Battery disconnect switch cheap amazon vs Blue Sea

[filippomasoni]

Hello,
I want to build a battery switch with precharge for my 24V 280ah battery. The recommended switch in the guide, https://diysolarforum.com/resources/inverter-disconnect-switch-with-precharge.60/, are not available in Italy, with shipping and taxes from the US they will be probably around €130, which I would like to avoid.
The best alternative I found is the classic Blue Sea, which is good quality and about €40 but is currently unavailable on Amazon: https://www.amazon.it/gp/product/B0070YEEI8


Otherwise, there seem to be so many of the same style switches on amazon, definitely lower quality from china, but available at around €20:

https://www.amazon.it/ZMYGOLON-Interruttore-1-2-Both-Off-disconnessione-Impermeabile/dp/B08BHTGX1T

Has anybody tried any of them? Do you think it's not worth it to go with the lower-quality one? My battery will probably see 100-120A max.

 

[Bvillebob]

IMO both have their place. In my batteries (4 x 15 kWh) I used the cheap $15 switches for disconnects. The reason is that they will only ever be operated a handful of times in their life and they never see more than 100 amps through them. In my camper I used a Blue Seas switch as I use it all the time and it's subject to more abuse in the vehicle.

The cheap switches work fine, but the contacts inside are just the top of the bolt that serves as the top of the lug, they're not hi-tech silvered or anything. They're passing 100 amps just fine for me. Mine have have been in operation for a year or so, no issues. In a perfect world I'd use the better switches "just because", but when you start buying a half dozen of them the difference in price adds up and the cheap ones do the job for many applications.

 

[brb58]

I would never buy those cheap disconnects. BlueSea only.

 

[filippomasoni]

IMO both have their place. In my batteries (4 x 15 kWh) I used the cheap $15 switches for disconnects. The reason is that they will only ever be operated a handful of times in their life and they never see more than 100 amps through them. In my camper I used a Blue Seas switch as I use it all the time and it's subject to more abuse in the vehicle.

The cheap switches work fine, but the contacts inside are just the top of the bolt that serves as the top of the lug, they're not hi-tech silvered or anything. They're passing 100 amps just fine for me. Mine have have been in operation for a year or so, no issues. In a perfect world I'd use the better switches "just because", but when you start buying a half dozen of them the difference in price adds up and the cheap ones do the job for many applications.

I like your thinking, makes perfect sense.
The battery I'm currently building is for a truck camper, it won't have a lot of switching as I plan on using it for very long trips at a time, but it will definitely see some abuse in terms of vibration, temperature and humidity changes. I'll go with the blue Sea, ordered on Amazon, they'll shop it when available, which means I'll have to wait a while. But the price is good, otherwise I've seen in in other stores going for around €70 once you add shipping.

I'll keep that in mind and if I ever build a stationary system where I'll need more of them I'll consider the cheap ones.

 

[Bud Martin]

Look at the spec to see if it is made for switching under loading condition or not, most of them will tell you not to switch under loading condition. also check the Vdrops during heavy load to see how much power it will be dissipating.

 

[filippomasoni]

Look at the spec to see if it is made for switching under loading condition or not, most of them will tell you not to switch under loading condition. also check the Vdrops during heavy load to see how much power it will be dissipating.

I don't think any of these are made to be switched under heavy load. They are not breakers, but battery disconnect. The purpose is you have a battery that can be switched off when not in use for long periods or for maintenance.
Al least this is how I understood.
A breaker would be better I think, but DC breakers for such high amps are much more expensive than using a disconnect and a fuse.

That being said, I don't think the cheap ones provide those info, and even what they provide can't really be trusted. I've seen some report vary different amp rating from 200-500a and they all look identical.
I've checked the blue Sea website but couldn't find any info on switching under load.
The vdrop would actually be a really useful information, but couldn't find that either