DC Breakers - Continuous Amperage Ratings

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DC Breakers - Continuous Amperage Ratings

Postby flboy » Tue May 30, 2017 12:08 pm

Can anybody recommend a good DC breaker that is rated by "continuous amps" that isn't a few hundred dollars? I have a 1500W Inverter that runs at 85% efficiency (1500/12/.85) or ~150A full load.

I started out with some 200A ANL fuses.. They got hot and dropped about 1.5V to 2VDC DC... No good for the application. I think those are more for Audio Systems anyhow. I just thought I'd try it.

I then got a 150A breaker from Amazon made by Scosche. It would pop after 1 minute running my 750W microwave (~73A) so I figured it was defective and then bought a 200A Schosche. It does the same, except it can go about 3 minutes.. They both drop about 1VDC. They perform like junk and I got what I paid for. I know DC breakers are thermal devices and can take a certain load over time before they pop... I am just having a hard time getting something that works as I need it to going by the specifications as I understand them.

I see some BUSS Blue Sea Systems 187-Series Circuit Breakers that appear like I may be able to run them continuous at their specified ratings (based on some reviews), but they are $90.00. I need a 200A so I can have plenty of margin. The inverter can take an instantaneous load of 3000W for startup. Also, I'd like one that drops less than .5V.. If these do in fact allow me to draw 150A continuous (would not happen often) and pop after a few seconds @ 200A to protect the wiring, I'd pay the price.

Do I have any options... Any recommendations? Thanks in advance. I am not typically working with High Current DC, so I have not thought about this too much in the past. I'd prefer a breaker in any case so it can be reset. Also good for isolation when working on the system.

If I were doing this all over again... I'd go with a 24VDC inverter and set my solar panels and batteries up for 24VDC.. Just to decrease the current by half would be a big deal... Oh well.. Live and learn. If I ever need to get a new inverter and also replace my batteries... I may go that route.. My solar controller can already take up to 48VDC.. :thumbsup:
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Re: DC Breakers - Continuous Amperage Ratings

Postby John61CT » Tue May 30, 2017 2:33 pm

Those big amp loads, fuses are so much cheaper and safer. ​Class T, ANL or MRBF, go with Bussman or Blue Sea, Samlex etc not cheap copies or generic.

CBs are relatively complex, lots of delay variables etc, and you really are talking big bucks even if you do figure out exactly what you need.

You should also have a robust switch, right at the bank positive, Blue Sea makes solid product.

If an Alt is dumping to the bank, get a pro to correctly wire the Field Disconnect feature so you don't fry your diodes.

Note you need to size for the max Total current * 150%, and locate right at bank positive, proper wire sizing, robust fittings properly crimped connections etc.
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Re: DC Breakers - Continuous Amperage Ratings

Postby dancam » Tue May 30, 2017 3:00 pm

How long are your wires? If their over 3ft you could put a large fuse at the battery that will only blow if you get a short and a properly sized one at the inverter end. Less voltage drop. Name brand fuses make a huge, huge difference. As does wire size. Whats your wire distance and size?

John, can you explain more about this field disconnect and what the issue is if you dont have it please? I have a 2000watt inverter in my vehicle but no switch like you mentioned

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Re: DC Breakers - Continuous Amperage Ratings

Postby flboy » Tue May 30, 2017 3:29 pm

John61CT wrote:Those big amp loads, fuses are so much cheaper and safer. ​Class T, ANL or MRBF, go with Bussman or Blue Sea, Samlex etc not cheap copies or generic.

CBs are relatively complex, lots of delay variables etc, and you really are talking big bucks even if you do figure out exactly what you need.

You should also have a robust switch, right at the bank positive, Blue Sea makes solid product.

If an Alt is dumping to the bank, get a pro to correctly wire the Field Disconnect feature so you don't fry your diodes.

Note you need to size for the max Total current * 150%, and locate right at bank positive, proper wire sizing, robust fittings properly crimped connections etc.


I am not charging with my Alternator and I do have a main battery disconnect at the Bank positive. Wires and all are proper gage with crimped and soldered connections and the run from the battery to the Inverter is about 4.5 Ft. ... 150A would be the max continuous current with 100A likely for 5 minutes or more when I run the microwave. I was getting close to the 150% of max usage with the 200A Breaker which will only allows me ~105A continuous for less than a minute. :-( I am attributing that to a cheap breaker however.

