Switch Run / Tow based on Charger Interlock status?

[fstop]

Wondering if there is a simple way to auto toggle Run / Tow based on No charger connected / Charger connected status respectively.

I'd also need another switch to disable this / return to normal operation so I could put it in Tow w/out a charger connected of course.

Appears if the negative charge terminal has continuity with the blue wire (3rd pin in charger receptacle) that the cart is aware of the charger being connected?

It also seems though that if the Run / Tow is in Tow, then of course the cart doesn't know what the charger interlock status is, but I guess I'm thinking a passive "if blue is grounded, Run / Tow should be Tow..." logic, but not sure this is possible passively. I don't want an active circuit, as this would defeat the purpose.

Was considering this if it could be done simply, in that it could be an easy way to reduce any pack draw down from the controller etc...

May be more trouble than it's worth, but thought I'd float the idea and see just how bad an Idea it might be, as there are probably consequences I haven't thought of...

[Dragracer_Art]

Not a bad idea at all... but sounds like alot of effort.

Might be easier to just flip the tow/run switch off whenever the cart is parked.

[fstop]

Originally Posted by Dragracer_Art

Not a bad idea at all... but sounds like alot of effort.

Might be easier to just flip the tow/run switch off whenever the cart is parked.

Yep, I think you're right...

Thanks for talking me down off the ledge.

[Dragracer_Art]

Originally Posted by fstop

Yep, I think you're right...

Thanks for talking me down off the ledge.

In all honesty... after thinking about it... a simple $7, 5 pole relay would do the trick.

Cut into the tow/run wire and have it pass through the NC (normally closed) side of the relay.
Trigger the relay with the blue wire that triggers the charger on/off.
When the OBC triggers the charger to turn on, it will open the relay and break the tow/run circuit just as if you flipped the switch to "tow".
When the charger kicks off, the relay closes and completes the tow/run circuit.
The tow/run switch still works manually as intended.

Just a thought.

[Fairtax4me]

Which charger, and which controller?
Charger lockout can be accomplished multiple ways. And if the controller has an interlock pin already then it’s usually pretty easy.

[Sergio]

You cannot connect anything to the OBC blue wire as it would affect the "sense" circuit.

You could wire a relay to the ERIC system blue wire, one side of the coil to +48v and the other to the blue wire.

Since the relay would be powered the entire time the cart is plugged, it would negate the benefit of removing power from the Controller and likely burn the relay after a few days of being powered.

The manual switch is the best approach.

[fstop]

Originally Posted by Sergio

You cannot connect anything to the OBC blue wire as it would affect the "sense" circuit.

You could wire a relay to the ERIC system blue wire, one side of the coil to +48v and the other to the blue wire.

Since the relay would be powered the entire time the cart is plugged, it would negate the benefit of removing power from the Controller and likely burn the relay after a few days of being powered.

The manual switch is the best approach.

Thanks - after doing some further testing I'm not sure it's worth it. My cart doesn't have an OBC but I don't think that matters.

Cart is only pulling about 62ma in Run, 19ma in Tow.
Interestingly, having the charging plug plugged in (but not having the charger plugged into AC) adds about 10% to the amp draw in either Run or Tow (closer to 15% in Tow).

Something else seems to be bringing my SOC meter (lithium) down a bar about every 2 days when cart is idle, as this isn't enough for that...

[fstop]

Originally Posted by Dragracer_Art

In all honesty... after thinking about it... a simple $7, 5 pole relay would do the trick.

Cut into the tow/run wire and have it pass through the NC (normally closed) side of the relay.
Trigger the relay with the blue wire that triggers the charger on/off.
When the OBC triggers the charger to turn on, it will open the relay and break the tow/run circuit just as if you flipped the switch to "tow".
When the charger kicks off, the relay closes and completes the tow/run circuit.
The tow/run switch still works manually as intended.

Just a thought.

Thanks for figuring out the logic - I don't have an OBC though, and after testing some more I'm not so sure that the load from the cart (controller, associated wiring) is enough to be making my SOC meter (lithium) drop 1 bar every 2 days. I'm thinking it is something in the BMS, or something in the SOC meter itself.

[Sergio]

Regardless of charger, controller, lithium or lead acid, if something is activated by the charger plug, it will drain battery power to operate.

The better 48v relay coil uses 20mA and the cheap ice cube types from Amazon about 50mA.

If You add that drain to how much You are saving by putting the cart in Tow, there is no much benefit.

A lot of Lithium chargers have LEDs that stay ON when the charger is plugged to the cart even if the charger is not plugged to AC.

The batteries in the cart are keeping the charger capacitors and LED's powered, on my cart it caused a constant 7mA draw.

That is why I did my BMS charger LV and HV relay on the DC output, but I had to design a delay circuit so the relay would not close with the charger capacitors in a discharged state as it would damage the relay contacts.

[fstop]

Originally Posted by Sergio

Regardless of charger, controller, lithium or lead acid, if something is activated by the charger plug, it will drain battery power to operate.

The better 48v relay coil uses 20mA and the cheap ice cube types from Amazon about 50mA.

If You add that drain to how much You are saving by putting the cart in Tow, there is no much benefit.

A lot of Lithium chargers have LEDs that stay ON when the charger is plugged to the cart even if the charger is not plugged to AC.

The batteries in the cart are keeping the charger capacitors and LED's powered, on my cart it caused a constant 7mA draw.

That is why I did my BMS charger LV and HV relay on the DC output, but I had to design a delay circuit so the relay would not close with the charger capacitors in a discharged state as it would damage the relay contacts.

I agree; I was hoping maybe there was possibly a passive way to do it, but I see your point. Looks to not be possible, and an active method would use the power you're trying to conserve.

My charger LEDs go out if the AC is removed and it is still connected to the cart.

When checking idle cart battery amp draw, I checked with and without the charger connected (charger not connected to AC, but connected to cart).

With Run / Tow in "Run", battery drain is 62.2ma w/out the charger connected and 69ma with the charger connected to cart but not to AC. Waited 15 min. or so to see if things stabilized but amp draws remain the same.