ScanGauge II Extended PIDS: Capacity and Specific Energy

First, thanks to AnthonyW for providing data, it’s a lot of effort. With regards to voltage and SOC, I was looking for li-NMC data because I read somewhere that’s the type used in the Clarity PHEV. I found a recent paper which tested a lg-chem nmc and provided a voltage soc curve. One observation is that nmc provides enough “curve” to use open circuit voltage to approximate SOC. What’s really frustrating though is that they talk about using Open Circuit Voltage ( no load) and then provide curves using charging voltage and discharging voltage. And, yes it makes a difference. For example, using 4.05 volts, measured under charge that’s about 80% SOC and under discharge it’s about 95% SOC. No idea about open circuit measures. So that tells us that we would need to know under what conditions the HBV is being measured in the OBD.

 

Here is the paper https://res.mdpi.com/def50200ff2cc418384e9ecbd6122dd88cb1f1113774149a3dad9c8e48c488f8dd33169c5f8762b04c216b6e3e5de395b5c7abee3d722956c4654c514cae5a0f9a6d0196b1244a957cd73a98a121a882b40614d4ce6272834c94919cf071f8a2070f94053d0367cbd949441f59b75dad1da2b1786d25d88bf95e99e8542e8e98a77a70d5763d66bbf144f0aa47b01ec1eb6ced6f40ac?filename=&attachment=1

 

Here it is and I also posted it in the thread I made on all the other goodies in this doc.
I didn’t get this at delivery and am having the dealer retrieve it from their off site records storage. I want to see their test of my batteries, both 12v and HV.
Here is the other thread I started on this doc:

https://www.insideevsforum.com/community/index.php?threads/lots-of-brand-new-info-from-pre-delivery-inspection-doc-esp-on-battery-replacement.2742/

 

I read this wrong the first time, if the car charges to 4.05 volts per cell, that is very reasonable and the same that the Chevy Volt charges to (which has had a very durable battery so far and also uses NMC chemistry). If the car charged to max voltage, that would be very bad and the batteries would fail like Leafs. Your curve for battery SoC may not be accurate for NMC and might be a discharge curve instead of a charge curve?
Anyway, glancing at this study: http://www.mdpi.com/2313-0105/4/1/11/pdf
A charge voltage of 4.05 is probably between 80-90%, but note that it differs between their two NMC cells and could be different for the Clarity.

My hunch is a simple software update to allow regen to charge 1 or 2% above what the car charges to using the AC charger would have negligible impact on life of cells and allow it to not start the engine so quickly (would still do it on a longer steep hill). Who knows though.

 

My understanding is that there is a difference between the loss of capacity that will trigger warranty replacement (33%) and the loss of capacity that will trigger a DTC (75%). If you're between those, then you would need to know to take the car into a dealer and get it checked in order to be eligible for replacement under warranty.

 

I think the Honda SAE article is fascinating, thanks for that AnthonyW. They key new understanding for me is the fact that the electric motor (a voltage controlled device) is powered through a DC-DC inverter off both the battery and the generator. That is, it doesn't matter what the battery voltage is i.e. where it is on the discharge curve, the inverter can boost the voltage to what the motor needs to operate at the desired speed up to 100MPH. The battery chart they show there is KW (power being delivered to motor) vs KWH (power remaining in battery, which we can think of as a proxy for SOC). Because it's showing power delivered to the motor it's not directly related to battery voltage. That flat curve they show is to demonstrate how well they can extract useable power from a range of SOC.

Another way of looking at it is that using the rather less flat NMC voltage/SOC curves, the Honda system inverters compensates for voltage fall off and can deliver a flat looking voltage curve to the motor.

The low end of those curves are also interesting, Honda shows what they call Charge Depletion (which I would like to call EV driving) lasting until about 4 KWH remaining on the battery. That's about 24% SOC. That should be the point when the ICE turns on automatically, which is at about 2 bars on the displayed energy meter (10% if I recall). In real terms then, actual SOC (rather than what the meter or Hondalink displays) that Honda wants to operate the battery at ranges between ~20% to ~95% SOC. Mapping that to 0-100% on a meter means the thing is non-linear, but then we expected that looking at the battery voltage curves.

One final thing I want to say, is that battery chemistry is the "secret sauce" for EV manufacturers. I think Honda has developed a drivetrain/powerplant able to extract the most usable amount of power while preserving cycle times and battery life. Future improvements will be in battery chemistry. Which is why it was interesting to see Honda, this month, sign on to GM's battery development technology. To date, Honda is buying battery's and seemingly not engaged in battery design, unlike Tesla, GM and BMW to name a few. Partnering with GM will allow Honda access to some secret sauce and keep pace with developments.

 

@bwilson4web has done some efficiency calculations for Prius and appears to be currently working on Teslas. If you can get something similar to what he asks for in this post, arrival of a drag number might be close at hand: https://insideevsforum.com/community/index.php?threads/tesla-drag-power-analysis.2746/#post-24558
I tagged him in another post to try to get his spreadsheets that we could then manipulate for the Clarity but either he saw it and ignored it or didn't see it.

 

Bingo!

I'm using OpenOffice and can't load the spreadsheet directly so I put it in a zip file.

Bob Wilson

 

Right. Read the PDI document and you see this sentence on pg 13: "But unlike earlier vehicles with high-voltage batteries, this vehicle does not set a DTC when the battery pack capacity value has reached the level for battery replacement under warranty." WOW! What's the logic behind that deviation? Hey, yeah, we'll replace the battery at this earlier degradation point, but if the customer never knows the battery's true state, we won't HAVE TO until the DTC pops up.

So this spawns yet another recommendation. It would seem appropriate to include a Battery Pack Capacity Check as part of the Maintenance Minder at some periodic interval (possibly MM Sub Item Code 9 or every 3 yrs). Since we've got Gen 1 models, I'd suggest every Clarity owner request this be done yearly when going in for other maintenance and the results reported: not just "PASS" but actual value (SHALL BE >/= 36.6Ah).

 

@bwilson4web ,

Here's the other message regarding the work you were doing on Prii:
https://insideevsforum.com/community/index.php?threads/modeling-clarity-phev-mpg.2186/#post-17274

These spreadsheets would have the equations used to generate the various graphs for MPG vs MPH and I also needed explanations of some of your parameters.

Thanks.

 

AnthonyW,
Have you tried the other Honda Hybrid xGauges to see what works?

 

If a DTC is set, the car will not pass emissions inspection.
So, the car could not legally be on the road (the laws vary by State/County on how long the car can be on the road legally to have the emissions fixed). Fwiw, in many States, after x-months, the car would then need a temporary (5-30 days, varies by State) license/permit to get the car tested again.
Yes, emissions testing can be a massive PITA.

As I understand, in some States/Counties, that also means that that the State/County has the right to impound the vehicle after ~6 months, if they find it on the road (Calf/SF). WTF????

Imho, they way that Honda is now doing the battery level check is correct.
A DTC should only be set for a bad battery pack only when it's critical to the operation of the vehicle.
Honda has decided that for the Charity, if the battery pack is below X%, then the battery pack has very limited use left in it.
If the battery pack gets to below a specific value (?maybe ~20%?) and stays there, Honda likely has the engine control software decide that it's no longer safe to charge and operate the battery pack because of heat/fire/explosion/death/etc concerns.

 

When a gen 1 Insight battery packs it in, it no longer charges the 12-volt battery. This problem makes driving the car significantly more difficult.

 

Well, it reduces your range anyway.
You could pack a 12v charger for extended trips.