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48V Disconnect

Tulex

Tulex

Solar Wizard
Joined
Mar 30, 2023
Messages
976
Location
Finger Lakes NY
I've seen the question asked, but never an answer. Many people are building 48V batteries.
I'm building 2 304AH batteries. At this point, I have two 200A Seplos BMSs, two 300A T class fuses, and a Sol-Ark 15K, which has 2 battery connections that have 200A each breakers, but max throughput is 160A on each connection. Will be connecting a battery to each connection.

Has anyone found a manual disconnect they trust for a 48V battery build?
I see people pointed to breakers, but even then it's never definitive.
 
The BEP 772 DBC Switch and its cousins are rated for 48V and should work for you. (Note: The specs say 48V... and that caused some concern that it could not handle the full voltage range of the battery. However, Marinco clarified that it is 48V nominal and can handle the voltage range)

You may be interested in this:
diysolarforum.com

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...
diysolarforum.com diysolarforum.com
 
Thank you for the info. I had looked at some BEP switches, but discounted them because of the 48V rating.
 
Tulex said:
Found this one. It's also 400 amps, so I assume it's a cousin. Interesting that it says 120V, as the BEP site doesn't have one at that voltage.

Click to expand...
I bought one just like that for my setup but I looked at the one FilterGuy posted the link to and bookmarked it just now. Its a lot nicer and I like the dual source choice of off or source 1, source 2 and the parallel setting to fuse both.
 
I use a cheap 200a 1p breaker as a disconnect/isolator

The type widely recommended NOT TO USE as a "breaker"

shopping
 
FilterGuy said:
The BEP 772 DBC Switch and its cousins are rated for 48V and should work for you. (Note: The specs say 48V... and that caused some concern that it could not handle the full voltage range of the battery. However, Marinco clarified that it is 48V nominal and can handle the voltage range)

You may be interested in this:
diysolarforum.com

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...
diysolarforum.com diysolarforum.com
Click to expand...
Do you have the reference/link for where Marinco clarified that? They also say "higher voltage on request" in spec sheet and you'd think they would be more careful on exactly what that voltage means in the spec sheet if it was "nominal", max, or what.
 
rhino said:
Do you have the reference/link for where Marinco clarified that? They also say "higher voltage on request" in spec sheet and you'd think they would be more careful on exactly what that voltage means in the spec sheet if it was "nominal", max, or what.
Click to expand...
It was an email exchange with BEP that @oc_geek shared with me.

@oc_geek, would you mind sharing the email with the broader audience?

​

 
These units are pretty standard in Australia since the latest regulation change.
 

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Tulex said:
Found this one. It's also 400 amps, so I assume it's a cousin. Interesting that it says 120V, as the BEP site doesn't have one at that voltage.

Click to expand...

That's what i noticed as well in many of their products pictures around the web... shops included
So i decided to ask them directly.. "how come?"

They confirmed (see above reply) the switches (marked 48VDC...) are fine for our Lifepo4 battery usage

I'm now considering those in my plan instead of Barkers (which i initially was pointing to) because of the much lower resistance they introduce along the end to end path from Battery to Inverter (in theory the lesser the better...)
 
Last edited:
FilterGuy said:
The BEP 772 DBC Switch and its cousins are rated for 48V and should work for you. (Note: The specs say 48V... and that caused some concern that it could not handle the full voltage range of the battery. However, Marinco clarified that it is 48V nominal and can handle the voltage range)

You may be interested in this:
diysolarforum.com

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...
diysolarforum.com diysolarforum.com
Click to expand...
Sorry for the slight thread highjack, but what would you recommend as a 24v LiFePO4 battery disconnect?

Thanks in advance!
 
SolaroSsaurius said:
Sorry for the slight thread highjack, but what would you recommend as a 24v LiFePO4 battery disconnect?

Thanks in advance!
Click to expand...
Take a look at the linked inverter disconnect resource. It has some Perko switches that work well.
 
Why wouldn't you use the switch that has been stated does work with 48V nominal? Cheaping out on something like this can cause a fire.
 
rhino said:
Why wouldn't you use the switch that has been stated does work with 48V nominal? Cheaping out on something like this can cause a fire.
Click to expand...
Using that logic, I should spend $500 on a 300 amp knife switch. Superior in all respects to the BEP. Why should I cheapen out with the BEP and risk causing a fire?

The BEP has a "nominal rating" of 48v, and only claims through e-mail to handle charging voltage (BTW: What do they define as "charging voltage"?). The isolator disconnect is advertised for 60v, above the 56-58v charging voltage of 48v LiFePO4.

Which mechanical disconnect would you trust more to disconnect under load? A rotary switch (who knows if there are plastic pieces that could shear under strain), or a pin that pulls out (although there is no design that shows how the internals would be forced apart when the pin is removed).
 
Watts 24/7 carries some nice breakers that can double as a DC disconnect. Amazon has about the same units under “DIHOOL DC breakers” They are big so check it for fit.
I got the Watts 400 double but it looks like they are out of that rating. Mounted mine in a box with pre charge and a 8 place buss (4 on each side of buss) for future expansion.IMG_0473.jpegIMG_0580.jpegIMG_0666.png
 
DIYrich said:
Using that logic, I should spend $500 on a 300 amp knife switch. Superior in all respects to the BEP. Why should I cheapen out with the BEP and risk causing a fire?

The BEP has a "nominal rating" of 48v, and only claims through e-mail to handle charging voltage (BTW: What do they define as "charging voltage"?). The isolator disconnect is advertised for 60v, above the 56-58v charging voltage of 48v LiFePO4.

Which mechanical disconnect would you trust more to disconnect under load? A rotary switch (who knows if there are plastic pieces that could shear under strain), or a pin that pulls out (although there is no design that shows how the internals would be forced apart when the pin is removed).
Click to expand...
I'm just really weary of buying such items off of Amazon that aren't available from other places since it is a dumping ground for some poor quality stuff. I did have same concerns about the voltage of the Marinco and am not sure why they won't state in the spec sheet what it truly is rated for if it is rated for 48V nominal system. I do have one for one of my 48V batteries and it definitely is heavy duty looking/feeling.
 
I bought the uxcell off Amazon, and it is a beast. Unfortunately no voltage or Amp ratings written on it. Two M10 bolts for power connection. Inside they have a flat top. A U shaped busbar is pushed against the tops of the bolts to complete the connection. The latch pushes the busbar down against a spring force. When the latch is released, the spring lifts the busbar off the bolt heads. Solid plastic rod is used to hold the busbar and isolate the latch from the electricity.

Busbar is 40mm wide and 4mm thick. Don't know what mettle is used. Looks like the hole for the plastic rod is about 7mm diameter.

someday I'll measure the temp after a large draw.
20230527_071610.jpg
 
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