I want to install a sump pump backup in my basement - When it rains a lot, my main pump kicks in quite often
I have a generator, but I am not fully covered if I am not here when power goes down, or if my main pump fails

So I want a battery operated backup
I have 2 options: a 12V system (such as Wayne ESP 25 or Watchdog basement) directly powered by the battery, or a regular sump pump (110 VAC) powered by the battery thru an inverter (1,200 or 1,500W I guess)

But I’ve heard that the inverter option will give less autonomy, since the inverter itself will consume energy even at idle, and is not 100% efficient either

However, how can I find out the difference in terms of autonomy: is it going to be only few % less with an inverter, or the impact is much bigger than that and I am better off with a 12V pump?

 

I would go with the 12 volt system. Less power consumption than with the inverter setup. Plus with a 12 volt system you can have it completely separate from your main power, you could get a solar panel to keep the battery charged (to not put any more load on your generator, and make it completely "self contained"), and install a bypass relay/switch to activate the 12 volt backup when your main power is shutoff....

 

I second that fwiw

 

I would go with the 12 volt system. Less power consumption than with the inverter setup. Plus with a 12 volt system you can have it completely separate from your main power, you could get a solar panel to keep the battery charged (to not put any more load on your generator, and make it completely "self contained"), and install a bypass relay/switch to activate the 12 volt backup when your main power is shutoff....

Either way i was planning to use a 12V battery:
Option A: 12V battery + 12V sump pump
Option B: 12V Battery + 12VDC/110VAC inverter + 110VAC sump pump

 

I say option b. Option a will need a float charger on it anyway which (i think) negates any efficiency savings over the inverter. Plus you don't have to buy another pump, which is likely the most expensive part of the upgrade.

 

Well, I will need a trickle charger for both options anyway, since it’s a backup running out of a 12V battery when the power is off
And I still want a 2nd sump pump, to be protected as well in case the primary pump fails

What will be more “easy” (less consumption) on the battery: 12V pump or 110VAC “regular” pump with inverter?

 

What will be more “easy” (less consumption) on the battery: 12V pump or 110VAC “regular” pump with inverter?

Depends on how much current a 12 Volt DC pump would draw versus how much the inverter + 110VAC pump would draw.....


One good thing about using the inverter option is that the inverter (if it has the capabilities) will cut off the power when the battery level gets too low (and sound an alarm), versus a straight 12 volt pump, which would run until the battery is useless...... and if you are not going to be using a deep cycle battery, discharging it below 10 volts will cause issues with an SLA battery, and you may have to replace it more often than you would prefer... but then again with a 12 volt system without an inverter, you could use a low battery cut off circuit to prevent the battery from discharging too low. So there are pro's and con's to both systems, you will just have to choose the best option for you.

 

Well, I will need a trickle charger for both options anyway, since it’s a backup running out of a 12V battery when the power is off

Sorry, when you said "inverter" my mind overwrote that with "UPS".

 

My preference is, "The simpler, the better". Even if the inverter was 100% efficient, it is still another part that can break, and a high tech part, too! You simply can not repair an inverter in a partially flooded room with a pair of pliers and a wire coat hanger, but you can steal the battery out of your car in an emergency.

 

My preference is, "The simpler, the better". Even if the inverter was 100% efficient, it is still another part that can break, and a high tech part, too! You simply can not repair an inverter in a partially flooded room with a pair of pliers and a wire coat hanger, but you can steal the battery out of your car in an emergency.

Yes, that's right.........
But in that case I will have to find a circuit (low voltage cut-off) to prevent to discharge the battery too deeply

 

Yes, that's right.........
But in that case I will have to find a circuit (low voltage cut-off) to prevent to discharge the battery too deeply

An UPS has a circuit like that...

 

A low voltage cut off circuit would not be too difficult to fabricate from scratch with a few components, like this one >> http://forum.allaboutcircuits.com/attachment.php?attachmentid=21204&d=1279557038
or you can purchase a pre-built off the shelf module like this one >> http://www.mcmelectronics.com/product/SECO-LARM-ST-BD01Q-/82-13990