Negative grounding spot

DrnalineDrnaline Registered Users Posts: 10
Long time lurker, first time poster. Got what may be a funny question. I'm putting together a 24v wind turbine set up with 3 24v in parralel 12 volts, a dump load with two 12v 300watt heaters. I have the pos hooked up straight from the first battery positive to the inverter. Negative to the neg on the the first 24V to the inverter.

My question. I have a pos and neg coming from the turbine head. The positive i would imagine going to the first battery closest to the inverter. Should the negative go anywhere in particular? Something tell me as far a possible?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot

    A couple of observational questions:

    1). Charge controller? Wind turbines need a diversion type controller. The turbine feeds that, and then the controller sends power either to the batteries or to the diversion load once the batteries are full. Without this bit it sounds like you're feeding the diversion load from the batteries all the time.

    2). For three battery strings in parallel you need common connection point for all positives and all negatives to equalize the length of wire to each battery. It sounds like you're "laddering" the batteries. Take a look at the SmartGauge wiring diagrams here: http://www.smartgauge.co.uk/batt_con.html
    For three parallel batteries you should be using method 3.
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot

    I have an SEA 440 http://www.survivalunlimited.com/diversionloads.htm controller. Batteries are hooked up pos to neg in the middle and there prospective outside polls tied to each other.
    I will see if i can post a makeshift diagram of how is wired sofar.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot

    Sorry; can't see the drawing here. :blush:
    Someone with a bigger screen and/or better eyesight?
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Negative grounding spot

    my eyesight is bad too, but the pic is small to begin with. i tried using ctrl + to the max and it blurred. i think i'd need a 50+ inch screen to make it semi-visible and i'd still need ctrl +.:-)
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: Negative grounding spot

    Not good enough resolution for me to read...

    However, I do have a question, are you pulling 12 volts of the 24 volt battery bank?

    Generally, not a good idea unless special measures are taken.

    How are the two x 300 watt 12 volt heaters connected?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • OK0KOKOK0KOK Registered Users Posts: 6
    Re: Negative grounding spot
    A couple of observational questions:

    1). Charge controller? Wind turbines need a diversion type controller. The turbine feeds that, and then the controller sends power either to the batteries or to the diversion load once the batteries are full. Without this bit it sounds like you're feeding the diversion load from the batteries all the time.

    2). For three battery strings in parallel you need common connection point for all positives and all negatives to equalize the length of wire to each battery. It sounds like you're "laddering" the batteries. Take a look at the SmartGauge wiring diagrams here: http://www.smartgauge.co.uk/batt_con.html
    For three parallel batteries you should be using method 3.

    I'm guilty of laddering:blush:
    Thank you for the SmartGauge Link:D
    I'll rewire my system ASAP
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    .
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot

    The only thing i pull 12 volts off of is the sensing wires for the dump load. The inline heater will be hooked up in series along with maybe some exterior auto light/s. None of this is in concrete, i'm just wondering if my thnking is right. dump load setup and windturbine are not wired yet. Thanks for all the input everyone.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot

    Sorry, but I still can't see your diagram well enough to comment on it.

    I'm a bit concerned about your statement of pulling 12 Volts off for the sensing wires for the dump load.
    A 24 Volt system should sense the full 24 Volt bank's Voltage to determine when the dump load should be switched in. Sort of sounds like you've tried to adapt a 12 Volt controller by monitoring 1/2 of the battery bank. Your link lists 3 versions of the controller, including 24 Volt (and the Voltage levels they list are a bit low for a deep cycle battery system).
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot

    As per my dumpload instructions. "Our inexpensive voltage/dump load regulator will work on 12, 24 and 48 volt systems by slaving off of only one 12 volt battery section." any one know how i could make my image bigger?
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: Negative grounding spot

    Your picture is only a few kBytes in size... If you end the file in .jpg extension, you can upload a photo/scan up to 253.9 KB in size.

    You could even take two photos (left/right) and post both for better resolution.

    It would be much easier to read.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot

    As per my dumpload instructions. "Our inexpensive voltage/dump load regulator will work on 12, 24 and 48 volt systems by slaving off of only one 12 volt battery section." any one know how i could make my image bigger?
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot

    As per my dumpload instructions. "Our inexpensive voltage/dump load regulator will work on 12, 24 and 48 volt systems by slaving off of only one 12 volt battery section." any one know how i could make my image bigger?
  • FullpowerFullpower Solar Expert Posts: 69 ✭✭
    Negative grounding spot

    Do NOT "tap" 12 volts for ANYTHING from a 24 or 48 volt series string.
    Even very small loads on "part" of a series string will raise terminal voltage on the unloaded cells, and lower the voltage on the "tapped" cells.
    dramatic voltage excursions result from even small tapped loads over time.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot
    Fullpower wrote: »
    Do NOT "tap" 12 volts for ANYTHING from a 24 or 48 volt series string.
    Even very small loads on "part" of a series string will raise terminal voltage on the unloaded cells, and lower the voltage on the "tapped" cells.
    dramatic voltage excursions result from even small tapped loads over time.

    Apparently he is following the instructions for the diversion controller. It's a pretty chintzy way to do it and makes me suspicious of the quality.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot

    Okay I can almost see those drawings. A bit fuzzy on the details. But it does look like the first thing you need to do is consult that Smart Gauge site I linked to. Your battery bank wants to have common positive and negative connection points for all parallel strings with equal length wiring to each. Those common points are where everything that connects to the batteries should connect. You do not want the inverter connected to one string and the turbine connected to another as there can be significant resistance in the wires leading to unbalanced charge/discharge between the strings of batteries.

    Also take a look at the simple diagram from Morningstar on page 2 here: http://lib.store.yahoo.net/lib/wind-sun/TSdatasheet.pdf It shows the basic use of one of their controllers as a diversion controller.

