I want to attach a battery backup unit to my sump pump to protect it from
power failures and was wondering what the best type of battery is to buy.
I'm not interested in a secondary pump, just a backup for the 1st pump's
power line. Can I use a PC UPS battery backup or would you recommend a
different type of unit? What would you recommend as far as the time the
battery will last?
The size of the UPS will be determined by the sump pump's motor size and
power consumption, along with the amount of time that you want the motor
to be able to run. Most small sump pumps are 1/4 to 1/2 HP. A 1/2 HP
motor will need about 2KW to start it, and 500 watts to keep it running.
For this amount of power you'll need either a motor-generator or an
industrial-grade UPS. The small UPS systems that are commonly used in
consumer PC applications likely won't be adequate to start the motor,
and if they do, they won't run it for more than a few minutes.
Information on sizing the power source:
For backup alternatives, take a look here for some ideas:
As noted the deep cycle batteries are your best bet. However keep in
mind that in the more severe situations (the ones you are most likely to
need it) the power is likely to be off long enough and the water coming in
fast enough to overwhelm any battery you can afford. Pumps take a lot of
I would like a bicycle-powered pump myself; they have ``trainers'' which
has a roller you clamp your rear wheel on, and resistance is supplied
hydraulically or magnetically. Instead of the ``resistance'' module
a pump would be easy to add, you'd think, running off the same roller.
You could keep up 200w indefinitely, which would be enough to keep your
All you'd need to add is a 9v high water alarm to tell you to get out
of bed and start pedalling.
that may not be as crazy as it sounds, a moderately handy person may
be able to rig a belt system to run one of these mini-pumps made to be
run by a drill. It hooks to a garden hose, and I suppose it would be
slow, but could be made to work.
Depending how much water you have to pump a 12 volt 'bilge pump'
designed and sold for boats may be the best choice. Some quite
small ones can pump many gallons per hour. Depends how much water
you have to move as a temporary measure while the power is off.
Many bilge pumps cut in automatically. You will need a 12 volt
battery kept fully charged and occasionally topped up; but do not
overcharge or you will ruin it in less than a year! Or a source
of 12 volts from a vehicle. The extension cord from a vehicle
will have to be 'heavy' to avoid voltage drop.
A 'rough' calculation ; let's say you obtain a typical 12 volt
car battery with 72 AH (ampere hours) capacity, at full charge
and in good condition. Let's assume the 12 volt 'bilge pump'
requires three amps? And that it runs continuously? (Small pumps
are not necessarily designed for continuous operation but it will
only be required in an emergency; right? Our bilge pump cost
about 25-30 dollars IIRC. So it's virtually an expendable item).
So as long as it lasts during the power emergency ............
for total life (when run continuously) of say 30 to 40 hours?
Then running time is 72/3 = 24 hours. That's roughly; so for
practical purposes you'd probably get 15 hours at least; that's
sufficient time to get an AC generator and get it going to either
recharge the battery or run the regular electric sump pump
directly. If the battery is cold, below freezing say, it may well
have less capacity. If you have great big stack of batteries,
then you will have the problem of charging them.
Would NOT suggest using the UPS battery or the output of the UPS
a) The UPS battery is only designed to run the UPS itself for a
brief period, say 20 minutes to one hour. Then
even cheap UPS will automatically shut down to protect components
from low voltage.
b) The UPS is only designed to recharge the battery for it's own
requirements, when AC power returns. Not power external devices.
b) The UPS output is not designed to start or run motors,
especially heavy AC motors on pumps and such. An excellent way to
blow 'the guts out of' UPS units (unless large expensive
'commercial' ones e.g. five to fifteen thousand dollars a throw)
is to plug printers into them. Especially laser printers, which,
like motors can require large amounts of power for short periods.
UPS don't like that. They either blow or cut out.
Overloading any electrical systems is rather analogous to someone
trying to tow a tractor trailer with a motor cycle. Or trying to
heat a whole house with one candle. Or send radio signals to the
moon using a children's hand held walkie talkie! The systems just
don't have the capacity!
Final suggestion. A solution might be a small compact new or used
gasoline powered pump with a pull start, piped and ready to go.
I've seen them for a few hundred dollars and they can be easily
started even by a 12 year old child who knows what they are
doing. (Safer than a lawn mower!) Such a pump will have a certain
amount of 'lift' (suction) so it would not have to be inside a
basement or other enclosed area, it could be at ground level
above a basement area sump? Compared to batteries there is a lot
of energy available from gasoline. Pumps will run for many hours
on a few gallons of gas. For the initial first cost of one
battery, quite apart from recharging it somehow, one could buy,
even at today's prices, somewhere of the order of 200 hours
running time of gasoline.
Batteries IMHO are not a good power source for most pumping
applications. Good luck.
Your first problem is the run current and amperage draw of the sump.
second problem is duration of power cut. I've heard that many UPS aren't
properly heatsunk, so they over heat if you use them very long. A UPS is
better than nothing, but think big so it will run the pump, and will last a
"Billy" < email@example.com> wrote in message
Hey Tim, hows it? Can you believe I finally moved? If you remember that I
was to give you a summation on my experiences trying to find a new home,
well...I'll need a separate book to write about the crazy issues now that I
The way things are going, I'll have it ready in about 10 years.
Thanks for the advice.
Wasn't sure this was the same Billy -- but I wondered! Shall we start a new
new newsgroup: alt.home.billys.buying.experiences?? <grin>
Back on the original subject: I put in a "Basement Watchdog" pump as a
backup and am very happy with it. I paid $100 for the pump (new) on ebay,
plus about another $80 for the battery and acid at Home Cheapo-- and add on
maybe $20 for pipe fittings, check valve, etc. For $200 I consider this
very cheap insurance. Last year we had a flash flood with a power outage,
and we came within inches of flooding our finished lower level. That was
enough to get me to install the backup pump ASAP!
Being a computer guy I looked into the UPS backup thing, but the ratings on
standard A/C pumps are quite a lot of wattage. My Basement Watchdog is
about 3/4 the capacity of my main pump, and claims it can pump 8 hours
straight on one charge (you can buy bigger batteries too). Since our main
pump only cycles once every 5-10 minutes even on a bad (wet) day this should
be enough capacity for us to go several days without power.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.