DC breakers keep tripping

[mezaal]

Hi All,

i have 5kw inverter connected to 5kwh lithium battery and 5kwh solar panela. Voltage of the battery pack 48v.The DC breakers between battery and inverter is 125 A. Almost everyday the dc brekaers trip one to two time a day, no specific time, randomly. the load is low, below 1kwh.

Could please help advice what could be the reason.

Many thanks!

 

[John From Detroit]

5000 watts / 48 volts =104.1666666666667 amps Now add 10-15% for conversion loss and you are at 115-121 amps your breaker is 125 amps at 126 it will trip fairly fast. but at 120 it will trip in fact at about anything over 100 it will trip.. EVENTUALLY. assuming it's a thermal breaker.

Also for thermal breakers other heat sources and bad contacts make it trip faster.

Magnetic breakers... are more .. Precise.. but I do not know where to find them.

But it sounds like you might need to review the breaker size.. generally they want a somewhat larger breaker for a 5KW inverter.. I'd have to read the manual for m ore.

 

[Gary RV_Wizard]

As John says, a 125A breaker will typically trip with a sustained load much over 100A. Unless the breaker is marked otherwise, the ratings are for peak loads, not continuous use. The continuous rating is typically 80% of peak, which would be 100A. And "continuous" is anything over 30 minutes at that amperage. The commonly used breakers are designed to trip fairly quickly if their max rating is exceeded, e.g. a short, but they still react to the slow build-up of heat at lower loads.

Breakers designated "long trip" or "slow trip" or "time delay" can operate near their max for longer periods. You need a breaker of that type, or just a larger breaker. 150A ought to do it, and it would still trip if the inverter or wiring shorted.

Note: GFCI and AFCI breakers are not included in the above.