Battery bank size for my project

TeapopperTeapopper Registered Users Posts: 13
Hi guys

Just setup my Windmax HY 1000 unit 24v.

Im planning my battery bank for my project, i have 1 24v hot water heater element rated 600watt with adjustable thermostat.
This will be used in a 30 gallon water heater tank that will be connected to the floor heating system that runs about 35-40c.
Not used for primary heat, just comfort so the floor is not so cold.

Is it enough with 2 AGM batteries 290 amps connected in series for this water heater setup ?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery bank size for my project

    Well that heater will draw roughly 25 Amps @ 24 Volts. That's a fairly hefty discharge rate for 290 Amp hours of battery. It might run it for 5 hours tops before you are at the point where the batteries may not recover.

    Unless the wind is blowing all the time, negating any actual draw on the batteries. But the load is not consistent in that the thermostat will turn the heating on/off as needed. This makes predicting results about as easy as picking the next Lotto numbers.

    The output from the wind turbine is as yet unknown, correct? It has the potential of perhaps 40 Amps @ 24 Volts? If you had some data on that you could pick a battery bank size suitable to the turbine (it won't recharge any larger amount) and hope for the best. As in: 40 Amps for a 400 Amp hour battery bank which might handle the heater for up to 8 hours constant running.

    Too many variables to be absolutely certain by my reckoning.
  • TeapopperTeapopper Registered Users Posts: 13
    Re: Battery bank size for my project

    Ok, i have looked up the average wind speeds at my place and its on average at 15mph (last year), we have a big windfarm behind us in the open that is owned by local power company.
    Unsure how much amps i can grab from that wind speed, i will know next week.

    I was down at the local hardware shop and they had a good deal on 4 batteries - 6Volt Rolls S-530.
    Any advice on buying 4 of these pieces ?

    Im instead gonna buy a much smaller element, 300watt 24v.
    What formula did you use on calculating the drainage on the battery bank with an appliance as the water heater element?
    Yes, the heating element usage is still unknown to me, i just have to test and see how much we use.

    But i got a bit unsure in buying a bigger battery bank when you wrote that the turbine will not recharge any larger amount ?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery bank size for my project

    My personal opinion on Rolls-Surrette batteries is that they should be avoided. Lately there have been problems with brand new ones, and the company hasn't exactly been stellar in its response. Just my opinion.

    If I read that windmill right, it's 1000 Watts. Divide by 24 and that equals about 41 Amps. It is not very likely it would actually produce that much power, but even if it did that would be 10% of a 400 Amp hour battery bank (recommended peak charging current). It will possibly average half that, or the minimum 5% peak charge current.

    And average 15 mph wind is pretty good. Most turbines don't reach appreciable output until 20 mph or more. It's not linear, of course, so only real-world testing will tell you what you will actually get.

    I'm basing my calculations on the fact the heater will turn on/off according to its (unpredictable) needs and the turbine will generate according to its (unpredictable) ability. You need the batteries in there to make sure the element has power when needed and the power has someplace to go when its available.

    You will also need some kind of dump/diversion load to handle turbine output when the batteries are full. Ironically, a water heater is one of the things most often used for this. Perhaps you can add a secondary element or tank to handle any surplus that might occur?
  • TeapopperTeapopper Registered Users Posts: 13
    Re: Battery bank size for my project

    Yes, you are right on the windmill specs.

