NoBeard
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More L2 Amperage=Warmer Preheat, Yes or No?

Mon Feb 09, 2015 6:47 am

Hi, we're looking at which L2 charger to get and we're wondering if a higher level of amperage will increase the heat provided during a pre-heat.
When using the L1 charger the pre-heat is nominal, but when I plug in to the in town commercial L2 chargers, the pre-heat we get from them is really significant. I'm wondering is it just the 240 volts that is doing it, or does the amount of amperage available being passed on to the heating coils or is there a threshold there.
Thanks,
NB

PV1
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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Mon Feb 09, 2015 7:39 am

Coming from the stock cord, you get both a voltage and amperage increase. All in all, it takes total heating (and charging) power from 900 watts to 3,000 watts. The heater is rated at 5,000 watts.

So, yes, you'll get much more heat by using a 240 volt EVSE rated at 16 amps or better. Plus, instead of a slight drain on the battery using the stock cord, pre-heating at 240 volts either won't use any battery or can still provide a trickle charge once the coolant is heated up.

What also helps, I find, is using the Defrost option instead of HEAT on the remote. This will also activate the rear defroster and heated mirrors (2012 ES with Cold weather/quick charge packages, 2012 SE with Premium Package, and all 2014's). Be sure to also have your heated seat turned on, as this will warm as well.
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Don
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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Tue Feb 10, 2015 6:21 am

PV1 wrote:So, yes, you'll get much more heat by using a 240 volt EVSE rated at 16 amps or better.
The pre-heat function is powered by the output of the charger which is limited to 3.3 Kw (which is about 14 amps @ 240 volts). How does using an EVSE rated at "16 amps or better" give you any more heat than one rated at 14 amps?

An upgraded OEM EVSE running 240 volts @ 12 amps preheats really well for the cost of admission. True, there could be just a tad more heat available if it could do the full 14 amps, but I wonder if you'd even notice the difference?

Don
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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Tue Feb 10, 2015 7:16 am

Don wrote:How does using an EVSE rated at "16 amps or better" give you any more heat than one rated at 14 amps?

Poor choice of words on my part. I think every charging station available can do at least 12 amps at 240 volts, which I agree gets the car pretty toasty. A station rated at 16 amps or more ensures the full output of the car's charger, but you have to have 240 volts (not 208) to max out the charger. Our cars can charge faster at home than at most public charging stations just because the voltage is higher (single-phase nets 240 volts where commercial 3-phase nets 208 volts).
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NoBeard
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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Tue Feb 10, 2015 7:48 am

So I'm getting from the posts that the heater is powered by the charger, and therefore limited to 3.3 KW, as opposed to the charging circuit being separate from the heater circuit as I would have designed it, so that excess available amperage could be used by the heater circuit all the way up to the 5000 watts it can draw, which would make a 20-25 amp charger a worthwhile investment in a few dollars more just to get max heat/cool when plugged in.
I know that the charger downtown that is available from the electric utility makes the car smoking hot in 30 minutes, and if a 16 amp charger will do the same then it's not worth the extra.

NB

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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Tue Feb 10, 2015 8:19 am

If you're looking to buy a charging station (Electric Vehicle Supply Equipment, EVSE), I'd go for a 32 amp version if you think you will add another EV to the fleet (since pretty much every new EV out there has a 6.6 kW charger instead of the i-MiEV's 3.3 kW). But if you plan to stick with the single (or two like a few of us) i-MiEV until it won't work anymore, then a 16 amp EVSE will work just fine. I only recommend the 32 amp EVSE if you want to be future-proof. Cars with a 6.6 kW on-board charger will work just fine with a 16 amp EVSE, but they won't be able to charge at full speed.

Also, some terminology suggestions to avoid confusion.

The box you install on a wall in your garage is called Electric Vehicle Supply Equipment, or EVSE for short. The "Charger" is built into the car. The only thing EVSE (or charging stations) do is safely supply electricity to the car's on-board charger through the J1772 connector. The exception to this are quick chargers, which connect directly to the car's battery through the CHAdeMO (or comboplug on other cars except LEAF) port, and are truly "chargers".
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acensor
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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Tue Feb 10, 2015 10:15 am

PV1 wrote:......So, yes, you'll get much more heat by using a 240 volt EVSE rated at 16 amps or better. Plus, instead of a slight drain on the battery using the stock cord, pre-heating at 240 volts either won't use any battery or can still provide a trickle charge once the coolant is heated up.

