24v Battery monitor

Discussion in 'The Projects Forum' started by Buxton137, May 16, 2013.

  1. Buxton137

    Thread Starter New Member

    May 16, 2013
    Ive been tasked to design a solar system (In sunny Scotland:() to power gate motors, i have the gates working form a wireless fob,

    I an using two 12v 110Ah leisure battery

    to save power i have introduces 555 timing circuit that allows power to the control board for the gate cycle this works by receiving a radio signal from the fob second channel

    I am having trouble designing a 24V battery monitoring system for a solar charger.
    i would like it to come on when the voltage goes below 20-21v and off if the voltage is any higher

    If any on can suggest an idea

    regards Mark
  2. Brownout

    Well-Known Member

    Jan 10, 2012
    I'm working on nearly an identical design, only for 12V. I am using a PIC development board and using the internal ADC to obtain the battery voltage. Once I have all the code working, it's just a matter of connecting a realy to one of the PIC's I/O ports to energize or connect anything I need.
  3. RodneyB

    Active Member

    Apr 28, 2012
    I currently build these into my regulator in sunny Zimbabwe. On the Output we put a LED with a zener diode as Long as the voltage stays above the level then the LED is on. When it goes off you know the battery is flat.

    We have in general 9 hours of grid power a day so our solar system is very important to the integrity of the system. Knowing the condition of the battery is paramount.

    We have 4 LED's over Charging, Good, Poor and Bad.
  4. wayneh


    Sep 9, 2010
    Those voltages will severely shorten the life of your battery. A lead-acid battery is best kept as near to full charge as possible, i.e. 26V. I think a 12V battery is considered "discharged" at 10V.

    You didn't mention the capacity of your solar panel. That influences your options for charging.

    There are commercial products to do what you want. Is there a reason you want to build one? I'm not sure you'll save any money, and the commercial devices may have nice features that would be hard to DIY.
  5. Buxton137

    Thread Starter New Member

    May 16, 2013
    Ta for that i will up them to a minimum of 23-24v, i am using two 40W solar panels in series to supply the Battery voltage,

    I am making the system because the company i work for designed and built on that only works in the continent and is useless in Brittan due to our bad weather,

    It also does not help that i have a tight budget to stick to to create the system to work in Brittan

    At the moment i have got so far a IC741 in a voltage comparator circuit
    this is working well for 12 volt system (one Batt) and the Led comes on when the voltage is below 10.5V which works well enough so far

    despite this my boss wants it to be over the 24V system,

    Any clue of a better IC that cold handle a higher voltage
  6. wayneh


    Sep 9, 2010
    A standard LM339 would work over that voltage range and, being a genuine comparator, might work better than that old op-amp. You could even use one comparator for one battery and another for the second one. And you'd have two comparators left for other duties. (I find comparators incredibly useful to drive LEDs to indicate connections and all sorts of things. But me with a comparator is a bit like a baby with a hammer - everything looks like a nail.)