What plug

[geekygrilli]

Thanks Paul

I got the one hour rated coil, at 12v, switching 250Amps continuous. It seems like the easiest safest option, for me, anyway.

[geekygrilli]

Hi there

Quick question for Paul....

I've just received my new 12v/96v contactor, to seperate the batteries from the controller when ignition is off, and wondering why you have suggested I put it on the negative side and not the positive?

Its not a problem either way, but I'd just like to understand!

Many thanks

Christopher

[EVguru]

Isn't there a already a contactor on the positive side?

[electricvehicles]

Would it not have been easier to fit a SW190 contactor. Double pole does it all. Job Done. Will be good when Albright bring out a Double pole line contactor/emergency disconnect unit. Currently they only make a single pole version but hopefully this will change

[geekygrilli]

Thanks for the quick reply!

Er...no, the only contactor present is the one which switches with the throttle micro-switch, connected through VMN.

So I will only have one contactor for the main supply to the controller, which i want so that I may charge without pumping power into the controller. Will this be OK, or should i switch both the negative and the positive?
My (humble and probably wrong) opinion is that it will be alright to just disconnect the positive from teh controller, and charge ther batteries. The negative still connected to the controller.

The charger will plugged and unplugged to the batteries for each charge. i don't like the idea of having it connected all the time.

As a side....
(For safety, I have a big red stop button mounted neatly on the dash which cuts the batteries, and an inertia switch in-line with the ignition. i have tested both whilst driving and work A-OK)

[EVguru]

I just dug out my H2 manual.

Zapi seem content to not use a precharge resistor. The means that when the battery is first connected to the controller there will be a large inrush of current limited only by the resistance of the batteries/wiring and the ESR of the capacitors. This can be into the 1000 Amp range. This is very hard on the contactors and the capacitors. On high voltage controllers like the Grizzly, DCP Raptor, and Zilla, you can dammage the contactor and capacitors in a single event.

The solution to this is to initially conect the controller via a current limiting device of some kind, the simplest being a resistor. On something like a forklift you could just put the resistor across the main contactor (most likely in the positive line) becuase the battery pack is usually unpluged whilst charging. On a passenger road vehicle that most likely carries it's own permenently installed on-board charger, the resistor would mean that the controller would be exposed to full charge voltage and any line transients.

To avoid this you need at a minimum an extra relay. This would connect the charger to the pack via the pre-charge resistor. When the capacitors in the controller were charged you could close the main contactor. This process can be manual, having the relay close when the key is turned to the acessory position, having a volt-meter accross the controller terminals and turning the key to the ignition position when the voltage stops rising. The problem here is remembering to follow the start sequence. You can also do it be 'dead recconing' simply closing the main contactor after a short delay long enough for the pre-charge to have finnished. Some of the more sophisticated controllers automate this process and close the contactor when they think they're charged.

You've still got one more potential problem. The controller is still connected via the negative terminal and you could be prone to leakage current between the pack and frame due to carbon dust in the motor. By having another contactor on the negative side, you completely isolate the pack from the frame and any leakage current indicates a genuine fault (acid tracking, frayed wiring etc.).

I don't like the use of a 'Big Red Button' in a car. It's not a normal car control and in the event of a runaway caused by a stuck throttle, failed controller etc. it will be the LAST device you use to stop the vehicle. Trust me, even professional race drivers crash before hitting the 'engine stop' switch. It is possible to build fault detection circuits that would sense a failed controller and drop the contactors out if the brake pedal was pressed. Putting a microswitch on the clutch pedal (at full travel) is one of the simplest solutions.

You shoud still have a 'service dissconnect' switch, that disconnects the pack. If you have two packs, then put it in the middle. This makes the vehicle safer when you're working on it.

Would it not have been easier to fit a SW190 contactor. Double pole does it all. Job Done.

A few problems with that. You can't do the pre-charge sequencing and it places the opposite poles of the pack uncomfortably close together. It also means you've got no redundancy. If one pair of contacts weld, the contactor won't drop out, but with two contactors you've got greater protection.