Batteries for UPS

Old 09-11-19, 07:10 AM
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Batteries for UPS

I want to add a battery with an inverter to power a sump pump in the case of emergency.

However I donít know anything about batteries other than some can explode and some need to be vented to the outdoors.

what are the safe no maintenance non exploding batteries called?
Old 09-11-19, 07:14 AM
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For your application a deep cycle battery is what you want. They are designed to be deep discharged and recharged many times.
They make them for marine or RV use.
You don't want a starting battery. They are designed for lots of cranking amps but not for deep discharging.

A most important part is a proper charger to keep it charged and not overcharge it.
Old 09-11-19, 07:47 AM
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Are you powering your main sump pump or an emergency pump?
What I've seen done and worked well for backup pumps is a boat bilge pump on deep cycle battery and a trickle charger.
If you are looking to run your main sump pump off this setup, you may be looking at a few $$ for an inverter that will support the draw of a pump alone with all the others.
Old 09-11-19, 10:17 AM
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I use AGM batteries for my UPS applications. They are sealed so there is no venting and they don't have the fire risk of lithium (which would be way too expensive for powering a sump pump anyhow). Make sure you do your math when sizing the inverter or UPS and batteries. Making 120 VAC from batteries takes a LOT of amperage and can quickly drain a battery.
Old 09-11-19, 10:49 AM
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You will have to be home to switch it over to your backup power unless you figure out some electrical switching. For what it would cost to have an "away" backup, you might look into a city water powered backup like a Zoeller
I've had one at my home and our condo for years.
Old 09-11-19, 11:36 AM
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I'd definitely look at a battery-backup pump that is installed a few inches higher than your normal pump. They are sold as a package so you don't have to worry about sizing and making sure everything works if you're building it yourself.

Something like this:
(Though I'm not recommending this one in particular)
Old 09-11-19, 09:08 PM
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Running pumps or any other motor loads off of UPS or inverter can be trouble some. You generally need much higher capacity inverter due to higher starting current. Most UPS cannot handle this current and will trip overload protection (unless you go for expensive server room grade ones). High output sine wave inverters can handle it, then you need separate charging and switch over circuit.

As others have said already, you are better off purchasing battery back-up pump than plugging your pump to UPS or inverter.

Battery back-up pump installs in addition to existing sump pump and most are 12V pump and runs directly off of 12V deep cycle battery. Much more efficient. Some plumbing work will be required.
Old 09-12-19, 05:14 AM
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So this would be a second pump, not my main pump. I already have it as a backup. Itís 3/4 hp so ~600w.

my house is semi below grade and when it pours, it comes in almost as fast as this little guy can pump it out, but storms rarely last that long at that intensity.

Also Iím not worried about power outages lasting more than 12hrs.

Is the math 600w/12v=50a therefor 100ah = 2hrs aprox? Iíd be happy with 1.5hrs of pump time.

when it comes to inverters, pure sine wave inverters are a lot more expensive than ďmodified sine waveĒ inverters. Can I use the cheaper modified ones?


Last edited by Esand1; 09-12-19 at 05:33 AM.
Old 09-12-19, 06:01 AM
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First, don't forget the conversion loss in the inverter. High quality ones may only loose 10% but a cheapie could loose 25%, converting it to waste heat. Then there is the increased inefficiency of your pump's motor so it will be consuming more power on a modified sine wave than it would on a pure sine wave.

I don't think anything with an AC motor is going to work at full power or efficiency (will consume more power) with a modified sine wave. It might cause overheating if run for a long period. Personally I would buy one of the battery backup sump pump kits where everything is designed and tested to work together instead of reinventing the wheel.

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