master switch for battery banks

robocop · October 2022

Hi good morning everyone
I have 5 battery banks each 48v 250ah gel batt. total 1250ah.
Had a master cut off swicth of 275a on it.
when i had to reset the inverter could not as the swicth was loose and turned out to have burned from the inside.
question : what amp swicth do i have to use now.
Appreciate your help.
Bob

BB. · October 2022

There have been issues with Marine Disconnect switches:

https://www.thehulltruth.com/
https://www.thehulltruth.com/boating-forum/703025-sea-hunt-gamefish-blue-sea-systems-catastrophic-main-switch-failure.html

Besides the mix of (possibly) poor design, over torquing connections, hanging multiple large AWG cable on the back of the switch, etc...

I have "issues" with the design of using a simple rotating set of contacts instead of a well designed snap action switched (used in circuit breakers, large AC and DC switch gear, etc.). If these are "switched under load", the risk of arcing is present (DC arcs sustain very nicely--Why the higher end arc welders typically have DC outputs).

If you mount correctly and don't switch under load (except in an emergency)--I guess these rotary type switches last OK:

https://www.solar-electric.com/blseabaswon3.html

Otherwise, standard (DC rated) circuit breakers also make nice switches:

https://www.solar-electric.com/mnedc250.html
https://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=16&productCatName=Breakers

What kind of switch/breaker did you have?

-Bill

robocop · October 2022

the swicth is a suqre grey box with a red knop bought via aliexpress

12V-60V 100A-300A Car Auto RV Marine Boat Battery Selector Isolator Disconnect Rotary Cut On Off Switch

Switch, CN

Dave Angelini · October 2022

No way that will work very long if you are switching with loads. As Bill said.

First of all they are a dubious brand. 2nd it is doubtful that a 17 dollar part from a company named xyz at Walmart was really tested for 60VDC. Battery switching costs for 48 vdc systems are well over $100 and are hard to find for your application. I make my own out of quality parts from Square D, Midnite, and the store here.

If you find something I am all ears. It is a pain to make these and I need one switch for each battery bank. They can switch under load but one should at least try and reduce the load for longevity.

master switch for battery banks

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