clarity PHEV dead after 3 weeks in garage

I figure my Wemo smart plug doesn’t register accurately any draw below above zero but less than 2 watts. It will tell me when it is zero watts and will indicate values above 2 watts but for values between 0 and 2 it says “<2 Watts”. So the value is something less than 2 Watts; it could be 1 Watt or half a Watt; who knows. I will have to break out the multi meter to know for sure. Even so 166ma at 12volt is probably not that much more than the normal drain from the electronics.

I am a big fan of my little Deltran battery tender. Let me make it clear that I don’t have a vested interest in the company but I do know not all battery tenders are smart and many will eventually overcharge your battery. I did a little homework before I purchased and I feel the Deltran Battery Tender Junior (their least expensive tender which is labeled as 750ma) was the best choice for my small motorcycle battery. It maintains the motorcycle battery in the offseason and now it also works well to maintain the Clarity‘s battery.

I have been alternating the one tender between the car and motorcycle every so many days depending on what I used last or when it occurs to me to swap. I may get a second one or not.

Anyway the tender I have seems to adjust to the need of the battery it is connected.

 

I think the input power to the tender is not a reliable way to infer the parasitic drain on the battery.

The tender doesn't just offset the parasitic load. Even if the parasitic load were zero (disconnect the battery cable, but keep the tender connected to the battery terminals) it is still going to be drawing current. Certainly with a battery that is not fully charged, the tender will transition through several modes while charging, and each of these modes will draw a different amount of current.

Once the battery is fully charged, the tender will transition into a 'float' or 'maintenance' mode. At this point, maybe it is possible to perceive parasitic current changes, but trying to know the actual load is clouded by the losses in the tender and the current used to 'float' the battery. Changes in parasitic current could momentarily be large enough that the tender has to drop out of maintenance mode and charge back up again.

Maybe some information can be gained by this, but it seems like the uncertainties make it difficult to draw any sound conclusions.

It would seem that the best way to look at parasitic current patterns would be a clamp-on DC milliammeter with some kind of logging capability. This is quite doable, but requires more specialized equipment and setup.

 

Isn’t the smart plug measuring 2W at 120V?

 

My smart plug measures in 1 watt increments at 2 watts and above.
If also says if there is 0 usage. It does not ever say 1 watt. It says “<2 Watts” (less than 2 watts). I do not know why it doesn’t just say 1 watt since it only increments in whole numbers anyway. My guess is at that low a power draw it may not be sensitive enough. The higher the wattages the less significant it is if the smart plug rounds off a watt too high or too low. My Kill A Watt EZ meter will do a better job at this. I will do a test.

 

Thanks. I realize that measurements are not precise below 2W. This, being the input draw of the Tender, likely indicates it is in standby mode.

2W at 120V would be 16.6mA.

However, my electrical math may be flawed as I’ve been doing construction math lately and helping some other folks who are having difficulty determining if 730,000,000,000 is:
a) 730 Trillion
b) approximately 3/4 of a Trillion
c) 7.3 Trillion

If only it weren’t true.

 

Your smart plug is measuring 1.06W from a 120V outlet. The Battery Tender will draw ~33W at 120VAC when providing its maximum output of 750mA at 12VDC.

The device is programmed to provide Bulk, Absorption and Float charging. It also has an Initialization feature. If you were to connect it to a battery with a known voltage of ~12.2V, your smart meter might show that it is drawing 20-30W. After a certain amount of time it would drop to 10-15W and eventually down to 1-2W.

I’d say that if you disconnected the device, waited an hour or so, and measured the battery voltage, it would read 12.7V. As it is fully charged and the Tender is in Float or standby mode with the smart meter showing 1.06W.

 

Could you add a second load, such as a light bulb to get your Wemo into its significant range? Measure the light bulb's wattage then add the battery tender and the power draw of the sub-2 watt battery tender will be easy to calculate by subtracting the light bulb's wattage.

 

I connected the smart plug, KilAwatt meter, and battery tender together. The smart plug showed 12w while the KilAwatt meter showed 10.6w. The difference is probably the smart plug’s overhead.

 

Some quick observations with a multimeter of my Clarity 12v battery.
12.5v sitting 24 hours, no charge cord connected
13.3v immediately went to this voltage while charging on 240v 16a cord
12.0v Ignition acc on, no cord
12.3v ignition off, no cord
14.6v Car on, no cord
12.4v ignition off, no cord
13.3v immediately went to this voltage while charging on OEM 120 10a cord
12.6v ignition off for 5 min, charging stopped from app, cord connected, no watts draw from outlet.
12.6v off, no cord
13.3v, climbed slowly to this voltage and may continue to higher but I didn’t wait around. Wemo smart plug shows 12 watts draw, KilAWatt meter show only 10.6watts.

 

My hypotheses is whenever any EVSE is connected and the Clarity is charging the traction battery the 12v battery is charging/tending as well. I suspect the electronics provide a consistent amp/voltage from the traction battery fed DC to DC converter to the 12 volt battery regardless of the amps/volts supplied to the EVSE.

However, once the traction battery is fully charge it appears all 12v battery tending stops.

If true then if you do not have a battery tender and do at least some driving during the pandemic you can get the most built in battery tending by charging at the slowest rate possible using the OEM 120V 10A EVSE cord because it would then spend the most amount of hours charging & 12v battery tending.

