New experience today. 2018 Clarity Touring with 32,000 miles. Drove it yesterday and all was normal. Started it today and every possible warning light on the dash flashed on and off. Seems similar to the descriptions people post when doing a hard reset by disconnecting the battery. Only thing is, I did not disconnect the battery. Drove the car to the store and back (about 25 miles) All the lights stopped flashing and turned off except the check engine light stayed on. Car ran normally. If it is still on next week, I will take it to the dealer. Question - Is my 12 volt battery getting weak?
Checked the battery this morning. Read 12.01 volts with multimeter (should read 12.35). Took car to Honda dealer without an appointment (I did call first). They checked and replaced battery. No charge - under warranty. I was pleasantly surprised.
Resting voltage of a fully charged 12V FLA battery should read ~12.7V. 12.35 is between 50-75% and 12.1 is between 25-50% SOC.
The voltage given, 12.7V, for a fully charged 12V lead-acid wet cell battery is measured with an open circuit which means no load on the battery. The voltage for a battery that has a load is somewhat less, going down to 9V or lower when the battery is cranking a starter motor (not on a Clarity, though). An idle (turned off) Clarity PHEV has a nontrivial load on the 12V battery. I measured the 12V battery on our 2018 Clarity PHEV before I connected the charging cable this evening. The 12V battery voltage was 12.1V (45F in the garage). This is a normal voltage for our 12V battery before we charge the car. I know the 12V battery is good because I periodically test it with a synthetic (electronic) load tester. We have not seen the multiple warning display since the car was new, before the update that was to fix this. Also, I cleaned the battery terminals around the time of the software update as the terminals had considerable white corrosion. BTW, our Clarity is usually only driven 2.1 miles each way to and from work twice a day during these times. The 12V battery does not get fully recharged on these short trips. The weekly recharging brings the 12V battery to fully charged along with the traction battery. LeoP
After the overnight charging, the 12V battery measured 12.3V (fluctuating between 12.28V and 12.35V, about 5 hours after the charging ended). I also took the time to measure the current draw from the 12V battery with the car idle (turned off). The current draw ranged from 60 milliamps to 150 milliamps with one spike at 650 milliamps for a few seconds. I did not have a record of the current draw but it looks (eyeballing) to average about 90-100 milliamps. The fluctuating current draw is consistent with the fluctuating voltage across the terminals. At 100 milliamps average current draw, the small 12V battery in the Clarity would be completely discharged in two to three weeks. I suspect that the electronic system starts to reduce the use of the 12V battery as the 12V battery voltage drops (same as some ICE cars) so that the 12V battery lasts for at least a couple of months before being discharged completely. Also note that the Clarity is shipped from the factory with a couple of fuses pulled that the dealer needs to install. I suspect this is also to prevent the 12V battery from discharging before the vehicle is put on the sales lot. LeoP
We neglected our Clarity PHEV for 3 weeks. Then it wouldn't start 2 days ago. Here I am after crawling sideways between the snow-blower/lawnmower to connect the battery charger under the hood I could raise only 7 inches due to an overhanging shelf. Until that day I never thought about having no way to put our electrified car into neutral if the 12V battery was discharged.
@insightman that is some tight space in your garage. You can get a pair of wheel dollies to lift the front wheels off and roll it out
You're right, I did consider that using dollies would be the only way to drag my Clarity out of the garage. However, my giant hydraulic jack could never work in that space to get the right front wheel onto the dolly. I don't believe there are bottle jacks low enough to get under the Clarity's jack points, so the remaining option would be a scissors jack that can support more than a ton. I'm so glad I built the shelf high enough that I could get the hood open the necessary 7 inches.
Note that not only is the gear shift electrically controlled, but the parking brake is also electric (and it locks the rear wheels!). So, if you were to try to dolly the car, you'd probably have to lift all four wheels. I remember when I had a similar problem on my mother's Impala, and I found instructions on-line for disconnecting the rear brake actuators in order to move the car. Instead, I used your system - raising the hood a few inches under the overhanging shelf so I could get the charger clips onto the battery. Whew!
Our Clarity is the daily driver. For my ICE cars that are not driven that much, I have added a charging cable to the battery so that I can plug in a charger at an easily reachable location without needing to open the hood. Many chargers sold today have the same charging cable connector and connector polarity. Given that the Clarity can have all four wheels electronically locked, it might be a good idea to add a similar cable to our Clarity. I think I have a project for later this year when the weather is warmer. LeoP
A set of Go Jacks would do the trick. Running wires from the battery to the front with a connector, maybe one that would plug directly into something like the Noco GB40 lithium jump pack, would have you rolling in less than a minute.
@Landshark, those Go Jacks are brilliant! I've never heard of them before, but they sure make sense. I watched this Go Jacks video to see how easily these $240 jacks+dollies work.
Is charging the battery through the 12V outlet, aka cigarette lighter, an option? Perhaps with a 5-10W solar panel or similar? I’ve left cars for months with a solar panel on the dash, even out of direct sunlight, and they’ve always kept the battery charged. It would be necessary to run a length of wire to a panel outside for a vehicle parked in a garage. I do that for a riding lawn mower.
One does not need a powerful boost or jumper battery to start a Clarity PHEV with a discharged 12V battery. The voltage across the battery terminals just needs to be about 12V and no more than about one amp of current needs to be supplied. The 12V supply just needs to be enough to power the ecu and to get the DC to DC converter working so that the main HV LI battery can supply the 12V. I suspect that a small 12V battery charger can have the Clarity PHEV with a discharged battery up and running within one minute or less. Please note that the above may not work if the 12V battery is damaged (a shorted cell for example) and the charger cannot maintain 12V across the 12V battery terminals. LeoP
This is true. Even the smallest lithium jump packs are capable of starting a conventional 4 cylinder engine, with a starter. All the Clarity needs is a small dose of 12V to power up. I don’t foresee ever parking the car where it would be difficult to impossible to pop open the hood. For someone who could be in such a predicament, and was considering running wires and a plug to an accessible area on the front of the car, it might be worth considering using a plug that would attach directly to a jump pack. That way there would be no need to dig out a charger and plug it in. And if there were no power source it would still be possible to get the car started.
