User avatar
Posts: 879
Joined: Thu Apr 24, 2014 6:08 pm
Delivery Date: 30 Apr 2014
Leaf Number: 424487
Location: Massachusetts

Re: OK to use 3-prong 'medium duty' digital timer with EVSE as Leaf 'S' timer? Bad idea? Overheating? OK if gets just wa

Tue Sep 25, 2018 7:08 am

oz10k wrote:Why not just skip using a timer?
I second this. And given the very slow charge rate, I'm not sure what you are trying to accomplish by using a timer.
LEAF '13 SL+Prem (mfg 12/13, leased 4/14, bought 5/17, sold 11/18) 34K mi, AHr 58, SOH 87%
Tesla S 75D (3/17) 29K mi
Tesla X 100D (12/18) 29 mi (replaced 3 reservation)

Posts: 1136
Joined: Wed Oct 21, 2015 10:24 am
Delivery Date: 06 Dec 2014
Location: Long Island, NY

Re: OK to use 3-prong 'medium duty' digital timer with EVSE as Leaf 'S' timer? Bad idea? Overheating? OK if gets just wa

Tue Sep 25, 2018 12:16 pm

I used a mechanical timer for about 8 months without problems when I first got the car... At 120 volts, the charger uses 12amps, and a timer is rated at 15 amps. No problem. . I used to set the timer for 5 % battery charge per every 1 hour of charging. So 10 hours of charging overnight gave me 50% increase in battery capacity. If you do not need the car in the evenings, or drive short distances (10-20 miles/ day), you can get away with the standard 120 volt level 1 charger.

If you want to have more flexibility, and willing to get an electrician to put in a 240 volt line, that is the way to go. you can easily calculate how much you are putting into the car because it takes such a shorter amount of time.... With the 240volt Level 2 charger, you charge at 30-35% charge per hour (or 1% of charge for every 2 minutes of charging). So if I want to only put 20% more into the battery, I plug it in, set a timer for 40 minutes (or eat dinner), and then come out and disconnect.

It is also great with the 240 volts that you can have your car at 100% with only a short amount of charging at any time of the day or night (24/7). For me, that is the way to go... Use the entire capacity of the car....

Posts: 2372
Joined: Fri May 04, 2012 8:25 am
Delivery Date: 16 Feb 2014
Location: Near Seattle, WA

Re: OK to use 3-prong 'medium duty' digital timer with EVSE as Leaf 'S' timer? Bad idea? Overheating? OK if gets just wa

Tue Sep 25, 2018 1:26 pm

goldbrick wrote:Totally agree but once again it would be good to know how the switch operates. If it is solid state it may actually ramp the current down gradually. If it's just mechanical contacts then I'd be more worried. But then any normal light switch uses mechanical contacts and they seem to last a long time with all kinds of various loads being switched on/off.

So let's look at a switch with different loads. ... 954897-_-N

Resistive (heater): 20 Amp, 120-277 VAC
Tungsten (incandescent): 15 Amp, 120 VAC; 6 Amp, 208-277 VAC
Ballast (magnetic): 16 Amp, 120-277 VAC
Motor: 1HP, 120 VAC; 2 HP, 240 VAC
DC Loads: 4 Amp, 12 VDC; 2 Amp, 28 VDC

The charger in the car isn't similar to any of these.

Notice that the range of current that can be supported ranges from 20 Amps for a pure resistance to 2 Amps for 28 VDC. Strange and wonderful things can and do happen with loads that are not simple resistive.

Motor of 1 hp draws 745 watts (assuming 100% efficiency, and ignoring startup currents, inductance and capacitance), or 6.2 Amps. Efficiency is usually fairly high, 90% or so, so why can this switch only support ~7 Amps for a motor? Oh, all the things I just ignored. During startup the current is rather larger, perhaps even rather more than the 20 Amp steady state limit, but as the duration is likely short time is usually not a problem.

Have an ohm meter? Measure an incandescent bulb's cold resistance. Calculate the startup current. Sure, a huge current, over ten times the steady state current, and it just flows for a tiny time until the filament is hot. That is probably why the above switch is rated for a lower current, 15 Amps of incandescent load, than for 20 Amps of resistive load.

Will using a timer work? Probably. Still, isn't a good idea. Not recommended. Suggest getting an EVSE, perhaps an EVSE with a timer.
Most everything around here is wet during the rainy season. And the rainy season is long.
2012 Leaf SL Red (Totaled)
2014 Leaf SL Red

Return to “EVSE / Charging Equipment and Networks”