How Much Does it Cost to Charge?

Not that I have done any statistics on the data, but no, the number I read off from the Kill-a-watt meter for zero EV to full charge has been consistent 6.5-6.8kwh year around. Of course, some variation exists in numbers when I drove a short distance thus less charge was needed, but for a full charge, it is always more than 6.5kwh.

 

Iostp

This a great post, but what does SOC mean and what number applies to my electric bill 5.5 or 6 .3?

 

SOC = State of Charge
Your electric bill is always from the wall so 6.3kWh applies. However, if you are using L1 charger that came with the car, I am finding at wall charge is more like 6.4-6.8 kWh. I usually use 6.6 kWh / full charge for my calculation.

 

So... i want to use this to calculate when a charge station might be work paying for, but i'm guessing the filter button is not what i think it is? is there a spreadsheet out there? the formulas are above my ability...

 

Your calculation maybe complicated. I've never used a public charge station myself, but my understanding is that the method of charge may differ from a station to station. Some charge fee per minute connected. Here I have even read someone reporting that a public charge station continues to charge a fee even after the battery was full. Some others calculate fee by kWh drawn on the session. This would be ideal to compare to the cost of gas. Yet others charge by flat fee. So, unless you can figure out the exact cost of charge per kWh or cost to fill the battery full from zero EV to 100% charged at any given public charge station for the specific session, it would be difficult to compare the cost to gas. The rule of thumb is that if the cost of electricity in $/kWh x 6.3 (in another words complete charge from zero EV) is less than the cost of a half gallon of gas in your situation, using public charger is more cost-effective. This assumes your EV range is approximately half of mpg by gas only.

 

True, ChargePoint is not clear how much you will be charged, until the end. I've only used it twice, and mostly for fun. Once i was charged 1.13 for 5.78kWh, the next time i was charged 3.30 for 6.55 kWh Yikes. I would like to think somewhere the charge was upfront, but ChargePoint like to put the blame on the location/facility. and it was not obvious what the cost was going to be at the start...
OTOH both times gave me some EV in town miles, and bumped up my trip mpg to well above 60. Of course, my car, and my experience is way too new to know what straight HV mpg will end up being. That said, I love my Prime, and I'm pretty sure it will beat our 2015 prius, which never really got even 50 mpg. that one was a bit of an anomaly compared to our 2011 prius, and my daughters 2017 prius.

 

Most L2 chargers by me are free (for now), so is always worth it to plug in when possible. At home it's $0.11/kWh.

 

In my experience with public ChargePoint stations, the fee calculation was displayed on the screen before starting the charge. The owner of each ChargePoint station determines the fee. This is different from Blink, where the fees are set by Blink based on what kind of account you have with them.

 

Just used a Blink charger at the Sacramento IKEA this morning and it was $0.59 per kWh.

Knew the price up front.

Then made a Plus account for a better rate in the future.

 

Wow! At that price, unless the gas is above $7/gal, it makes no sense to charge PRIME.

 

Meh, I had an 85% full battery.

It was more for the kids than anything (they like to help “charge the car”).

So total charge was $0.79 and we spent $2.97 inside while the kids played for 1.5 hours in Smalland. We were killin time until we had to arrive in Elk Grove this afternoon. Holiday traffic in Nor Cal can be bad on holiday weekends so we leave early.

We put flags on the graves of the vets at the Sacramento Valley Veterans Cemetary too. Always a good way to spend the morning recognizing those that have served.

 

For what it is worth: I charged my new 2021 Prius Prime XLE traction battery from 0% to 100% with a power meter similar to the kill a watt meter, and with the current set at 8 amps (not the default 12 amps) and it took about 7 hours and registered 6.8 kwh. My power comes from FPL (Florida Power & Light) and costs 11.55 cents per kwh (includes 2.5% power tax and the current fuel surcharge for over 1000 kwh), so it cost me $0.7854. I get about 30 miles range, so it is about 2.6 cents per mile. The best part is no road tax.

I have a question: does the 12 volt battery charge while the car is charging? When the car is in the Ready state, the 12 volt battery voltage is around 14.1 volts; but it is not over 13 volts when the traction battery is charging from the wall and I have seen it as low as 12.5 v, so I am not sure if it charges but if it does it is different from the Ready charging. Prof Kelly at Weber U said in one of his YouTube videos that the 12 volt battery does charge during plug in charging to protect the 12 volt battery from being drained by the two battery cooling fans. Until I heard that, I did not think the 12 volt battery was charging.

