I run a pump off some solar panels that both run the pump and charge the battery to run it at night (I hope it's charging the battery). I have run into some issues where the recharge rate was not adequate and sucking air and losing prime so I connected wires and plates (+,-) to the bottom of the pump so the pump only ran when covered in water (copied off a bilge pump design)...which fixed the problem...so it constantly stops and starts but does not lose prime. But now for some reason it is still stopping and starting but it will only run properly if I earth the positive connection...only found out when trying to sort out the problem and touched the positive connection... So can't work out why this makes it work or why it is still starting and stopping and not running all the time and sucking dry. My knowledge is quite rudimentary. Any advice appreciated.

 

More information would be greatly helpful like for what exactly do you have the + and - hooked up to read the water level and how much current are you running through it plus what are the + and- electrodes made out of.
Things like that.
Also the systems voltage, pump current draw and what sort of controls you are using with everything too would make figuring things out far more easier on this end.

 

[QUOTE

I have put a steel spike in the ground at the x and attached the bare cable join at this point because it ran a lot better when I moved it but I don't know if the battery would still be charging or just running down. The pump is a 60w diaphragm pump.




="tcmtech, post: 911875, member: 222921"]More information would be greatly helpful like for what exactly do you have the + and - hooked up to read the water level and how much current are you running through it plus what are the + and- electrodes made out of.
Things like that.
Also the systems voltage, pump current draw and what sort of controls you are using with everything too would make figuring things out far more easier on this end.[/QUOTE]

 

From that diagram it looks like you are using the Earth as a conductor which is just not going to work well (and I have no idea why anyone would design it that way). You need to use real conductors.

Never mind; I misinterpreted the diagram

 

I run a pump off some solar panels that both run the pump and charge the battery to run it at night (I hope it's charging the battery). I have run into some issues where the recharge rate was not adequate and sucking air and losing prime so I connected wires and plates (+,-) to the bottom of the pump so the pump only ran when covered in water (copied off a bilge pump design)...which fixed the problem...so it constantly stops and starts but does not lose prime. But now for some reason it is still stopping and starting but it will only run properly if I earth the positive connection...only found out when trying to sort out the problem and touched the positive connection... So can't work out why this makes it work or why it is still starting and stopping and not running all the time and sucking dry. My knowledge is quite rudimentary. Any advice appreciated.

To turn your transistor on, you need some small amount of current to flow from the positive battery terminal to the copper plate. I would remove the copper wire hanging off of the negative terminal and hang it off of the positive terminal instead. That should eliminate the need to ground your battery at the X.

 

Given it's a DC system your electrodes should be made of stainless steel not copper.
Also switching from a NPN transistor to a N channel Mosfet with a ~100,000 - 500,000 ohm pull down resistor between its gate and the source leads to make sure it turns off when the water level is too low would greatly improve the electrode life and reduce losses in the switching device as well.