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Thread: Back-up Battery Sump Pump --> Can you use two batteries?

  1. #1
    DIY Junior Member katchat6's Avatar
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    Default Back-up Battery Sump Pump --> Can you use two batteries?

    Hello-

    We recently had a "check-up" of our sump pump configuration after buying our home. The good news is that the everything appears to be functioning (although it does not look all that pretty-see attached pic). We have a Zoeller Aquanot II Pedestal as the battery back-up sump pump. The problem is they have it connected to an incredibly cheap battery ($75.00 from Home Depot) that requires acid and is rated for only a couple of hours use. In our old house we had the same type of pump, but instead had the battery made specifically for that pump from Zoeller, which is long-lasting as well as maintenance free (sealed...no acid). I was just going to buy one of those batteries to replace the cheap one that is there now. However, in talking with one of the plumbers, he suggested buying two of those batteries so that in the event of a power outage, I could have one run and if needed go charge the other via a car battery charger and then swap them out. Of course, I'm all about having as much contingency as possible, but I wanted to reach out to see what other people thought of this idea:
    1. Should I assume at one single point of time, only 1 of the batteries would be attached to power the pump? OR could it be configured such that if one were to die, the other would be ready to pick up without manual intervention?
    2. Just how easy is it to charge these batteries via car charger cables? Any idea how long it takes?
    3. Is there any specific cable set-up required?

    Thank you....any and all feedback is greatly appreciated.

    Kat
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  2. #2

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    Well first your charge controller needs to be matched to your battery. If this is the same system you had before, you should be fine with swapping back in the long life sealed battery. What you can't do is swap in an even bigger battery - such as connecting two of those batteries in parallel - because while the pump would run for twice as long, the charge controller would either blow an internal fuse or self destruct trying to recharge the now twice as big battery.

    Charging the battery off of the car alternator is not going to really work. Again its back to the charge controller. The alternator in the car is designed to recharge CAR batteries (low capacity - high output) not long life (high capacity - low output) batteries. I'm not saying it won't charge at all, but it would take forever and it would not be good for the batteries or the chargers.

    You could design yourself an A-B switch and switch between the two sealed batteries. That way only one would be connected to the pump and controller at any one time. You would have to remember to switch it once a month to keep the batteries charged up AND in an emergency you would have to manually switch between the two. (Remember you are dealing with low voltage but high current so you need heavy gauge wire and an appropriate switch, but this is standard stuff at a marine supply store.) But of course once both batteries were out of juice you would be out of luck. Personally I'd just go with the single battery and put the money toward a quality inverter type generator so I could have some lights and run my pump and charger during long outages (Oh and charge controllers generally HATE cheap big box store generators and will produce little or no charging power for your batteries when connected to one so if you go the generator route and want the battery to charge (you could always just assume that the pump will run off a cheap generator from that point until power is restored and skip the inverter generator) you'll be looking at a generator that costs 50% more for the same wattage as you see in the big box stores.)

    -rick
    Last edited by drick; 12-02-2011 at 03:30 PM.

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    DIY Senior Member Chad Schloss's Avatar
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    alternator? did you even read what was wrote? he said nothing about an alternator on a car;he said a car battery CHARGER. you can run two batteries in parrell. it will give you 12v at whatever amperage the batteries are x2. it will effectlively double your run time. you could have a switch in between the two batteries, but then you would need two different chargers, and a switch to shut off the dead battery. if the good battery was hooked up to the dead battery, it would not work very well. it would be better to parrell the batteries and charge them that way. no switches needed. you could also do what you suggested, one battery to run the pump and swap out the battery if it dies. some types of batteries require different chargers. gel batteries like certain chargers, acid batteries like certain type of chargers, etc. look into that if you want to.

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    Test, Don't Guess! cacher_chick's Avatar
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    You would need a real battery charger to re-charge the battery before the 2nd one went dead.

    If you had electricity to run a real battery charger, then you wouldn't need to run the backup pump in the first place.

    An automobile charging system is designed to maintain the charge of a battery, not recharge a dead one. Particularly with today's computer controlled charging systems, it would not be recommended. It would take too long to achieve a full charge anyway.
    Last edited by cacher_chick; 12-02-2011 at 04:22 PM.

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    General Engineering Contractor ballvalve's Avatar
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    You can use 10 batteries and a 49$ Schumaker charger on maintenance charge... just slower to bring up to full.

    Seems like a generator would be cheaper.

    Finally, go to wallymart and buy a MARINE battery, acid sealed or not. They take deep discharge, maybe 90$.

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    Jack of all trades DonL's Avatar
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    You can run Two Identical 12 Volt batteries in Parallel to get double the run-time. Different Types should be avoided.

    Two batteries would take Twice as long to recharge, After a power outage when power does get restored.


    Or, You could just buy a battery that is Twice as big.

    Like Ballvalve said a Deep Cycle Marine Battery would be ideal. Many are sealed.

    The original charger should work, It will just take 2 X the time to Top off the Larger Battery.
    Last edited by DonL; 12-04-2011 at 05:56 AM. Reason: Op Error
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    DIY Junior Member katchat6's Avatar
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    Thanks everyone for your feedback...I truly appreciate it...I think I need to consult someone local to come to the house...while I am comfortable with a single battery install...I'm not so much with the duo and with all of the varied feedback just on this thread...I want to make sure I get it right.

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    DIY scratch-pad engineer leejosepho's Avatar
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    You definitely want a deep-cycle battery, some of which happen to be called "marine", and I would suspect that is what the pump manufacturer sells with a bit of mark-up added. However, I personally stay away from so-called "no maintenance" batteries since there is really no such thing as a maintenance-free lead-acid battery. No matter what, a lead-acid battery is eventually going to need some water added or it will be ruined. And as to charging, you want a charger specifically intended for deep-cycle batteries and that will actually control (reduce) amperage output as it raises voltage to "condition" the battery at the end of the charging cycle.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

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    Master Plumber master plumber mark's Avatar
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    Red face get the jel battery

    the better jel battery from Zoeller will cost you about 300 bucks....

    it would be wiser just to use that one battery and forget trying to rig up
    a series of them....

    the Zoeller jel battery has a pumping life of 4 solid pumping hours....
    that is a long, long time comming on and off.... and unless you are in
    a disaster it will propably do fine till the power is back on ....
    this has been tornado tested here already..by a customer of mine....

    you could always just keep a spare trolling motor type marine battery
    around and keep it separately charged if you are worried about it
    I have seen some huge massive ones at sams club for about 130.00
    you will probably never , ever need this battery in any normal situation

    if you are in the east in the conniticiut area where that snow storm hit last
    month ... and you have been without power for a month...

    you would be better
    off to buy a decent honda generator as a back up plan...


  10. #10
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by master plumber mark View Post
    the better jel battery from Zoeller will cost you about 300 bucks....
    Ah. Those are truly "maintenance-free" and can even be mounted upside-down!
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

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