48V battery double throw switch options

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solar12345

New User
Location
Washington
Occupation
Residential electrician
Dual battery back up system. 48VDC batteries (two different lithium banks) with hybrid inverter, existing DC solar. I'm looking for a double throw switch (on off on) that's rated to 48V and at least 200a to switch between battery banks. Trying not to break the bank.. Marine battery switches don't seem to be rated to 48VDC. Any suggestions? Thank you!
 
solar12345 said:
Dual battery back up system. 48VDC batteries (two different lithium banks) with hybrid inverter, existing DC solar. I'm looking for a double throw switch (on off on) that's rated to 48V and at least 200a to switch between battery banks. Trying not to break the bank.. Marine battery switches don't seem to be rated to 48VDC. Any suggestions? Thank you!
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What mean Trying not to break the bank?
An idiom or you want closed transition change over?
 
This is a real problem with 48V systems IMO, at least in the US. To pass muster with any given AHJ, and really to do due diligence and not open yourself to too much liability down the road, you need something like what ChesterDawg posted. A big-ugly-box-on-the-wall that costs about $300 min for a 10kW circuit. Whereas at 240VAC your 10kW disco is a quarter the size and price. Not to mention similar difference for your conduit and wire. Or at up to 600V DC maybe you can at least do like 30kW with that $300 disco and a 60A circuit. So basically 48V systems are really limited to applications where you can put the batteries right next to the inverter which has a breaker in it (a foreign company's breaker that probably wouldn't have a UL listing on its own but is really just fine for the purpose).

Deltaforce said:
Cost more 240V DC to 48VDC
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240V (120V to ground) is 'light duty' in the US and lower voltage rated standard electrical equipment for NEC installations isn't really a thing here.
 
In my experience with telcom -48V systems the 48 is just a 'nominal voltage' the equipment is designed to, I never worry about 'float' voltage, they are well aware of it.
Also you might look at square D QO and NQ, square D used to make stuff for the telcom industry and tons of their gear to this day is dual rated for 48DC.
 
You’re right, many marine battery switches are not rated for 48 V DC at 200 A ，so you’ll need one that explicitly supports 48 V+ and high current. I’d recommend looking for a transfer switch or DPDT contactor rated for ≥ 200 A at a voltage higher than your nominal 48 V (since a 48V battery bank fully charged may go up to ~58.4V).
Make sure the device is for DC switching, has proper arc suppression and contacts sized for the current.
 
200A rated DPDT switches are just plain expensive. If anyone knows a cost effective way to do this, please let me know!

The comment about confirming that a switch id DC rated is a good one. I checked, and the Siemens switch posted above is both AC and DC rated to 200A.
 
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