WARNING: Potentially lethal voltages exist within an inverter/charger as long as the battery supply and/or AC input are connected. Please consult the manuals that came with your inverter/charger and batteries for important safety information.
1. Battery Backup System Overview
- The basic setup
- Inverter/chargers vs. UPS systems
- Eaton's inverter/charger families: UT vs APS
- What kind of batteries will I need?
- How many batteries will I need?
- Other things you will need:
The basic setup
A battery backup system for a sump pump consists of two main components: an inverter/charger and one or more batteries. The inverter is responsible for converting the power stored in the batteries into a form that can be used by your sump pump. It is also responsible for keeping the batteries fully charged at all times. You plug the inverter/charger into your wall outlet and then plug your sump pump into the inverter/charger, like this:
Note the red arrows showing the flow of electricity. During normal operation, the inverter/charger just passes the electricity coming from your wall outlet straight through to the sump pump as though the sump pump was plugged directly into the outlet. While it is doing that, it will also automatically charge the batteries and keep them fully charged as long as it continues to receive power from the wall outlet.
When your power goes out, the system will automatically send power from the batteries to the sump pump, like this:
Inverter/chargers vs. UPS systems
The inverter/charger is the heart of the system, and is responsible for three jobs:
- Charging the batteries and keeping them fully charged at all times
- Sensing when the power has gone out and automatically switching to battery power
- Converting the power stored in your batteries from "direct current" (DC) into "alternating current" (AC), which runs your sump pump
This description of an inverter/charger sounds an awful lot like the description of an uninterruptible power supply (UPS), which might lead you to wonder, "Why can't I just install a UPS and be done with it?" Well, it basically boils down to the fact that a UPS is just not designed to do the job.
Although inverter/chargers and UPS systems work in very similar ways and perform similar functions, the battery in a UPS is not large enough to run a sump pump for any significant length of time. Most UPS systems are not designed to provide enough power to start a sump pump. In addition, UPS systems have very small battery chargers.
An inverter/charger also allows you much more flexibility to decide how much power you need. You can think of it like buying stereo equipment: you can buy the "all in one" model, which is inexpensive and easy to assemble but offers less powerful sound (the UPS), or you can buy individual modular components, which gives you increased flexibility and more powerful sound (the inverter/charger). And if your needs change in the future, you can expand the system without having to start over again.
Eaton's inverter/charger families: UT vs APS
We recommend that you select one of the inverter/chargers from our "UT" family in this situation because they have GFCI outlets. The inverter/chargers in the APS line do not have GFCI outlets. GFCI outlets protect against the possibility of shock near a water source.
What kind of batteries will I need?
An inverter/charger doesn't do anything unless you hook it up to a battery, which is sold separately. These aren't the kind of batteries you put in a flashlight. Instead, we're talking about 12-volt deep-cycle lead-acid batteries similar to the battery in your car. "Deep-cycle" means that they can be almost completely discharged without losing their ability to produce their specified output. And, although they are similar to the battery in your car, the batteries that you use with an inverter/charger are not the same. Instead, they are the kind of batteries that you might use in a golf cart, boat or RV.
All deep-cycle batteries are rechargeable, so it's not like buying AA batteries where you have to choose between disposable and rechargeable. The main decision you have to make is whether to get sealed or unsealed. Sealed batteries are often called "maintenance free" because you don't have to periodically top them off with distilled water, which makes life much easier.
How many batteries will I need?
The more batteries you connect to your inverter/charger, the longer you can keep your sump pump running. This is one of the advantages of the modular nature of an inverter/charger versus a UPS system because you get to decide how big the system needs to be and how much money you want to spend. Theoretically, you can connect an unlimited number of batteries and get an unlimited runtime, but there are practical limitations including cost, space, weight and charger size, so you will likely end up with just a few batteries. You can get by with just one battery if you really need to, but chances are good that you are probably going to want at least two.
You also have the option of using 6V batteries instead of 12V batteries, but you are going to have to connect them properly. For instance, four 6V batteries can provide the same amount of power as two 12V batteries if they are connected correctly. The key thing to understand is that you must provide a total of 12V to the inverter/charger regardless of the voltage of your batteries, so it will be easier if you just use 12V batteries.
Please refer to the Planning for Your Battery Backup System section for more specific instructions about how to calculate the number of batteries you will need.
Other things you will need:
Fuse and fuse holder
You must install a fuse between the batteries and the inverter/charger. This is an important safety feature, and it's not optional. Please note that the fuse and fuse holder are not included with either the inverter/charger or the battery; they are separate items that you must purchase on your own.
