Eliminating Parasitic BMS Loads from Always-Energized Golf Cart Contactors

BentleyJ

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Am I the only one who wants to replace a wasteful, always-energized, golf cart type contactor with something else to eliminate the parasitic load? The stand-by current draw on a 200A contactor is 111mA while a 400 contactor uses a massive 345mA 24/7. Do the math for 30 days and it turns out to be significant.
Due to an unexpected, forced early retirement I finally had the time to come up with a couple of solutions.

1) Midnight Solar Remote Trip Breaker with PCB Control board to supply the required Momentary 24V nonpolarized pulse when the BMS relay opens. This approach is the most elegant because it combines the required Over Current Protection Device with a means of disconnecting the load when the BMS opens. Of course once the breaker trips, someone has to manually reset it. The PCB Control Board cost approx. $45 including PCB Fab, through hole components and shipping from the various suppliers.

2) A Permanent Magnet, Latching Contactor with PCB Control board to supply the required momentary current with correct polarity to Open or Close. The advantage to this approach is that the load will automatically be reconnected IF the problem is corrected and the BMS relay once again closes. A 12V Shallco latching contactor (300A Contacts) and PCB have been successfully tested. The PCB Control Board cost approx. $60. The 5F Maxwell SuperCaps account for $25 of that.

Waiting for a 48V AMETEK latching contactor (400A Contacts), PCB from the fab shop and a few through hole components. The Contactor is non-stock so the wait may be up to 6 weeks.

In the interest of keeping this brief, here are the YT links for the 2 items discussed above with more detailed info.

At the moment, there is no life cycle testing data on the PCB Controller boards. They are fairly simple, not much to go bad.
I do plan on installing the 48V system in my DIY battery cabinet as soon as the items arrive.

If anyone wants a fully assembled PCB Control board let me know I have a few components available. Alternatively, I would be happy to send the KiCAD files and BoM if you wish to build your own PCB.
 

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Roswell Bob

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Am I the only one who wants to replace a wasteful, always-energized, golf cart type contactor with something else to eliminate the parasitic load? The stand-by current draw on a 200A contactor is 111mA while a 400 contactor uses a massive 345mA 24/7. Do the math for 30 days and it turns out to be significant.
Due to an unexpected, forced early retirement I finally had the time to come up with a couple of solutions.

1) Midnight Solar Remote Trip Breaker with PCB Control board to supply the required Momentary 24V nonpolarized pulse when the BMS relay opens. This approach is the most elegant because it combines the required Over Current Protection Device with a means of disconnecting the load when the BMS opens. Of course once the breaker trips, someone has to manually reset it. The PCB Control Board cost approx. $45 including PCB Fab, through hole components and shipping from the various suppliers.

2) A Permanent Magnet, Latching Contactor with PCB Control board to supply the required momentary current with correct polarity to Open or Close. The advantage to this approach is that the load will automatically be reconnected IF the problem is corrected and the BMS relay once again closes. A 12V Shallco latching contactor (300A Contacts) and PCB have been successfully tested. The PCB Control Board cost approx. $60. The 5F Maxwell SuperCaps account for $25 of that.

Waiting for a 48V AMETEK latching contactor (400A Contacts), PCB from the fab shop and a few through hole components. The Contactor is non-stock so the wait may be up to 6 weeks.

In the interest of keeping this brief, here are the YT links for the 2 items discussed above with more detailed info.

At the moment, there is no life cycle testing data on the PCB Controller boards. They are fairly simple, not much to go bad.
I do plan on installing the 48V system in my DIY battery cabinet as soon as the items arrive.

If anyone wants a fully assembled PCB Control board let me know I have a few components available. Alternatively, I would be happy to send the KiCAD files and BoM if you wish to build your own PCB.
Some contactors/relays have a very low pull out voltage. Hit them with full voltage to close then relax the voltage some for efficiency. It's easy to do with a parallel RC.
Am I the only one who wants to replace a wasteful, always-energized, golf cart type contactor with something else to eliminate the parasitic load? The stand-by current draw on a 200A contactor is 111mA while a 400 contactor uses a massive 345mA 24/7. Do the math for 30 days and it turns out to be significant.
Due to an unexpected, forced early retirement I finally had the time to come up with a couple of solutions.

