Bait tank batt - timer switch vs reverse polarity
 

Hey guys,
Building another bait tank that will be smaller than my current one. I've got it all figured out except for one thing... I'll be running a rule 360gph pump on a 12v battery. On the fence on whether I should add a timer switch, or simply reverse the polarity of the battery to slow the flow rate. Any of you electronics experts know how much switching the polarity will slow the flow?

Thanks

easier solution, just go with a 6v battery. No need for timers, or elaborate wiring. You don't have one buy one, you don't have the money to buy one save, then buy one.

And no, switching the polarity should not slow the flow.

One thing I remember about going from 12V to 6V is that the reduction in current is not linear. I think rather than cutting the current in half it cut it to 1/3 of the 12v current or something. Something to keep in mind when sizing your battery. In the end it really didn't matter though since 12Ah is very common so it ended up being cheaper than the lower capacity, less common, batteries.

Install a ball valve to slow the flow.
http://www.bigwatersedge.com/bwevb/p...pictureid=1227

runs backwards
 

Reversing polarity run will run your pump backwards and empty your tank. My tank was not working properly, bought it used with my kayak. The pump was sucking my tank dry. I thought the guy who owned it just got the wiring wrong. Actually, the battery pos and neg where identified wrong. Pump ran backwords. I had never seen a battery misslabled before.

Unless it was not the pumps usually used, reversing it will slow the flow, not reverse the flow as the fins on the impeller will not push as much water running backwards. 6 volt is my only answer.

Thanks guys. Looks like 6v or a valve are the way to go. Back to the drawing board.

Thanks again.

If your running a single 12v battery you can always put a VW 6v line drop in prior to the pump. we use them on VW restorations so that you can keep the
6 volt wiper motor and yet run a 12 volt electrical system for the rest of the car.

If your concern is that the 12v battery will pump too much water then:
A timer switch is not really going to help (just cycle between too much and none at all).
A 6v battery will help.
Anything restricting the flow will help (valves, spray heads etc.).
Reversing polarity will help (how much depends on your impeller type).

If your concern is that the battery will drain too fast then:
A timer switch will help.
A new 6v battery with more amps will help.
Flow restriction will not help.
Reversing the polarity will not help.

who is "we"?

The voltage dropping resistors are not water resistant though.

http://www.empius.com/vwcatalog/2013/279.html

I am not sure how the bilge pumps are rated but I used to be heavily into saltwater aquariums. Using a valve to reduce the flow adds back pressure to the pumps and can significantly shorten their life. Aquarium pumps usually have a maximum head height to limit the back pressure (usually in inches of water). 6V is a better option IMO.