jonr ✭✭✭✭


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Solar Expert
  • Re: Single solar charge controller Two battery banks Two inverter/charger

    > Is it possible to connect both the inverter/chargers to a same battery bank

    Generally speaking, connecting two power sources in parallel depends on the design - imagine that supply A produces a .1V higher voltage than supply B.  And that B then tries to reduce/regulate this voltage down by acting as a current sink.  Ie, they are fighting each other.  Fortunately, most chargers don't act as current sinks.

    But some do - for example (the only one I can think of), a motorcycle alternator typically has a shunt regulator and if some other charger were to produce a "too high" voltage, it would try to short it out.
  • Re: battery bank

    Be sure to de-rate VMP for temperature (perhaps -4V).  One source says to take the charging voltage needed plus a 2V margin for the controller and 2V for possible wire loss.   So I get something like 73.2 - 4 -2 -2  = 65 which is greater than 59. 

    I think it is OK to run close to the limit - as I understand it, if the charging voltage is slightly low, the batteries won't accept as much charge.  So the current output from the panels will drop and the panel voltage will rise to above VMP.  Ie, the situation is partially self correcting, resulting in slightly slower charging, not no charging.  Plus, high temperatures tend to happen when there it lots of sun.
  • Re: Can a 24v inverter run from half of a 48 volt bank?

    Low OR low duty cycle intermittent and there is no doubt that it's best to not do it at all (especially if you don't know what you are doing).  The balancer listed claims 10A of balancing.   Not sure I quite believe that, but it's not milli-amps.
  • Re: Can a 24v inverter run from half of a 48 volt bank?

    The only case where I would consider tapping a string is if a) you have a balancer installed and b) loads (from the tap) will be low or intermittent.
  • Re: Off grid electric cooking and opportunity loads

    A 90W compressor seems about right to opportunistically cool water surrounding a set of batteries in an insulated box.  Evidently reducing lead acid battery temp from 33C down to 25C can double life.  That's significant.