1) Midnight Solar Remote Trip Breaker with PCB Control board to supply the required Momentary 24V nonpolarized pulse when the BMS relay opens. This approach is the most elegant because it combines the required Over Current Protection Device with a means of disconnecting the load when the BMS opens. Of course once the breaker trips, someone has to manually reset it. The PCB Control Board cost approx. $45 including PCB Fab, through hole components and shipping from the various suppliers.

2) A Permanent Magnet, Latching Contactor with PCB Control board to supply the required momentary current with correct polarity to Open or Close. The advantage to this approach is that the load will automatically be reconnected IF the problem is corrected and the BMS relay once again closes. A 12V Shallco latching contactor (300A Contacts) and PCB have been successfully tested. The PCB Control Board cost approx. $60. The 5F Maxwell SuperCaps account for $25 of that.

Waiting for a 48V AMETEK latching contactor (400A Contacts), PCB from the fab shop and a few through hole components. The Contactor is non-stock so the wait may be up to 6 weeks.

In the interest of keeping this brief, here are the YT links for the 2 items discussed above with more detailed info.

At the moment, there is no life cycle testing data on the PCB Controller boards. They are fairly simple, not much to go bad.
I do plan on installing the 48V system in my DIY battery cabinet as soon as the items arrive.

If anyone wants a fully assembled PCB Control board let me know I have a few components available. Alternatively, I would be happy to send the KiCAD files and BoM if you wish to build your own PCB.
 

BentleyJ

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this part claims 1.7W of power to keep latched.
Thanks for the product info, I am aware of these type of contactors with economizers but not this specific brand. I will add this product datasheet to my library. The 48V model only needs 30mA to hold closed, this is quite an improvement. As you point out it's easy enough to design a control PCB that switches over to a low power mode. My thinking is as follows: If I'm going to take the time and money to design and build a controller PCB why not go "all the way" and use a latching contactor that has 0 power consumption when closed. Of course the capacitors and/or power regulator on the PCB would have some parasitic load but that would typically be less than 10mA which is approx a 70% improvement over the economizer.

As a comparison, the Remote Trip Breaker PCB has a stand-by draw of only 7mA. The 12V latching contactor PCB uses about 40mA stand-by, 30mA of which is due to the 15A automotive style relay needed to handle the massive 6A Open/Close current on the Shallco. The 48V, 400A contactor I just ordered the other day only needs 0.7A to Open/Close. Therefore a smaller, micro relay can be used that would have a 6-10mA stand-by current draw.
 

BentleyJ

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Finally received the AMETEK 48V, 400A Latching Contactor, took the full 6 weeks per the manufacturers stated lead time. I've posted a short video on YT explaining the PCB controller and the operation of the contactor.


If anyone is interested I am happy to send the KiCAD files, Gerber & Drill files for the PCB, BoM and Design Spark files for the 3D printed cases or mounting base. Also, since I have a few extra parts would be happy to assemble a working PCB for cost of components and shipping.

Based on the above I don't believe I'm violating any self promotion or commercial product guidelines. Simply sharing potentially useful product designs with others on the Forum.
 

BentleyJ

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Messages
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Location
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Hello All, I've posted a YT video showing the test results of a DuraKool Bi-Stable, Latching Contactor. 300Amps, 48V single bipolar coil design.

Here is the link to the earlier YT video showing the Ametek Bi-Stable contactor. 400Amps, 48V single bipolar coil design.

And attached a couple of pics the DIY BMS and Nextion display I'm working on. Still needs quite bit of firmware work.

If anyone on the forum wants the KiCAD project files for the Bi-Stable contactor PCB controller. Send me a PM.
 

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