Posted: 2/17/2012 7:05:07 AM EDT
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Last summer we lost power over night and the basement flooded to the tune of 5" of water causing a lot of damage.
I decided to make a battery back up that I could plug the pump into and prevent a repeat. I finished it last night took it over to the pump and plugged it into the inverter. After a few minutes the pump float switch activated the pump and I watched to see what happened. The pump called for power, the inverter started the power and then within a second, tripped off. I waited it for a few cycles and the same happened. A bit info, 1/2 HP Flow-tec submersible pump drawing 5.5 to 6 amps (Per flow-tec web site) 1000 Watt Black and Decker inverter 115 amp hour Marine Deep Cycle battery Doing the math the pump should be drawing under 700 watts so what am I missing? Thanks for any help. |
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Although it may be drawing 700 watts after it's running, the starting surge could be a lot more than that.
Also, that 700 watt rating assumes the pump is being operated with sine wave power - and the B&D inverter doesn't produce anything that even remotely looks like a sine wave. There's no telling how much power it's actually drawing from the inverter. More Bad News: Even if the inverter could start and run the pump, a single 115 AH battery won't supply 700 watts for very long. 
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Last summer we lost power over night and the basement flooded to the tune of 5" of water causing a lot of damage. I decided to make a battery back up that I could plug the pump into and prevent a repeat. I finished it last night took it over to the pump and plugged it into the inverter. After a few minutes the pump float switch activated the pump and I watched to see what happened. The pump called for power, the inverter started the power and then within a second, tripped off. I waited it for a few cycles and the same happened. A bit info, 1/2 HP Flow-tec submersible pump drawing 5.5 to 6 amps (Per flow-tec web site) 1000 Watt Black and Decker inverter 115 amp hour Marine Deep Cycle battery Doing the math the pump should be drawing under 700 watts so what am I missing? Thanks for any help. Insufficient battery power 700 watts from a 12 volt battery is 58 AMPS. You want 4 or 5 times the battery capacity to run a 1/2 horse pump @ 12 volts. shoot for at least 400 Amp-Hours, a thousand would be better, allowing you to run some lights, etc. |
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I lived like that for years, I finally used a 12v bilge pump with elaborate anti airlock and screening to keep it working unattended. the pumps last about a year, if you don't replace it regular you will come home to a flooded basement. battery+auto charger. My Mother has a finished basement, along with French drains and a sump pump to keep the basement dry. A few power outages ago I couldn't get there in time to get her running on backup power, so her basement flooded and caused thousands of dollars worth of damage 
Long story short, after looking for ways to power her sump pump with a backup battery/inverter I decided that adding a second (12v) backup pump made a lot more sense. I bought a Rule brand bilge pump with a float switch at the local marine supply store, and configured the switch to kick on only after the water level rises past her regular 110v A/C sump pump. A battery tender keeps her two 55Ah AGM batteries topped off, so for her everything is completely automatic-she doesn't have to do a thing  The Rule bilge pump works well for it's intended purpose, which is essentially to buy me enough time to get over there to get her generator started and plugged into the transfer switch.
Since she is unable to run the generator herself, one of my goals this year is to upgrade her genset to an electric start model with remote start and automatic transfer switch. I already have the new panel and switch-now I just need to pick out a genset and find the time to get it installed for her. The only other obstacle is convincing her that I didn't spend money out of my own pocket for the equipment. She doesn't like it when I spend money on her-even though she busted her ass to make ends meet when I was growing up. That's a whole different thread topic though 
Good luck OP! If you decide to go with a 12v pump I will happily look up the model I got, along with the check valve and other parts needed to plumb it into the existing drain. Posted Via AR15.Com Mobile |
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Last summer we lost power over night and the basement flooded to the tune of 5" of water causing a lot of damage. I decided to make a battery back up that I could plug the pump into and prevent a repeat. I finished it last night took it over to the pump and plugged it into the inverter. After a few minutes the pump float switch activated the pump and I watched to see what happened. The pump called for power, the inverter started the power and then within a second, tripped off. I waited it for a few cycles and the same happened. A bit info, 1/2 HP Flow-tec submersible pump drawing 5.5 to 6 amps (Per flow-tec web site) 1000 Watt Black and Decker inverter 115 amp hour Marine Deep Cycle battery Doing the math the pump should be drawing under 700 watts so what am I missing? Thanks for any help. Insufficient battery power 700 watts from a 12 volt battery is 58 AMPS. You want 4 or 5 times the battery capacity to run a 1/2 horse pump @ 12 volts. shoot for at least 400 Amp-Hours, a thousand would be better, allowing you to run some lights, etc. Fullpower wins the prize! Exactly. Run a quick test by paralleling [for the test] another battery [from your vehicle] with the first and see it the inverter can handle the starting load. It should be able to. Then head over to Sam's and buy 4 golf cart batteries and a genny. Buying a bigger inverter on ebay would be a good idea too. |
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you need a larger setup.
Recommend a 2000 watt (running not startup) inverter, with atleast two golf cart batteries (220amp hr) in series which will net 1.5 hours (give or take) until the batteries are completely dead....which you don't want to do, never run them below 50%, so you will have about 40 minutes of pumping power to drain your basement. You need more batteries, or pair it with a small generator with a battery charger. Total cost $600+ if you buy cheap/ or you could go balls out, get all of the mentioned above and add a water-powered backup sump pump. |
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Been there and done that, my wife & I have the T-shirt.
A sump pump running off power from an inverter and a car battery will not move near the water needed to keep a basement from flooding. If you are lucky enough to wake up when the power goes out and spend 3 hours crouched over your sump bailing like hell with a Quicky Mart cup, (it fit into the sump) you can, theoretically keep your basement from flooding. The lesson learned was have a generator running backup power duty for the sump. Semper Fi |
| One more thing. If you decide to use an inverter to backup the sump pump you need to use heavy gauge wire to connect the inverter to the batteries (something like 2 gauge maybe). With smaller wire there may be enough voltage drop when the inverter tries to pull 100 amps or so during the initial pump motor startup surge that the inverter drops out. |
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One more thing. If you decide to use an inverter to backup the sump pump you need to use heavy gauge wire to connect the inverter to the batteries (something like 2 gauge maybe). With smaller wire there may be enough voltage drop when the inverter tries to pull 100 amps or so during the initial pump motor startup surge that the inverter drops out. .....2 gauge is what we use on car stereo amplifiers. for running 12 volt inverters, you want 4/0 cable, and make it as short as possible. Give some consideration to using a 24 volt inverter, as you will have slightly higher efficiency, much lower amp draw from batteries, and somewhat reduced power loss in cables. |
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Although it may be drawing 700 watts after it's running, the starting surge could be a lot more than that. Also, that 700 watt rating assumes the pump is being operated with sine wave power - and the B&D inverter doesn't produce anything that even remotely looks like a sine wave. There's no telling how much power it's actually drawing from the inverter. More Bad News: Even if the inverter could start and run the pump, a single 115 AH battery won't supply 700 watts for very long. +1 Motor inrush is shutting down your inverter. I have been looking at getting a Power Bright PW2300-12 for my work van to run power tools. That will be close to the size you will need. |