Charging levels in theses Covid times

[John E Barbato]

Are there any specific guidelines on keeping a certain charge level while my Clarity is pretty much sidelined these days. Tesla suggests keeping their batteries at between 36 and 50% charge in a non-operative state. Whasup, Honda?

 

[Landshark]

Here’s what is stated in the manual.

 

[Dan Albrich]

Also, and not battery but Covid related. If my car basically sits for month with only grocery runs, should I intentionally run the gas engine (press HV) periodically? I'm guessing want to run gas engine once every 2 weeks, but I also know there are some in these forums who basically never run gas engine and seem OK.

 

[KentuckyKen]

Also, and not battery but Covid related. If my car basically sits for month with only grocery runs, should I intentionally run the gas engine (press HV) periodically? I'm guessing want to run gas engine once every 2 weeks, but I also know there are some in these forums who basically never run gas engine and seem OK.

I run about 95% EV with long stretches between HV out of town trips. I’ve found that the ICE will start about every month or so for what I assume is a System Check. So I never run HV unless I’m going our of town and I trust the software to start the ICE as needed to keep it lubed and ready to instantly run when needed. I’ve added Stability to the tank since I go 6 months or more with no HV trips. The current tank is coming up on 10 months so soon I’ll run HV just so the gas wont be more than 1 year old. Heck, I may even run HV Charge just for the fun of it and so that button wont feel left out. Since I’ve never run HV Charge, I wonder if I will finally hear some engine revs?
With just me and no passenger or luggage, and a goodly amount of charge, my ICE runs very quietly in town and is not objectionable at all. In fact I’ve never heard the angry bees and only have had the ICE run in what sounds like mid range when going up a long steep hill at 65 mph. BTW, the System Checks are very infrequent and only last a few minutes and don’t even cost a single bar on the gas gauge over a year. Yep, I love this car!

 

[Cash Traylor]

A "storage" state for our chemistry lithium cells is between 40% and 60% open circuit voltage (OCV) for an 84S2P pack. This is for long term storage of months to years. The battery and system self discharge, so you basically aim for the top, and accept the slow decline over 3-6 months. Covid will last a while, but you will likely drive more than once in 3-6 months, so this is really not a concern. Also, 40-60% is the actual battery, not our "buffered" pack. We don't get the full 100% of the cell so your HondaLink reported percentage is not the same as the SOC percentage stated above - so it is really going to be based on voltage. Don't freak out, if you really wanted to know this, most $10 OBDII plugs that run on a phone app will report the HV battery voltage if you dig through the readout (car needs to be in acc-on not just acc, but it does not have to be "ready to drive" on) - the second push of the start button without brake. The target voltage would be around 320. Tesla pads the bottom SOC for their packs too, all EV's do, so their suggestion of 36-50% on the driver display is actually 56-70%, which follows IEEE and IEC document guidelines.

The above was just background. The absolute easiest and BEST way to do this is using the method Honda gave us. Run your HV Charge mode until it turns off (don't do this in a closed garage please, CO is really much worse than covid) saying you are at the maximum state of charge for HV Charge (about 57.7%). This happens to be the perfect storage state of charge for the Clarity. It is one of the reasons why they did that (from a dealer inventory "memo" I have been told about, but not yet found). Apparently if the dealer had lots of cars on the lot, they can just go to each, start in HV Charge mode once a month, and that runs the ICE for lubrication and fuel sediment, AND charges the battery back up to storage mode. Honda thought about the roll out of the Clarity to unequipped dealer lots so built a way into the car for them to take care of this. Most dealers have gas easily on hand - so this was a, in my opinion, brilliant solution. To bad most dealers never did it.

Cheers,

Cash

 

[Landshark]

The above was just background. The absolute easiest and BEST way to do this is using the method Honda gave us. Run your HV Charge mode until it turns off (don't do this in a closed garage please, CO is really much worse than covid) saying you are at the maximum state of charge for HV Charge (about 57.7%). This happens to be the perfect storage state of charge for the Clarity. It is one of the reasons why they did that (from a dealer inventory "memo" I have been told about, but not yet found). Apparently if the dealer had lots of cars on the lot, they can just go to each, start in HV Charge mode once a month, and that runs the ICE for lubrication and fuel sediment, AND charges the battery back up to storage mode. Honda thought about the roll out of the Clarity to unequipped dealer lots so built a way into the car for them to take care of this. Most dealers have gas easily on hand - so this was a, in my opinion, brilliant solution. To bad most dealers never did it.

