The inverters load on the battery is proportional to how much the LOAD is not the rating of the inverter. In fact, the steady state current draw is probably only about 5A. The problem is having headroom for starting the thing. You don't want to trip the protection on the inverter if you're intending this thing to be a backup.

I'm not clear how you intend to charge the battery or handle the switchover from the utility to the inverter.

Many thanks for the response.
My intentions are to monitor weather reports and if a storm is approaching to have the battery fully charged.

I will be storing the waterproof bin containg the battery and inverter inside the basement door. I only live a mile from where my elderly relatives live so should the power go out and rains are heavy I can be there in minutes.

I will place the waterproof container outside very near to the pump, then disconnect the pump's plug from the 110V out and plug it into the inverter.

I downloaded the specs on the pump and it only states 830 watts, does not indicate continuous or peak. and only shows 10 amps RUNNING. That 10 amps seems rather high to me for a 4/10HP motor. It may be Little Giant is making it appear the motor is more powerful then it actually is.

I looked at 12V bilge pumps to bypass the inverter but I don't think they would be powerful enough to pump the water up about 8 Ft into the yard. This also entails discoonecting the hose from the Little Giant pump and connecting it to the bilge pump.

It's not like this pump will be running for hours on end, it's just to make sure the water level in the staircase will not rise above 6" and seep into the doorway.

My biggest concern is the amperage only being 9.2 Amps on the smaller inverter as opposed to the 12.5 on the larger model.

You know, off the shelf battery powered sump pumps are readily available for just this purpose - they use a 12 volt pump and come with the charger, charge controller and battery box. You might want to Google "battery powered backup sump pumps" to get an idea of what's available..

Thanks for that suggestion but I've already researched that and don't think those pumps will do as an efficient of a job as the existing Little Giant pump. I neglected to mention the discharge hose travels up about 8 ft, then continues an additional 30 ft or so away from the house.

I think my best bet with the least amount of modifications will be to purchase the 12.5 Amp 1500 Watt inverter.
I will pay the price difference since I've spent more time researching this than I had planned. Perhaps when I'm as old as the folks I'm doing it for, somebody will be there to help me.

"Thanks for that suggestion but I've already researched that and don't think those pumps will do as an efficient of a job as the existing Little Giant pump."

Without inverter losses they will likely do better.

The boat industry uses plenty of 12 V pumps for bilge clearing.

If that inverter is a modified sine wave inverter, which is a stepped square-wave, it's going to introduce a DC component into the induction motor which will cause increased heat and current draw.

I would derate the inverter down to at least 80% as a starting point. I would then measure the AC current to the pump while under load using an inline volt/amp meter (as opposed to clamp-on) to see how much current the pump is actually drawing.

Thanks for the education on sine waves, more discouraging information.

Yes the inverter is a modiified sine so it seems like it will require more current draw. This project is becoming more and more difficult. I don't wish to purchase an inline voltage/amp meter to test since I'd never use it again.

I think I'll continue to search more for 12V bilge pumps and bypass this inverter all together.

I will continue to look for a 12V bilge pump that has a built in float switch, can pump up to an 8 ft wall, and are fully submersible.
Looking at some of the marine Rule pumps i can't see how the wiring is since they don't show a power chord., it must be completely water tight for my application.

I looked at the specs on the Little Giant Model 8-CIA (508157) and it's 45 gpm - without knowing the details, are you sure you need that capability to pump out a 4x4 area?

I use rain water catchment for agriculture purposes and one inch of rain over 1000 sq feet will provide about 600 gallons of water. 16 sq feet would provide around 10 gallons from one inch of rain. Obviously flooding is much different than rainfall but like I said - I don't know the details.

Here's a link to a battery powered backup sump pump at HD which should also show higher capacity pumps offered as well.

Here is a link that might be useful: Battery Powered Backup Sump Pump

@yosemitebill
The pump has been there for many years and has done an excellent job. Indeed it may be overkill for the area covered but why replace something if it works with newer that I'm sure is not as well made.

Thanks for the link to HD, that was kind of you, I've seen that already and was considering it but some of the reviews have me on the fence. Below is one reviewers experience:

"It did pump as a back up, but audible alarm will not silence even when turned off. If battery drains a little due to pumping, alarm will sound until battery is completely charged. Imagine a smoke alarm that will not shut off."

That's not encouraging, who wants to hear an alarm constantly blaring. That person may just got a defective unit but then I question quality control of the company.
It would be the most practical application and the price is about the same as the inverter.

I too am no spring chicken and my decision making ability is not as keen as in my younger days. The more I read, the more confused I become. I just don't want to make a mistake with other peoples property.

I'm not an engineer but it seems to me that any conversion from 12 VDC to 120 VAC (or visa versa) has some inherent inefficiency (waste). Now that can't be eliminated but in this case the inefficiency occurs at the worst possible moment - when the pump is needed. Plus the unknown factors of duration of the power outage and the condition of the battery. Might it not make more sense to use a 12 VDC pump and let the inefficiency occur during charging of the battery when 120 VAC power is essentially unlimited?

The drawback to any kind of battery system is that they require regular maintenance and the batteries require regular replacement even if they are not used. Given you said that power outages are relatively uncommon I might suggest you look at a water powered backup pump. Assuming the property has municipal water, the pump will run as long as water pressure is available. From what you describe, you may need to do some plumbing but it might be a feasible, low maintenance alternative.

@mike_kaiser
Thank you for your input and suggestion.
I've made up my mind and decided not to use a power inverter. Today I'll visit the local Marine store and look at 12V bilge pumps. The battery backup kit that Home Depot sells was not in their store and probably only sells online. I want to see it before purchasing and make sure the battery we have will fit in the case. I believe they sell their own batteries made for those kits, mine may be too big.

