Is it even possible with off-the-shelf parts?

Old 11-20-07, 03:09 AM
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Question Is it even possible with off-the-shelf parts?

Come Hell, or highwater, I am building a hybrid go-kart. The electric part of the drive system is a pair of 24vdc/250 watt motors. Each motor drives a rear wheel by chain & sprocket. The rear wheels are mounted on stub-axles. Changing over to an electric powered drive system was the easy part. Now I want to go from "electric" go-kart, to "hybrid" go-kart. Unfortunately, my lack of a budget precludes both having a 24vdc alternator custom made, or frying a dozen 12v alternators attempting to "fake it until I make it".

I originally intended to use the 3hp Briggs & Stratton engine that came on the go-kart to charge the battery bank by turning an automotive alternator with internal voltage regulation. Having to stop the go-kart, pull start the engine, and wait a bit is OK with me. If it can be done, I know it won't be very fast, but it will be quite efficient and novel as Hell.

This is the part that is killing me. The battery pack is composed of two, 12v batteries connected in series to give the 24vdc the motors require. Can anyone out there in cyberspace please explain (assuming it's even possible) how to use a 12vdc automotive alternator to charge a 24vdc battery pack?
Old 11-20-07, 04:21 AM
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Are you sure you even need 24V to charge a 24V power supply? Your not really putting voltage in. You are reversing an electro chemical process. Use a marine or diesel alternator rated for 24V. Use two 12v alternators series wired. Use a heavy duty switch or relay to change the connection on the batteries from series to parallel.
Old 11-20-07, 06:01 AM
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a couple of easy ways

Find a wrecked Cessna and use that one. Failing that, use a older automotive alternator with a ext regulator; substitute a 24volt regulator.
Old 11-20-07, 06:15 AM
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Originally Posted by telecom guy View Post
Find a wrecked Cessna and use that one. Failing that, use a older automotive alternator with a ext regulator; substitute a 24volt regulator.
Cessna alternators don't come cheaply. Any aviation related part comes with a very premium price. However, if you do look for something like that, it will need to be from a 1977 or newer Cessna as most of the earlier models were 12 volt. I would suggest that a trip to a heavy duty truck junk yard to find a more affordable alternator. Good luck with your project!
Old 11-20-07, 05:00 PM
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alot of off road equiment useally run on 24 volt alternators that is very common methold and also you can find 24 volt alternators from miltary equiments [ that is the standard run of mill voltage system everything from small genny to large aircraft and tank use same voltage to make it easier to jump start anything along the way]

other option is you can stop one of the starter/alternator shop and ask for a 24 volt regulator and they can work with almost anytype of alterntor to run on 24 volts but have to change the reficer to work properly on 24 volts system.

cost wise it will be some how little more over standard 12 volt system.

even my service truck it allready rewired for 24 volts due i have some equment that run on 24 volts so i set up that way.

3 HP briggs engine can bearly squeak by with standard automove alterator more typically 5 hp or larger.

Merci , Marc

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