 

Edit: I wanted to add that I think the variation in power needed to charge 0 to 100% might be because sometimes the hybrid part of the battery can be partly discharged as well as the traction part of the battery, so more power is needed to charge it all. Also the battery temperature management will use differing amounts of power ... fans, battery heater, a/c depending on ambient temp. When I took my measurements my traction battery was 0% and the engine just came on as I hit the garage so I let it run to fully charge the hybrid part of the battery, then shifted to Park, turned it off and charged the traction battery, so I think I just needed to charge the traction part of the battery.

 

The answer is Yes and No. It does trickle charge to maintain the level of charge in the 12v battery, but No it does not actively charge to bring the 12v battery SoC to a fully charged state. We have a long thread discussing this. And the word of caution is that this minimal maintainer function is ON only during the time the traction battery is actively being charged. That means, if you keep the car plugged in long after you have finished the charging the traction battery, then the 12v battery will drain quicker because of the control function of the EVSE and chager has to remain active as long as the car is connected to the EVSE.

12v Battery Is Discharging, Re-Charge Now ! | PriusChat

BTW, your observation of 6.8kWh for full charge seems to agree with many others using OEM L1 charger. I don't think the difference in 8A and 12A is much. An extra hour you have taken will cause a slight increase in the power consumption, but my 2021 PP using a Kill-a-Watt and OEM L1 EVSE is currently using an average 6.76kWh at 12A. This is a slightly higher number than the 2017 PP 6.68kWh for the first 4 months.

 

I have a related question ... I read in the manual that the 12 volt battery cannot be charged in the usual way with a usual car battery charger. That seemed odd to me because it is a lead acid battery in my 2021 P Prime. My battery is in the front of the car, not in the trunk. I am not sure whether it is AGM or flooded lead-acid. Is the normal charger a problem because this battery is not designed to provide massive starting current to run a starter motor, which might imply it cannot accept charging at high amperage? My charger is only 10 amp max, reducing to nothing as the battery charges. Or I can set it to charge at 2 amps max, Is that not safe to use? What about a battery maintainer that just maintains a full charge but will not charge the battery? Is that safe to use? It only provides a fraction of an amp. My car can sit a week or more without use so I am used to using at least the battery maintainer. Maybe the problem is that my battery is AGM which needs a different charger? Thanks for any help.

 

PP and Gen4 have a regular flooded lead-acid battery. I don't know where you read in the manual that said "the 12-volt battery cannot be charged in the usual way with a usual car battery charge". I have charged my PP's 12v battery with a regular 12v battery charger many times. The manual states to disconnect the ground cable off from the 12v battery when charging, but I have done it without removing the cable, no problem. The battery is very small, so you probably do not want to go too high on the Amp. The manual recommends not to use higher than 5A. I use a 5A smart charger from Victron, but many people use other brands. You can also use a maintainer without a problem.

 

Salamander-King, I very much appreciate all your help. And I do look for answers before asking but there seem to be so many changes to the 2021 Prius Prime that I don't trust the old threads.

One last question on the 12 volt battery. Right now I have not used my car for 4 days and the 12 volt battery is just under 12.4 volts. If I wanted to top it up but was too lazy to get out my charger, what if I just put it in READY and left it that way in my garage. After an hour it will turn off and in the meantime I would get 14 volts applied to the 12 volt battery to charge it. When I leave the car unused I leave the traction battery about 80% in case a quick trip comes up unexpected and I don't mind taking a little power out of that battery. Would that be a healthy thing to do? I know that flooded lead acid batteries like to sit fully charged.

I'll see if I can find what worried me in the manual, but it is probably just my bad memory.

 

There has been a long discussion of the 12v draining of the charge on PP and to some extent on Gen4. If you care to read more detail, you will find tons of information in this thread.
12v Battery Is Discharging, Re-Charge Now ! | PriusChat

As far as your question of keeping the car in READY to charge the 12v battery, yes, that will do the job. But for only 4 days of inactivity, my feeling is that it is not necessary. In my experience, as long as you are driving at least 30min or longer once a week (the engine does not need to come on for this), the 12v battery will be topped up and keep sufficient SoC above 12v. If your driving is less frequent or the battery is old and weak, then you may benefit from turning on to READY for a while when you can't drive the car. The replacement 12v battery is not very expensive. You can get aftermarket battery for ~$100 if you look for a sale. Toyota OEM battery is ~$180 IIRC. In your climate, the 12v battery can die quicker than in our cooler climate, but still I think with regular use, you should be able to get 3 years of longer.