greenleaf said:
I am thinking of get the JuiceBox. Since I don't want to upgrade the house wiring, can anyone comment how easy (or difficult) is it to limit the current draw to say 16A max?
Very easy if you have a way of measuring it. But be very careful because there is 230-240 volts live within in this box and it can kill you.
There is a yellow pot on the main board that you turn with a screwdriver to adjust the duty cycle, while the device is plugged into the vehicle.
And you have a choice. You either need access to a scope or a multimeter that measures duty cycle (like this:
http://www.amazon.com/Extech-EX330-Autoranging-Multimeter-Thermometer/dp/B000EX0AE4/) or a current clamp (like this:
http://www.amazon.com/Uni-Trend-UT202A-Auto-ranging-Clamp-Meter/dp/B005FSSKJA/) or both.
In the trigger wire case, set the vehicle to charge based on a timer so it doesn't begin charging as soon as you plug it in (and risk blowing your breaker or worse).
Then as soon as you plug in, the juicebox will report the current it allows to be drawn over the pilot line.
Following the formula on this page:
https://code.google.com/p/open-evse/wiki/J1772Basics, turn that pot until the duty cycle reads 26.6% for 16Amps. Then cancel the timer (or set it whatever you actually need), and let it charge as expected.
Or with the current clamp, you'll need to actually have the vehicle charging. Not waiting to charge. So you'll need to set it conservatively low to avoid blowing the breaker.
This method is less exact and may require a short ramp-up period for the vehicle to react to your change on the duty cycle pin. And just read the current on the clamp and ramp up until you reach 16 amps.
I prefer both methods. Set the duty cycle first. Then confirm with the clamp at a few points during the charge cycle.
Then you're free to set the timer or whatever you need. The Juicebox will re-sample the pot every time it starts so your new setting is locked in. I put a little hot glue on mine. It's a habit I've developed over the years from working on electronics. It's easy enough to peel off when you need to change it, but it's strong enough to keep subtle earthquakes or people bumping the box from turning your knobs.
Or if you're not comfortable doing any of this, if you ask nicely when you place your order for an assembled JuiceBox, the folks at EMW may be willing to set the current for you. It can't hurt to ask.