Even a small dedicated battery tender is still the best way to go if your Clarity will sit for weeks. The Clarity’s small battery seems to by gets fine with my 12v 750ma Deltran which I originally purchased for my motorcycle.

 

I may consider getting a Li-on 12v battery when my OEM battery dies. Haven't checked yet to see if that chemistry is available in the size used in the Clarity.

 

Don't do it. Li-on batterys need to be charged with a charger that is compatible with that battery. The charger in your Clarity is not compatible and may overcharge the Li-on battery which could cause it to explode or start a fire.

 

x2. It’s not that simple....

 

Li Ion batteries designed to replace a car battery have a BMS system built in that will be compatible with the charging system in the Clarity and post no significant safety risk. That being said, they are expensive and will not likely solve the issue of vampire drain and many (most? all?) will actually be worse than the OEM battery in that regard - particularly when the weather is cold.
It will shave a few pounds of weight and theoretically improve your EV range . Maybe by as much as a couple of hundred feet!

 

Antigravity makes a Group 51 Lithium battery for $660.

1000 Cranking Amps. How could anyone resist?

Battery Tender Jr, $40.

 

@Mowcowbell
You can install a Lithium 12 volt battery in your Clarity if you want to spend around $600-700+ on the battery. The charging system in your car does not matter. The advice above about not doing so is wrong. All 12V replacement LIB's in the industry are using LiFePo4 (Lithium Iron Phosphate) cells. These are HIGHLY stable 3.2 volt cells that work great because 4 of them approximates the voltage of a 12 volt lead acid battery very closely. The "charge" management is built into the battery (the "BMS" and charge controller). It is not possible for your car to over charge or over discharge these "smart" batteries as long as their BMS is functioning correctly. The "failure mode" on these batteries 99+% of the time is to fail Open Circuit. They are designed this way for safety to prevent just such an issue. Add to in the fact that no car on the market can over charge a LiFePo4 to the voltage required to cause it to fail (almost 17 volts) and the failure is almost always smoke, no fire, no explosion. This misinformation about LIB's is a real problem in the industry. I have taken many of these batteries, and charged them to extreme voltages and temperatures during UN38.3 certification and then cut them open, crushed them, and put fire to them. Critical destructive failure is vary rare and almost never seen in commercial use.

For your edification and entertainment, here is a common video of this chemistry being UN38.3 tested. The "comparison battery" is a common LiPo LCO
"cobalt" based battery. No, our HV packs are not LiFePo4 batteries, they are likely NMC, so yes - the "exciting" kind. If they were not, we could only drive about 20 miles on a charge...


The only reason not to do it is that it is not called out for in the Clarity OEM maintenance program so if something went wrong they "may" say something about warranty. Why is it different, well - LIB's can "recharge" much faster than PBA batteries and draw a lot more current in the process. The 12 volt binding post on the Clarity has built in "fuseable links" on it at varying amperage. The system current comes in via a different path than the "out" current. Although 175 amps is a lot of current, it is technically possible for a fully depleted LIB to draw that much current during charge. However, that is unlikely (you drained your battery completely and installed it dead) so not a worry. I just want to put that out as the only concern from a charge system engineering standpoint. The batteries are very durable, and in a car that runs cool (most are driving EV so the ICE close to the battery rarely gets warm) a Lithium 12 volt will likely outlast the HV pack. They are also not damaged by deep discharges or being stored partially charged (they don't care).

Here is a vendor I have not purchased from but listed a compatible battery for the Clarity on their site. I wouldn't recommend it only due to the cost, and a battery tender is cheap - a flooded lead acid battery will last a long time in this car if properly maintained. The Clarity/Honda charging system does a good job of charging the battery during use (running) without over charging. It cycles the 14.4-14.8 charge voltage while operating to maintain a full charge without baking the battery. I have seen it "rest" the voltage at 12.5 often while driving after "charging" initially.

https://antigravitybatteries.com/products/starter-batteries/automotive/ag-51r-rs/

Finally, on the whole watt meter on a trickle charger - none of those watt readings matter if the "charger" wall wort is based on a transformer (it is somewhat heavy). The power factor will be quite low and those watt readings not even close to true RMS power. If it is buck/boost switch mode then that "can" be worse. Those meters are very inaccurate at low currents with low power factors (if it reads power factor PF, you can check) if it is below .7 then just disregard watt you are seeing. The best way is to measure with a direct (not clamp on) amperage meter or one that can do coulomb counting. They are cheap if you get one for RC use (ubiquitous) but they are not 100% accurate and you will have to build you own adapter cables. For the Clarity, I recommend a maintenance charger (any of them) and a flooded cell that is NOT maintenance free. You can hook it up, add water when needed, and not worry. If it is holding the battery at a voltage between 13.3 and 14 volts it really doesn't matter. 14v is a bit high, but the battery will not sulfate at that voltage, and you can just add the water every 3-6 months that you are losing. It is easier really to prevent sulfation than remove it (with special chargers). If it is maintenance free, then yes - get a good 4 stage tender with desulfation funtions.

Here is one: https://www.amazon.com/RC-Electronics-Inc-Watts-Analyzer/dp/B001B6N2WK

Sorry, just wanted to get some info out there are this seems to be a point of concern for some. I get it, I am obsessing over the HV pack (literally "morbid" curiosity) and a few of you know my pending solution to my now expensive curiosity (arrives this week).

Cheers,

Cash