Switchable/programmable 12/24V supply?

I'm looking for a switchable 12/24V DC supply to run a Shurflow 9300
submersible pump at either 1GPM or 2GPM. I only need an amp at 12V
and maybe 2A at 24V, as my lift isn't that high.

I'm keeping a cistern full from a well, and depending on how many
people are in residence (2-15), I'd like to pump slowly or somewhat
faster from the well.

Ideally I'd like to have a couple of float switches, so if my cistern
is (say) 2/3 or better full it'll run at 12V, and if it's 1/3 or lower
it'll run at 24V, but I can probably settle for a manual switch.

My fallback of course is just run it on 24V all the time, but that may
draw too quickly from the well...

Thanks for any thoughts!

 

Relatively simple set-up - you need a diode and a relay. Operate thr
relay with a float switch.

IIRC you connect the batteries in parallel - to give you 12 volts with
the relay(between the 2 positive ends, or the two negative ends -
your choice -connected, and connect the two OTHER ends of the battery
with a diode set up to be forward biased. Then connect the diode
isolated end of theisolated battery to the other end of the non
isolated battery with a diode that is forward bised when the relay is
open - connecting the batteries in serial and giving 24 volts


Battery
| |
|--||||----t------------ to load
| | | ^ Diode
|----------|
/ Switch |
/ ^ Diode
| | | |_
|--||||----|
| | |
|----------------------- to load

I used a similar setup on my Electric Fiat years ago.
Close the switch to charge at 12 volts. ( I used 24 and 48)