Conversely, the lower the draw (relative to the rate at which it was tested – typically the 20-hour rate), the higher the amp hours. The higher the draw, the lower the amp hours of the battery. But, if you were to give out 50 amps, you wouldn’t get 2 hours. Peukert’s Law basically states that the higher the draw you put on a battery relative to its AH rating, the lower the overall AH capacity will be.įor example, a 100AH battery can give out 1 amp for 100 hours, and probably 2 amps for 50. I made sure to include Peukert’s Law in my findings as well and I assigned a Peukert Constant of 1.1 to the AGM batteries and 1.2 to the flooded ones. So, if a pump was rated at 600 watts did the following math: 600 watts/12-volts(battery) = 50 amps =>50 amps/0.85 efficiency factor = 58.8 amps being drawn from the battery to overcome the loss in efficiency with the inverter and still deliver 50 required amps to the pump. The final thing to note when using an inverter is that they are about 85% efficient, or 15% inefficient when switching the DC power from your battery to AC power for your pump. If you’re just buying an inverter to have on hand and use with your pump here and there, you will probably get away with a modified sine wave inverter. If you’re looking to make this a dedicated system, I would go with a pure sine wave inverter which will deliver cleaner and more reliable electricity to the pump. It is best to consult the manufacturer’s sticker on your pump and even contact the manufacturer to get an idea of exactly what watts are required. Still, though, I would stay north of 1,000 watts for sure and try to make sure your peak watts will be high enough. It is enough to cover the 6 running watts of the sump pump along with the start-up watts which can be 2-3 times as much as the running watts.įor some of the 1/3 horsepower sump pumps, you might be able to get away with a 1,000-watt inverter. What size inverter do I need for a sump pump?Ī 1,500-watt inverter with a surge rating of 2,000+ watts is a solid choice for powering most 1/3 and 1/2 horsepower sump pumps that you’ll find in most households. The inverter you choose will need to be able to adequately power the running watts and handle the initial start-up surge. They also have a start-up requirement that is usually 2-3 times the running watts that will last for a second or so. Sump pumps typically have between 600 and 1,000 running watts with 1/3 horsepower pumps on the lower end and 1/2 horsepower pumps on the high end. If you size your inverter too small, it doesn’t matter how large your battery is. Having a properly sized inverter is critical to operating your sump pump with a deep-cycle battery. Inverter and Sump Pump Energy Requirements I figure this may be of interest if you’re not too interested in doing quarterly battery maintenance. I’m only using lead-acid batteries in my examples, but the AGM’s are maintenance-free as opposed to the flooded types. I also took a look at what two 215AH GC2 6-volt golf cart batteries could do when hooked up in series.Īll of the AH ratings are at the 20 hour rating.
I took a look at some common sizes and types, and made my examples using a 100 amp-hour (AH) AGM, an 80AH AGM, a 105AH Flooded an a 90AH Flooded battery.
BATTERY BACKUP SUMP PUMP MENARDS FREE
If you’re just looking for a quick chart of the results to get an idea, feel free to click here.Ĭombined with a properly sized inverter and cables, a 12-volt deep-cycle battery should be able to power your sump pump for a little while. There were 3 considerations to be made when I came up with my numbers regarding the batteries, the inverter, and Peukert’s Law. In the below examples, I looked at 5 different deep-cycle battery set-ups and with so many makes and models of pumps I used a range of sump pumps from 600 to 1,000 watts and in increments of 50. If the pump is only turning on a couple of times per hour you can easily get 1 or more days of use out of the battery. If you’ve got a deep cycle battery on hand, or if you were looking to plan ahead, you’re probably wondering just how far that brick of lead and acid can take you.Ī deep-cycle battery can run a sump pump motor continuously for 45-80 minutes depending on the size of the pump. There’s probably nothing more nerve-wracking during a power outage than to watch your sump overflow and flood your basement.
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