. Dsinned, I'm well aware of the "extra" cell-balancing-or-whatever-it-does charge mode, but I'm going to completely ignore that here and just focus on the time to complete the "bulk" charge. That's when entune sends the "charge complete" email, so that's the only universal yardstick we have to measure by.

It's good to know that there's not really any tapering for a normal charge (ok I guess we only saw that for a 30 amp charge, but it's close enough either way I think), so we can safely keep things simple in that case. The extended charge prediction could possibly use a little extra padding, but since the taper period seems so short I think we're well within close-enough territory already. Keeping the efficiency factor a little conservative will help with that too.

One thing to keep in mind is that however precise we get with our voltage/amperage/efficiency/tapering inputs, the one thing that's really driving things is the relatively untested entune SOC value. The time-to-charge estimate can only be as good as the estimate of how many kwh we need to pump in to the pack, and that completely relies on our reading of SOC (and assumptions about degradation and/or the as-yet-unresolved question of how many kwh exactly constitute a full normal charge.)

From the limited testing I've done, the SOC value seems an "ok" estimate, but certainly not very precise. I've compared my actual miles driven and dash efficiency readings to what the SOC tells me about how many kwh I've used in a day, and it seems to have a tendency to read a little high with relatively high SOC and low with low SOC (assuming the dash numbers are correct.) Also, I still don't know what the 0 in the SOC actually corresponds to.

So until we know more about how exactly this SOC value works, we're in ballpark estimate territory anyway. But regardless, even this simple first attempt at calculating time-to-charge is wayyyy better than Toyota's estimate.

 

[fooljoe]

seems to have a tendency to read a little high with relatively high SOC and low with low SOC (assuming the dash numbers are correct.) Also, I still don't know what the 0 in the SOC actually corresponds to.

Here are a couple examples to clarify:

High with high SOC: Yesterday I drove 54 miles at 4.1 miles/kwh, for an indicated consumption of 13.2kwh, and my SOC at the end of the day was 64%, which indicates (assuming a 35kwh normal charge capacity) only 12.6kwh consumed. Note that if I assume <35kwh to account for degradation or a lower starting capacity (as Tony espouses) then this discrepancy would only widen.

Low with low SOC: A few days earlier I drove 73.7 miles at 3.7 miles/kwh, indicating 19.9kwh consumed, with an SOC of 40% indicating 21kwh.

Both readings are fairly close, and of course these are only two data points, but I've been logging the data enough that it seems to be a pattern, especially with the high/high case. I don't really get in low SOC territory enough to have much confidence there yet, however. If anyone else has such data or would like to start keeping it I'd love to see it to try to make some more sense of the SOC number. Logging actual energy consumption during charging along with these data would of course also be helpful.

 

[waidy]

I've been logging the data enough that it seems to be a pattern, especially with the high/high case.

Hello, did you log your data manually or can it be retrieved online ? If it is the later, please let me know how. Thanks.

 

[fooljoe]

Hello, did you log your data manually or can it be retrieved online ? If it is the later, please let me know how. Thanks.

Manually. At some point I may be able to pull Eco Dashboard data and combine it with your SOC data automatically in RavCharge, but for now you've just got to reset the trip/efficiency meters after each charge and then record them and your RavCharge SOC before charging.

 

[miimura]

One more data point from my car last night.

Ravcharge Settings: 240V 40A 35kWh
Ravcharge Estimate: 41 minutes
Entune Email Time Difference: 42 minutes

Set Ravcharge to 235V 40A 35kWh

We'll see if it is more accurate. However, one minute is the "resolution" of the estimate. Also, I'm not sure how much if any latency or accuracy there is on the timestamps of the e-mails from Entune. So, making the adjustment may not result in a more accurate estimate. I typically drive the car a lot more on the weekends, so there will be more charging time to average over, making the time resolution less relevant.

 

[Dsinned]

I will be doing an extended charge tonight (after midnight) and keeping track of "time to charge" according to RavCharge vs. Entunes email msgs vs. charging station HEM. In addition to other very good qualities, I consider Ravcharge's prediction of "time to charge" the most important information. Also, I will have "tweeked" (i.e. calibrated) all settings in RavCharge to correlate as closely as possible to Entune's precharge estimates for projected range and the in-car's prediction for time to charge. All pertinent initial conditions are as follows:

Ravcharge settings & info:
220V and 32A EVSE settings (actually 235V typical)
30.6kWh normal charge capacity (very conservative)
2.9 mi/kWh driving efficiency (3.1mi/kWh actual in-car)
15kWh approximate charge
49% SoC remaining
43 miles range remaining
3 hrs 49 mins charge time

In-car settings & precharge info:
Climate control status: Off
Plugged-in, extended charge pending
Number of bars on GoM: 8 bars
Last GoM range reading: 43 miles
Dashboard charging est: 3 hrs 50 mins

Btw, I have observed if you shutdown the car with the climate control still in operation, the range indicated by Entunes will differ from the range indicated by Ravcharge, if they would have been otherwise the same. For this reason, I'm now in the habit of making sure my climate control system is turned "off" BEFORE I shutdown the car. This helps keep Ravcharge and Entune's range estimates in sync.

 

[miimura]

One more data point from my car last night.

Ravcharge Settings: 240V 40A 35kWh
Ravcharge Estimate: 41 minutes
Entune Email Time Difference: 42 minutes

Set Ravcharge to 235V 40A 35kWh

We'll see if it is more accurate. However, one minute is the "resolution" of the estimate. Also, I'm not sure how much if any latency or accuracy there is on the timestamps of the e-mails from Entune. So, making the adjustment may not result in a more accurate estimate. I typically drive the car a lot more on the weekends, so there will be more charging time to average over, making the time resolution less relevant.

Sat night charge.

RavCharge Settings: 235V 40A 35kWh
RavCharge SOC Indicated: 65%
RavCharge Estimate: 1:37 hr:min
Dashboard Estimate: 2:45 (after plug-in)
Entune Email Time Diff: 1:39

So, at 240V setting, the charge took 2.4% longer than RavCharge Est. and at 235V setting and a longer charge, the charge still took 2.0% longer than estimated. Anyway, compared to the car's estimates, this is really splitting hairs. The actual charge only took 60% of the time estimated by the car. If you want a conservative estimate from RavCharge set the voltage to 220V and the car will certainly finish a few minutes before the time given.

 

[fooljoe]

If you want a conservative estimate from RavCharge set the voltage to 220V and the car will certainly finish a few minutes before the time given.

Thanks for the data! I'm not so sure about this recommendation though. Of course it would be conservative, but for a charge starting from a low SOC it might be very conservative. Remember my observation about the SOC tending to read high for high and low for low - that means charges starting from a high SOC (>50% let's say) will tend to take a few minutes longer than RavCharge predicts, just as you experienced, but it also means charges starting from a low SOC will probably tend to take a few minutes less than RavCharge predicts.

 

[TonyWilliams]

There needs to be an adjustment for temperature adjustments. It's all fine in mild climate California, but for somebody in one of the those really cold places where the battery heater will also be running, the time will be extended, both because of the cold battery and because of the increase energy consumption of the battery heater.

Hot batteries won't have much of an impact.