That’s an interesting theory and I’d love to see that “memo”. It would also be interesting to know, how many dealers who are too lazy or ignorant to plug the car in for a few hours would have the time or knowledge to go out and start all the Clarities, one we looked at in So Cal was in a remote lot several blocks away from the dealer.

HV Charge is a viable way to charge the batteries to ~60%. The manual recommends using HV Charge while operating at freeway speeds, not stop and go traffic. They don’t even mention using it while sitting in a parking lot.

It is a great feature. A more plausible reason for adding HV Charge is the creation of Green Zones in metropolitan areas, primarily Europe at the moment. Operation of ICE vehicles within these zones may be restricted, prohibited or charged accordingly. So, if you plan to enter one of these areas, a vehicle with the ability to charge depleted batteries as you approach would be a nice feature.

Currently in the US, gas prices are so low it is less costly to charge the batteries with the ICE that it is to plug in. This possibility was probably not discussed at Honda.

Some owners have suggested that using HV Charge to gain EV range is as efficient, or more efficient than driving in HV. The idea being to use EV range, charge on the fly when the batteries get low, rinse and repeat.

In summary, while Honda has made some peculiar decisions, I would put Dealer Charging Convenience near the bottom of the list as to why they added the HV Charge
feature to the vehicle.

 

[insightman]

I would put Dealer Charging Convenience near the bottom of the list as to why they added the HV Charge
feature to the vehicle.

I've always wondered why HV charge isn't allowed to charge more 60% of max SOC. Making the job of clueless, but diligent, dealers easier is the only reason for this limit anyone on this forum has proposed. Of course, I doubt there are any clueless, but diligent, dealers out there. Either they know what they're supposed to do and do it, or they just let the car sit there until some weirdo eco-freak who can't be talked into buying a Pilot takes it off their hands.

 

[Landshark]

Making the job of clueless, but diligent, dealers easier is the only reason for this limit anyone on this forum has proposed.

I have proposed that HV Charge limits charging to ~60% because it appears to charge at a rate above 0.8C, which is a limit some battery manufacturers have determined to be a maximum recommended for battery longevity. Level 2 charging is at ~0.4C on the PHEV, for example.

The basis for this estimate of C-rate is my observation of HV Charge bringing SOC from 2 bars to 10 bars (0%-50%) in ~30 minutes. This would indicate a C-rate of ~1.0C. It is also possible, although this is pure speculation, that the BMS cannot properly control the HV Charge rate above 80-85%, were it allowed to charge to that level.

HV Charge borders on being a “fast charge”. Many EV manufacturers limit fast charging to 80%.

 

[insightman]

I have proposed that HV Charge limits charging to ~60% because it appears to charge at a rate above 0.8C, which is a limit some battery manufacturers have determined to be a maximum recommended for battery longevity. Level 2 charging is at ~0.4C on the PHEV, for example.

The basis for this estimate of C-rate is my observation of HV Charge bringing SOC from 2 bars to 10 bars (0%-50%) in ~30 minutes. This would indicate a C-rate of ~1.0C. It is also possible, although this is pure speculation, that the BMS cannot properly control the HV Charge rate above 80-85%, were it allowed to charge to that level.

HV Charge borders on being a “fast charge”. Many EV manufacturers limit fast charging to 80%.

Couldn't Honda reduce the charging rate as the SOC increases beyond 60%?

 

[Tek_Freek]

Also, and not battery but Covid related. If my car basically sits for month with only grocery runs, should I intentionally run the gas engine (press HV) periodically? I'm guessing want to run gas engine once every 2 weeks, but I also know there are some in these forums who basically never run gas engine and seem OK.

Also driving rarely. Usually Walgreens for meds.

Yesterday, in EV mode, our engine started while "coasting" down the hill from our house to visit friends for bridge. Ya, I know, "What?", but we are all four extremely careful about other (as in none) social interactions. Between us we have heart problems, lung problems, and Parkinson's. So yeah, really careful. Nice to be able to visit and play cards.

My wife asked why it would and I told her it knows when to start for certain things, like moving oil through the system.

 

[Tek_Freek]

Currently in the US, gas prices are so low it is less costly to charge the batteries with the ICE that it is to plug in. This possibility was probably not discussed at Honda.

It's still cheaper for us to use electricity. Gas has to drop below $0.90 a gallon before it flips.

 

[Landshark]

Couldn't Honda reduce the charging rate as the SOC increases beyond 60%?

Probably.

Let’s say they would be comfortable with a L2 charge rate from 60-100%. We know a full charge at L2 takes ~2.5 hours. It would take ~1 hour to charge from 60-100%. That may not meet the efficiency mandate of which the engineers are so proud.

