Originally Posted by SimonCh
with a float switch, approx how much pumping are we talking to kill a battery?
Depends on your pump and your battery.
Assumptions: small pump like this: RULE BILGE PUMP 500 GPH 12V - Rule Electric Bilge Pumps - RULE BILGE PUMP 500 GPH 12V - Rule Electric Bilge Pumps - Discount Marine Chandlery and Sailing Equipment. Bargain Boat Spares and Clothing
Will pump 500 gal/h
You'll probably find starting draws more power and pumps less so if on and off a lot then it may be less.
So if you have a 100Ah battery you can only really run it it to about 40% of that before the voltage drops too low. So you have about 60Ah. That means you've got less than 30hours of pumping. Then depends how much water you are shipping. A big wave would easily be the quivalent of chucking a gallon bucket at you. Will depend on the hull and where you are moored etc. If that happened every minute you'd be shipping 60gal an hour. So you'd probably be pumping for 9minutes in every hour. So you'd keep pumping from a fully charged battery for 200 hours at that rate... So just over a week. And thats not in a major storm...
If there were no waves or leaks and just rain.... Assuming you have a 6m Rib x 2m Wide so have a 12msq (120,000 sq cm) free surface. Last year we had an average of ~1300mm rain. 1mm of rainfall is 1litre over a msq. So 1300mm is 1300litres per metre, so 15,600litres over the boat --> ~ 4000 gallons So I don't think there is a major problem with rain alone... Even if you had a months rain in a day you'd get 400gallons so only an hour of pump running which would only use 2Ah of battery...