Step 3: The Battery

The battery I chose for this is an AGM (Absorbed Glass Mat) Lead Acid type - 12V(volts) 7ah (amp hour). It's a maintenance free deep cycle battery that's designed to be used periodically. You'll find them in security systems, computer battery backups, etc.

A word (or two) about this kind of battery.
12V is perfect for this - the pump is designed for 12V.
It's not spillable - can be mounted in all positions.
Can put up with quite a range of temperatures.
Packs a punch - could run "safely" for a few hours at 1 amp drain - we only need this for a few mins here and there.
Small & cheap (~$26).

I could have gone with a slightly smaller size - 12V 3ah - but this was just a few dollars more.

Great idea, I'm building something similar and wonder if you might know how/what could be used to turn on/off your pump at 1-2-3-4 designated times 7 days a week. This switch must be battery operated, economical/cheep and no bigger then a common paperback book?????<br /> Any answers out there?????
<strong>joeinventor2</strong> : Just buy an automatic bilge pump that runs whenever water is detected. Would you still&nbsp;need a switch for this? You could&nbsp;still add a SPDT switch, one that has &quot;On/Auto/Off&quot; positions (the center position is Auto). OR, buy an (<strong>expensive, about $80</strong> ) <strong>DC timer</strong> . Those have lots of settings.<br /> <br /> I just installed a solar powered 100ah battery system to run my 12 volt sump pump (we often get a LOT of rain). It is a Rule 360 GPH (gallons per hour) 12 volt bilge pump, requiring 2 amps at 12.3 to 13.6 volts, assembled basically as jedi27's is. The solar panels provide about 3 amps&nbsp;per hour <strong>unless </strong>it is raining (which is <strong>where the battery comes in!!).&nbsp;</strong> If the pump runs about 3/4 of the time,&nbsp;it's using 1.5 amps per hour.&nbsp;100 ah /&nbsp;2 (max. recommended discharge) = 50 ah. 50 / 1.5 = 33 hrs. In other words, if it rains for 1 day and a half, the sump pump probably will run the battery too low to do much pumping. Add to that: the solar controller has a disconnect setiing of 12.2 so you just won't get even that far! I have been forced to connect a 2 amp battery charger to the battery&nbsp;pack at times to keep the voltage up.<br /> <br /> Next task for me is to find the user manual for the controller to see if the LVD is user adjustable.<br /> <br /> I hope this is all of some use. I'm a new guy, liking this forum very much.
The battery operated portion makes it more complex, otherwise I'd say grab a timer from big blue and have done with it...<br /> <br /> You COULD look up a 555 timer based circuit - have a small counter circuit - calc that out to run every so many hours - have it activate a relay for so many sec /.mins - which would then power your pump.<br /> <br /> This would be better suited for a micro controller... a lot of folks use the arduino (look them up in instructables) - it's a great hobby level pic that would allow some interfacing to things such as a relay - low power consumption, small, $35ish?&nbsp; depends on model...&nbsp; this would allow a lot of flexibility.&nbsp; You could modify the logic to only run if moisture detected within the allotted periods - perhaps warn if low battery - log run times, etc...&nbsp; <br /> <br /> (I'm curious how this will be used... the requirements are a bit off kilter...)<br /> <br /> Good luck!!!!&nbsp;<br />
I have heard that if you do not add a diode into your circuit the battery will discharge through the solar panel at night. I am not that familiar with this but maybe someone else can enlighten me.
I suppose the panel could do that, but I left the original solar panel circuit intact - which is (probably) designed to disallow that type of discharging. I didn't poke around the circuit too much - looks like it's just a cap, resistor, LED, plus another diode (the LED is a diode too!). Keep in mind that my cheapo panel was designed to trickle charge a car battery - even noted in the manual that it wouldn't drain the battery at night - so I'm putting some faith into that! (i believe) The purpose of the diode is prevent current from flowing the wrong way - in that case, from the battery to the panel.

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