We recommend a 200-amp DC fuse, which is not a normal fuse like you might have in the fuse box in your home, as it's much bigger and intended for DC instead of AC current. One of the easiest types of fuses to use in this situation is an "ANL" fuse that can be spliced into the positive wire coming from your battery pack. ANL fuses are often used in high-end car stereo installations and you can buy them from places that sell high-end car audio equipment, like Best Buy and other electronics stores.
You will also need to buy a fuse holder, which is the part that actually connects the fuse to the wire coming from the battery. Many vendors offer combo packs that include both a fuse and a fuse holder, but you can also buy them separately. Either way, make sure that you get both the fuse and a fuse holder because neither one will do you any good without the other.
Although it's not absolutely required, it is a good idea to get some sort of enclosure for your batteries in order to keep them clean and prevent accidental short circuiting. Eaton makes a two-battery enclosure that is perfect for this job, model number BP-260. The BP-260 also comes with all of the cables you need to connect the batteries to each other and to the inverter/charger. If you don't purchase the BP-260 battery enclosure, you may need to provide the cables on your own.
Heavy-duty storage rack
When fully assembled, your new battery backup system is going to be fairly large, and awfully heavy, so it's a good idea to get some sort of rack or shelving unit to put everything on that will keep it away from the floor and any water that might wind up there.
2. Planning Your Battery Backup System
There are several decisions you have to make while designing and planning your new system:
- Select an inverter/charger
- How long do I want my sump pump to run?
- Calculate how many batteries you need
- Select a battery enclosure
- Select a fuse and fuse holder
- Other considerations
Select an inverter/charger
The first thing you need to do is pick an inverter/charger based on the wattage of your sump pump.
Determine total watts required
6 amps x 120 volts = 720 watts
Adjust for maximum efficiency
720 watts ÷ 0.90 = 800 watts
Adjust to compensate for higher starting current
720 watts x 3 = 2160 watts
Now that you have the peak wattage, you can pick an appropriate Eaton inverter/charger. Choose an inverter/charger that supports the start-up current (peak wattage) of your sump pump.
How long do I want my sump pump to run?
It's important to understand that "power," in this case, is defined in terms of "amp-hours," which can be calculated as follows:
Determine the amount of battery power required
720 watts ÷ 12 DC volts = 60 DC amps (This is the DC amp-hours required to run the system for one hour)
Determine your required runtime
Next, determine how long your pump runs when it's activated, and how long it rests between activations during a heavy storm. This doesn't have to be exact, but the closer you are to reality, the better your estimate. Everyone's situation is different, so it may be worthwhile to observe your sump pump during a storm. Record the total time you observe the pump and how long it actively pumps during that time. When you have those numbers, plug them into the formula below, along with the desired total runtime in hours, to estimate the active runtime requirement.
Active runtime required = minutes of pumping ÷ minutes of observation x total runtime in hours
Assuming that the sump pump runs for 5 minutes during 10 minutes of observation.
5 min. pumping ÷ 10 min. observation x 4 hours total runtime = 2 hours active runtime.
Note: If observing the sump pump during a storm is not possible, assume that it runs constantly (10 minutes on during 10 minutes total observation). This may give you more runtime than you need, but that's better than having too little.
Estimate battery amp-hours required
60 DC amps x 2 hours = 120 amp-hours
Adjust for inefficiency
120 amp-hours x 1.2 = 144 amp-hours
You can get a general idea of how long it will take your inverter to recharge your batteries after a storm. To estimate the minimum amount of time you need to recharge your batteries given your application, divide your required battery amp-hours (from step 7, above) by your Inverter's rated charging amps.
144 amp-hours ÷ 40 amps inverter charge rating (UT1250UL) = 3.6 hours recharge
Calculate how many batteries you need
When you calculated the battery amp-hours required (steps 5-7), the final number was the total number of amp-hours that you need to get the coverage you want. Most batteries are rated for a certain number of amp-hours. If the battery you choose supplies fewer amp-hours than the total required, you'll need more than one. The combined amp-hours of the batteries should be greater than the total amp-hours you need.
Eaton sells a 12V DC sealed maintenance-free battery (model 98-121) that is good for 82 amp-hours. In the previous example, we would need two batteries to supply the 144 amp-hours we calculated.
Select a battery enclosure
Although it's not absolutely required, it's a good idea to get some sort of enclosure for the batteries to keep them safely tucked out of the way and prevent accidental short circuiting, especially considering that the system is going to be operating near water.
