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Thrown fridge into cabin mix, wondering about system configuration and efficiency

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  • SunEagle
    replied
    Originally posted by Kaduyuizo View Post
    I'm so great full for the knowledge plz now that I may use 4 batteries 2 in series and 2 pairs in parallel to make it 24V hope its OK for 4hrs
    However you wire your batteries together you need to create a 24volt 1000Ah system. I am not sure how you are going to get that with 4 x 12volt batteries.

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  • Kaduyuizo
    replied
    I'm so great full for the knowledge plz now that I may use 4 batteries 2 in series and 2 pairs in parallel to make it 24V hope its OK for 4hrs

    Leave a comment:


  • SunEagle
    replied
    Originally posted by Kaduyuizo View Post
    Hi I just want to know , what's best Inveter to use to run a hotplate of 1200W for 5 hours on a 24V system and two batteries @ at 200AH plz
    Unfortunately a 24v 200Ah battery can safely provide about 1200 wh a day (24v x 200Ah x .25 = 1200Wh). So your hotplate may work for about 1 hour or less.

    You would have to increase the size of your battery system by 5 times to maybe run your load.

    Leave a comment:


  • whazzatt
    replied
    Originally posted by azdave View Post

    FYI...He is a new member and new members are not allowed to start a new thread so they find someone else's to hijack.
    Okay, thanks, didn't know that.

    Leave a comment:


  • azdave
    replied
    Originally posted by whazzatt View Post
    So, um, what does your question have to do with my fridge?
    FYI...He is a new member and new members are not allowed to start a new thread so they find someone else's to hijack.

    Leave a comment:


  • whazzatt
    replied
    Originally posted by Kaduyuizo View Post
    Hi I just want to know , what's best Inveter to use to run a hotplate of 1200W for 5 hours on a 24V system and two batteries @ at 200AH plz
    Hi Kaduyuizo, and welcome to the forum. Yes, we are all fine thanks.

    So, um, what does your question have to do with my fridge?

    And another 'so, um...'

    Lol, you're kidding, right?

    Short answer, USE GAS.

    Longer answer: let's assume this is an off-grid system. If it is grid tied, use the grid!!

    1200W * 5 hrs = 6000 watt hours

    For that, you will need the following 24V system, taking into consideration inverter losses (and a lowest insolation of 2.5 hours):

    * 862 Ah battery bank
    * 4200 watt panel array
    * two the biggest charge controllers you can get, i.e. 90 or 100A units (do these even exist? 80A is the biggest I've seen).

    On a 48V system:

    * 430 Ah battery bank
    * same panel array
    * one charge controller at 90 or100A

    This is a 3 day battery bank, i.e. if the sun shines today and it is very cloudy for the next 2 days you will have to stop cooking and when its sunny again you will have to wait for the batteries to charge again, which will take a while.

    But to really answer your question, a true sine wave inverter with a capacity bigger than 1200W! But with your batteries, all you'd have is a short stint of cooking before those batteries drop below 70 or 60% and then they will not last you long.
    Last edited by whazzatt; 08-17-2018, 09:55 AM.

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  • Kaduyuizo
    replied
    Hi I just want to know , what's best Inveter to use to run a hotplate of 1200W for 5 hours on a 24V system and two batteries @ at 200AH plz

    Leave a comment:


  • whazzatt
    replied
    The new thinking is:

    * Keep the 130W panel and 20A CC LED unit in place on/in the cabin.

    * Install the new 320W panel and 40A MPPT LCD unit.

    * Change out the old silver calciums for the two new T105REs (the old ones will be used somewhere else).

    * Connect both set ups to the battery bank separately. I've read a lot about this being done successfully, i.e. using two MPPTs with their own separate panels.

    * Use all loads straight from battery bank, as said by Sunking.

    * Use a 12V timer switch to run the 12V fridge during daylight hours.

    Wondering if the small 20A and bigger 40A MPPTs joined to the batts will cause interference?

    From what I've read about multiple MPPTs being used (like in Mike's setup, which he mentions frequently), there shouldn't be any problems.

    Leave a comment:


  • Bala
    replied
    You can use the load terminal for the timing functions of the cc but you should run any devices through relays.

    Leave a comment:


  • whazzatt
    replied
    Originally posted by Sunking View Post

    I have no clue where you came up with 320 watts, but will not work with your 20 amp controller.
    Original plan, before I pursued this other train of thought, was to remove the 130W and 20A MPPT and replace with a 320W panel and 40A MPPT. I'll use the 130W panel elsewhere or store it for later projects.

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  • Sunking
    replied
    Get everything off the Load Terminal, and take power directly from the battery.

    OK a 20 Amp MPPT Controller maximum input power vs battery voltage:

    200 watts @ 12 volt battery.
    400 watts @ 24 volt battery.

    You already have a 130 watt panel which means you are pretty much stuck with using the same model panel for expansions, and at 260 watts of panels does not gain you much as anything over 200 will be clipped off. So to add a panel, it would be wise to upgrade the controller and make sure the replacement Controller can handle wiring two panels in series. I have no clue where you came up with 320 watts, but will not work with your 20 amp controller.

    As for the batteries, keep them for now to learn how not to kill your new set of batteries down the road.

    As for drain on the batteries has been answered in 2 diferent threads today. Not going though it a 3rd time. [U][I][B]This post[/B][/I][/U], replies 4&5.

    Leave a comment:


  • Thrown fridge into cabin mix, wondering about system configuration and efficiency

    Bought a Dometic CF50 12-24V fridge. Requires a big step up in the cabin's set up.

    Have 204Ah running happily off a 130W (32 Vmp) panel with a 20A LED MPPT. Car stereo system, 12V lights, and cigarette style laptop charger all run from the load output of the basic MPPT.

    Was planning to upgrade the terrible silver calcium batteries to two 6V 225Ah (Trojan T105RE) to stay in 12V, get a 40A digital display MPPT, pick up panel size to 320 watts. The new MPPT would not have a load output though, so in the new set up, everything runs straight off the batteries via a connector box.

    However, I have been wondering, could I save a whole lot of cash and do the following?:

    [B]Keep the 20A MPPT and upgrade panels to maximum of 240 watts. Still get the Trojans (maybe kill the silver calciums first). Run the fridge off the load output, setting it to switch off half hour after dusk, and on half hour after dawn[/B] (surprised that the basic MPPT can do this).

    Would this increase efficiency? I was thinking about a timer switch for the thing anyway, and then realised the current MPPT can do this.

    Maybe someone could kindly tell me [B]if this wishful thinking is correct: going via load output doesn't drain batteries when they are at max charge rate, and the MPPT diverts excess charge to the load?[/B] Oh please, please let it be true!
    Last edited by whazzatt; 08-06-2018, 02:01 PM.
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