Is this sump you're pumping draining anything other than just the exterior stairway? Frankly, if not, it would seem to me that fixing the stariway draining so that it doesn't need to be PUMPED would make more sense than throwing lots of money into battery backup systems.

You do know they make already packaged standby battery sump pumps that are already packaged to operate either in replacement or in parallel with the existing pump. There's a couple at HomeDepot for $250 and $500 depending on how much capacity you need.

@ronnatalie
"Is this sump you're pumping draining anything other than just the exterior stairway? Frankly, if not, it would seem to me that fixing the stairway draining so that it doesn't need to be PUMPED would make more sense than throwing lots of money into battery backup systems."

Yes it's only draining the staircase. I went to the house this morning and inspected again. What you say makes sense and that is the route I'm going to go.

I saw an Emergency battery backup system in Lowes (Watchdog) and was not impressed. Reviews also say they are unreliable and the battery trickle charger that comes with them are terrible.

Then I went to the Marine store and looked at Rule Bilge Pumps with built in float switches, reviewers said they too were bad since they use a diaphragm switch and sometimes never shut off. If I use a manual switch I would have to epoxy it to an aluminum plate and lay it on the concrete foundation so it doesn't float around. Not practical since I would have to move all these components into the stairwell if the electricity fails.

I want to thank everyone with their suggestions and close the thread since I have formed a plan.

If you're going to have to go over there & manually get this thing going, which I think is a bad way to attack it, why not just buy a small generator? At least it would be potentially useful for more than the task you have at hand & wouldn't require shelling out a couple hundred dollars every few years for a battery.

"wouldn't require shelling out a couple hundred dollars every few years for a battery."

Instead you get to pay for fuel that goes stale sitting around , and maintenance on the generator.

Even with stabilizer added gasoline does not last forever.

That's why the gas I store for my generator gets dumped in my car's tank every 4 months. Not a big deal.

"That's why the gas I store for my generator gets dumped in my car's tank every 4 months. Not a big deal."

Just one more thing to remember to do.

Make sure your tank is almost full or your car's performance may not be as expected.

Daveho wrote
"If you're going to have to go over there & manually get this thing going, which I think is a bad way to attack it, why not just buy a small generator? At least it would be potentially useful for more than the task you have at hand & wouldn't require shelling out a couple hundred dollars every few years for a battery."

Having a generator would require me to go over and get the generator running since the elders don't have the strength to start it. They are also not capable of refueling it so that would mean several trips to them to monitor the situation, not very practical for me.

BTW my battery for my ride on lawn mower is going into it's 6th season and still remains strong.

"BTW my battery for my ride on lawn mower is going into it's 6th season and still remains strong."

Discharge rate, depth, battery technology, etc. have a large affect on battery life.

For a standby use on a sump pump a deep cycle battery with a float charger would probably last a long time.

Do not use the cheapest charger available.
They inevitably seem to overcharge.

This post was edited by brickeyee on Fri, Apr 5, 13 at 17:24

why don't you look at something like this?

http://www.tripplite.com/en/products/model.cfm?txtSeriesID=821&txtModelID=3603

I have a larger version for my set up(2 pumps, a primary and a backup) that works flawlessly.

I still believe this problem would be greatly simplified by choosing a 12 V pump.

No inverter required, just a battery, float charger, and a pump.

You should also measure the starting load of any AC pump with a peak reading clamp on ammeter.

They can be surprisingly high when they try to spin up with the pump cavity filed with water.
Most of the 'peak capacity' numbers on the inverters are pure bovine scatology.

Just like Sears 'peak developed horsepower'.
Fantasy numbers that cannot actually be achieved.

They are based on the stall current of the equipment, a damaging place to be except during normal start-up.

ETA:

The small DC motors using newer permanent magnets are VERY efficient.
They often get away with putting the permanent magnet on the rotor, and then creating a rotating magnetic field to pull it around.

This post was edited by brickeyee on Thu, May 30, 13 at 16:46

Here is another way of looking at the same thing. Lead-acid batteries provide huge surge power capacity compared to their energy storage. They can puke it out very quickly It is a mistake to put an inverter in their the way if you can avoid it. You have to provide a very large inverter to get the surge capacity to start the motors or you will strangle the batteries.

Inverter efficiency is measured wrt power output and given at full power. Any inverter is much more efficient at full power than at partial power output. That means that to start your motor you need a big inverter that will be "wasting" a lot of power while it only needs to run the motor.

" Lead-acid batteries provide huge surge power capacity compared to their energy storage."

That depends on the batteries design.

Large plate area and low plate clearance reduces source impedance, but penalizes total A-hour capacity.

Deep cycle batteries typicality have a larger plate clearance to allow for more capacity (A-hours) at a lower discharge rate.

Even deep-cycle lead-acid batteries have huge power delivery rates compared to a gensets, inverters and to the other battery types familiar to the average person. NiCads have a low internal resistance as well, but you don't see them much anymore.

"NiCads have a low internal resistance as well, but you don't see them much anymore."

The cadmium content is an environmental problem.

Lithium ion batteries in a number of technologies have similar high power outputs (but can actually explode or catch on fire at short circuit discharge rates).
About the same as nickel-cadmium used to do.

It is all about battery design, even with a particular type and technology.

Lead acid gel cells used for alarm systems are designed for very long life at relatively low power draws.

This post was edited by brickeyee on Sun, Jun 2, 13 at 8:37