Should I be able to run ~150A continuous through a 200A fuse and not drop more than .5V? Many thanks.
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
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https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: DC Breakers - Continuous Amperage Ratings

Postby flboy » Tue May 30, 2017 3:46 pm

I ordered a Blues Seas 300A ANL Fuse and Fuse Block. I am going to give that a shot. It should handle the max surge of the inverter and run comfortable at 50% of rating for max continuous. Fuse block is right after the Battery cutoff switch.

The reason why I like the Breaker was I did not have to cutoff the battery which kills the lights. Oh well, now I will just have to use a flashlight if I need to work on the inverter side. :-)
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: DC Breakers - Continuous Amperage Ratings

Postby dancam » Tue May 30, 2017 3:50 pm

flboy wrote:
John61CT wrote:Those big amp loads, fuses are so much cheaper and safer. ​Class T, ANL or MRBF, go with Bussman or Blue Sea, Samlex etc not cheap copies or generic.

CBs are relatively complex, lots of delay variables etc, and you really are talking big bucks even if you do figure out exactly what you need.

You should also have a robust switch, right at the bank positive, Blue Sea makes solid product.

If an Alt is dumping to the bank, get a pro to correctly wire the Field Disconnect feature so you don't fry your diodes.

Note you need to size for the max Total current * 150%, and locate right at bank positive, proper wire sizing, robust fittings properly crimped connections etc.


I am not charging with my Alternator and I do have a main battery disconnect at the Bank positive. Wires and all are proper gage with crimped and soldered connections and the run from the battery to the Inverter is about 4.5 Ft. ... 150A would be the max continuous current with 100A likely for 5 minutes or more when I run the microwave. I was getting close to the 150% of max usage with the 200A Breaker which will only allows me ~105A continuous for less than a minute. :-( I am attributing that to a cheap breaker however.

Should I be able to run ~150A continuous through a 200A fuse and not drop more than .5V? Many thanks.

Where are you measuring the voltage drop at? Each side of the fuse? If your measuring at each end of the wire your still gonna see a 0.2v drop with 2awg and a 0.35v drop with 4awg even with no resistance in the connections.
With my setup a 1500watt load draws the battery down to 10.5v after 2min or so. When your voltage drops your amp draw goes up as does your line loss. Could it be dropping enough to blow your fuse?

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Re: DC Breakers - Continuous Amperage Ratings

Postby John61CT » Tue May 30, 2017 4:00 pm

flboy wrote:I ordered a Blues Seas 300A ANL Fuse and Fuse Block. I am going to give that a shot. It should handle the max surge of the inverter and run comfortable at 50% of rating for max continuous. Fuse block is right after the Battery cutoff switch.
Good kit. Remember you're just protecting the wiring against heat, the inverter should have its own protection.

How are you charging, what amps current?

Maybe get one of those infrared temp shooters to look for hot spots, I got one for $12 delivered in <5 days from HK on eBay (how do they DO that?)

I don't think solder's a good idea but I know many disagree.
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Re: DC Breakers - Continuous Amperage Ratings

Postby John61CT » Tue May 30, 2017 4:03 pm

dancam wrote:John, can you explain more about this field disconnect and what the issue is if you dont have it please? I have a 2000watt inverter in my vehicle but no switch like you mentioned
nothing to do with inverters, it is to protect the alternator from accidentally being disconnected when it is running, prevent dumping a load to Nowhere which will fry the diodes.

Cutting off the field current from the regulator before disconnecting the output wire.

Google "afd blue sea".

They are often wired wrong, even by pro's
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Re: DC Breakers - Continuous Amperage Ratings

Postby flboy » Tue May 30, 2017 4:18 pm

John61CT wrote:
flboy wrote:I ordered a Blues Seas 300A ANL Fuse and Fuse Block. I am going to give that a shot. It should handle the max surge of the inverter and run comfortable at 50% of rating for max continuous. Fuse block is right after the Battery cutoff switch.
Good kit. Remember you're just protecting the wiring against heat, the inverter should have its own protection.