    What you've got appears to be a non-programmable Voltage controlled switch which is actuating a standard automotive-type starter relay, turning it on a a pre-set Voltage and off at another. It assumes the Voltage set points are correct and will correlate to 24 or 48 Volt systems based on monitor 12 Volts worth of battery. I would not agree with either of those assumptions.
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot
    Okay I can almost see those drawings. A bit fuzzy on the details. But it does look like the first thing you need to do is consult that Smart Gauge site I linked to. Your battery bank wants to have common positive and negative connection points for all parallel strings with equal length wiring to each. Those common points are where everything that connects to the batteries should connect. You do not want the inverter connected to one string and the turbine connected to another as there can be significant resistance in the wires leading to unbalanced charge/discharge between the strings of batteries.

    Also take a look at the simple diagram from Morningstar on page 2 here: http://lib.store.yahoo.net/lib/wind-sun/TSdatasheet.pdf It shows the basic use of one of their controllers as a diversion controller.

    What you've got appears to be a non-programmable Voltage controlled switch which is actuating a standard automotive-type starter relay, turning it on a a pre-set Voltage and off at another. It assumes the Voltage set points are correct and will correlate to 24 or 48 Volt systems based on monitor 12 Volts worth of battery. I would not agree with either of those assumptions.
    "Okay I can almost see those drawings. A bit fuzzy on the details. But it does look like the first thing you need to do is consult that Smart Gauge site I linked to. Your battery bank wants to have common positive and negative connection points for all parallel strings with equal length wiring to each. Those common points are where everything that connects to the batteries should connect. You do not want the inverter connected to one string and the turbine connected to another as there can be significant resistance in the wires leading to unbalanced charge/discharge between the strings of batteries."

    This is how my set up is basicly (if the pic attached)but using 12 volt batterys, i have then inline because of space constraints. I went trough your first link but cannot find anything to do with a 24 volt system using 12 volt batts. What i've found so far is i should use the negative ground from the "diagonally opposite posts." to ground my system. If i understand i should have the + and - from my wind turbine attach to the same points? On the inverter i guess.

    "What you've got appears to be a non-programmable Voltage controlled switch which is actuating a standard automotive-type starter relay, turning it on a a pre-set Voltage and off at another. It assumes the Voltage set points are correct and will correlate to 24 or 48 Volt systems based on monitor 12 Volts worth of battery. I would not agree with either of those assumptions"

    24 Volt Bank - Turns on and starts dumping power at 27 volts. Turns off at 25 volts (+ - 5%)
    Thanks for all your help, what i'm looking for is that i'm not gonna blow anything up, that my idea of the hookup is somewhat sound. I've never been good with electricity so i have a lot of apprehension.
    t2.png 74.2K
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: Negative grounding spot

    One option is to attach the bus connections "kitty corner"... For example, move the + connection to the lower right battery.

    Right now, as drawn, the left batteries will get most of the charge/discharge current and the right batteries will get less (because of the extra length of wiring to reach those batteries).

    Storage batteries have very little resistance (on the order of 0.020 ohms or less)... So any additional couple feet of wiring will "steer" the current to the shortest/lowest resistance path.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot

    I need to do some of these battery diagrams in a larger size and post them up permanently here under FAQ. In my spare time, ha ha.

    Until then, this little attachment should give you an idea of what Bill & I are driving at here.
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot

    Gets me headed in the right direction, thanks again guys.
  • DrnalineDrnaline Registered Users Posts: 10
    Re: Negative grounding spot

    Another question. From what i can understand you can wire small 300w 12v fan/heaters in series to a 24volt system. I understand you have to, to keep the heater from burning up. My question is do you have to keep the loop to two 12 vollt items for the 24 volt system or can i add other items such as 24 voltdump load resistors, 12 volt headlites?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot
    Drnaline wrote: »
    Another question. From what i can understand you can wire small 300w 12v fan/heaters in series to a 24volt system. I understand you have to, to keep the heater from burning up. My question is do you have to keep the loop to two 12 vollt items for the 24 volt system or can i add other items such as 24 voltdump load resistors, 12 volt headlites?

    300 Watts on 12 Volts is a lot of power: roughly 25 Amps. I wouldn't use one. You'd need a massive battery bank to supply that for very long.

    As to the other issue, any two identical 12 Volt loads in series will, theoretically, run off 24 Volts. If you connect two dissimilar 12 Volt loads in series they will not have the same resistance and will not draw equally from the 24 Volt bank; one inevitably will get more power than the other.

    Be advised that in the case of something like a heater it will have a thermostat that will turn it on/off as needed. This will affect the operation of the other as well, as it will interrupt current for the whole circuit. In the case of a heater with fan, if the fan does not also shut down with the T-stat there will be a real problem as one unit could have current flowing through just the fan (high resistance) and the other could have current flowing through both fan and heating element (low resistance) resulting in a Voltage imbalance.

    On the whole, not a good idea to do this.
  • KerryKerry Registered Users Posts: 9
    Re: Negative grounding spot

    Hi Cariboocoot ,

    Re: "Until then, this little attachment should give you an idea of what Bill & I are driving at here."

    Thanks for confirming my connections.

    Question: Does it matter which posts I connect the 2/0 cables to the Charge Controller? I ask because if I connect the positive cable to the CC as shown in your diagram it will take a bit more cable.

    Thanks,

    Kerry
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Negative grounding spot

    Welcome to the forum Kerry.

    Yes, it matters. The whole reason behind the diagonal connection is to even out the wire lengths through both strings of batteries. If you connect positive and negative to one battery string the batteries are 'laddered': one string has the extra resistance of the two interconnecting parallel cables added to it. That, in a nutshell, is the whole problem.
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