12V 3A Bilge Pump (powered by a computer monitor AC-DC adaptor)

SurfpathSurfpath Solar Expert Posts: 347 ✭✭
edited September 15 in Solar Water Pumping #1
Howdy,
Next week I plan to install a new 18 watt solar panel on my small boat to keep the 12v boat battery charged.  When my boat is not in use the battery also periodically runs a 3A 12v bilge pump to keep rain water out of the bilge.  My last (5w) solar panel seemed to work fine with this arrangement - until it, and the battery, were recently stolen.

In the interim, I now have about 400 gallons of water in the boat.  If I want to pump it out using the mains this weekend do you think I could use this AC-DC adapter wired directly into the pump?   

https://www.amazon.com/gp/product/B000VE7GQQ/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
(it's a 12v 6A 72 W AC Adapter that's normally used to power a large computer monitor)

Here's the link to my pump:
https://www.amazon.com/gp/product/B00N6HDRLS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Do 12v pumps like this have a big "surge" where 72 watts is not enough?
Thanks!


Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, no genny, 100% off grid.

Comments

  • BB.BB. Super Moderators Posts: 26,758 admin
    Wire up the pump as you normally would. Use the 400 gallon water pumping as a test to make sure connections are reliable and wiring does not get hot.

    A sump pump should not have much surge ("much surge" is 5x or more rated current)--But only lasts for a fraction of a second to a few seconds (depending on pump and application). Pumps that pump against pressure (40-60 psi or more--such as well and fresh water plumbing pumps tend to have higher starting surge).

    You have not told us much about the electrical system of the boat. Say you have roughly 200 AH of 12 volt "Marine" type batteries (not really deep cycle) and you only want to discharge by 15%. And lets say that your pump is ~400 GPH (smaller pump). Your battery bank would supply:
    • 200 AH * 0.15 discharge = 30 Amp*Hours
    • 30 AH / 3 amp pump = 10 hour run time
    • 400 Gallons to pump / 400 gallons per hour = 1 hour of pumping
    So--From a nominal batter point of view, the sump pump is not a very large load (all guesswork on my side) and I would not worry. Even if you had a single ~85 AH battery, this is still not much of a load.

    Of course, you will want to get the battery bank recharged again.

    The next question--Your 18 Watt panel (~1 amp) will recharge 3 AH in a day or two--No issue. Starting your engine is probably harder on the engine (run at idle for an hour) and I would not bother unless you wanted to take the boat out.

    If you have AC power, get a simple battery charger and run the pump with it... And, very likely, if you have a new battery, it has sat around for awhile and could use a charge anyway (good smallish AC charger running for 12-24 hours would be more than enough--really depends on how discharged the battery is).

    It is not good to let lead acid batteries set for days/weeks at a time at less than ~75% state of charge as they will sulfate and eventually ruin your battery. If you cannot get the solar panel connected for another few weeks, I would go with the AC battery charger to bring the battery up to near full charge now (while the pump is running) to keep the battery "happy".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dennis461dennis461 Registered Users Posts: 81 ✭✭
    DO you already have a battery charger in the boat or was the solar panel your only source? Most bilge pumps are wired to the boat battery.  Put a battery back in, start the boat motor and get the water out, 400 gallons would sink my 20' Cuddy cabin.

    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • SurfpathSurfpath Solar Expert Posts: 347 ✭✭
    Ok. A little more detail

    I do not have an engine. Currently.
    I do not have a traditional ac to dc charger.
    I do not have a battery

    My boat can handle about 600 gallons of bilge water. But I'd rather not like to test this limit.

    What I do have currently is ac power on the dock and a 6 amp "wall wart". the question is will the latter help me with running my pump in the short term. I know it's not ideal.
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, no genny, 100% off grid.
  • BB.BB. Super Moderators Posts: 26,758 admin
    Assuming the ac power adapter is "cheap"--Why not try it. Just check the voltage and make sure that you do not over voltage the pump.

    I would also make sure you have a GFI outlet to power the ac adapter (assuming that your dock has GFI already--you should be good to go).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 1,416 ✭✭✭✭
    My guess is it will probably work. If it does though, I'd keep on eye on the temperature of the wall wart.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators Posts: 26,758 admin
    I was going to add "monitor the adapter temperature" to my post. Estragon beat me to it.

    I have had multiple AC adapters, over the years, that either have smelled of smoke, or even opened up like a clam shell (exposing the raw electrical internals while still working) from excessive current/heat/load.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dennis461dennis461 Registered Users Posts: 81 ✭✭
    I have a Schumacher Electric Battery Maintainer (120 VAC input) which I use all the periodically on my boat, cars motorcycle.
    I have accidentally left it in the rain charging batteries overnight, and it works real good with no bad odors.

    I also have a 15 watt solar panel on the boat with a CMTD battery maintainer.
    I use this while fishing to keep VHF, fish finder, and bilge pump powered up.
    I think what you plan on doing will work, but the battery will most likely drop too low on the first day of pumping.
    You will need to shut off the bilge pump at around 11-11.5 volts IMHO.
    Then let it recharge the next day.

    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • SurfpathSurfpath Solar Expert Posts: 347 ✭✭
    edited September 18 #9
    Hi Dennis,
    Thanks for the note.  You said "I think what you plan on doing will work, but the battery will most likely drop too low on the first day of pumping".  That's exactly why I wanted to pump out the 400 gallons using AC power from the dock before I get a battery. We are thinking alike.

    ------

    So, I will now wire up my 3A bilge pump to my 6A wall wart, plug it into the dock AC power, turn it on, and monitor as many of you advise

    Do I need a fuse??

    Hopefully it will work.  I am planning this to be a one time event before I get:

    a) A security alarm installed on the boat (see the original post)
    b) a "new" battery (I have a "marine type" battery that is a couple of years old that may be appropriate (perhaps more on that later).
    c) the new 18 watt panel installed.

    The joys of boating, is it worth it?

    I love that my home solar system just sits there quietly humming and blinking.  All it needs is water in it, not out of it.
    :-)
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, no genny, 100% off grid.
  • EstragonEstragon Registered Users Posts: 1,416 ✭✭✭✭
    Yes, you should really have a fuse on the DC + to the pump. I keep a couple of cheap inline fuse holders and a small assortment of glass fuses around for temporary duties like this.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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