What also helps, I find, is using the Defrost option instead of HEAT on the remote. This will


Wait, wait....
I use the upgrades stock charger that can do 120 or 240v.
But seeing little or no need in our use pattern to charge faster than the 12amp 120 mode opted to avoid the in our case considerable cost and hassle to put a 240 plugin in the garage.

So what's this "slight drain on the battery" you say I'm getting when I preheat (and may I presume also when I precool)?
First I've heard of it. Are you saying if I overnight did a full charge, preheated in the morning, when I step in to drive off I'd have less tha a full charge?

Also... When I preheat I set it to not charge .... Presuming that at 12 amps 120v it either will not have enough juice to do both ... And unsure which it would give priority... Or at least would be heating less robustly. Anyone can confirm this take? Or could I set it to charge and preheat and it woul just do both slower.

Also... It's my impression that when I preheat (as I said with no simultaneous attempt to charge) that it does so for about 1/2 hour then quits. Works out OK for me,.
but curious ....does anyone know if that's a timeout (like so one diesn't accidently leave it heating in the garage for two days) or if it's thermostatic... Shutting off heating because my heater control is set at the halfway green dot and it has reached that temp?
That is, would it preheat interior higher if I turned the temp setting higher on the upper dial?

Yeah, I sometimes use defrost often instead of "heat" on a preheat...but mainly because in my usually pretty mild chill wanting to try to avoid window condensation-fogging is higher priority than warming the whole interior. Besides, defrost seems to warm whole interior.
Alex
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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Tue Feb 10, 2015 11:15 am

I mean stock stock, 120 volts at 8 amps, can cause a slight drain on the battery in Defrost mode, less than 1 or 2 percent of charge, not enough to notice on the instrument cluster. That was a while ago when I observed that, so I don't know for certain what the actual behavior may be. Charging faster than that (which you are at 12 amps) shouldn't cause any drain on the battery, and at 12 amps, 240 volts, the battery can continue charging very slowly with the heat on. For example, I charge at 120 volts, 12 amps overnight. In the morning, I switch over to 240 volts (some fancy electrical work on the plug side, nothing to do with the EVSE, essentially change plugs) to preheat. I notice with OVMS (Open Vehicle Monitoring System) that my car sometimes stops at 98 or 99% in cold weather. After preheating on 240 volts, the percentage usually goes up by 1%. There wouldn't be any drain when pre-cooling, since it is more energy efficient. The AC maxes out at 3 kW, and once it has the pressure difference reached, it only uses a few hundred watts.

Pre-conditioning runs for 30 minutes, timer based. Originally, we thought the temperature knob had something to do with pre-heating, but we found out later it was the difference between input voltage, how long the car preheated, and which mode was used.

I recommend Defrost over HEAT simply because HEAT runs the fan at low speeds, and directs air to the floor. Defrost runs the fan close to or at high with air going to the defroster vents, which does a better job at pushing warm air towards the back of the car, plus the rear defroster heats up.

If you set a timer to delay charging, then trigger pre-conditioning, I'm not sure on its behavior. I think the car gives pre-conditioning priority all the time, and charges the battery with whatever wattage is left over. The charger doesn't hook directly to the heater, the battery is in between. The heater doesn't sustain 3.3 kW the entire time, or it would overheat, so there some give and take regarding battery charge. I notice my car, even after 25 minutes of preheating, that it is using a decent amount of power based on the blinks of my kWh meter. I'll have to observe my car preheating with CaniOn to confirm most of this.
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Don
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Re: More L2 Amperage=Warmer Preheat, Yes or No?

Tue Feb 10, 2015 5:30 pm

NoBeard wrote:So I'm getting from the posts that the heater is powered by the charger, and therefore limited to 3.3 KW, as opposed to the charging circuit being separate from the heater circuit as I would have designed it, so that excess available amperage could be used by the heater circuit all the way up to the 5000 watts it can draw, which would make a 20-25 amp charger a worthwhile investment in a few dollars more just to get max heat/cool when plugged in.
The 5 Kw heater was designed to heat the car while underway, using the up to 5Kw from the car's 330 volt DC traction battery . . . . it cannot run using EVSE power which is either 120 or 240 volts AC. You couldn't design it any different unless you put another, separate heating element in the heater box to use household power and then you'd open another can of worms with programming and relays and such to get AC power to it

Preheating is done with the same 330 volts DC except the power comes from the on board charger which is usually charging the car and of course it's limited to the output power of the EVSE - Just 960 watts if you're using the OEM unit on 120 volts. If you are charging and then hit the preheat button, charging all but stops (even with L2) as the heater is then using all the power from the charger

Don
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