Hello dickymate

I am not an Electrician

I have the same amount of solar, and the same amount of battery but a different controller/regulator/charger

There may be something wrong with your 30 amp PWM controller side of things if it is getting hot
If your controller is an el-cheapo $30 EBay one then the markings on the outside may not be what is inside
If your controller is a reputable $300 plus one then as dragonfly 1 has already said, it may be loose wires or dirty connection

My controller/regulator/charger is a CTEK DC/DC

I see something like 14 plus amps going from the solar to the battery and the controller is not warm
With the engine running the full 20 amps go to the battery and the controller is warm, but never hot

I believe that the consensus for us laymen, is that you should not have two regulators/controllers/ chargers, going to the same battery bank
Some techs say that it can be done

At the moment my system is suitable for my needs
I am thinking of a lightweight portable 200 watt, for the times I am under the shade, or not facing the sun

I have a thermal 30 amp re-settable fuse from the solar to the solar charger
My intention is to stop the roof solar going into battery, while the portable solar is connected either through the controller or direct to the batteries

Hope that this info is useful to you

Is the compartment that it is mounted i well ventilated? That will have a big bearing on how hot it gets.

My Mppt is under the bed near the battery I have only portable panels and being in a confined space it does not get hot at all,I would think that most regs would be inside there Rvs not outside in the air streams??...

Outside cabinetry ð

The bed has not gotten any warmer with the reg under it.

Hi dickymate, with an absolute max output of 20 amps from your 300w of solar there should not be any appreciable heat produced in a PWM controller because until it reaches the set voltage point it is just passing the current straight through to the battery. MPPT controllers do get hotter because of the inherent losses using electronics to change a high voltage @ low current to a low voltage @ high current, there is no such thing as a free lunch or electronics that don't converter some of the electrical energy into heat energy because they haven't made anything that is 100% efficient yet.

So, can you tell us the brand/nodel number of controller you have please?

T1 Terry

oldtrack123 wrote:

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T1 Terry wrote:

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Hi dickymate, with an absolute max output of 20 amps from your 300w of solar there should not be any appreciable heat produced in a PWM controller because until it reaches the set voltage point it is just passing the current straight through to the battery. MPPT controllers do get hotter because of the inherent losses using electronics to change a high voltage @ low current to a low voltage @ high current, there is no such thing as a free lunch or electronics that don't converter some of the electrical energy into heat energy because they haven't made anything that is 100% efficient yet.

So, can you tell us the brand/nodel number of controller you have please?

T1 Terry

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 So you are saying while passing current  it should not have any heat generated , but when not passing current it will heat

While conducting there is a small voltage drop across the regulator [easily measured]

Simple basic OHM's law Watts = V x Amps  , 0.5V x 20A = 10Watts

Yes , Mppt will get hotter due to extra electronics involved, so you have that right

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The PWM does generate a very small amount of heat, the better to quality the lower the heat generated. This does change when the unit goes into current control to stop over voltage charging damage because the Mosfet being turned on/off/on requires a diode across it to defuse any voltage spikes that would damage the Mosfet. Diodes do get hot when they are passing current and that needs to be dissipated via a piece of heatsink. The losses are still much smaller with a PWM controller so natural convection is enough the move the heat out of the heatsink and that is why the heat sink is much smaller for a PWM controller than for an MPPT controller and doesn't require a fan to stop it overheating.

This means if the PWM controller is getting hot while in bulk charging mode it is either current limiting because there is more coming in than the max current programmed into the controller, or, the Mosfet used is rather poor quality and has a serious voltage drop across it.

 

T1 Terry 

T1 Terry wrote:

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oldtrack123 wrote:

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T1 Terry wrote:

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Hi dickymate, with an absolute max output of 20 amps from your 300w of solar there should not be any appreciable heat produced in a PWM controller because until it reaches the set voltage point it is just passing the current straight through to the battery. MPPT controllers do get hotter because of the inherent losses using electronics to change a high voltage @ low current to a low voltage @ high current, there is no such thing as a free lunch or electronics that don't converter some of the electrical energy into heat energy because they haven't made anything that is 100% efficient yet.

So, can you tell us the brand/nodel number of controller you have please?

T1 Terry

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 So you are saying while passing current  it should not have any heat generated , but when not passing current it will heat

While conducting there is a small voltage drop across the regulator [easily measured]

Simple basic OHM's law Watts = V x Amps  , 0.5V x 20A = 10Watts

Yes , Mppt will get hotter due to extra electronics involved, so you have that right

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[a]

The PWM does generate a very small amount of heat, the better to quality the lower the heat generated. This does change when the unit goes into current control to stop over voltage charging damage because the Mosfet being turned on/off/on requires a diode across it to defuse any voltage spikes that would damage the Mosfet. Diodes do get hot when they are passing current and that needs to be dissipated via a piece of heatsink.

The losses are still much smaller with a PWM controller so natural convection is enough the move the heat out of the heatsink and that is why the heat sink is much smaller for a PWM controller than for an MPPT controller and doesn't require a fan to stop it overheating.

 [c]

This means if the PWM controller is getting hot while in bulk charging mode it is either current limiting because there is more coming in than the max current programmed into the controller, or, the Mosfet used is rather poor quality and has a serious voltage drop across it.

 Terry 

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 Well one last go to try help you . 

[a]thing passing electrical current WILL develop heat , perhaps you have forgotten that simple fact  [OHM's LAW]: Watts = VxI 

 That law applies even with that mysterious stuff like extra low voltage DC.

When no current is flowing ,or  power being used within  unit there will be no heat generated.

IF a PWM is passing, say 20A & has say 0.5 volts drop within it [meaning the voltage on the input side is 0.5V  higher than on the output side]  there WILL be 10 WATTs of heat generated

If 50A with 0.5V drop will be 25W

That covers ALL the internal losses no matter where it is generated in the unit, [switching components   including MOSFETS ,SCR  transistor , diodes  what ever. ANY thing that has a voltage drop across it when passing current ]

The quality /amount of cooling surface   & surrounding ambient temp will determine  how hot it gets 

You seem to think the switching  generates  the heat in solid state switching ,IT DOES not ,unlike contacts which generate heat mainly due to arcing.

The diode   is there for the reason you say,but the heat generated in it would be minor  due to extremely small current it has to pass

Have you looked at the size of it ?

Yes ,the heat losses will be less in  PWM compared to a  similar rated MPPT ,which naturally must have more components carrying CURRENT.

Again using  OHMS laws,easy to work out

 

[c]   IF it is a PWM ,[ PULSE WIDTH MODULATIONi ]t is simply switching the current on & off as determined by the SOC of the battery. It does not ,cannot alter the actual current value ,just the average [mean] value .

If a cheap one & have a amp meter in line you could even see those pulses  ON/ OFF ON /OFF

The better ones are faster & require a Scope to see the switching action.

And before you get carried away, they also have  stages,   but still with the PULSE WIDTH MODULATION of the current 

 Better quality may have an inductor  to smooth the OUTPUT  current, as all  quality MPPTS have

Hi all I don't know if this will be helpful to any one but I just purchased 4 full river 150 amp Hour batteries from the automotive super store for a what I think was a good price $ 510.00 per battery buying 4 helped , their nominal price is the cheapest I had found $ 525.00 As I am new at this and will be hitting the road in August after 4 years building my motor home out of a Mercedes Benz lo812 bus we are so looking forward to our new way of life. This is the link to the super store
Cheers Stumpy. automotivesuperstore.com.au/