    I was thinking of a secondary water heater element on same size 250 watt connected to the same water tank as a diversion load, the first element is connected to the battery bank.
    Ok, thanks for the tip, i will start very light on the battery setup just to get started, maybe try to find some scrap batteries somewhere.
  • solarvicsolarvic Solar Expert Posts: 1,060 ✭✭✭✭
    Re: Battery bank size for my project

    I got one of those waterheating elements with the thermastat and tryed to put it in my geospring waterheater. Couldn,t get it to seal and broke off the can on outside of heating element trying to remove it. Make sure you have a waterheater that will give you lots of clearance for the can to install the heating element. Basically my geospring didn,t have enough clearance and I didn,t want to hog out any of the insulation and sheetmetal to get the clearance since My water is still under warranty and I paid about 1300.00 or more for the geospring. Now that the geospring is made in the USA the price dropped about $400.00 for a usa made one. Geo spring waterheaters were previously made in China. :Dsolarvic:D
  • TeapopperTeapopper Registered Users Posts: 13
    Re: Battery bank size for my project

    Im living in Norway so there are barely any alternative energy products here, so getting a good waterheater i can modify or replace the element is difficult.
    Would be nice to find a waterheater that has 2 elements i can replace, but it seems i have to make a simple tank myself.
    Have to try with a simple small tank to start with and just insulate it with a ton of rockwool on the outside.

    The geospring looked like a nice unit.

    Where did you get your waterheating element with thermostat solarvic ?
  • WallyWally Registered Users Posts: 11
    Re: Battery bank size for my project

    I’ve had a HY-1000 1KW unit for a couple of years now at a off grid --- pheasant and deer hunting camp site here in central South Dakota.

    The battery banks are two strings with four of Sam’s Club 6V golf cart batteries in each (24 volt system) --- a little over 400 amp-hrs total.

    The turbine has worked out pretty well, I do also have a couple of 220 watt solar panels to help keep them charged up when the wind is not blowing.

    You will find that with a 24 volt setup, it takes a wind of close to 15 mph to make any appreciable power.
    A 10 to 12 mph wind makes it look like the blades are turning fast --- but it takes some serious rpm to get
    the turbine output up to the 27 volts or so required for the bulk charge.

    And you will need a pretty substantial dump load unit for even a turbine of this size, because when the winds
    are really blowing, it will put out way above rated power. I have seen it output for over 24 hrs with continuous
    45 to 55 mph winds, at 50 to 55 amps and 29 volts. You will definitely know when that output gets in the over
    50 amp area --- the blade tips are designed to flex / bend to feather and control the overspeed and this will make
    a really loud moaning noise from the blades as they flex.

    I didn’t use the controller that came with this unit, but went with a Xantrex C60 set up as a diversion controller
    and built my own load dump unit. The load dump unit is made up of 12 -- ten ohm -- 100 watt resistors in parallel
    and also a couple of 24 volt box fans controlled by a 120 F thermal switch --- works well.
  • solarvicsolarvic Solar Expert Posts: 1,060 ✭✭✭✭
    Re: Battery bank size for my project

    I got mine from Missourri Wind and Solar. It didn,t come with any info but has a name SES on the can. I was going to use it on the bottom spot where the heating element goes in my geospring waterheater. I got the can back on my element and might try to use it later.
  • TeapopperTeapopper Registered Users Posts: 13
    Re: Battery bank size for my project

    How can i stop my water heater element to not drain my battery below 50% volts that is directly connected to the battery bank.
    Is there somekind of unit i can use ?
  • mike95490mike95490 Solar Expert Posts: 9,261 ✭✭✭✭✭
    Re: Battery bank size for my project
    How can i stop my water heater element to not drain my battery below 50% volts that is directly connected to the battery bank.
    Is there somekind of unit i can use ?

    I don't think there is a battery bank large enough to run a water heater. :cry:

    They draw a LOT of power, and you should be using solar thermal panels to heat water, not electricity. Solar thermal panels are several times more efficient at heating water than electric.

    A battery voltage sensor will only cut it off when the voltage sags down low, and after a couple minutes rest, the battery will recover, and the switch will come back on.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • 65DegN65DegN Solar Expert Posts: 109 ✭✭
    Re: Battery bank size for my project

    I wouldn't use a battery bank at all for this type of system. Connect the turbine to properly sized heater elements and couple an on-demand water heater in the system to take up the slack. If you use batteries I suspect their short life span and high cost will make wind powered hot water cost prohibitive.
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