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Old 05-14-2009, 09:20 PM   #13 (permalink)
TomEV
Ford Escort 2.0
 
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Join Date: Feb 2008
Location: Alameda, CA
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Electricar - '89 Ford Escort LX Hatchback
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Depending on your tolerance for 'possible' burn-out of components, since you appear to have a contactor set up it will be easy to test it at a higher voltage. Coil -type contactor setups normally do not have a series/parallel system, and run the full pack voltage through the resistors (coils) to move at slower speeds.

Other, obsolete 3-speed contactor systems use 2 batteries (low, 12v) 4 batteries (med, 24v) and all batteries (high, 36v). You probably don't have this type of setup because you have resistor coils.

The most sensitive part will be the contactor coils (part that pulls the contactor closed, not the resistor). If they are running at 36v (full pack voltage) they won't like to be operated at 48v or 72v and will tend to burn out very quickly. If you can trace back to where the contactor coils get their power, you can re-tap the traction pack at 36 (or 12 , or 24v, whatever they use) to make them work with a higher voltage pack. The two or three amps won't be a significant mismatch across the battery pack considering your motor uses about 150 amps.

Aside from that, you can temporarily install old 12v car batteries for a test to see how it will do. 4 for 48v, and 6 for 72v. You may be able to sweet talk a junk yard or battery store into 'borrowing' a few old batteries for a test before you buy a whole new set...

One last note - If you replace the batteries with a higher voltage set, check where your 12v power (lights, etc.) comes from before you turn anything on. In many utility carts, 12v is tapped off from two of the traction batteries. You won't want to put 24v to your headlights!
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