Eaton sells a metal battery enclosure (model BP-260) that is specifically designed to hold two model 98-121 batteries. It also includes all of the necessary cables that you will need to connect your system components, which is convenient.
Select a fuse and fuse holder
You are required to install a 200-amp DC fuse between the batteries and your inverter/charger. This is an important safety feature, and it is not optional. The fuse and fuse holder are not included with either the inverter/charger or the battery pack, so you will have to purchase them separately. The best type of fuse to use for this is an "ANL" fuse in an appropriate fuse holder that can be spliced directly into the positive wire between the batteries and the inverter/charger.
The Kicker ANL Fuse 2-Pack (model #09ANL200/AFS200) with the Kicker AFS/ANL Fuse Holder (model #09FHA/FHS) works well, although there are many other brands and models available that are just as good. Some manufacturers sell combo packs that include both the fuse and the fuse holder, but it's important to check and make sure that you are getting both parts.
Think carefully about exactly where you are going to install your system and how much space it is going to take up because it is likely to be larger than you were expecting. It's also going to be very heavy (the batteries alone weigh 50 lb. each), so it will be hard to move after you are done.
The battery enclosure is the largest component. Its dimensions are 10.5" high x 10.5" wide x 17.75" deep, so it's roughly the size of a medium-sized microwave. The inverter/charger is almost a perfect cube with each side measuring about 12".
It's a good idea to get some sort of shelf or rack to keep the batteries and inverter/charger off the floor, especially considering that they're going to be near water. Three-shelf wire "bread rack" models sold at most home improvement stores work well. They stand about 30" tall and can support up to 250 lbs. on each shelf, so the weight of the system components is no problem. Putting the battery enclosure on the middle shelf and the inverter/charger on the top shelf keeps everything off the floor and away from the water.
3. Installing the Battery Backup System
- Component List
- Tools and materials needed
- Step 1: Set up shelves and double-check placement
- Step 2: Prepare lead cables
- Step 3: Install the batteries in the battery enclosure
- Step 4: Connect the negative terminals of the two batteries
- Step 5: Connect the positive terminals of the two batteries
- Step 6: Close up the battery enclosure
- Step 7: Attach the leads to the inverter/charger
- Step 8: Connect the battery temperature sensing cable
- Step 9: Configure the inverter/charger
- Step 10: Connect the inverter/charger to utility power and the sump pump
- Step 11: Testing the system
- Step 12: Battery maintenance
This is a list of all of the components needed for a typical installation. Your installation may be different.
|Inverter/charger||Eaton||Eaton||UT750UL||PowerVerter® 750W Utility/Work Truck Inverter/Charger with 2 Outlets||1|
|Battery enclosure||Eaton||Eaton||BP-260||Ideal battery housing for use with Eaton PowerVerter APS inverter/charger systems with a 12 or 24V DC system voltage||1|
|Batteries||CD Technologies||Eaton||98-121||12V DC Sealed, Maintenance-Free Battery for All Inverter/Chargers that Accept 12V DC Battery Connections||2|
|Fuse||Kicker||Best Buy||09ANL200/AFS200||Kicker 200-amp ANL Fuse (2-Pack)||1|
|Fuse holder||Kicker||Best Buy||09FHA/FHS||Kicker AFS/ANL Fuse Holder||1|
|Shelving unit||Perfect Home||Home Depot||31424PS-YOW||Perfect Home 350 Series 3-Shelf 24 in. W x 30 in. H x 14 in. D Steel Commercial Shelving Unit||1|
Tools and materials needed
The list below includes all of the tools and materials that you will need to complete this job.
- Socket wrench
- Phillips head screwdriver
- Flat head screwdriver
- Wire/cable cutters (ideally heavy duty, able to cut at least 1/0 cable)
- Electrical tape
- Utility knife (for stripping the cables)
- Allen wrench
Optional (but very handy):
- Rubber mallet (for assembling the shelving)
- Plastic zip ties (for keeping everything neat and orderly)
- Ballpoint pen or awl for setting dip switches
The schematic below shows how all of the components will be connected when we're done. This is just a conceptual drawing that shows the logical connections between the components. It does not represent the physical setup of the system, and it is not to scale.
Step 1: Set up shelves and double-check placement
- Assemble your shelving unit and make sure it fits in the space next to your sump pump. The assembled system is going to be very hard to move, so make sure that you will not have to move it after everything has been set up.
- Make sure the battery enclosure and the inverter/charger fit on the shelves of your shelving unit.
