Breaker from controller to batteries getting too hot!

YostFMX

New problem... Its been 100 degrees in my garage where the controller inverter and batteries are. The 80A breaker in the picture that goes form the controller to the batteries it getting very hot and trips that breaker. It was worked fine till the weather has gotten so hot. The thing is its not hot where it comes out of the controller, not hot at the batteries, just at the breaker. The wire is 4 AWG and about 2 feet long with no more than about 33A at 12V. How do I fix this? Fatter wire? Move the breaker closer to the controller? I was thinking of doing both... Why would it be getting so hot? And the breaker in the picture from solar panels to the controller is pretty warn (hot) but not as bad as the other on that trips.

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

Cooling fan perhaps. Or else a larger breaker.

Problem is these bi-metalic breakers work on a basis of heat: too much current causes too much heat making the bi-metalic element bend and switch the power off. Yours is operating in a very hot environment which reduces the amount of heat that can be dissipated. Current capacity of wires, fuses, breakers, anything is dependent in part on how much heat they can shed. That's why wires have different rating for use in conduit, for example.

So you either have to cool the environment or go with a larger breaker. If you do the latter, make sure the wiring can take the additional current capacity as well; it won't always be that hot in there.

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

These similar breakers are meant to operate at up to 185F: http://www.solar-electric.com/mr60ampdccib.html
Check the specs on yours.
4AWG ought to be able to handle 33 Amps. 6 AWG ought to be able to handle that.
However an 80 Amp breaker is actually too big for 4 AWG.

BB.

Re: Breaker from controller to batteries getting too hot!

What are those bus bars? Aluminum? If so, or the screws are not properly tightened, you may be generating heat there (Aluminum is a very difficult metal to get good conduction through).

80 amp breaker with ~32 amps--That should be more than enough derating for reliable operation.

Take your volt meter and set to 2 volt or 0.2 volt full scale and check the voltage drop across each point in the circuit (wire to bus bar, bus bar to breaker, breaker to breaker, etc.) and see if you have "significant" voltage drops somewhere (I²R = V²/R = V*I = Power). The heat may be generated elsewhere (although, the breaker heater is probably the prime culprit).

-Bill

YostFMX

Re: Breaker from controller to batteries getting too hot!

If I go with a bigger breaker or no breaker, how hot is too hot for that wire to get before its going to be dangerous or start a fire? The only reason I have that breaker there is so if I cross the batteries + and - so I don't fry the controller. That block on the breaker was so hot I couldn't hold my finger on it for more than 5 seconds.

YostFMX

Re: Breaker from controller to batteries getting too hot!

Yes aluminum buses and they are very tight! I'll check. Would copper work better?

YostFMX

Re: Breaker from controller to batteries getting too hot!

Controller 13.55v
Top Bus 13.53v
Bottom Bus 13.44v

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

YostFMX wrote: »

Yes aluminum buses and they are very tight! I'll check. Would copper work better?

Much.
So would just having terminal ends properly secured to the wires. Seems like you've added a few unnecessary extra connections.
It really should not be getting untouchable, even at 100F. Heat build-up inside the breaker is one thing; finger-frying terminals is another. Definitely follow Bill's advice and look for V-drop across these and other components.

4 AWG ought to handle 60 Amps of current in a job like this. Not sure what wire you have exactly, and different wire has different thermal specs. But at 33 Amps it shouldn't be getting that hot. Like I said, 6 AWG should actually be enough for that.

Maybe recheck that current and wire size just to be sure.

BB.

Re: Breaker from controller to batteries getting too hot!

Aluminum forms a very thin/tough/clear oxide layer within seconds to minutes of exposure to air. That oxide is very similar to sapphire and is really a great insulator.

To make good connection you need to both "punch through" the oxide (star lock washers), you need to make it "gas tight" (some sort of grease) at the very minimum to have a reliable connection.

As the joint gets hot, the aluminum tends to swell and cold flow--Then joint cools and aluminum contracts--causing an air gap... Repeat until joint fails or cooks.

Here is a "NOOXID" type grease... You need to really rough up the aluminum surface prior to making the connection:

SPECIFIC ALUMINUM CABLE APPLICATION
When splicing aluminum cable with compression-type connectors, brush NO-OX-ID A-Special to the inside surfaces of the connector. Using a wire brush, brush these inside surfaces through the through the A-Special coating. This roughs up the surface assuring positive contact. At the same time the NO-OX-ID A-Special is providing protection against the oxide film, that can occur in the short space of time between roughing up the surface and final connection. Apply a thin coat of NO-OX-ID A-Special to cable ends to complete the splice to prevent aluminum rust.

