15 Amp Charger

Charger (North American Version)

The charger actually produces slightly in excess of the rated 15 amps.  It stops charging at a battery voltage of 58.68 volts.  Efficiency varies during the charging cycle but overall is quite good at about 92.5 percent.

The charger's DC side uses a Neutrik NL4MP connector.  The battery-side mate is a panel-mount Neutrik NL4MX connector.

The plug and socket wiring is a bit weird, but this is what they did: 

• Terminal  “1+” is Positive 

• Terminal “2+” is Negative

• Terminals “1- and 2-” are jumpered together inside the plug.  This is what allows the charger to turn on/off automatically when it's connected to the battery. 

Charging is performed at a constant current of 15 amps until a battery threshold voltage is reached (about 58 volts).  This is the period during which the lion's share of the energy is transferred (and takes somewhat more than half the total charging time).  There are rapidly diminishing returns in terms of energy delivery versus charging time toward the end of the charge.

When the charger's fan turns off, it continues to source current into the battery at about 0.86A (about 50 watts).

The charger continues to draw about 13 watts after it is unplugged from the battery.

The charger is basically a switch-mode power supply (SMPS) similar to that found in a desktop computer.  An SMPS's front end is formed by a bridge rectifier and one or more filter capacitors.  As such, it only draws current when the AC line's rectified sine wave voltage exceeds the voltage across the filter capacitor.  Thus, the AC-side current flow is discontinuous.  This results in the current waveform shown below and is responsible for the poor power factor (approximately 0.66 with current leading voltage).

Charger Improvements

The ePure's charger and charging methodology are improved over that of the 5.7:

• There's no longer an on/off switch on the charger itself - it's now automatic.

• The charger/battery interface uses a better socket/plug and location.  

• It's more efficient, 92.5% versus 87%.

• The motor controller is not needlessly powered-up during charging as with the 5.7.