The e-max Charger - Fxing it and Making it Reliable

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PJD
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The e-max Charger - Fxing it and Making it Reliable

Of all the bugs and annoyances that need to be addressed to turn the e-max into reliable transportation, problems with the chargers certainly top the list. But, most e-max chargers can be repaired and made into reasonably good chargers with the replacement of a couple key components and the addition of some provisions for extra cooling.

1. The most common problem is a charger that suddenly goes dead. The cause of this is almost always due to the inferior quality "NTC 5C" inrush supressor. This inrush supressor looks like a dark grey ceramic disc located at the corner of the PC board next to the soldered-in mains-in (not the 10A charging-out) fuse. On a limited number of the latest versions it was relocated to a hard to see space under the overhanging heat sink on the left side of the PC board (looking from the fan end), behind the big inductor coil at the fan end of the PC board. This newer arrangement is quickly recognized because the corner of the PC board nearest the mains-in fuse contains a soldered wire jumper labeled "CON", where the inrush suppressor was on earlier versions.

The failed "NTC 5C" inrush suppressor should be replaced with a better quality, US-made, Thermometrics CL-40 inrush suppressor. It is a good idea to replace it even if it hasn't failed yet. In those later versions, it is easier to abandon the old inrush suppressor in-place - solder a wire across the old suppressor's solder points on the back side of the PC board and put the new one in the original location in place of the jumper.

2. Another problem is a slow fan speed and abnormally slow charging rate. The most common cause of this is the failure of the two 470uF rectified-output filter capacitors - the biggest ones on the PC board. They are cheap-Chinese, and often overheat and fail due to inadequate ripple current rating. Their failure will be evidenced by a bulging top. A aluminum electrolytic capacitor that hasn't overheated will always have a flat top.

These capacitors should be replaced with better quality 680 uF 200V high-ripple capacitors, I also add a parallel .39 uF polyester film capacitors to each of the big capacitors. They fit on the underside of the PC board with addition of stub of wood dowel next to them to prop the board up a bit.

There are also some chargers with the scooters imported early in '06 with a slow fan speed of unknown cause but otherwise seem to charge normally. Some were also missing the thermal protection switch, had incorrect power-cord polarity and other forms of very poor Q/C, but these are less common. I am working on some ideas for a work-around for the slow fan.

3. Cooling can be enhanced by drilling three or four holes, at least 1/4" in diameter, on either side of the indicator lights (near the ends of the heat sinks) on the front face of the charger, This helps direct along the axially-finned heat sinks and improves cooling.

4. Cooling fans sometimes fail. They should be replaced with a ball-bearing type of comparable wattage. Some users have commented that the fans seem to be positioned backward and should draw air from the enclosure instead of blowing air into it. But, I tried both fan positions and blowing-in is the best fan orientation for cooling.

Here's some operational checks for your charger:

The charging amperage for a normal charger will be about 7 amps. The charging voltage will increase with state of charge, reaching a constant 59 to 60 volts in the absorption stage before switching to float - indicated by the green light. Float voltage should be 55.0 to 55.5 volts. The AC line in will consume about 430 to 460 watts of power at a power factor of about 0.68.

The e-max charger is not temperature-compensated, but the charge and float voltages are good compromise values for normal temperature conditions. However, in very hot southern-US summer conditions, with charging-related heating of the tightly-confined battery pack, this can result in overcharging and damaging gassing of the batteries. You should charge the scooter in as cool a time and place as possible, and open the seat and the access-cover in the bottom of the seat-well when charging.

Here's some useful links for buying parts:
http://www.mouser.com/search/ProductDetail.aspx?R=527-CL40
http://www.mouser.com/search/ProductDetail.aspx?R=5985-380-200V681
http://www.mouser.com/search/ProductDetail.aspx?R=5989-250V.39-F
http://www.mouser.com/search/ProductDetail.aspx?R=433-BP501012H


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