Connection suggestion for solar and aux system





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  1. #1
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    Default Connection suggestion for solar and aux system

    Hi Guys

    Perhaps someone can give me the best suggestions on the following, I have recently changed my vehicles aux system from a CTEK DC-DC to a NL smart solenoid and Victron Smart MPPT controller 75/15. it is currently wired as follows on the Solar side

    Solar - PV port on charger
    Battery port on charger - battery
    Battery to the fridge and other aux appliances (all very small except fridge)

    Over the weekend I was told I should rather go as follows.

    Solar - PV port on charger
    Battery port on charger - battery
    Load port on the MPPT to the fridge and other aux appliances (all very small except fridge)

    the reason suggested was as follows, with the load connected to the MPPT I can check the App for the amps produced by the panel and keep an eye on the amps drawn by the load. also if the appliances run off the panel during the day the extra amps produced feed to the battery to top and float the battery and only when the amps from the panel is too load will the MPPT controller allow the extra to be take from the battery so the battery will only be worked and discharged over night.

    But from what I have read the way I have connected is exactly as it has been done for ages so there is no real right or wrong way to do this.

    Can someone give me their opinion and suggestion on this please .
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  2. #2
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    Default Re: Connection suggestion for solar and aux system

    Hi, i also have the Victron 75/15 MPPT charge controller in my trailer. I have it connected as follows:

    1. Solar to PV input on MPPT
    2. Battery connected to Battery output on MPPT.
    3. All 12V equipment (fridge, LED lights, hella plugs, USB charger/Voltmeter) connected to the MPPT Load output.

    My reasoning is that the MPPT will protect the system and possible damage to the battery due to it being discharged beyond safe limits. There is a jumper connection that allows the MPPT to cut off the output at 11,8V or 11,1V. I opted for the 11,1V position.

    Your connection will work 100%, the only issue is that you don't have any protection for your battery from being discharged too much and being damaged in the process.

    The only change I would like to do is to move the Voltmeter to the battery side as the display goes off once the 11.1V limit has been reached and then you cannot see the battery level anymore.

    Hope this helps.
    Last edited by Birra; 2019/11/05 at 08:55 PM.
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  3. #3
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    Default Re: Connection suggestion for solar and aux system

    Battery monitoring.
    Battery over-discharge protection.

  4. #4
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    Default Re: Connection suggestion for solar and aux system

    Just be careful to limit the current you draw from the load terminal. Ie, donít run a car wheel pump, etc.

    Also beware of voltage drops when trying to run fridges that have their own low voltage cutout circuits.
    Cheers

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  5. #5
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    Default Re: Connection suggestion for solar and aux system

    Also, something else to note:

    The Victron 75/15 MPPT has short circuit protection at the load and has automatic load disconnect when the rated 15A is exceeded.

    But like Fluffy stated it is best not to use equipment that draws high amounts of current as the possibility of damage is always present.
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  6. #6
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    Default Re: Connection suggestion for solar and aux system

    Thank you all for the response

    I dont usually place anything else on the system other then fridge, water pump and LED lights.

    I think its an easy task to change the current set up to have it the way explained here and try it out for a few weeks and decided from there.

    Please confirm if set up like this in the morning when the sun is on the horizon and producing say 1amp will the Victron take the required amps (2amp) from the battery to top the total amp draw to the 3amps required to run the fridge on low and then again over night the victron will take amps straight from the battery to keep the fridge going
    98' Defender Hardtop 110 (300tdi)
    54' Moto Rumi Formichino (project in progress)
    58' Vespa GS150
    62' Vespa GS160
    66' Vespa SS180
    69' Vespa Rally 180
    69' Lambretta LI150

  7. #7
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    Default Re: Connection suggestion for solar and aux system

    I have the same Victron MPPT and very limited knowledge on the load part of it. After a bit of searching I found multiple people said it switched off when in Float mode for some reason. Works fine in Absorb and Bulk charging modes as well as with no PV panel connected.

    I would like to play with mine but Iím not sure Iíll leave my fridge running on it permanently.

  8. #8
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    Default Re: Connection suggestion for solar and aux system

    Hi guys

    I've fitted a victron 100/20 some time ago to my setup and the load, consisting of a fridge and a few lights, to the load output. I've not had the opportunity to test it properly till this past weekend but in the small tests leading up, found that every time the fridge would start, the victron would disconnect and reconnect the load.

