Karen Nakamura: July 2009 Archives

My little Piaggio-EV is back up and running. I made the following mods:

• My replacement HV-110 is now installed in an external plexiglass box with (much) better airflow and forced as well as passive air cooling. The forced cooling is on full all the time rather than the temperature variable fan that I used to have.
• Extra caps (470 uF x 6) soldered in parallel with input leads
• (Slightly) beefier wiring used -- 8 gauge rather than 12 ga
• 75 amp Andersen PowerPoles used instead of 30A
• Wiring shortened a bit
• Thermometer probe directly on caps to monitor heat

So far, it seemed ok. After my ride to work this morning, the caps heated up a bit -- from 17°C ambient at the beginning to 37°C ambient at the end of the 5 kilometer ride. I'm working on getting even more cooling in there.

6 amps used. 30 watts/kilometer average energy expenditure.

My project has expanded to use standard size servos (link back to my micro servo comparison). Here's a little table that I'm using to compare various options.

Model	Mode	Size	Wgt	Speed@5V	Power@5V	Speed@6V	Gears	Street
TowerPro MG930	Digital	36.2x15.2x28.7 mm	26g	0.14sec/60°	3.6 kg/cm	0.11 sec/60°	Metal	$16
Hitec HS-225BB	Analog	32.4x16.8x30.8mm	27g	0.14 sec/60°	3.9kg/cm	0.11 sec/60°	Nylon	$20
Hitec HS-225MG			31g				Metal	$30
Hitec HS-5245MG	Digital	32.0x17.0x31.0mm	32g	0.15 sec/60°	4.4kg/cm	0.12 sec/60°	Metal	$48
MKS DS9660	Digital	35.0x18.0x28.0mm	35g	0.13 sec/60°	3.7 kg/cm	0.10 sec/60°	Metal	$57
Futaba S9650	Digital	36.0x15.0x29.0mm	26g	0.14 sec/60°	3.6kg/cm	0.11 sec/60°	Nylon	$65

The conversion for torque from kg/cm to oz/in is to multiply by 14.7. So a servo with a torque of 1.0 kg/cm has an imperial torque of 14.7 oz/in.

I just bought a used iMax B6AC charger (LiPo/Li-Ion/NiMH) to complement my previous Turnigy Accucel-8 charger. I had trouble finding the user manual but finally located it. I'm posting a copy here just in case anyone wants it:

• iMax B6AC Charger User Manual (pdf)

And here's a little comparison table that I drew up comparing the iMax with the Turnigy units:

	iMax B6AC	Accucel-6	Accucel-8
Max Power	50 watts	50 W	150 W
Max Current	5.0A	5.0A	7.0A
Max LiPo Cells	6	6	8
Max NiCD/NiMH Cells	15	15	27
Max Pb	20v	20v	36v
Power Input	100-240 VAC 11-18 VDC	10-18 VDC	10-18 VDC