Inverter for emergency aquarium use?

Discussion in 'Electricians' Talk' started by Spiderman, May 26, 2017.

  1. Spiderman

    Spiderman New Member

    Hi,

    We've been notified of a 6 hour planned power outage next Thursday. No big deal except that since we were last cut off we've acquired an aquarium with some nice tropical fish. They'll survive fine without lights and heat this time of year, but any more than 1 hour without the filter/pump running and the ammonia starts building up to dangerous levels. The pump/filter draws 11w and I've also an air pump which draws 13w, so total 24w. I've got two 12v batteries for my golf trolley which are rated 12v 21Ah, enough for 18 holes each. I was thinking about getting a cheap-ish inverter to run these two pumps off the batteries. Question is, would 300w inverter be enough and how long could I expect to run the pumps for assuming that the batteries are, say, 75% efficient?

    I don't want to spend a fortune (otherwise would buy a genny) - would either of these be OK?...
    http://www.screwfix.com/p/ring-power-source-inverter-single-socket-12v/22290
    http://www.screwfix.com/p/ring-power-source-inverter-single-socket-12v/51612

    Or any other suggestions under £100?

    Many thanks
    Spidey
     
  2. CraigMcK

    CraigMcK Screwfix Select

    I'm not sure why you ask if 300w would be enough when you have said the total load is 23w?

    Anyway, lets assume they draw 120w by the time you account for inefficiencies (and it makes the maths simpler), 120w/12 = 10A, so your 21Ah battery would run for 2 hours, two would give you 4 hours.

    I would have thought it would be better to miss out the conversion through the invertor and try to get a 12vdc pump/filter setup. That I would expect be much more capable, then your ~23w solution would last 10h from one battery, so paralleling both up would give you plenty of overhead to spare.
     
  3. Spiderman

    Spiderman New Member

    Thanks Craig,

    yes, the reason for the question is really my lack of understanding of the maths involved converting between the 12v DC and 230v AC supply/load requirements; nor do I know if the pump/filter draws a larger load on startup. I appreciate the comment regarding the 12v solution, but the pump/filter contains the biological media that "does the business" with ammonia and nitrites, and as it normally takes 4-6 weeks to "cycle" one of these to the point that you can put fish in, I'm a bit limited on time!

    One other question for all - the example inverters I linked to are not pure sine wave, as such devices are far more expensive. Is PSW really necessary for this type of application? Or would a surge protected lead be enough?

    Spidey
     
  4. PhilSo

    PhilSo Screwfix Select

    Please don't take offence if you have already checked this.
    But is it possible that you already have a 12 volt dc pump powered by a (transformer / rectifier) 12 volt dc power supply?
    Just a thought !
     
  5. Spiderman

    Spiderman New Member

    No offence taken, and I wish there were such a product on the market (well, at least I've never seen one!). It would be such a good idea given the low wattage involved, having a separate transformer!
     
  6. PhilSo

    PhilSo Screwfix Select

    By my calculations your 24 watt load draws 0.1 amps at 240 volts . The draw on the 12 volt battery will be 20 times this figure, 2 amps. Assuming your battery can provide 16 ampere/hours you'll running the pump for 8 hours

    Pure sine wave inverter. Recommended for operating motors.

    https://www.tlc-direct.co.uk/Products/SK652100.html

    Hope this helps
     
  7. Spiderman

    Spiderman New Member

    Thanks Phil, that's really helpful. And a PSW inverter for a sensible price. Excellent!
     
  8. PhilSo

    PhilSo Screwfix Select

    You're welcome.
     
  9. MGW

    MGW Screwfix Select

    0.15 amp stand-by current plus 24W so call it 26W so around 2.2 A so 21/2.2 = 9.5 hours. In real terms likely will not last that long but should do your 4 hours on one battery without a problem, more of a problem is it is a simulated sin wave, most small items will run with a simulated sin wave, but not all. It would be safer to buy the pure sin wave inverter then sure it will work, I have a 150 Watt inverter, I have found it will maintain my mothers mobility scooter battery, idea was to charge it while travelling in the car, but once discharged it will not recharge the battery because the battery charger takes too much power. But laptop it will charge without a problem, I have not had any problems with the simulated sin wave with any small items I have tried.

    However my son had a 3000 watt inverter, and he did have problems with the simulated sin wave, the only washing machine he could use at the time was the LG with inverter controlled motors.

    So likely you don't need a pure sin wave type, but is it worth the risk, I have considered one for my freezer, however for 4 hours it will stay cool, so never bothered.
     
  10. JP.

    JP. Screwfix Select

    Looks a decent bit of kit, and a good price to boot.
     
  11. Gluggy

    Gluggy Active Member

    Have you considered using a UPS? That would combine, battery charger and inverter in one unit with the added bonus that it could be left in place to guard against any unplanned power cuts. In your situation a simple standby UPS would be fine, no need for the added cost of a line interactive unit.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice