My Clarity eats up 12V batteries

I'm still on my original 12v battery. 2018 Touring, 51,000 miles. I am now in Illinois after driving 1,200 miles from Florida. 5 fill ups, 28.458 gallons of gasoline, 1203.8 miles, 41.5 mpg (after subtracting 23.8 miles of EV use).

 

I just had to check - we used to use gallons in Canada - IMPERIAL gallons which are bigger than your gallons so your mileage calculated here would be 50.76 miles per gallon - sounds so much more doesn't it... ( course we are metric now so 1936 km and 108 liters = 5.6 L / 100 km - most 'regular' gas guzzlers like my Volvo are much worse 8.8 L / 100 km)

 

NJ, '18 but 40K. Still original battery and probably pushing it - 4yrs is typically what they last.

 

I have a 2018 Clarity with 46K miles on it. I never had a problem with the battery, but changed it this week. After 4 1/2 years, I wasn't taking any chances. I'm sure the price was no bargain, but nothing is these days. I normally have AAA come to my home, but they don't carry this battery model.
Pluses: One less item to have to think about.
Minuses: MPG stats disappeared and I think the car is back in learning mode.

 

Before buy the Clarity, I had a Acura TL and the 12v battery was drained if I didn't drive it for several days. Took me several batteries to find out why the battery was being drained. It was the bluetooth mother board. I disabled bluetooth but battery was still being drained. Finally, saw on Youtube that this was a common problem and followed instruction to disconnect the motherboard. Problem solved and later traded the TL for the Clarity

 

I bought my 2018 Clarity end 2017. It is coming up on 14,000 miles, mainly short drives in SC where it is garaged. I still have the original 12 V battery, but will change this year. I do carry a jumper pack.

 

I've had mine since 2018 and had to change the battery out once about a year in. The strange thing was, the battery would test test good, and it would work for a while once fully recharged, but then start crapping out on me again. It got to the point where I had to take a wrench and tap on the negative post sometimes before it would start after I'd turned if off for the night, or after working a full day (8-12 hours). I later found out that the discharge I was seeing and also the cause of the strange issue with the negative post were both attributed to a process called sulfation: this is caused by the battery being undercharged by the alternator prior to the car electrical system shutting off, leaving the battery to undergo a chemical process resulting in those symptoms. This is typical for those who don't regularly charge the Li-Ion battery to full and also drive in short "bursts" (such as to and from work). The beginnings of this process is reversible by supplementing your 12V charging with a plug-in charger/conditioner, but once it reaches a certain point the sulfation can become permanent, at which point the only thing you can do is replace it entirely (which was what happened to me). I now regularly "top off" my 12V about once a quarter to once a month, depending on my driving habits, the weather, and condition of the battery.

 

I now have 53,792 miles on my 2018 Clarity Touring. I bought it 4 years and 4 months ago in May 2018. My original 12v battery seems just fine. My high voltage battery has lost a significant amount of its original capacity. I am guessing it has somewhere between 75 to 85 percent left. I believe that the battery must hold only 66 percent or less of the original 14.4 KWh before Honda will replace it under the warranty. I doubt it will get that bad within the warranty period.

My Clarity is kept in my garage and is driven almost everyday. Because of reading this thread, I have double checked the electrolyte level in its 12v battery and it is normal. My wife's 2017 Honda CR-V's 12 volt battery failed suddenly at the end of December 2019 just before we were to drive to visit family in Ohio for New Years. Although the battery/CR-V were less than 3 years old, it had over 36,000 miles and as a result the battery was out of warranty. My Clarity made the journey in place of our CR-V without a problem.

 

Lithium batteries are not subject to sulfation. The only issue with not fully charging a lithium battery is that it may not go through the process of cell balancing.

Keep in mind that the 12V battery in the Clarity is not used to start the engine. About the only way to discharge the 12V battery would be to put the car in accessory or on mode rather that ready mode and leave it that way for a period of time. In ready (driving) mode, the 12V battery receives a charging voltage from the DC/DC charger of 14.x volts.

 

My apologies for the confusion, what I meant was that by not having the lithium ion battery charged, the 12V loses out on the opportunity to draw from it. This, combined with the other factors I mentioned on a consistent basis, can lead to the 12V undercharging.

 

To that point, at what SOC on the HV battery would you estimate that the 12V battery is no longer able to receive a charging voltage from the HV battery through the DC/DC charger?

 

I thought someone more knowledgeable would have chimed in by now, but I'd very much like to know the answer myself! Something I did only very recently learn about (just one of those glaringly obvious things you somehow entirely miss for an absurd amount of time) was that you can hold down the "HV Mode" button and it will kick the gas engine on manually and dedicatedly charge the HV battery up to 50% full. Of course, this would have been so much more useful back before gas prices were what they are now, but in a pinch (like when you know you're about to do a lot of uphill driving and won't have the opportunity to get a charging session in), you can somewhat mitigate totally emptying out your HV battery at the (very expensive) cost of gas.

 

Understanding the features available on a vehicle certainly has benefits. HV+, (aka: HV Charge) will charge the battery up to approximately 60%, or 12 bars out of 20 on the battery status display.