Try measuring the voltage drop across a couple of those connections.

Personally--I would replace with copper/bronze or similar bus bar material. I do not trust aluminum except for very specific compression type fittings (like used by utility companies for service drops).

-Bill

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

YostFMX wrote: »

Controller 13.55v
Top Bus 13.53v
Bottom Bus 13.44v

Um, you need to check the Voltage across the connections. Like one lead on the "IN" to the breaker and the other on the "OUT". You want to see readings as close to zero Volts as possible. Higher Voltage indicates power is turning into heat as it forces its way through a resistance point.

BB.

Re: Breaker from controller to batteries getting too hot!

A 1/10 volt drop at 32 amps = 3.2 watts of heating.

Depending on ability to cool--Fairly significant amount of power to dissipate.

Try using your two leads right across each electrical connection--It will be easier to see issues and more accurate.

-Bill

YostFMX

Re: Breaker from controller to batteries getting too hot!

BB. wrote: »

Try using your two leads right across each electrical connection--It will be easier to see issues and more accurate.

I don't follow?

YostFMX

Re: Breaker from controller to batteries getting too hot!

When I reconnect the breaker, the inverter fan starts running faster. Whats up with that?

BB.

Re: Breaker from controller to batteries getting too hot!

Take one meter lead and place on wire, place other meter lead on bus bar (you are looking to measure the 0.10 volt drop directly--not from a common ground point). Many meters will "show more digits" when set to 2 volt or 0.2 volt full scale, vs 20 volts full scale (20.0 volts vs 2.00 volts on display). It will allow you to measure the voltage drops with much more accuracy.

The high speed fan on restarting the inverter--You may have "heat soak"... When the fan stopped for a minute or so, the heat sink (where the fan speed sensor may be mounted) starts warming up because of lack of air flow... Restart the fan, and within a minute or two, the heat sink temperature will drop and the fan will slow down (my guess).

-Bill

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

YostFMX wrote: »

When I reconnect the breaker, the inverter fan starts running faster. Whats up with that?

When you reconnect which breaker? I would presume the one feeding power from the charge controller to the batteries? Sounds like there may be resistance problems causing V-drop to the inverter as well.

What Bill is getting at:

Positive Meter Lead ===> Terminal block in
Negative Meter Lead ===> Terminal block out

You're looking for a Voltage across the terminal bloc, not in reference to the negative wiring.

waynefromnscanada

Re: Breaker from controller to batteries getting too hot!

YostFMX wrote: »

When I reconnect the breaker, the inverter fan starts running faster. Whats up with that?

If it's the breaker between the controller and batteries, and if the sun is shining, closing the breaker will allow the panels to start charging the batteries, driving up battery voltage in the process, thus spinning the inverter fan faster.

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

Looking at the picture again, you seem to have these aluminium terminal blocks everywhere, including the inverter input. Why?
Crimped copper terminal ends on the wires will work far better and be much simpler.

Not sure what size that inverter is, but a 1 kW 12 Volt inverter ought to have at least 0 AWG wire as it can easily draw over 100 Amps. This should be connected through a fuse or breaker of appropriate size and then to the battery.

There also appears to be a "splice" with yet another of these aluminium blocks in the negative wire at the top of the picture.

YostFMX

Re: Breaker from controller to batteries getting too hot!

In - out breaker reads 0.06v

Yes when the breaker from controller to batteries is reconnected the inverter fan speeds up.

I use all those buses and connectors is because they were the cheapest way to do it. I used those things for everything.

So when I first hooked up my solar system I had a loud buzzing sound till I mounted everything on rubber. Maybe that has something to do with my heat problem...

The inverter is a 600w but changing it out with a 2000w and going to use fatter wire

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

This is sounding very much like a Voltage drop problem.
Can you measure the Voltage potential on the aluminium blocks? Use the screws as reference points.
You should also check the Voltage at the inverter (+) & (-) both with the charge controller disconnected and connected. Chances are it will be noticeably higher with the panels feeding in.

If you are losing Volts this way (possibly five * 0.06 on the charge circuit) the batteries will not get up to full charge. The problems compound.

john p

Re: Breaker from controller to batteries getting too hot!

DUMP THE ALUMINIUM BUSS BARS.
You are ALWAYS going to have problems with copper /steel/brass connected to aluminium buss bars.
no matter what you coat them with ie noalox etc.. you cant coat the screws successfully.
Keeping away from aluminiun to carry DC is the only and best solution.. Its about the "worstest" conductor you can use.

silvertop

Re: Breaker from controller to batteries getting too hot!