 

[Cash Traylor]

Greetings,

I've been gathering data. Still more to do but finally put my inverter cover back on, and removed the welding shunt I used to confirm current flow with data from the OBDII stream. That was pointless I must say....and dangerous, not recommended but now I know for in the future (it is sealed, red RTV). Had my lineman gloves on though...

There has been some speculation after my above post regarding the HV Charge Cycle/Mode and Lithium storage levels (40-60% total capacity). Some said that HV Charge is a "fast DC" charge, that it wasn't intended for static use, only while in motion. I agree that those were the intentions for the end users, however based on what I see system wise, the "unseen letter" makes sense to me. I can tell you that the behavior of the system appears to makes no preference. In fact, when used in motion, the current swings are very dramatic when regen braking is used (but I will save that for a separate thread). It also seems to be relatively efficient considering the inherent losses of a ICE-gen-storage systems, thermally and mechanically. Not going into the fuel efficiency, as a gallon of gas has about 33kWh of energy in it, little of which a gas engine releases for mechanical use....

I will start another thread for most of this charge/discharge behavior in the various modes while driving once I finish a few more tests. However, only in relation to my prior post here, as it pertains to "storage charging" this is what I found. Using HV Charge while the vehicle is parked to "top up the batteries" and blow out the dust (in the ICE), this is what happens.

Assuming the battery is below the 57% HV Charge Mode functional initiation range.

Condition tested: vehicle sitting in driveway, ICE cold as the high idle warm-up which of course only lasts a short time.
ICE warm-up runs between 1500-1800 RPM in my tests (temp outside was 75 deg), estimated HP based on fuel flow is 9 HP
ICE Idling at ~1200 RPM, estimated HP based on fuel flow approximately 4.5 HP (however I do not have a specific measure for an Atkinson cycle engine, this is based on Otto)
* this is never "free idle", like a regular car in neutral with the accessories off, as the generator is attached and always engaged. I never found a mode while not driving or stationary that the GEN was not producing some current. It gets really interesting when the "gear" is engaged (but again for another thread).

1. ICE cold (1500+ RPM), HV battery at fully discharged (20% SOC/Total Capacity)
2. ICE cold, HV battery at 55% SOC to HV Charge shutdown
3. ICE warm (1200 RPM), at 20% SOC
4. ICE warm at 55+% SOC run until HV Charge cut-out at the ~57.7% SOC. (For my car it was almost 60% before it cut off at 315.2 volts)

1) Charge current into HV Battery ~20 amps peak, average at ~18 amps or ~C/3 for rate of charge (about 6KW, or L2 rates) . This is not even close to DC fast charging or the C1 rate.
2) Almost same rate of charge as far as watts (around 5500) , however the amps decrease slightly as the pack voltage increased (with engine RPM's a constant this makes sense)
3) Charge current into HV Battery averages around 8 amps, or ~C/1.5 for a rate of charge (wattage around 2500).
4) Was surprised, there was no taper of current before cutoff. It was holding around 2200-2300 watts until it simply turned HV Charge mode off (~7 amps at 315 volts)

During all of the above, the 12volt battery was of course held at the 14.4 range (charging). So, this charges all the batteries, and runs the ICE and vehicle systems.

Interesting is that there is only about a 600-800 watt loss in ICE power output (shaft HP) to HV charge current input. I know that some of this is lost to loads other than the HV pack (which is all I was monitoring power input wise). Some of that wattage is going to the 12 volt battery and all the other vehicle systems (fans, lights, pumps, computers, etc). This is expected, however I found it amazingly low based on the torque calculations. Considering conversion and efficiency losses (thermal etc) I am pretty impressed. Again, it seems Honda was concentrating on efficiency in the system.

Again, this applies to the use of HV Charge at idle / stationary - not driving. I'll do that later, when I can go through the spreadsheets more. However, I will say that current swings exceed 150 amps charge / 250 amps discharge frequently while driving. Coasting down a big hill or mountain can result in charge rates greatly exceeding 2C if you use regen. I now have no doubt why the ICE turns on and motors to dissipate excess current. I watched the ICE (when running) in HV mode dissipate surge current (150 amps without to 35 amps with) while braking with full regen selected from moderate speeds.

*If this info has been reported before, I missed it during my searches, sorry...

Ok, killed one day of boredom due to covid, on to the next project and back to the CAN hacking.

Cheers,

Cash

 

[KentuckyKen]

Cash, you are my hero and proof positive that not all super heroes wear capes!
Finally we have some empirical data and explanation on the “engine start when battery full supposedly to protect from excess regen” phenomenon. @insightman and I will finally be vindicated since early on we have some doubters that the ICE would fire up for this.

