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Old 15-11-2018, 18:47   #1
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MMPT show more amps going in than coming out? ( see pics )

I added a solar panel, hooked up an MMPT power controller.
I have four photos attached.
One shows ‘ all power OFF’
One shows ‘ only the fridge/ freezer’ ON
One shows ( I believe ) Amps going IN to battery
One shows , Amps coming OUT of battery.

Was a fine sunny day.

Would I be correct in thinking therefore, that, on a such a fine sunny day, I can run the fridge /freezer ( and not much else)
And NOT drain the battery?Click image for larger version

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Old 15-11-2018, 18:49   #2
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Re: MMPT show more amps going in than coming out? ( see pics )

2nd question,
What does the drop from 13.4 v to 12.8v
( upon switching fridge/freezer on )
What does that indicate?
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Old 15-11-2018, 19:31   #3
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Re: MMPT show more amps going in than coming out? ( see pics )

Your interpretation is correct. You are using virtually all the power you are producing to run the refrigerator with nothing left over to charge the batteries. You don't indicate what the time of day is, or your latitude. In the winter, only a little more than 30 days from the solstice you are in your worst power producing months in the northern hemisphere and it is even worse at a high latitude, especially if your panel is laying flat. The voltage drop to 12.8 is simply indicating your battery voltage, because you are using all of your putting all of your power into the refrigerator and none into the batteries. The good news is that at that instant you were not taking any out of your batteries. The bad news is That if that was your peak power then you are going to drain the batteries at night and be unable to recharge them during the day. If you are in the southern hemisphere you definitely need a bigger panel.
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Old 15-11-2018, 20:07   #4
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Re: MMPT show more amps going in than coming out? ( see pics )

it has no way of showing you amps out of battery. unless it has a load output, but you shouldn't be using that if it does.

what you really need is a battery monitor. or a shunt at the battery.

if the battery is droping to 12.8 with solar. then the solar is barly keeping up. likely the amps in / out of battery is around 0. (you can't have different numbers going into and out of the battery. either power is going in or coming out, not both.
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Old 15-11-2018, 20:33   #5
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Re: MMPT show more amps going in than coming out? ( see pics )

Steelcruiser,
Smac999 was correct in most everything but there are a few things that have not been covered.
1) You have not indicated the size of you solar panel you installed. It is impossible to indicate whether the current being produced at the time was at its highest efficiency.
2) While you indicated it was sunny you did not indicate time of day to estimate if the solar panel was operating at its peak performance therefore producing it peak current
3) You are not reading the output current from the battery under load from the fridge. As stated you required a battery monitor with a current shunt to determine this (or a DC clamp ampmeter)
4) You also did not indicated the size cable you ran from the MPPT controller to the battery. Incorrect sizing can have a significant influence in reduing the current to you battery.
5) Have you installed suitable fuse or circuit breaker between the battery and MPPT controller. Failure to do this can lead to serious issues from overload short circuit currents.

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Old 15-11-2018, 20:51   #6
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Re: MMPT show more amps going in than coming out? ( see pics )

I think Captain bill got it correct.also It all depends on the controller some you can use the load for higher amperage some you only use it for small loads and they almost always have a timer so it's perfect for an anchor light. Yes having 5 amps going in and 4 amps going out is really one amp going in. But truthfully it's more helpful to know what your charging source and your loads are doing, and just a simple way of stating it.
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Old 15-11-2018, 21:58   #7
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Re: MMPT show more amps going in than coming out? ( see pics )

Steelcruiser,
I just had a closer look at your photos, particularly the photos showing connections. Am I correct in that I am seeing three sets of cables going to the controller. I assume that one set is connected to the solar panels, the second set I assume is connected to the battery and I assume that for some reason you have connected the third set to the load side of the MPPT. Can you tell me what purpose this load connection is. These terminals are normally only for very low loads such as anchor lights. Perfect for those situations.


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Old 16-11-2018, 11:50   #8
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Re: MMPT show more amps going in than coming out? ( see pics )

Nothing in the OP’s post addresses the title that he put on his thread.