Several owners have reported that HV+ charges with remarkable efficiency when it is used as recommended in the owners manual. Even with higher gas prices some owners may find the difference in the cost of a gallon of gas or 14kWh’s of electricity to be insignificant. I was recently in Connecticut where regular gas was $3.00/gallon and the average cost of electricity is $.22/kWh, or $3.08 for a full charge.

Another well documented practice that many owners follow is to engage HV at the start of a trip where there may be demanding driving conditions or the distance will exceed the EV range. Doing that preserves the HV battery SOC for use at another time.

 

I don't think I would know about 50% of what I do without these forums. And actually the important 50% I learned here. I spent about six months not really understanding how to best drive Clarity. I actually did read the manual almost cover to cover the first week of the new car. My wife found me sitting in the car sometimes at night trying to understand features.

HV charge is in the manual as in "what it does," but not necessarily "how to best use it." Key things that I learned on this forum include:
- In Clarity, the *electric motor* is absolutely more powerful than gas. I found this very counter-intuitive to the point where I'd use the gas engine up a big hill. Now I do the opposite. If significant hill and I have charge, I drop out of HV mode, go all EV up the big hill (and maybe down to get the recovery) then re-engage HV.
- In my first six months I used to routinely let my car go to EV range=0. I now never allow that. I find Clarity does best including in HV mode, with EV estimated charge of 5-10 or more miles. If I go below 5-10, press and hold HV until I go back to 60%.
- In practice, if your driving on flat ground, one typically doesn't need HV charge unless on a long trip; i.e. EV in my car goes down slowly even when in HV mode, and it loses EV range when doing brief stops. The other place HV charge is super important is going through mountains and hills. It can help you retain EV charge (not let it go to zero).
- If you have one of the blessed Clarity's that never does angry bees, you can allow EV=0, but I still wouldn't risk it. There's no downside to leaving some EV range all the time. My Clarity absolutely "borrows" from the EV charge while driving around in HV mode, and then tries to replenish it. If EV=0, I presume the car has less flexibility in its power-management.
- Oh and of course and as Landshark mentions, on a longer trip, I guard and protect my EV range and "spend" it where it has the best utility. My commute is all electric, so I spend it freely when I know I'll be back at my charger before EV=0 anyway.

But the tips above while simple to do, were not obvious to me, and in my car's case make a world of difference. And finally, even an "uneducated" driver can just get in and drive. I would tell family that borrow the car to just push HV right away. This tends to yield the best experience for the uninitiated.

-Dan

PS: There are Clarity owners who claim they can drive with EV=0 same as normal hybrid mode. That has never been my experience even when the car was brand new. I only hear high reving aka "angry bees" when EV=0, that literally never happens otherwise, and does not occur in HV charge mode. YMMV.

 

Meanwhile, here in California...

 

Not everyone lives in your bubble. Electricity isn’t cheap in CA either, and assuming that electrical energy remains readily available, it isn’t likely to get less expensive over time. At least you have a choice with a PHEV.

 

Here’s the guidance on HV Charge from the manual. Pretty straightforward on when to use it or not use it

This statement needs some clarification. The electric motor is most powerful when receiving electricity from both the battery and the ICE driven generator. The gas engine contributes in several ways:
1) In conjunction with an adequately charged battery.
2) On it’s own, driving the wheels directly in Engine Drive Mode.
3) Essentially on its own, as a generator when the battery is depleted or nearly depleted.
Just to list a few possibilities.

With the exception of EDM, the electric motor is always providing the motive power for the vehicle. The motor can produce more horsepower from the energy provided by the batteries than it can from the energy provided by the gas driven generator.

 

Thanks for the Clarification Landshark. I find the car most pleasant and feels powerful in EV-only mode going up a hill. (i.e. I tap HV to turn off HV mode temporarily when going up hill). I would believe that the HV mode, is more powerful, but it is not as pleasant (quiet). So I tend to select EV-only (HV off) going up hills if I can also keep sufficient EV charge. For shorter trips this is easier to manage. i.e. going up a mountain causes the length to exceed EV-only range, that, and rolling hills may not permit.

I also don't know if this is literally true, but it feels to me like the car is a little better going down hill generating EV charge when in EV only mode (as compared to HV). So I tend to flip from HV to EV on a downhill to build charge. I realize it is possible to build charge downhill with HV engaged, but it seems to work better with EV going down. So what I'm really saying is I tap HV off, both going up and down hills, then return to HV on the flats if that's the profile of my trip.

One area this strategy (above) works well here in Oregon is trips to/from the coast. The hills are quiet in EV, and not so many as to drain EV completely.

Hope folks don't mind the threat going off the original topic.

 

Not to be a pill, but the Clarity PHEV has no true EV-only mode.

I’ve experienced the same thing. My explanation is that when in HV Mode the car attempts to maintain the SOC set point of the traction battery. Whereas in EV mode there is no set point and the car will allow regeneration to increase the SOC of the traction battery.

This is a belt and suspenders theory as I only utilize the battery charge level display on the dash for confirmation when performing this laboratory work. I do not use the EV Range estimate as it is prone to producing useless data, particularly under these test conditions.