Step 2: Prepare lead cables
Step 3: Install the batteries in the battery enclosure
- Remove the cover from the battery enclosure and remove the cables and wires that came with it.
- Remove the top shelf from your shelving unit and put the empty enclosure, with the top removed, on the middle shelf.
- Place one battery in the battery enclosure making sure that the positive ("+") and negative ("-") terminals on the battery line up with the holes on the end of the enclosure marked "+" and "-".
- Attach the temperature sensing cable near the negative battery post with a small amount of cyanoacrylate adhesive (Superglue).
- Snake the other end of the temperature sensing cable out of one of the holes in the end of the battery enclosure, then place the second battery in the enclosure next to the first.
- When you are done, the system should look like this:
Step 4: Connect the negative terminals of the two batteries
- Connect the short black cable that came with the battery enclosure to the negative ("-") terminal of the battery furthest away from the openings in the battery enclosure (put the ring terminal down first, followed by the flat washer, then the lock washer, and finally the bolt).
- Thread the long black cable through the opening on the end of the battery enclosure marked "-" with the ring terminal inside the battery enclosure and the stripped end outside the enclosure.
- Connect the free end of the short black cable along with the black lead cable that you just threaded through the hole to the negative terminal of the other battery. Again, put the ring terminals down first, then the flat washer, followed by the lock washer, and finally the bolt.
- It is very important that you avoid connecting the negative terminal of one battery to the positive terminal of the other, so be careful!
- When you are done, the system should look like this:
Step 5: Connect the positive terminals of the two batteries
- Connect the short red cable that came with the battery enclosure to the positive ("+") terminal of the battery furthest away from the openings in the battery enclosure (put the ring terminal down first, followed by the flat washer, then the lock washer, and finally the bolt).
- Thread the long red cable through the opening on the end of the battery enclosure marked "+" with the ring terminal inside the battery enclosure and the fuse outside the enclosure.
- Connect the free end of the short red cable along with the red lead cable that you just threaded through the hole to the positive terminal of the other battery. Again, put the ring terminals down first, then the flat washer, followed by the lock washer, and finally the bolt.
- It is very important that you avoid connecting the positive terminal of one battery to the negative terminal of the other, so be careful!
- When you are done, the system should look like this:
Step 6: Close up the battery enclosure
- Double check your connections and then put the red plastic terminal covers that came with the battery enclosure over the positive battery terminals. You may need to cut additional openings in the terminal cover using your utility knife in order to get them to fit snugly. If you do not have terminal covers, use heat shrink tubing over each battery terminal.
- Put the cover back on the battery enclosure and secure it with the screws you took out when you removed it.
- Put the top shelf on your shelving unit, and place the inverter/charger on it.
Step 7: Attach the leads to the inverter/charger
- Remove the electrical tape from the stripped end of the black lead and connect it to the negative ("-") terminal on the inverter/charger, then connect the stripped end of the red lead to the inverter/charger's positive ("+") terminal.
- It is very important that the black cable is connected to the negative ("-") terminal and the red cable is connected to the positive ("+") terminal, so be careful!
- You may see some sparks when you touch the red lead to the terminal on the inverter/charger. This is normal because you are completing the circuit between the batteries and the inverter/charger, but it can be surprising if you are not expecting it.
- When you are done, the system should look like this:
Step 8: Connect the battery temperature sensing cable
- Connect the battery temperature sensing cable to the jack on the back of the inverter/charger labeled "Remote Temp. Sense." Ideally, the temperature sensor should be as close to a negative terminal as possible.
- When you are done, the system should look like this:
Step 9: Configure the inverter/charger
There are some dip switches on the front panel of the inverter/charger that control important settings that affect the way it works. You should refer to the owner's manual that came with your inverter/charger for more information about exactly which settings to select.
Step 10: Connect the inverter/charger to utility power and the sump pump
- Plug the inverter/charger into your wall outlet (note that you may hear a slight humming coming from the unit as the batteries start charging; this humming will stop once the batteries are fully charged).
- Plug the sump pump into your inverter/charger.
Step 11: Testing the system
It's important that you test your system to make sure it's operating correctly. The most thorough way to test the system is to use a hose or a bucket to fill your sump well with water until the sump pump activates. Do this once with the inverter/charger plugged into utility power and then again with the inverter/charger disconnected from utility power, which will force the sump pump to run off of the batteries. If the sump pump operates normally in both situations, you have successfully installed your battery backup system!
Step 12: Battery maintenance
Batteries must be maintained and tested to ensure optimal performance. The average battery life is 5 years; batteries should be tested on an annual basis, before they are needed.