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windowguy 10-02-2011 06:04 PM

Not your normal sump pump question..(electrical)
I'm sure you're tired of sump pump questions, this one is more intriguing. Hurricane Irene caused the water tables to be so high that my sump runs for about a week following the storm. (not continuously, cycling about every 2 minutes). My existing sump works excellent and basement stayed bone dry. IF HOWEVER power had gone out i probably would have had 6 feet of water in the basement. I OWN A GASOLINE POWERED 2000 Watt GENERATOR. If power goes out i would fire up the generator for the sump.

But what if power was out for several days, as it was in NJ after Irene? I don't think i could run my coleman generator for 4 days straight (how much gasoline would that take?!) I would like to buy a second sump pump as a precaution. BUT THIS PUMP HOWEVER I WISH TO RUN OFF A BATTERY.

I've read ad nauseum about the "watchdog" systems and i'm not impressed. Frankly, i don't want a system that needs to be plugged in, and maintained constantly (and are prone to fail). What i would really like is just to construct a battery backup sump that i will "keep in a box" tucked away until i know a violent storm is coming. What i would like is a system where i would drop the 2nd sump in the hole, and then run it off a battery when i need it, and then i could recharge the battery while my generator is running. This way in a case of an extended power outage i could switch between the generator and the battery powered sump.

So here is where i need ideas. Can i just buy a 110 volt powered sump and use a "12 volt to 110 volt converter" to run the pump? DO THEY PUT OUT ENOUGH AMPERAGE? My plan would be to just buy a 12 volt car battery before the next hurrican comes (more practical than keeping a Watchdog in the basement that may never ever be needed). Second question, what would be the best way to recharge the 12 volt from my generator?

So summary: Need battery system that will power a 110 volt sump pump when i take it out of the box very rarely, but also need to be able to recharge the battery after it draws down.


CuHead 10-02-2011 06:16 PM

you can buy 12v powered sump pumps, no need for inverter. the cost of an inverter + batteries to run the 120v pump will probably exceed the cost of a 12v pump. plus you will get longer run time on the 12v.
also you mentioned that your sump cycles every two minutes, you may want to check and adjust your float, let the pit get a little fuller before it turns on, rapid cycling like that will quickly kill the pump motor.

Wildie 10-02-2011 06:34 PM

I have a Coleman 1800 and it provides both 120 volts and 12 volts.

It runs from gasoline, but I'm considering converting it to natural gas. I have found a site on the net that sells these kits.

The problem with gasoline is that the provided tanks are limited in size and must be topped up often.

As for a battery operated one, you would need a bank of many batteries to provide power for an extended time. The capacity that would be required can be calculated but there isn't enough space here to go into that.

I would suggest natural gas as a first option. Failing that, how about propane. You would need a tank that is similar to one that would be used for cooking and heating a house.

Ron6519 10-02-2011 08:03 PM

Standby generator powered by propane or natural gas.

Jackofall1 10-02-2011 08:19 PM

Regardless of what battery you buy, you will have to keep it charged, a standard automotive battery will not work as well a deep cycle battery. Either will need as you put it constant maintenance to be ready in the event. If you leave a battery laying around it will be of no use when the time comes to need it.

I am sure there are plenty of 12V pumps out there, my first guess would be a marina, boat bilge pumps come in various sizes.

A invertor 12v to 120v is possible, but you would have to know the amperage add at least 25% and then calculate wattage. They make these in a multitude of sizes as well, but as all things, the bigger they get the more they cost.


joed 10-02-2011 08:23 PM

Problem with a battery is it goes dead. It would not run for four days either. They are good for short power outages of a few hours. More batteries would extend the length of run time. The generator is best option for extended outages.

Gary in WA 10-02-2011 08:47 PM

Please limit your identical question to one forum, thank you.


AllanJ 10-02-2011 08:49 PM


Originally Posted by CuHead (Post 740642)
also you mentioned that your sump cycles every two minutes, you may want to check and adjust your float, let the pit get a little fuller before it turns on, rapid cycling like that will quickly kill the pump motor.

Letting the pit get too full can cause the perimeter drain system to resaturate which can then cause flooding at the far sides of the basement even if the pit itself is not about to overflow. Generally the ends of the drain pipes as seen in the pit should not be more than half submerged when the pump comes on.

If you can't shorten the pump cycle without letting the level in the pit get too high, then the real solution is to dig a larger or deeper (or both) pit. My own suggestion for pit size is at least 20 gallons (about 3 cubic feet) of room in the pit not occupied by crushed rock and gravel and below the lower edge of the drain pipes emptying into the pit.

itguy08 10-03-2011 09:10 AM

We went through a similar thing here in central PA with the storms. Lost power for 1.5 days during the first hurricane and 4 hours during the second. We do have a generator, a 5500W Harbor Freight unit.

During Irene we lost power from 1-4:30am and ran the generator that whole time running 3-4 sump pumps to keep the water below 6 inches in our basement. So I'm all too familiar with keeping pumps running to help keep the basement dry.

