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Blue Sea Battery Switch for 48v Systems?

KalebTheMaker

KalebTheMaker

New Member
Joined
Oct 22, 2022
Messages
30
Location
Northern California
Hi all,

I'm slowly putting my system together and have gotten to the point where I am installing batteries and making all of the cables. The other day I had called the company who sold me all of my equipment and he told me that he "mis-spec'd" the battery switches, which are the 48v Blue Sea switches that I see in just about every install I have seen online.

What he told me is that they have a *maximum* rating of 48v, which of course in my 48v system charging voltages can get to the 55-56v range. He called Blue Sea and spoke to them and they said to absolutely NOT use them on a 48 volt system. They are rated at 48v for 36v systems and under.

But, I see quite a few of these switches being used on 48v systems on the internet. I know I shouldn't trust any youtube video that I see, that is why I am posting here.

What are your thoughts on this? If this is true, I'm not sure what switch I should use. My dealer wasn't sure either, he suggested some big 250A breakers that were like $111.00. These specifically.

Thanks,
-KalebTheMaker
 
You would probably be fine, but just because some professional YouTube experts (/s) are doing it, doesnt mean it’sa good idea or safe. ESPECIALLY now that the manufacturer of the switch is telling you very strongly to not use it for a 48V system.

There’sa big difference between a 36v system that might occasionally hit 48v (or near it) and a system operating 24/7 at 42-54v.

I’m not an electrician, but I would not do this. I’d suck it up and buy the correct item.

Have you seen the Up in Smoke sub forum yet?

diysolarforum.com

Up in smoke... learn from my mistake!

Did your experimental battery or home built inverter experience a rapid, unplanned disassembly? Reverse polarity a $3K inverter, and see it go up in smoke? Share it here!
diysolarforum.com diysolarforum.com
 
Here is my OPINION on the Blue Sea switches. When they are on or off - no issues.

The problem will be in switching states from on to off or off to on. If your system will not turning on or be shutting off with much current flow, then there will not be a problem. But if you shut off with a current flow - it could have trouble extinguishing the arc - and you can damage the switch- same with turning it on - if there is a current flow it could damage the switch.

So if there is not much or any current flow - I would use them - if not find another switch.

Good Luck
 
I tried a cheap switch off Amazon. It looked heady duty, but heated up after just a minute of use. Epic fail. Regarding blue sea: voltage rating is also the rating of insulation between the input and output.
 
Rocketman said:
Here is my OPINION on the Blue Sea switches. When they are on or off - no issues.

The problem will be in switching states from on to off or off to on. If your system will not turning on or be shutting off with much current flow, then there will not be a problem. But if you shut off with a current flow - it could have trouble extinguishing the arc - and you can damage the switch- same with turning it on - if there is a current flow it could damage the switch.

So if there is not much or any current flow - I would use them - if not find another switch.

Good Luck
Click to expand...

Thanks, good information for the procedure in any case. I'll make sure to turn off the main AC breaker before actuating battery cut-off switches (whichever I end up with) so there is no load on the system before disconnecting.
 
DIYrich said:
I tried a cheap switch off Amazon. It looked heady duty, but heated up after just a minute of use. Epic fail. Regarding blue sea: voltage rating is also the rating of insulation between the input and output.
Click to expand...
I think I know which ones you are talking about. I have a couple of those on my temporary 12v 2000w system currently. Seem to be OK for that. Though I don't think I have pushed that system over 800w or so.
 
I wouldn't use a switch that wasn't rated for the use.
Period
In an emergency, you may need to turn it off.
Doing so, with an under rated switch. Can make the emergency worse.
 
Would you use that Blue Sea switch to interrupt high current from a 36V system?
I figure it is for isolation, but not break under load.

The insulation is obviously good for much more than 48V.
Opening under load would be a problem.

I suspect it has to do with "Safe extra low voltage", which is acceptable for access by the Great Unwashed.
To be rated for higher voltage, it needs to keep fingers out.
Would be nice to find an economical, rated DC switch. Maybe it would have wrap-around insulation.
 
Blue Sea for the batteries works perfect. Be aware that they have 3-4 different ranges where f.ex. max amps are different.
Also dimensions, build thickness etc. are different. The cheapest are not as well built.
I went for the 350A version of the switches.
See my battery build thread in my signature.
 
Last edited:
Chewing gum and duct tape can do amazing things, sometimes. But it's always better to use products that are designed and rated for the purpose you use them for.
Blue Sea doesn't even recommend their switches for a 48v nominal system. In fact, they say not to.
 
LydMekk said:
Bullshit. Show me where.
Click to expand...
Actually, it is on you to show where they allow you to exceed the stated limit of 48v. Unless they state it is "nominal" voltage, you have to assume it is a hard design limit.

If you put 50v on the switch, and it shorts causing a fire, then the manufacturer can limit responsibility because you used it beyond the stated limit.
 
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