Yes. That is what MMPT controllers do. They convert volts to amps and give out more amps than they take in.
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Old 16-11-2018, 12:53   #9
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Re: MMPT show more amps going in than coming out? ( see pics )

MPPT controller take excess voltage and a given amperage from the panels, and convert that excess voltage to a higher amperage at a lower voltage. Think 18v in, 14.4v out, Amperage goes up in the process.

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Old 16-11-2018, 13:28   #10
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Re: MMPT show more amps going in than coming out? ( see pics )

The third photo, 5.1 amps, is with the fridge on. The fourth photo, 4.9 amps is with the fridge off. The voltage drop is due to the load on the fridge. With the fridge on or off your panels are still putting out about 65.5 watts. (5.1x12.8=65.3, 4.9x13.4=65.7). A lot of the 12v fridges draw between 3 and 4 amps or around 44 watts. He could still be making more power than he is using. There is no way to tell from the information given how much the fridge draws. Watts is the only true measurement of the power gained or lost. Amp readings depend on the voltage. Volts x Amps=Watts. Mppt readouts show the volts and amps going in, and the volts and amps going out. Multiply them and you get the same amount of watts in and out (minus readout error and inefficiency). You fridge should cycle on and off so you might be able to make enough power to run it day and night without depleting the batteries. You would need to be able to measure the power draw from the fridge to answer your question.
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Old 16-11-2018, 13:40   #11
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Re: MMPT show more amps going in than coming out? ( see pics )

Quote:
Nothing in the OP’s post addresses the title that he put on his thread.
The title is backwards. You should show more amps going out than coming in (but at a lower voltage)
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Old 16-11-2018, 14:59   #12
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Re: MMPT show more amps going in than coming out? ( see pics )

If you look at the icons in the photo it shows that the 5 amps are coming from the solar panels and the four plus amps are going to the load. If his load circuit is designed to handle that kind of amperage and has the ability to set on and off times he could set it to just have the refrigerator run in the middle of the afternoon to keep things cool. I did this for many years. it's not True refrigerator temps but when daily Temps are in the 90° to 100 degree range it allowed me to keep eggs and cheese no problem. Helped with the veggies too. It makes it so much sweeter now having all the solar panels I need and a True freezer.
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Old 17-11-2018, 00:12   #13
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Re: MMPT show more amps going in than coming out? ( see pics )

Quote:
Originally Posted by SteelCruiser View Post
I added a solar panel, hooked up an MMPT power controller.
I have four photos attached.
One shows ‘ all power OFF’
One shows ‘ only the fridge/ freezer’ ON
One shows ( I believe ) Amps going IN to battery
One shows , Amps coming OUT of battery.

Was a fine sunny day.

Would I be correct in thinking therefore, that, on a such a fine sunny day, I can run the fridge /freezer ( and not much else)
And NOT drain the battery?Attachment 180669Attachment 180670Attachment 180671Attachment 180672

For a start, you need to compare power in and power out. Power (Watts = Volts x Amps). 5 amps at 40 volts is a lot more than 5 amps at 12 volts. Also you will need a clamp meter or shunt on the output side to measure the power.
However battery voltage drop says you are using more power at that stage, than the panels can deliver.
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Old 17-11-2018, 07:46   #14
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Re: MMPT show more amps going in than coming out? ( see pics )

I looked up the manual for this unit: https://www.jaycar.com.au/medias/sys...manualMain.pdf
I was wrong in my assumptions. This controller does have a load measuring and switching function but does not display input amps from the panels like the "high end" controllers do. The last photo (4.9A) is the amp draw of the fridge plus whatever else you might have connected. It does indicate that you have only a .2 amp surplus.

This unit seem to be cheaply made, has a high failure rate,Powertech MPPT controller - is it working as it should? inaccurate voltage sensing, and has poorly written instructions that don't mention fusing.

YOU NEED TO AT LEAST INSTALL INLINE 15 AMP FUSES TO ALL THREE OF THE POSITIVE CONNECTIONS!!!

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