I received my contactor in the mail (ZJW 96V/400A), and wanted to give it a little "test", by just putting 12V across the terminals, without plugging it into the controller or anything. I expected to hear or feel the solenoid engage or something, but got nothing at all. Am I doing this right? Does the contactor have to be under load in order to engage? Should I expect to hear / feel anything when I put 12V across the terminals?
How to "test" a Contactor?
1 - 16 of 16 Posts
Joined
·
124 Posts
I would have expected a click too. But how about you test continuity across the HV terminals as you apply power?
Joined
·
124 Posts
Also, the specs for that contactor say <=16 W consumption on the coil, so are you providing at least 1.4 amps of 12v current?
Joined
·
2,984 Posts
It has a really low voltage rating...what is your battery voltage on the high current side?
edit: before Brian jumps in my poop, nothing to do with testing or actuating it. Observation.
edit: before Brian jumps in my poop, nothing to do with testing or actuating it. Observation.
All excellent questions!
Continuity across the HV terminals is zero.
Well, I'm plugged into a standard 12V car battery, so 1.4A should be no problem. Actual current draw on the LV terminals is zero. (coil problem?)
Not sure I understand. Do you mean on the HV terminals? I have literally nothing plugged into the HV terminals. On the LV terminals, voltage is ~12.5V. Where do you see the "low voltage rating"?
Measure the coil resistance, you should be getting something close to their datasheet. And to double check - is yours definitely a 12v coil one ? This model seems to be available with different coil voltages, any chance you got the wrong one ? Either way, coil resistance will tell you if you got the right one.
Resistance is around 350Ohms (I have a back EMFdiode soldered across the coils, so that may also be affecting the resistance? It's 350Ohms both ways). BUT, I may have ordered the wrong contactor. The one I ordered (off AliExpress) said "400A / 96V", which I assumed was referring to the Pack voltage, and not the coil voltage. Did I just read it wrong?
Joined
·
2,984 Posts
That's 96 Chinese Volts, which is 80 worldwide volts.
Seriously, look at the datasheet. It's rated at 80V max.
That's why I asked what your pack voltage was.
With a back emf diode, it should read short in the diode forward direction and 350ohms in reverse (the direction of current in your application).
If you're using a current limiting supply, a forward biased diode will short the coil and no clickey, no cooking of the diode.
Seriously, look at the datasheet. It's rated at 80V max.
That's why I asked what your pack voltage was.
With a back emf diode, it should read short in the diode forward direction and 350ohms in reverse (the direction of current in your application).
If you're using a current limiting supply, a forward biased diode will short the coil and no clickey, no cooking of the diode.
Good catch!
Dammit. Pack is going to be a 32S LiFePO4, so... ~102V?
Seems super weird then that the resistance would read the same forward and backward, with the diode in place.
(EDIT: The diode by itself measures ~265Ohms forward, and re-measuring the coil resistance, it looks like ~348Ohms forward, ~345Ohms back with the diode in place.)
Either this thing is FUBARed, or (more likely) I just ordered the wrong one. Think I'll switch to the GigaVac GV200 instead...
Personally I wouldn't worry about slightly overdriving the contact voltage as long as you're staying within the current rating. Coil voltage is a bigger problem though - sounds like your pack voltage may be too high for it, and 12v is too low... if you have PWM on your motor controller, perhaps it can supply it with expected voltage by reducing the duty cycle ? The only other way around it is with a DC-DC converter, but it starts getting convoluted and introduces points of failure.
That diode may have been fried "from the factory"
Disconnect one side of it, and test it.
Joined
·
2,984 Posts
Diode should be close to short circuit when fwd biased, especially considering the current it should be rated to carry.
Probably an Alibaba diode...used....harvested out of failed devices....that diode was probably why the donor box didn't work 😂
![]()
Probably an Alibaba diode...used....harvested out of failed devices....that diode was probably why the donor box didn't work 😂
The Datasheet that you supplied shows that a 12V coil on that contactor has a resistance of 17.1 ohms.
Your contactor coil is not 12V and that is why it is not activating.
Joined
·
2,984 Posts
Good point. Looking again at the coil resistance table, it's likely a 96V coil vs the 96V contact rating I/we had assumed they were spec'ing.
1 - 16 of 16 Posts
Join the discussion
