renogy 40 amp mppt charge controller

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Quarry
Quarry Registered Users Posts: 3
in Solar Beginners Corner #1
ok i'm new to solar and need some help.
I went to Renogy.com and bought 3-300 watt solar panels, a 40 amp mppt charge controller. I went to a store and bought 2-12 volt AGM batteries. Also bought a power bright 24 volt pure sine wave inverter. I got it all hooked up (load,batteries,pv in that order) i go to switch the charge controller mode to 17 (which is on/off mode). I cant seem to get it to switch on after. When i first hooked it all up the load ran for a short time and then turns off.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: renogy 40 amp mppt charge controller

    Welcome to the forum.

    I'm not familiar with that particular charge controller but it sounds as though it has 'LOAD' terminals on it. Be advised you do not want to use them for connecting your inverter. Connect the inverter to the batteries through a fuse or circuit breaker, making sure that all wiring is suited to the expected current. You didn't say what size your inverter is, but the LOAD terminals on controllers usually aren't capable of more current than the controller rating, in this case 40 Amps and that's <1000 Watts @ 24 Volts.
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  • Quarry
    Quarry Registered Users Posts: 3
    #3
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    Re: renogy 40 amp mppt charge controller

    1000 watt inverter is what i got. I was trying to run the inverter through the load terminals of the charge controller. Thank you that explains alot for me.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,456 admin
    #4
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    Re: renogy 40 amp mppt charge controller

    1,000 Watt inverter * 1/0.85 inverter eff * 1/21.0 volt batt cutoff = 56 Amps at full load / min battery voltage

    That is a fair amount of current and not many (if any) charge controllers can supply that level of current through their "load" connections.

    Also, make firm/bolted up connections (with short/heavy gauge wire capable of the current) between your devices--Just using a set of automotive jumper cables will not work--And can make it appear that you have bad hardware.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Quarry
    Quarry Registered Users Posts: 3
    #5
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    Re: renogy 40 amp mppt charge controller

    What kind of fuses should i use.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: renogy 40 amp mppt charge controller

    The inverter manual should give you recommendations for wire and fuse sizing. Don't be surprised if the fuse/breaker recommended is 70 Amps or more and the wire size accordingly very large like 4 AWG minimum.

    As Bill pointed out the current draw on this with minimum Voltage and maximum Wattage is in the 50 Amp range. Hence the need for at least 4 AWG which would be on a 60 Amp fuse/breaker. If you go up in wire size you can increase the fuse capacity but never do it the other way around; the fuse must be the 'weak link' in the wiring. Larger wire size will reduce Voltage drop under load.

    Some choices for fuses/breakers here: http://www.solar-electric.com/infubr.html
    Another good choice is the Blue Sea battery terminal post fuse which you should be able to get at a local marine/RV store.

    And in case we've glossed over it, the output of the charge controller should also have over-current protection.
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  • Alaska Man
    Alaska Man Solar Expert Posts: 252 ✭✭
    #7
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    Re: renogy 40 amp mppt charge controller
    Quarry wrote: »
    ok i'm new to solar and need some help.
    I went to Renogy.com and bought 3-300 watt solar panels, a 40 amp mppt charge controller. I went to a store and bought 2-12 volt AGM batteries. Also bought a power bright 24 volt pure sine wave inverter. I got it all hooked up (load,batteries,pv in that order) i go to switch the charge controller mode to 17 (which is on/off mode). I cant seem to get it to switch on after. When i first hooked it all up the load ran for a short time and then turns off.

    Are your batteries hooked up in Series and Parallel?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
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    Re: renogy 40 amp mppt charge controller
    Alaska Man wrote: »
    Are your batteries hooked up in Series and Parallel?

    With two 12 Volt batteries on a 24 Volt system there is only one way to connect them: in series.
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  • TorontoTim
    TorontoTim Registered Users Posts: 11 ✭
    #9
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    Re: renogy 40 amp mppt charge controller

    How has this setup been working out for you? I'm working on piecing together a similarly small system just to run a few lights etc. at an off grid cottage. Trying to keep costs low while not succumbing to buying poor quality components that won't last.

    The Renogy MPPT charge controller seems to be one of the lower cost MPPT units, but the same unit seems to also be sold under multiple brands like SainSonic and RioRand, which is never a good sign.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #10
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    Re: renogy 40 amp mppt charge controller

    I would like to know as well. Specifically the Renogy 300 watt panels. I have been looking to buy 4 Trina or Canadian Solar panels in around the same operating range but have found it hard to find someone that will ship under a pallet at a time.
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