# Wiring a Nissan Leaf precharge circuit



## electro wrks (Mar 5, 2012)

You may want to reconsider using this contactor unit as the contactors are, I believe, rated at only 200A and used in a system( the Leaf) fused for only 225A.


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## Sentinel Rock (Mar 15, 2021)

electro wrks said:


> You may want to reconsider using this contactor unit as the contactors are, I believe, rated at only 200A and used in a system( the Leaf) fused for only 225A.





electro wrks said:


> You may want to reconsider using this contactor unit as the contactors are, I believe, rated at only 200A and used in a system( the Leaf) fused for only 225A.





electro wrks said:


> You may want to reconsider using this contactor unit as the contactors are, I believe, rated at only 200A and used in a system( the Leaf) fused for only 225A.


Thanks. Makes sense.

could the precharge circuit still work with a different set of relays?


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## Isaac97 (Jun 3, 2019)

Yes, the precharge circuit would work well with any contactors.
With regards to your questions (which apply to most contactors):
1. Use a common ground and one signal wire for each; it doesn't matter which is positive or negative in my experience -- this might be different for other contactors (which will then have a red and black wire to indicate that).

2. Yup, that's the precharge relay. 

3. Nah, you just leave them open when you shut the system off. There is a self discharge resistor inside most motor controllers.


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## Sentinel Rock (Mar 15, 2021)

Isaac97 said:


> Yes, the precharge circuit would work well with any contactors.
> With regards to your questions (which apply to most contactors):
> 1. Use a common ground and one signal wire for each; it doesn't matter which is positive or negative in my experience -- this might be different for other contactors (which will then have a red and black wire to indicate that).
> 
> ...





Isaac97 said:


> Yes, the precharge circuit would work well with any contactors.
> With regards to your questions (which apply to most contactors):
> 1. Use a common ground and one signal wire for each; it doesn't matter which is positive or negative in my experience -- this might be different for other contactors (which will then have a red and black wire to indicate that).
> 
> ...


Thanks for this. Alas a little more help still needed. I’ve drawn the until (not technically) enough to show flows and signal wires. There are six “control” wires two into each relay: pos red brown; neg orange and blue w/stripe and the small (precharge) contactor. The same 6 run to the round control wiring plug on the battery box.

so...does the following plan make sense:

1: 12v to brown and red to open precharge

2: timer, activated by #1 above, then sends power in 10 seconds to yellow-purple, and to orange and blue w/stripe.

Putting aside issues of amperage ratings on the controllers, does the above properly outline things.


under this scenario the off sequence is more simple, key is turned off and all three relays close (pos, neg and precharge).


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## electro wrks (Mar 5, 2012)

ZEVA makes a precharge control: https://www.zeva.com.au/Products/datasheets/PrechargerManual.pdf
EVWest(maybe others) has a version of it: ZEVA Smart Precharger for High Voltage EV Motor Controllers, EV West - Electric Vehicle Parts, Components, EVSE Charging Stations, Electric Car Conversion Kits
If you have some way of timing contactor engagement, you can use a system like this EVTV one that eliminates the potentially troublesome precharge relay altogether: Bench Envy - the GEVCU begins to show its stuff. - EVTV Motor Verks


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## Sentinel Rock (Mar 15, 2021)

This question seemed lame. I know, it was mine. But none of the relays would work given 12vs. Prob: my 12vs was at such a low milla amperage that it was not triggering the relays. Hit it with another source, e.g., car bat, and all worked well.

As you’d expect I’ve added a smaller timer to trigger the pre-charge then it fires up the other relays.

now, second batter box, with same ish parts, pictured. This will be in or super adjacent to my rear bat box.

Question: does the rear battery box even need a precharge if the front battery box, where max positivevoltage is, has a precharge - thus your rear bat box relays open on same signal timing as front which it itself delayed behind the precharge relay.

perhaps, this also asks, can a ‘front [max pos]” battery pack precharge circuit work at all if the in line rear battery pack negative remains closed until after the precharge. I’m thinking yes because of some negative potential in capacitors (then again I just made up the term “negative potential” so...)

why it matters: using these oft discarded parts makes a pretty sweet, pretty cheap, stout (600v/250a?) battery junction box.


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## Isaac97 (Jun 3, 2019)

You only need one precharge system in the circuit.
However, you do need to be careful with which contactors you have turned on.
Let's assume you have in the front pack a precharge contactor and a main contactor, and in the rear pack one contactor.

If you turn on the precharge contactor but not the rear contactor, nothing will happen -- no precharge -- because you don't have a complete circuit.
So you need to connect the precharge contactor to the rear contactor to complete that circuit. And also don't forget to keep the rear contactor on when the main contactor is on.


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## Sentinel Rock (Mar 15, 2021)

Isaac97 said:


> You only need one precharge system in the circuit.
> However, you do need to be careful with which contactors you have turned on.
> Let's assume you have in the front pack a precharge contactor and a main contactor, and in the rear pack one contactor.
> 
> ...


Thanks. Very helpful.
You’ve described it super accurately except that the rear bat pack has both a pos and neg contractor. So am I understanding you properly to say, both rear battery pack neg and pos relays can/should open with precharge relay, then post delay, full front pack pos and neg go live?

you are also saying, to keep all relays on thereafter - until shut down of course.

thanks


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## Isaac97 (Jun 3, 2019)

With packs in series, yes, you keep the rear pack contactors on. And of course if you turn them off you'll get no power.

I suggest you do some testing with a voltmeter before connecting to your controller, make sure the voltage rises when it should and stays on when it should. Neither contactors nor controllers like the inrush current if it's done wrong...


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