Block heater plus car charger on same circuit?

The block heater we had was about 400W. The L1 charger will draw about 12A including the efficiency loss, etc so that's 1440W. If both drawing power at the same time you're looking at 1840W draw which is 15.3A @ 120v. The rule is that for "continuous draw", something that will be on a long time versus something like a toaster that is on for 5-minutes a day, you don't want to load the circuit more than 80%. So you'd need a circuit just over 19A capable to safely provide that load assuming the breaker, wiring, and outlets are all properly connected.

If you have a 20A outlet with nice wiring, then you're good to go. Just plug it in and don't worry about it. If you have a 15A circuit you'll be tripping the breaker when they're both on. If you have a 20A outlet with poor wiring to a 20A breaker you'll potentially have nuisance tripping and/or fire.

If this outlet ONLY serves that outlet, meaning it isn't daisy chained to other outlets which would be unusual but awesome, then I would recommend swapping out the 5-15P/5-20P outlet to a 6-20P, and change the circuit over to 240vac. Tie the neutral wire to the second leg of the hot (and mark it with some black tape so that others that follow you know it is now a live hot wire) and now your outlet will have 240v across the 2 terminals and a ground. You can use a cheap EVSE to charge the car, and get a block heater compatible with 240v instead of 110v. Then the current draw in the wires will be halved for the same load.

 

You might consider one of these:
Titan Controls® Apollo® 9 - Two Outlet Digital Timer | Titan Controls

You'd probably need a water proof housing and short extension cord rated at 20 A. The battery backup should work just fine. Conservative, I would stop the charger about 30 minuets before departure time and start the block heater. However, last winter's cold operation suggests a block heater might be of marginal utility. Better to have a block heater and not need it than the reverse.

Good Prius friend @john1701a has more cold weather experience than me. You also have the option to use pre-conditioning to prepare the car including the cabin. This works best if you are still plugged in.

Bob Wilson

 

If the garage is heated, why a block heater?
Why not get an L2 circuit installed for charging?

So, if the car is charging and you plug in the block heater and it blows the circuit, get an L2 charger, but why the block heater in a heated garage?

 

or does he mean at work.

 

No one I know of, here in Minnesota, use block heaters anymore. That warmth to help with the startup simply isn't necessary for traditional vehicles nowadays. With a Prius, that's even more so of a non-issue... especially with a Prime. Think about how power that battery-pack can provide for turning over the engine. There's simply no real benefit, especially with regard to starting with a warm engine... since you won't with your drive starting from EV.

The battery-pack in Prime has heating elements to keep it at a more efficient operating temperature. That's automatic. Nothing is needed. You can plug in to top off the EV capacity, but it isn't necessary.

Pre-Conditioning the cabin prior to leaving work is meaningful, from a comfort perspective.

 

Pre-Conditioning is only for the cabin using the electric heat-pump. At those extreme temperatures, just take advantage of the block-heater by starting the engine.

This video is the cooldest I was able to capture last winter, which showed the warm-up process...

This one wasn't as cold, but I started from being parked in the cold ramp all day rather than the garage at home...

 

With a 20km (12 mile) drive each way, the total round trip might not deplete the battery even in the cold and snow. Your idea of reducing the draw to 8 amps is a good idea. Use that and the block heater.

-35°F at the time school lets out? Even full synthetic 0W-20 oil in the engine will be like glue. Good to get it warmed before driving. The engine will run to provide heat--too cold for the heat pump to do its job. Will the traction battery be drawn down at all? Be ready to plug in both, but maybe only the engine heater will be what you need--she'll see the battery capacity remaining.

Does anyone there use a battery heater (12 volt battery in the Prime, not the traction battery)? How about an oil pan heater under the transmission?
Battery Heaters
Silicone Pad Heater 25 Watt

Watts = volts x amps. Or, amps = watts ÷ volts (neglecting power factor, line loss, etc.)
Wattage is the measure of electrical power
Voltage is the measure of electrical force
Amperage is the measure of the rate of flow of electrons

 

Cutting charging to 8 amp is likely the way to go. You need to double check if that would allow cabin preconditioning. That is probably going to be more important than charging the battery with temps that low. The heat pump can only operate down to 14F(IIRC), so the the engine will be coming on anyway for heat, and if the defroster is turned on.

Come to think about it, how does the car preheat the cabin if the temperature is too low for the heat pump? Does it simply not do it, or does the ICE come on like in most other cars?

For the winter, you and your wife might have to accept that the Prime will be mostly running as a hybrid, at least for the return trip. The block heater will help with the start up penalty to efficiency. Yes, the engine warms up faster than in previous models, but these are extreme temps, and the commute borderline short trips. Good news is that you may not need the charge at work to drive home in EV during the summer, if they shut the heater block circuit off.

Don't know if the oil pan heater is really needed. The oil will be hot after the drive in, the belly pan may supply some shelter to the oil pan from any wind, and the block heater will provide some heat to the oil. You might even be able to switch to 0w16 once it becomes available. That is what the new Camry calls for, I wouldn't surprised in older cars get recertified for it after some time, like Ford did with 0W20.

I thought the battery heater was only powerful enough to keep the pack above freezing(0C), and not heat it enough for efficient charging?

 

Was this dealer installed block heater Toyota OEM or aftermarket? My Prime does not get as cold as your place, but being charged outside in subzero temp, I was considering installing one to mine.

 

Those outlets very likely do cycle on and off. Just stick to charging the hybrid battery at home, simpler? She should be able to verify that on/off factor, checking with whomever manages the parking lot.

I would plug in the block heater though. If it's per 3rd gen it's 400 watts.

 

Wow, that's a bargain. If I can get OEM block heater on mine for that price ~$300USD, I would do it at once. Thanks for the info, I will look into the OEM parts and cost here in US.

BTW, about charging your PRIME in cold, someone might have mentioned this already, but PRIME will starts ICE automatically when temp is below 14F (-10C). So, even if you have plenty of charge left in battery, when it gets extremely cold, your ICE is going to start. Depending on your travel, it may not be worth the trouble charging the battery full in -35C temp.

 

Log into Toyota Canada, "build" a new car purchase, add the block heater accessory, should show the current suggested retail cost. It used to be around $250 CDN, but I think of late it's jumped, low to mid $&300's.

FWIW we were dinged $400 too, when we bought in 2010.

 

Thanks. @www.toyota.ca it is listed at $347.50 installed for a new PRIME purchase. The price must be CAD. That's only $266USD. I am going to ask about this option at my dealer, but I doubt I can get it installed after purchase at this price.

Edit: I searched for TOYOTA OEM engine heater and found this on ebay. Toyota OEM Engine Block Heater SEE BODY FOR VEHICLE FIT | eBay It's only $54. So, how hard is it to install it DIY?