I'd say skip the batteries as working in IT batteries need constant care and feeding to make sure they work when needed. We're talking about at least monthly exercising and replacement every year or 2. Not something you want to deal with. You'll need TONS of batteries to keep this running for a couple days straight.

We plan to keep our generator running as long as needed. Prior to a planned emergency, I plan to ensure the generator is filled, the gas cans are filled, and the cars are filled. I have 2 5 gallon gas cans in the shed filled with stabilized gas, the generator is usually filled with stabilized gas and we have tons of gas stations nearby. The generator will run 8-11 hours at 1/2 load on a 6 gallon tank of gas. We'd just fill with the cans and run to the gas stations as needed. We've got tons of stations within a 30 mile radius. We also have 2 cars with tons of capacity (16 and 19 gallons) we can siphon off of if needed.

I figure we could go as long as needed with the generator running the pumps and other necessary items. Yes, it would get expensive but cheaper than a flooded basement or spoiled food.

windowguy 10-03-2011 11:45 AM

Thanks for all the other options, but my question really is about the battery.. electrical. I will not be buying a 12 volt sump, i'm buying a 110 sump, but i want the OPTION of running off battery.

How do inverters work? Can one 12 amp marine battery power a sump pump for several hours? How do i recharge the battery after it runs out? The idea is for me to be able to switch back and forth between generator power and battery power (for as long as i need).

also, i do not plan on having this system "live" all the time. Irene was a 100 year flood, and perhaps i will never need the battery system at all. So i don't want to keep the battery charged all the time. I would simply buy the battery next time the 100 year flood is coming.

itguy08 10-03-2011 12:04 PM

I looked into that too instead of buying a generator.... Not feasible.

We have a 1/3 hp sump pump which uses around 800 watts at 120v to run. Startup could use about 1,600 or more watts. So you would need at least a 2,000 watt inverter. Those are quite pricey. Then you will need a couple batteries as even a deep cycle battery only has 200 or so amps available.

What you will be using (approximate):

800w @ 120v = 6.6a This translates to 12v requirements of about 66a per hour.

With 1 deep cycle battery you may get 2.5 hours use. Then you have to recharge it for about 4-5 hours as lead acid (what deep cycle batteries are) doesn't like fast recharges.

IOW: Your best bet is to fire up the generator and run that for how ever long it takes. You'd need a bank of batteries and a charger, and have to run your generator for long periods of time to run the pumps and recharge the battery bank. Then you have to maintain those batteries so that they are ready when you need them. Forget to maintain them and they may not work or will not give you full power when you need them most.

I gave some serious thoughts to a battery + inverter setup and after looking at all the costs it was cheaper and more effective to just buy a generator and keep it fed with gas and oil. Run the genny once a month for 20 minutes or so with a load to keep things working and you will be all set.

Ron6519 10-03-2011 12:05 PM

Gasoline generators for the long term are a pain in the rear end. We lost power from Irene for 5 days. Filling up the generator on a daily basis was cumbersome. I shut it off at night. The constant drone of the engine was bad enough during the day. We didn't have the water issue, so off at night was an option.
We were lucky gas stations had power and could still pump. Large scale outages would limit the long term use of this generator.
Which is why I'm researching standby generators. They're a little quieter and basically run by themselves. Turn on and off automatically, while supplying power to the necessary circuits. You don't even have to be home.
I can pick up a 10kw unit to operate 10 circuits for about $2500. If you need to have it installed, add another $1500. Well worth the price.

slickwilliam 10-03-2011 12:06 PM

Couple of things to consider:

For any inverter (and neglecting inverter efficiency losses), power out requires power in. So an output of 2a for a 120v pump will require an input of 20a at 12v from the battery. And you'll run down a single battery fairly quickly with a steady-state 20a load. You can check the battery's amp-hour rate to determine how long it will last, then subtract a fair bit since the inverter will almost certainly stop working before the battery gets too low.

To recharge the battery, you're gonna have to crank up the generator and run it for a good long time (several hours) since batteries don't recharge nearly as fast as one can discharge them.

Frankly, what you're wanting to do within the constraints you give appears a bit impractical.

EDIT: Oops! Talk about responses all coming in at the same time!...

itguy08 10-03-2011 01:17 PM

While everyone's needs are different - there is a lot that needs to go into thoughts for generators. Standby units are great - can power the whole house and are quieter. However, from what I gathered reading on the Net they can be quite expensive to run. They use a lot of natural gas or propane.

For the few times we use it, I'll deal with the engine noise - close some windows and it sounds almost like a lawnmower. Offer to let the neighbors plug in and they won't care about noise either. :)

It's definitely something that everyone needs to take into account their own situation and how they plan to "live" without power.

I know for us during both storms a generator saved our butt. First one it saved our fridge and freezer and sanity (had Internet). For the second it saved our basement.

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