what size circuit breaker for battery and inverter

[knewzie20]

I apologize first off because I know that someone else had this question/problem also but I can't find the thread. I tried to deplete my battery (fully charged) to see how long I could run my space heater or a high watt appliance like my insta pot. I ran the heater (1100W) for 2 minutes and the battery circuit breaker tripped( I have BattleBorn 2(100A) with 250 amp fuse; second time after reset the inverter fuse tripped after 3 minutes (inverter is 3KW/6KW) with 250 a fuse. Nothing on the setup was hot but extension cord was hot. Battery was instantly depleted to half per meter. Any idea why? The fuse should be higher? Wires are 2/0 (battery to busbar and busbar to inverter).
I also tried a heat gun(3 minutes before disconnect) and my hot pot for heating water (that was the longest of 8 minutes before disconnect) Thanks in advance.

 

[Zil]

My microwave uses 150 amps on high. Coffee pot less. You should not blow a 250 amp fuse. Maybe the extension cord is not heavy enough. Or a short along the cord? Did you try plugging something into the inverter direct with no extension?

 

[knewzie20]

Thanks for the response. The hot pot was directly plugged into outlet because we thought of the extension cord. Could it be the system got too warm after the first time then we did the heat gun with the extension cord, then the hot pot directly. (It was really hot here so that's why we tired the extension cord to place the heat outside). The extension cord is a heavy duty but long.

 

[Zil]

You mention breaker and also fuse. Just what do you have? Mine= 300 amp fuse at battery terminal, 2/0 cable to bus bar, 250 amp fuse to 2/0 cable to inverter. 2000W inverter. Is the inverter shutting down because of low battery voltage? 100 ah is not much of a battery for that much power.

 

[Mex Rider]

I think you need to eliminate that extension cord before you will know anything...

 

[knewzie20]

I have ( 2) 100 Amp batteries in parallel with 2/0 wire to 250 fuse (re-settable). Then from the fuse to busbar to Inverter PSW 3k/6k with 250 amp fuse (resettable). We had disconnected the solar panels so system was running off the batteries only to use only the battery system with the inverter, to check it all out. Even without the extension cord my hot pot caused the battery to trip the fuse after 8 minutes (again at the battery not the inverter). The temperature monitor said the battery temperature was up to 37C. Could the heating up of the batteries with the extension cord cause the next 2 incidents to trip the fuse?

 

[knewzie20]

I will try the suggestion to plug into the inverter directly with a cord to see if that causes the same disconnect. Thanks for that suggestion.

 

[Mex Rider]

Fusing is to protect the cables first to prevent a fire. I don't think 37 C is particularly hot but feel your 2/0 cable and see how hot that is. Of course I'm another newbie so hardly an expert on any of it. I think 2/0 is one size small for a 3K inverter and 250 amps also but how much you are drawing when it trips is the real question in my mind. I would speck 1/0 300 amp for a 3000 watt inverter but if your only drawing 1100 watts that should all be a moot point.

 

[Zil]

1/0 is smaller cable than 2/0. 2/0 marine grade cable is safe to 330 amps. The length determines voltage drop. What DC fuse is "re-settable" ? To trip any 250 amp interrupt needs lots of amps. Short circuit or faulty breaker?

 

[Mex Rider]

1/0 is smaller cable than 2/0. 2/0 marine grade cable is safe to 330 amps. The length determines voltage drop. What DC fuse is "re-settable" ? To trip any 250 amp interrupt needs lots of amps. Short circuit or faulty breaker?

Thank you, I was obviosly confused on cable size, thinking 1/0 was the larger of the two. A little misinformation is dangerous....

 

[knewzie20]

Thank you for the help. Now it looks like battery is not charging though solar monitor says it is actively charging. After checking the inverter with shore power and nothing tripped it seems to be battery related(?). None of the wires were hot (except the original extension cord, then the plug part of the appliance was warm). Could it be the batteries? Should I be talking with the BattleBorn peeps? I so want this to work but can't find why the battery bank won't charge. it is suppose to be fully sunny today, and plan to set panels out in full sun to see if some shade is blocking the charge (it charged so quickly before). Definitely a beginner here.

 

[Just John]

Many cheap Chinese breakers are garbage, you did say the breaker tripped first. If the breaker and fuse both tripped, you automatically have found two spots on the DC side that are getting warm. You should check for more.