    This past weekend on a short fishing trip the opportunity presented itself when the ac supply was interrupted. I connected the solar panels and checked the settings from the app, even with the load set to "always on" the victron would disconnect the load. I then switched the load to connect directly to the battery and not only did the fridge run but the app measured the highest solar yield I've seen to date.

    I would have thought that the solar controller would supply power to the load to prevent cycling the battery and provide valuable information by measuring consumption. Do I just give up on using three load output or is there a fault with the system?

    I must mention that my battery is not in the best condition and needs to be replaced before I consider camping where there is no electrify.Name:  Screenshot_20200209-132010.jpg
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  9. #9
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    Default Re: Connection suggestion for solar and aux system

    I have the victron 75/15 mppt with blue tooth, 150w of solar, alternator/solenoid, deepcell battery set up. It only runs the national lunar 52l weekender fridge.

    In my research journey majority advice was connect the fridge to the battery and not the mppt device port. Sure you cannot then get an amp use reading but the issue is that whenever the fridge starts up ( which it does fairly regularly because of the built in on/off cycle to extend battery life), there is an electricity use surge. Re these start up surges - connecting the fridge directly to the battery - no problems. But mppt device port and associated elecrtics are apparently not designed to handle these surges and sh1t then happens. Who knew? Only Victron I suppose. The Victron instruction manual somewhere in the small print does mentions this and recommends direct battery connection for things like fridges. Frustrating, but there it is. Bottom line mppt is the way to go even for a modest set up and victron is mainstream.
    Seen the results on the road.

    Only solution if you want to know and monitor fridge draw especially when charging via solar is to spend the bucks and install an in-line amp meter between the battery and the fridge. Got to love electrickery.

    .

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  11. #10
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    Default Connection suggestion for solar and aux system

    Quote Originally Posted by rudyb View Post
    I would have thought that the solar controller would supply power to the load to prevent cycling the battery and provide valuable information by measuring consumption. Do I just give up on using three load output or is there a fault with the system?
    As Roadman mentioned, itís due to inrush current. My 60L fridge did the same to my victron 100/20, but the victron was happy to run the 30L fridge.

    The cheapest workaround option is to use two 30A relays that switches itself over from the battery to the victron load output when the compressor starts. The time delay of the mechanical switchover from the relays will be long enough to filter out the inrush current. Then youíll be able to log/measure everything but that initial power surge.

    Or with one relay you can at least use the load output for voltage sensing, utilizing the built in battery protect. That will prevent your battery from being drained below a user defined set point.

    However, the easier and best way to manage your battery consumption is to add a victron BMV712. Yes itís expensive but youíll never have to guess again how your battery is doing. It costs about the same as a new battery, but Iím sure it will eventually pay itself off by informing you exactly whatís going on. Then youíll also be able to log consumption of bigger equipment like air compressors and inverters.

    The BMV712 and SmartSolar share data regarding Voltage and Amps via Bluetooth, so that the SmartSolar can do an even better job of charging your battery.
    Last edited by MrTolbos; 2020/02/16 at 02:36 AM.

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  13. #11
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    Default Re: Connection suggestion for solar and aux system

    Quote Originally Posted by Roadman View Post
    But mppt device port and associated elecrtics are apparently not designed to handle these surges and sh1t then happens. Who knew? Only Victron I suppose.

    .
    The Victron MPPT is very very sensitive for any voltage drop and will on most partially used batteries switch the load output off. The drop can be so small that you cannot even see it on a multimeter but using a scope one will find even a 30mV drop will switch the load output off.

    I tested this with a 8A load. When using a brand new battery the MPPT would not switch the load off.

    Just my 2c as to why one would prefer to use the battery for the load and not the MPPT output on a Victron. Some sellers have asked Victron to make it less sensitive but have not been successful.

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  15. #12
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    Default Connection suggestion for solar and aux system

    Here they have a good explanation and test regarding the in rush current vs load output:

    https://community.victronenergy.com/...ntrollers.html
    Last edited by MrTolbos; 2020/02/17 at 07:41 AM.

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  17. #13
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    Default Re: Connection suggestion for solar and aux system

    Thank you for the advice guys. Looks like I will need to go camping for a weekend to get a proper feel for how well the system works with the fridge connected directly to the battery

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