A Victron MPPT 75/15 solar charge controller question.





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  1. #1
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    Default A Victron MPPT 75/15 solar charge controller question.

    I have a Victron MPPT 75/15 solar charge controller in my gravel road caravan. The controller gets connected to the battery, but the battery does not get connected to load.


    There is a separate outlet on the controller for load.


    Does this mean that this connection is permanent and that I never need to connect load to the battery? What if the fridge is connected to a power pack and current flows back to the controller - will that be OK?


    What if a smart charger is permanently connected to the battery? Obviously not powered when on solar.


    Please advise -


    Interestingly enough, with this controller the battery (100 Ah lead crystal) shows no voltage drop whilst the fridge runs (upright 12 v fridge, not a freezer), which to me means the 140 watt solar panel provides more power than what the fridge can use. Is my thinking OK?
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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Quote Originally Posted by Poen View Post
    I have a Victron MPPT 75/15 solar charge controller in my gravel road caravan. The controller gets connected to the battery, but the battery does not get connected to load.


    There is a separate outlet on the controller for load.


    Does this mean that this connection is permanent and that I never need to connect load to the battery? What if the fridge is connected to a power pack and current flows back to the controller - will that be OK?


    What if a smart charger is permanently connected to the battery? Obviously not powered when on solar.


    Please advise -


    Interestingly enough, with this controller the battery (100 Ah lead crystal) shows no voltage drop whilst the fridge runs (upright 12 v fridge, not a freezer), which to me means the 140 watt solar panel provides more power than what the fridge can use. Is my thinking OK?
    Poen, I have exactly the same MPPT Victron charger permanently coupled to a LC battery (also 100Ah). A smart Victron Battery charger is also permanently coupled to my battery. They are obviously used separately to charge the battery but both are permanently coupled to the battery. No problems.

    I do not use the separate load output on the Victron Solar regulator for anything.
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    Last edited by Carel Kriek; 2016/04/14 at 10:38 AM.
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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Quote Originally Posted by Poen View Post
    I have a Victron MPPT 75/15 solar charge controller in my gravel road caravan. The controller gets connected to the battery, but the battery does not get connected to load. 'Load' on the controller is there for other specific purposes where the controller can be used to protect the battery from getting discharged beyond set limits. Even to operate lights automatically after dark.

    There is a separate outlet on the controller for load. Yes, that is normal for small controllers.

    Does this mean that this connection is permanent and that I never need to connect load to the battery? What if the fridge is connected to a power pack and current flows back to the controller - will that be OK? It is OK.

    What if a smart charger is permanently connected to the battery? Obviously not powered when on solar. Normal and no problem.

    Please advise -


    Interestingly enough, with this controller the battery (100 Ah lead crystal) shows no voltage drop whilst the fridge runs (upright 12 v fridge, not a freezer), which to me means the 140 watt solar panel provides more power than what the fridge can use. Is my thinking OK?

    Solar controllers are connected to storage batteries, and they remain connected regardless of whether the batteries are charged from the network, generators or other sources. This is the way they are designed to perform.
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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Thanks Eggie.


    In the owners manual they say:


    Ultra fast MPPT tracking


    Especially in case of a clouded sky, when light intensity is changing continuously, a fast


    MPPT algorithm will improve energy harvest by up to 30% compared to PWM charge


    controllers and by up to 10% compared to slower MPPT controllers


    Does this mean one can get away using a smaller solar panel? Space is at a premium. I have 1 x 140 watt and 1 x 40 watt


    Also, when standing a solar panel on its own enabling directional movement to face the sun, I would prefer a horizontal stance instead of vertical because of the danger of being blown over and break. Does this make sense?

    Last edited by Poen; 2016/04/14 at 03:36 PM.
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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Quote Originally Posted by Poen View Post
    Does this mean one can get away using a smaller solar panel? Space is at a premium. I have 1 x 140 watt and 1 x 40 watt

    Also, when standing a solar panel on its own enabling directional movement to face the sun, I would prefer a horizontal stance instead of vertical because of the danger of being blown over and break. Does this make sense?
    Theoretical yes, if you can belief the 30%! Rather work on 15 to 20% max

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    Last edited by JLK; 2016/04/14 at 02:12 PM.
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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Quote Originally Posted by Poen View Post
    Thanks Eggie.


    In the owners manual they say:


    Ultra fast MPPT tracking
    Especially in case of a clouded sky, when light intensity is changing continuously, a fast MPPT algorithm will improve energy harvest by up to 30% compared to PWM charge controllers and by up to 10% compared to slower MPPT controllers

    Does this mean one can get away using a smaller solar panel? Space is at a premium. I have 1 x 140 watt and 1 x 40 watt

    Also, when standing a solar panel on its own enabling directional movement to face the sun, I would prefer a horizontal stance instead of vertical because of the danger of being blown over and break. Does this make sense?

    Last year I lost 1 panel from a set of 2 in the Richtersveld. My panels have been blown over many times before without damage, but his time they were standing on a bed of rocks. A sudden, strong gust of wind blew them over and they smashed face down onto those rocks with a catastrophic result for 1 panel. The glass outer part of the panel is made of toughened glass which will withstand almost any hailstorm that your imagination can cook up, but I still lost my panel.

