Backup battery for sump pump

 Can the backup battery like I use for my computer be used as a backup
for a sump pump? The batteries I saw advertised for sump pumps cost
considerably more plus you had to add acid bought separately. They were
not maintenance free and seem to have a very limited life. The computer
backup battery works fine, is maintenance free, costs less, and has
enough power for my computer, monitor, and modem, with several outlets
to spare. Can I get a battery like this for a sump pump or don't they
have enough power?

 

start up load will be much heavier.

if you haven't already thought of it, use a water driven pump from your domestic
supply

 
Beware:  what works fine for powering a computer may not work well,
or may be damaged, trying to power an inductive load like motors.
Inductive spikes are known for taking out semiconductors like those
used in DC-to-AC conversion (whether it hurts the actual batteries
or not).  I've managed to kill a few power inverters powered from
my car battery to AC to power a laptop, just from inductive spikes
coming from the car engine, with ratings WAY over the power actually
taken by the laptop.

Some DC-to-AC converters produce a square wave or a triangle wave
rather than a true sine wave.  This may not be much of a problem
for computer power supplies, but it may be a big problem for motors,
possibly causing overheating without actually powering the motor
much.

Try to find a power spec for your sump pump, in VA or Watts.  (Also,
1 Horsepower = 735 Watts, but that's output power, so you have to
add about 40% to that, so 1HP = 1000 Watts).  Compare this with the
VA rating on your backup power.  I'd want a VA rating on the backup
power about 5 times that of the motor.  Also note anything stated
about powering inductive loads in your backup power device (look
it up on the Internet if you don't have the instructions).  It may
just not work at all.

Now, how long did you want the sump pump to run?  During a near-flood,
or collapsed roof combined with heavy rain, it's going to be running
continuously.  If that computer backup runs, it might keep going
for 3 minutes before running out of juice.  That's not enough.

I googled "UPS for sump pump".  It recommended some APC units with
a VA rating of 2200 or 3000 VA ($250 - $500, discounted).  (These
are also good for powering racks of computers.)  Your common UPS
for computers have ratings from 250 to 750 VA ($28 - $49, discounted).
I don't think attempting to cascade 10 cheap computer backups is
going to work very well.

Also, consider how well your backup solution will work if it gets
wet.  You might want to mount it on the basement ceiling or on an
upper floor.

 Gordon Burditt wrote:

Thanks for the informative reply.

 
Try using a bilge pump with a 12V deep cycle battery maintained with a
trickle (a.k.a. float) charger as your backup. All can be found at any
boating/marine supply store or online at Harbor Freight Tools.

Also has the advantage of being rechargeable with a car and jumper
cables.


  Gary