Crimped copper terminal ends are definately a better choice, you can obtain an inexpensive hammer crimper for about $25.00. If you need to stack two wires at one location (Blue Sea Systems )makes a good power post terminal, a very neat, inexpensive terminal connection. As others stated there are better fuses/breakers......Blue Sea also has these..... I don't know about the breakers you have; someone else might but one thing to be aware of in D.C. is the AIR rating of a fuse/breaker meaning that you want it to trip/blow at high current not weld shut and continue to send out of control current through.

mike95490

Re: Breaker from controller to batteries getting too hot!

Screw terminals, aluminum blocks, extra connection interfaces. And you know it's getting hot.

I agree with the others, dump the aluminum blocks. I was offered some "drilled out" setscrew type battery terminal adapters, and they looked so flakey in the photo, I went and designed my own.

You can also take a IR thermometer, and shoot the different parts in your system, and see if it's the wires or the blocks, or the breakers.

YostFMX

Re: Breaker from controller to batteries getting too hot!

Ok, so I'm going to switch the connectors to copper. I'm going try some other cheap $6 breakers (I know, I know.. but $50 a breaker is too much for me right now). So on my new 2000w inverter when I use 0/1 wire, what breakers if any do you guys use (says 250A)? And can you even get copper 0/1 connectors that big?

One more thing. My charge controller has aluminum screw bus where you hook to it! Look at the picture. Why would they use those then?

Cariboocoot

Re: Breaker from controller to batteries getting too hot!

Yes you can get really big lug connectors: http://www.solar-electric.com/teluwiha.html

The 250 Amp fuse recommended for your inverter is based on the NEC rating which goes something like maximum Watts / minimum operating Voltage = maximum current * 1.25 rounded up to nearest size or:
2000 Watts / 10.5 Volts = 190 Amps * 1.25 = 238 > 250

However you don't have to operate at that level providing you understand what's going on. "0" or 1/0 wire is good for about 190 Amps continuous, so you could use a 200 Amp fuse or even smaller. Especially if you keep system Voltage above 12 (as you should) and don't max out the inverter (as you shouldn't). The fuse/breaker must always be the weakest link in the circuit. 2kW on 12 Volts is roughly 166 Amps, so you could give yourself a built-in limitation of 150 Amps. But know that if you do spikes above that can shut it down.

There will be those who disagree with my take on this, and I'm good with that. So long as the circuit is designed so that the protection is what "gives" before anything else you're okay. Actually meeting code is another issue.

Are you sure that's an aluminium screw bus? Hard to tell by looking; it may be tinned copper (which is typical).

nsaspook

Re: Breaker from controller to batteries getting too hot!

YostFMX wrote: »

One more thing. My charge controller has aluminum screw bus where you hook to it! Look at the picture. Why would they use those then?

Most likely hard tinned copper. Even the Chinese don't use aluminum buss connectors for the junk they sell.

Joe_B

Re: Breaker from controller to batteries getting too hot!

There are different types of breakers, bimetalic operate on temperature, the other common type are magnetic breakers which are much less prone to tripping from heat. They use a solenoid type mechanism instead of a temperature sensitive bimetalic element.

YostFMX

Re: Breaker from controller to batteries getting too hot!

Ohhhh, didnt know that! They looked the same as the aluminum ones I have. And I really didn't know that those 12v connectors that you buy at auto parts stores are tinned copper! I thought thoses were super cheap steel one. I thought I was doing a good thing with aluminum. By the way, the copper connectors at Home Depot are like $7 each, thats why I thoght it was too much to use them, not $1 like on here!

YostFMX

Re: Breaker from controller to batteries getting too hot!

Is there a to tell by looking at a breaker if its a bi-metalic or magnetic?

Blackcherry04

Re: Breaker from controller to batteries getting too hot!

Big current generates heat for sure. Even with 4/0 cables and everything tight it'll melt the heat shrink off @175 amps at times. If your feeling the heat, at 130 Deg or so it will feel very hot, but thats not all that hot. With high amps you should be checking the tightness of everything every couple months, it will surprise you how much the thermal cycling will loosen things.

Joe_B

Re: Breaker from controller to batteries getting too hot!

It depends on the manufacturer but usually they put the info on the side of the case. Here is a wiki link to the different types.

http://en.wikipedia.org/wiki/Circuit_breaker

ETA: If you google magnetic breaker you will see links to cutler hammer, eaton, etc.

YostFMX

Re: Breaker from controller to batteries getting too hot!

Is it bad to solder on copper terminal? Will they come off if it gets too hot? or will it never get that hot?