    Nowadays I have a an adjustable piece of string (same as on my tent) that I use to peg them down, and it is real easy to use. You can still angle the panels at various settings during the course of a day to get the maximum from the sun if/when you need it.

    The MPPT will indeed give you more than a conventional controller, but the quoted figures (30%) are theoretical and optimistic.


    Edit: If someone wants a smashed panel (87W) that still gives a reduced output, you are welcome.
    Be warned, it gives off millions of small shards of glass that you would have to stabilize somehow.
    Last edited by Eggie; 2016/04/14 at 09:33 PM.
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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    "Solar controllers are connected to storage batteries, and they remain connected regardless of whether the batteries are charged from the network, generators or other sources. This is the way they are designed to perform"

    So just to confirm, on this controller, I can use the solar panels while driving, and not worry about overcharging or buggering up the charger??

    Also, the data sheet is a litle vauge on the earthing of the negative. I dont mind the PV negative floating, but in my current dual battery system the 2nd battery and loads are all negative tied to the chassis.

    I am new to the solar charging game, but this unit looks popular and tough, am I correct or is there better stuff
    available.

    G

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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    You should have no problems running the controller while driving, mine runs inside the caravan connected to the battery while driving. When I arrive at my camp I just plug in my solar panel and put it out in the sun on a 20m lead.

    I have the 75/15 SmartSolar with the bluetooth app for monitoring which makes everything so much easier. Made use of it this past long weekend and it performed extremely well.

    My setup consists of a 80w panel charging a 105ah battery via the Victron to power a Dometic CF50 fridge and a 2x3w LED lights. The app shows the fridge drawing on average 3.5amp while the compressor is running (fridge set to -5C), and it only runs for around 3-5min every hour after which the draw was showing around 0.2amp. Panel started registering charge at around 7am every morning and by around 11am the battery was fully charged and the controller had changed from bulk/absorption to float charge on the battery. After the battery is charged the controller switches to bulk charge every time the compressor starts up and while there was good sun my panel was always producing the exact same amount of amps as the compressor was using so I am happy with the performance of the Victron.

    Future expansion for me will be to run a second 80w panel on my setup, still deciding on series vs parallel for my application.
    Last edited by plakkie; 2019/08/14 at 08:15 AM.

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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Ok, so nobody yet addressed the solar controller output.
    This output can be used for your fridge or any other load.
    The controller will try and use solar power rather than battery for the output.
    It will also disconnect your your load if your battery power runs low, thus protecting your battery.


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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Let me add my 2c. I would not use the load output but rather have all loads connected to the battery. That circuit is very very sensitive and does switch to off for even the slightest drop in battery voltage. I could not even see a drop on a digital meter yet when we looked on a scope one could see a small drop. That small drop was enough to switch the load off. One then had to use the APP to get the load on again.

    As indicated there are special reasons where one might want to use it.

    Also you would limit your load current to 15A when you use the load output while from the battery you can go to any safe current that you want to draw.

    When using say a 30V plus sol panel the MPPT would provide an easy 30% plus if you compare it to PWM. In my case I got a charge of 17A with the 100/20 Victron but only 9A using a PWM at the same state of charge of the battery.
    Last edited by ekkekan; 2019/08/14 at 09:07 PM.

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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Quote Originally Posted by ekkekan View Post
    Let me add my 2c. I would not use the load output but rather have all loads connected to the battery. That circuit is very very sensitive and does switch to off for even the slightest drop in battery voltage. I could not even see a drop on a digital meter yet when we looked on a scope one could see a small drop. That small drop was enough to switch the load off. One then had to use the APP to get the load on again.

    As indicated there are special reasons where one might want to use it.

    Also you would limit your load current to 15A when you use the load output while from the battery you can go to any safe current that you want to draw.

    When using say a 30V plus sol panel the MPPT would provide an easy 30% plus if you compare it to PWM. In my case I got a charge of 17A with the 100/20 Victron but only 9A using a PWM at the same state of charge of the battery.
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    Default Re: A Victron MPPT 75/15 solar charge controller question.

    Quote Originally Posted by ekkekan View Post
    Let me add my 2c. I would not use the load output but rather have all loads connected to the battery. That circuit is very very sensitive and does switch to off for even the slightest drop in battery voltage. I could not even see a drop on a digital meter yet when we looked on a scope one could see a small drop. That small drop was enough to switch the load off. One then had to use the APP to get the load on again.

    As indicated there are special reasons where one might want to use it. Perhaps like when you don't want to flatten your batteries beyond redemption.

    Also you would limit your load current to 15A when you use the load output while from the battery you can go to any safe current that you want to draw. Hmmmmm?

    When using say a 30V plus sol panel the MPPT would provide an easy 30% plus if you compare it to PWM. In my case I got a charge of 17A with the 100/20 Victron but only 9A using a PWM at the same state of charge of the battery.
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