May I suggest you start a new thread labeled HV/HV Charge Observations?
Then we can put all our observations and explanations/opinions there.

I will add some from this week when for the very first time since purchasing in 3/2018, I hit the HV Charge. (In preparation for running out my full tank that is getting to be a year old) I then ran (just as you’re not supposed to do) in town until HL showed 60% and it would only run HV. I have some observations and ideas to share to HV efficiency in town vs hwy. And I couldn’t make it rev hardly past the fast idle noise in town and then only under acceleration.

 

[Cash Traylor]

Also, before anyone asks. I am not posting pictures or video up regarding the inverter tap. Unlike most, my real name is on this forum. What I did could be deadly, and I can't write a big enough legal "don't do this" form to click on before seeing photos. 300+ volts at almost unlimited amps (it's more kilojoules than I want to calculate) for all practical purposes, death and very painful quick death. I can't afford a law suit... I'm sure there are photos somewhere else, I'll let Google deal with that.

* I should also point out that regarding reduction in regen surge, I had HV Mode or HV Charge on at those times, and the engine was already running. I have never been able to create a situation in the flat area I live where I could cause the ICE to kick on to achieve that presumed same function as others have. This was only my observation while researching data for this specific HV Charge topic. I am assuming, if it happens when the ICE is on for HV or HV Charge, that it would happen when the computer turns it on for overcharge protection. The amount of current the traction motor is capable of producing in regen is very high.

Cash

 

[Landshark]

1) Charge current into HV Battery ~20 amps peak, average at ~18 amps or ~C/3 for rate of charge (about 6KW, or L2 rates) . This is not even close to DC fast charging or the C1 rate.

3) Charge current into HV Battery averages around 8 amps, or ~C/1.5 for a rate of charge (wattage around 2500).

Looking forward to more data.

For now, is ~18A 0.3C or 3.0C if 8A is 1.5C?

Wouldn’t a charge rate of 3.0C provide a full charge in ~20 minutes and 1.5C rate fully charge in ~40 minutes?

What do you consider a fast charge?

Did you measure the voltage from the generator?

 

[Cash Traylor]

@Landshark

What I (and everyone has their own value of time) consider "fast charging" is anything equivalent to level 3 or higher (not necessarily Tesla's offerings as so defined, or CHAdeMO).

DC or any source of "Fast Charging" is generally considered any charge rate that approaches the C (capacity in Ah) rate of the HV pack. Often the system charges the first 50% of the pack at rates above C, then taper to C or below at the 80% mark, and achieve full charge prior to 90 minutes. Less than one hour charges are possible, chemically, but not "economically."

****Oh crap! I just saw what you are asking about. When I first typed the 8 amp idle sentence, I was going to compare it to the "level 1.5 chargers" out there that charge at watt rates above 1900 (level 1 limits) and push up to what a 20 amp 120 outlet can do (2400 watts) of course the charger is in the car so that determines actual performance, the EVSE just tells the car what is "available." The Level 1/2 Duos and other china-chargers. Ugh, edited my sentence wrong after changing direction and didn't fix the math error. SORRY! No, the wattage was stated correctly, the C rate not! It would be C/7 rates, NOT C/1.5. C/1 is 54.6 amps.... I can't go fix my earlier post now....

Sorry, when I wrote C/3 that is the battery capacity divided by "X" so your restatement of .xC is mathematically the same expression. 54.6Ah divided by 3 = 18.2 amps per hour. 0.3 times 54.6 is the same. No, at no time other than regenerative/braking did I see currents peaking above 3.0C (163.8 amps).

I measured the voltage at the HV Pack connection. The voltage at the generator is not DC, and I could not easily get to that for probing (would require two clamps versus my single shunt at the battery). Since the generator voltage goes directly into the inverter assembly and is always under load (the HV pack) I would have to "free wheel diode" that and it would likely blow up the buck inverter. Although answering your generator voltage question is possible (and Honda already knows the answer) it is unnecessary. What we really need are the electro-mechanical specs of the traction motor and generator (motor). Just knowing Kv, Rm, and Io would be nice. Once you know RPM then you can calculate the rest (idle was 1200). Also, I only did the shunt to confirm my CAN data stream was accurate. I used CAN data after that as it is WAY safer (I didn't drive on the highway with two wires coming out of my hood to my arduino card with mv adapter).