How are you charging, what amps current?

Maybe get one of those infrared temp shooters to look for hot spots, I got one for $12 delivered in <5 days from HK on eBay (how do they DO that?)

I don't think solder's a good idea but I know many disagree.


The inverter has protection.... correct.. wire protection..

I charge two ways... 55A converter when plugged in or running from the generator and I also have 500W of solar panels on the roof going through a 40A MPPT charge controller. I am charging a 345Ah battery bank (3 Exide 12V Deep Cycle Batteries).

I actually have one of those infrared thermometers.. I love that device for finding hotspots.. or duct leaks, etc.. I'll try it on the wiring.. just a small target. I know the breaker terminals and old ANL fuse holder use to get hot... I can feel that!

I don't think solder by itself is good enough unless for low current electronics.... I always crimp and then solder... If the wire were to heat up, the solder may flow and without the crimp, things may start coming apart.

Why don't you like the solder. I am interested to know.. maybe I am wasting my time?
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
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Re: DC Breakers - Continuous Amperage Ratings

Postby John61CT » Tue May 30, 2017 5:07 pm

flboy wrote:I don't think solder by itself is good enough unless for low current electronics.... I always crimp and then solder... If the wire were to heat up, the solder may flow and without the crimp, things may start coming apart.

Why don't you like the solder. I am interested to know.. maybe I am wasting my time?

The rigidity can create resistance and/or a break point with vibrations.

A proper crimp connection will create a completely fused watertight mass, at that point solder adds nothing positive.

https://www.google.com/search?q=Maine-Sail+%22wire+termination%22+battery+crimp
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Re: DC Breakers - Continuous Amperage Ratings

Postby flboy » Tue May 30, 2017 5:18 pm

Thanks. I learned something new today.

I do really need to invest in better crimp tools. I am use to soldering because I don't have confidence in my cheap crimp tools. I always figured the solder would make sure of a good electrical connection since I don't have access to proper tools and pull testers and etc.. like we have at work out on the factory floor.

Very good information. Thanks.

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Re: DC Breakers - Continuous Amperage Ratings

Postby bdosborn » Tue May 30, 2017 8:33 pm

Blue Sea circuit breakers are made by Bussman. I know you already bought fuses but here is a link if your interested in a CB down the road:

Amazon Linky.

How did you measure the current draw of the microwave? Microwaves draw more current on a modified sine wave inverter so 73A seems low. I wouldn't be surprised if you weren't up over 100 amps figuring in inefficiencies and modified sign wave effect. Finally, a single battery usually has a bad Coup de feut response, meaning the voltage drops quite a bit when under heavy loads. I've read on other forums that using two batteries is a minimum requirement for microwaves. FWIW...

Bruce
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Re: DC Breakers - Continuous Amperage Ratings

Postby MtnDon » Tue May 30, 2017 8:41 pm

Try Midnight Solar breakers.... their breakers are all continuous rated IIRC.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: DC Breakers - Continuous Amperage Ratings

Postby flboy » Tue May 30, 2017 8:57 pm

bdosborn wrote:Blue Sea circuit breakers are made by Bussman. I know you already bought fuses but here is a link if your interested in a CB down the road:

Amazon Linky.

How did you measure the current draw of the microwave? Microwaves draw more current on a modified sine wave inverter so 73A seems low. I wouldn't be surprised if you weren't up over 100 amps figuring in inefficiencies and modified sign wave effect. Finally, a single battery usually has a bad Coup de feut response, meaning the voltage drops quite a bit when under heavy loads. I've read on other forums that using two batteries is a minimum requirement for microwaves. FWIW...

Bruce


Hi Bruce. I have 3 115Ah batteries and a pure sine wave inverter. I was reading the current across a shunt in the battery return in this case. I can also use my watt meter on the inverter output and work backwards with Ohms law taking into account the inverter is only 90% efficient. Either way is pretty close. In any case... nowhere near the 200Amp stated for the breaker.
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: DC Breakers - Continuous Amperage Ratings

Postby John61CT » Tue May 30, 2017 9:01 pm

bdosborn wrote:Amazon Linky
Wow that's cheap, almost suspicious?

And I would definitely test it out, check for delay. . .
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