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Precharge Diagram

2376 Views 6 Replies 4 Participants Last post by  racunniff
I've been studying how precharging works and have deciding i want to use a 60 watt 120 v lightbulb (unless someones has a better bulb recomendation) and a relay so that when the key is in the first position the car precharges, and when it is in the second the contactor closes.

My car is a 120 v setup and im still looking for a relay that does the job. Any suggestions would definitely help

I am terrible at diagrams so sorry in advance

Hopefully you can read that. Is it right??

Thanks for any feedback :)
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Hope its not too confusing

One thing you are missing is a "healthy" signal from the controller. You don't want the main contactor to turn on unless the controller is actually precharged. With the circuit you show, someone could just turn the key straight to the start position (as most people would do), and damage the controller or blow a fuse.

I am also using the aux contact on the main contactor to keep the main contactor latched since the "start" position on the ign. switch is momentary. Looks like you are using position II to energize the main contactor , so this might not be needed.
The key second position is usually the start position, unless you are talking about the accessory and ignition positions. The start position is a momentary connection so that wouldn't work without adding a latching relay. What you have drawn looks like a pretty normal precharge system. It requires the driver to remember to wait a couple of seconds between the time they switch on the precharge relay and main contactor. Another consideration is that the relay used should be rated to switch 120 volt DC. There are not that many relays available with high voltage DC ratings. It is possible to use a 5 or 10 amp 240 vac rated relay with appropriate snubber.

My buggy runs a Curtis 1221B controller and a 120 volt system. On the buggy the coils of the relay and contactor are parallel to each other, they both turn on and off together. The relay provides power to the ksi terminal and the contactor to B+. A 7.5 watt, 120 vac, bulb is across the contacts of the main contactor (this is the little round bulb that is barely larger than its Edison base.) This system leaves the controller capacitors always precharged to about 4 volts less than the battery pack.
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I have my precharge set to work when I turn on my main power before I put power to the controller. That is how I did my first setup. My second setup is controlled by my controller. The precharge is built in so my contactor will not engage before it's precharged. My first setup was tapped from behind the main circuit breaker so if I shut off the main breaker the power is totally off to the controller. When I flip it on then power is tapped off that at full pack voltage but very low amps and used to precharge the controller. Within a few seconds the controller was precharged. Worked perfect.

Pete :)

Why a light bulb. If the bulb is in the motor compartment how do you know when it burns out? I just use a resistor. I trust the resistor more than a light bulb. Driving around with house hold light will put undue stress on the filament. It is not as durable as you might think. Never understood the use of the bulb.
Ive heard lightbulbs do what resistors do, but quicker
Ive heard lightbulbs do what resistors do, but quicker
Incandescent lightbulbs *are* resistors. The only difference between them and a packaged resistor is that you can see the blackbody radiation emitted from a lightbulb.

That, and as previously mentioned, the resistive element (the filament) is only supported at the ends in a lightbulb, leaving it more vulnerable to breaking.
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