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I need to prevent a battery from discharge?

i want to connect an air pump (5-12v) to a car battery. that battery is also connected to a solar charger panel (seen on other instructables). What i need its a circuit where i can monitor the batterry (a 12v cuttoff) so that when it goes below charge, it turns off the air pump, letting it to freely charge and start again. i thought of a NE555 or a relay. appreciate any help.

AndyGadget8 years ago
Hmmmmm........ Interesting one. There is a potential problem with this which needs to be avoided :- Battery charging so pump turns on and loads the battery so voltage drops so pump turns off so voltage rises so battery charges . . . It could easily oscillate. Off to work now but I'll give it some thought later. What charging current are we looking at here, and how much does the battery voltage drop when on-load?
kelseymh8 years ago
I tried a Google search for "voltage sensitive relay", and got an early hit: http://continuouswave.com/ubb/Forum6/HTML/000612.html.

Why not try the same search, and see if that hit or any of the others would be useful to you?
gmxx8 years ago
you might be able to program something with an arduino... otherwise, im not sure....