Either way the generator voltage and current doesn't really matter - as again I was looking to specifically answer the question or debate posed here where HV Charge could be used to "top off" the HV Pack and 12V battery in a lot, based on hypothetical assumptions. The "adage" that HV Charge should only be used in motion, or presented "fast DC charging" complications needed investigation.

https://energsoft.com/blog/f/c-rate-of-batteries-and-fast-charging

Cheers,

Cash

 

[KentuckyKen]

Cash, it was my understanding that the metric “C” is calculated by dividing the charging rate in kW by the total kWh of the battery. As in my 32 Amp ChargePoint Level 2 EVSE charges at 7.2 kW (until the ending taper charge), so 7.2/17 = a C of ~0.4. And a 32 Amp Level 2 EVSE is the max that the Clarity PHEV can take advantage of. So it will never be charged by any EVSE at more than 0.4 C.
I was also under the impression that anything below a C of 1 is in no way stressful to a Li-on battery pack, especially one that has liquid cooling. I believe I read that some where but can’t remember the source. I know that at least one poster has agreed with this. So, is this right or not?

 

[Landshark]

C/1 is 54.6 amps....

1.0C would be ~54.6A at 345VDC, correct?

Cell target voltage of ~4.1VDC x 84 cells = 344.4 VDC rated at 27.3Ah wired in parallel with 84 additional cells creates a ~345VDC battery pack rated at 54.6Ah. Or ~18kWh, 345 x 54.6 ~18,800.

The built in charger can’t charge at a 1.0C rate, so what voltage and current is being created by the ICE generator and how is it being converted to a voltage and current that is capable of charging the batteries at a rate that exceeds the capability of the built in charger?

I only have a rudimentary understanding of the subject from having a solar array with a 48V LA battery backup at the house and a motorhome with a 12V house battery bank and inverter/charger. And now, a Clarity.

I’m trying to learn and greatly appreciate your efforts.

 

[Cash Traylor]

@KentuckyKen "C" as far as I am speaking, has nothing to do with EV's or EVSE's and only to do with chemical energy storage (batteries of any chemistry).

"C" is the amp hour capacity rated nominally for a battery/cell at least as far as I am referring to it. "C" can obviously have a considerable number of variable assignments (as nightmares of Calculus come flooding back). Amps are the measure of coulombs of energy. Watts is volts times amps and is representative of work, or the potential for work (storage). You get a "watt hour rating" for cells by taking the nominal voltage (either 3.6v or 3.7v for our Li-polymer cells) times the Ah rating. However, as they say - a watt is a watt! For us, that is a 84S2P pack for a total of about 54.6 Ah (27.3Ahx2, the 2P part) at 310.8 volts (84x3.7, the 84S part) nominal for a wattage rating of 16,970 watts (17kWh our Clarity battery). That is 84 cells in series, twice, then paralleled. It is likely that Honda de-rated the pack by using the minimum Ah rating versus the nominal from the cell OEM. I plan to get a module in this summer to take apart and bench test an individual cell, and finally put that to rest. AZ has modules but they are not "taking them apart."

Your EVSE is not the charger (I know you know that...), only the voltage/current supply to the actual switch mode battery charger and BMS in the rear of the car. That "charger" is rated for a maximum of 6.6kW of charge energy, so your 7.2kW EVSE is not putting that in the battery, it cannot. You can divide that into volts and amps depending on state of charge. When our HV pack is low say only 20% or about 295 volts, then that would be about 22 amps of charge current (slightly higher voltage potential required, WAG at 300). As the voltage goes up in the pack towards full around 345 or so, the amps decrease to around 18 or so. The car's charger is a constant power factor converter and will put out the 6.6kW of charging energy unless it self limits for thermal loading or supply current issues (which the EVSE is supposed to communicate with it over the very simple pilot protocol) The watts stay the same until cut off - which since we never "fully charge" the pack happens rather abruptly versus the usual slow taper/balance stage. Yes, it does taper, but not along a C/90 end of charge you would use for passive cell balancing, as that would take forever and the BMS does that actively. Our system does a pretty good job of balancing the packs throughout the charge (as far as I can tell) as we are charging it pretty slowly relative to "C" rates. Yes, you can express C as a function of wattage, however that is usually when are talking about a charger pairing with a battery pack. Since we cannot change the charger (built in) we can only reduce our rate of charge. We can charge between the OEM (slightly de-rated level 1 at 12 amps versus 15) up to a 6.6kW level 2 - all AC source of course as in the US we did not get CHAdeMO for DC charging, and really don't need it being a PHEV.

https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

Attached a spec cell for grins and giggles, it is NOT our cells.

*I had to get up for chores with the kids about 50 times during this post... all the technology at the beginning is no longer relevant at the end...

Cheers,

Cash