12 volt battery on 2018 clarity plug in

[Alec]

Then again this is their theory for how their system could possibly cause your 12V battery to die, since you asked them about it, although I don't think it has been proven yet that the Juicebox is the actual cause for your 12V problem?

Correct, the car is in the service right now and they will keep it overnight to try to simulate my experience.

 

[insightman]

JuiceBox support said that seems to be a poor vehicle design, they are working on a workaround and will push a firmware update to address this issue.
At this moment, the Juicebox keeps constantly "pinging" the Clarity that it is about to start charging even when it isn't and that is keeping the 12V system active till the 12v dies.

Did JuiceBox say all Clarity PHEVs with their "poor vehicle design" will have this problem? There are many forum members who have JuiceBox EVSEs, but I don't remember others complaining about that brand draining their 12V batteries..

 

[Alec]

Most likely only those who have 2 or more boxes installed and configured for load balancing.

 

[Alec]

I started experiencing 12v battery issues ~33 months into ownership. The same symptoms OP described. Had the battery tested at the dealership and replaced under warranty with a much better honda OEM 100 month battery.

Before I went to the dealership, I got it tested in 5 minutes at my local autozone for free who verified my battery needed replacement. You can do that to get a 2nd opinion if you don't agree with your dealer although they don't replace it under warranty unless their test shows its bad.

Did that twice - the 12v battery is good.

 

[MrFixit]

@Alec,

It would be interesting to observe this drain effect directly. You did see the end result with your voltage measurements, but the smoking gun would be to observe this excessive load current while this phenomina is happening.

This could readily be done with a DC Clamp-on current meter on the battery lead itself. I have measured the normal parasitic current to be about 100 mA. When in 'accessory' mode the battery current is ~5A, and it goes up to ~15A when the vehicle is "ON". You can see the detailed results of this testing here: Parasitic Current Readings

The 12V battery used in the Clarity has an 85 minute 'reserve capacity' which means it should be able to deliver 25 Amps for 85 minutes (or theoretically 1 Amp for 2125 minutes). Of course, you would expect that the normal parasitic current would not drain the battery for a very long time (at 100 mA, the battery should last for 21,250 minutes, or ~15 days).

So, depending on your time frame for these failures, the amount of this excessive current determines how long it takes to drain the battery. In order to fully drain the battery in 24 hours, the drain would have to be ~1.5 Amps.

This is the meter that I used...



You have to be careful to look for a "DC" clamp-on ammeter as many are just AC. They sell for around $50.
You probably just want to be through with this ordeal, and hopefully the dealer and/or Juicebox will get you there. If you continue to get nowhere, then you may be interested in doing more sleuthing yourself...

I remain skeptical of the JuiceBox sharing theory. It is hard for me to accept that interacting with the EVSE (while not actually charging) would require more than a trivial amount of current from the 12V battery... But, stranger things have happened !

 

[Alec]

I will do this test once I get a car back from service and get the appropriate meter.
I will post the results.

 

[Gokhan]

Correct, the car is in the service right now and they will keep it overnight to try to simulate my experience.

Hi Alec,
I am having same issues with my 2018 clarity,its happened 2 times in lst week when its HV and service said battery is good.
An they figure out yours problem?

 

[Mowcowbell]

I feel like the anomaly here with my original battery and a Chinese "it will burn your house down" evse.

 

[Arctiic]

I went through a similar experience before having to replace the battery eventually. I've noted this in a different thread, but in my case "sulfation" was occurring due to my driving and charging habits, which caused the issue. This is purely speculation on my part, but perhaps the battery was testing good because despite its insipient decline into its demise, it still qualified as "good" (I've no idea what the testing criteria are) but wouldn't start the vehicle due to the build-up on the negative terminal post physically interfering with the circuit? After all, I was able to get by for several months by simply tapping the post with a wrench prior to starting the car.

 

[Landshark]

I went through a similar experience before having to replace the battery eventually. I've noted this in a different thread, but in my case "sulfation" was occurring due to my driving and charging habits, which caused the issue. This is purely speculation on my part, but perhaps the battery was testing good because despite its insipient decline into its demise, it still qualified as "good" (I've no idea what the testing criteria are) but wouldn't start the vehicle due to the build-up on the negative terminal post physically interfering with the circuit? After all, I was able to get by for several months by simply tapping the post with a wrench prior to starting the car.

Sulfation occurs INSIDE the battery. Reversing sulfation can be an elaborate process. Whacking the battery with a wrench will not reverse sulfation.

What you are describing and experiencing is battery post corrosion. Get some CRC cleaner and protectant.