mike95490 ✭✭✭✭


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Solar Expert
  • Re: New build off-grid

    reconsider the cheap dorm fridge.  They are usually poorly made and not efficient,   The new, full size energy star fridges will consume less power then a dorm fridge (unless it's an energy star model
  • Re: How to size battery and panels to run my well pump.

    How about looking at a new pump?  Grunfos makes some solar pumps, run on a couple solar panels, and a fancy new variable speed pump, that needs no batteries ?

    40A locked rotor (start-up) @230V means the inverter has to supply 9,200watts and then there's going to be some power factor monkey business too.  Can't do that at 12V .

  • Re: Off grid design check

    Another gotcha, is the propane cookstove  -  specifically the OVEN.  What sort of ignition system does it use.
    Spark = 3 watts
    GloBar = 300 watts the whole time the oven is on.

    Both of my backup generators are diesel, and I've had no starting issues down to +20F, as long as the crankcase oil is the right weight.
  • Re: How to tweak absorb

    mike95490 said:
    This is what the generator is for, start it at dawn, and get the batteries charged.  Bulk with genset, Abs & Eq with solar if you can.
    Sorry, to clarify a bit.  To rescue your batteries and get into an EQ cycle, if you don't have enough solar to get to EQ, you :
    start the Generator in the morning, and BULK charge the batteries at no higher than the batteries max rate - till your solar can finish the Absorb and then into EQ.
    Should be less than $5 of fuel for 1 day.  This process may take 1-3 days, depending on how sick the batteries are.   New battery bank costs way more than $15 if you don't get them charged and sulfate them to death,
  • Re: Relation between measured Isc/Voc and power produced by MPPT controller

    Sealed batteries, while they have several attractive qualities, are a less than ideal choice for starting off with.
    Roughly, they cost 2x as much, and last half as long, as quality Flooded Batteries.  Any mistakes, and you can easily damage the bank. and being sealed, there is no way to really check the state of charge with a hydrometer.
     What needs to be done, is to get a solid number for the ACTUAL SOLAR hours (well aimed panels will generally produce 80% of nameplate for 20 minutes daily, the rest of the time is somewhat less and nowhere on earth, is there a usable 10 hours.)
    You need (even for AGM) to allow for replacing 120% of what was consumed, within 48 hours.  Adding up all the loads, conversion losses and recharge losses, and you roughly need solar nameplate rating to harvest 2x your loads