How long before bilge pump kills battery?

[kshelly]

Brand new marine battery. Not sure of the brand, but bought it at Pep Boys. I run a 2 battery system. My aux battery powers everything but engine start (main battery used for engine start only). When I shut the boat down, I have a kill switch that drops power from everything EXCEPT the bilge pump and radio clock memory. Last week we had about 4 straight days of rain. Lots of rain! Went to the boat only to find out my bildge was completely full of water and aux battery was dead. I run a Rule 2000 bilge pump. Should I expect limited bilge use from one battery? Today I installed another float switch above the existing float switch and connected it to the main battery. Now I have two batteries to operate my bildge pump. Any thoughts?

 

[crazy charlie]

Re: How long before bilge pump kills battery?

Make sure the pump is connected to either a deep cycle or combo battery.It would really take a lot of pumping to kill the battery.Do you have a cover for the boat and are you sure you dont have a leak????Charlie

 

[Luna Sea]

Re: How long before bilge pump kills battery?

I used to use a solar panel out on the mooring to keep the battery charged. Could be your float switch got stuck open, seen that happen. 2nd switch is a good thing too though.

 

[ThomWV]

Re: How long before bilge pump kills battery?

A Rule 2000 draws 8.4 amps. If you have the everpresent Group 27 battery you may assume that it had a capacity of about 100 amp hours when it was new and if you are lucky it still has about 90. Any non-deep cycle battery can be thought of as being stone cold dead when it has been discharged to 50% of its capacity. That means that you had about 40 amp hours to work with. Divide that by the draw of 8.4 amps (which will actually be higher than that depending on how high above the waterline both the pump and the outlet are and how long the hose is) and its pretty easy to see that you'll kill your battery in about 4 hours and 45 minutes of continous running, a little less if it cycles on and off.<br /><br />By the way, contrary to what half of the people on this earth will tell you, if your boat is a day boat, which is to say you don't overnight on it and run stuff like spreader lights or something else all night long, using a separate starting battery and a house battery is just about the worst way you could wire up the boat. Basically what you are doing is carrying around a 60 pound battery that you get to use 15 seconds out of each trip. It just doesn't make any sense at all for most guys but I'll just bet that three quarters of the boats out there with dual battery setups are wired that way.<br /><br />Thom

 

[navigator336]

Re: How long before bilge pump kills battery?

I'm not sure what the current draw is on a Rule 2000. Let's say it is 1.5 amps. After 1 hour of continuous use it in theory would draw 1.5 amp-hrs. Your battery should have an amp-hr rating on it, which will be a theoretical valve (probably will deliver 80-85% of this if in good shape). A 4D wet cell battery will typically be rated at about 200 amp-hrs. So if you have a typical automotive size it will be rated much lower than this. Let's say it is rated at 90 amp-hrs. You could run the bilge pump continuously for about 50 hours of two days. A Rule 2000 might be discharging 1500 gph. So for an 18 foot runabout, it would have to be raining about two feet an hour to keep the pump running continuously. So I think the stuck open float switch was the culprit.

 

[kd6nem]

Re: How long before bilge pump kills battery?

Do we know that the new battery was really fully charged? If it sat on a shelf for best part of a year then got hooked up without a good charging it might pump fo a couple minutes before rolling over dead. Stuck float switch would be the other guess.

 

[wezie]

Re: How long before bilge pump kills battery?

Bearcat brought up a great point. <br />Batteries are charged on the shelf; but they need to be fully charged. <br />If you put one on the starting circuit and run the engine all day and then some more the next day; It will be fine.<br />If on the house circuit it will not get charged with a couple of hours operation.<br />We should place on the proper charger for 24 hours. That will fully charge them and life can start with a firm foundation.<br />Thanks for the story!<br />Great reminder.

 

[BrianTindall]

Re: How long before bilge pump kills battery?

If you have power nearby, get one of the 1.5 amp battery maintainers. Yes it's somewhat small, but it will keep the battery topped off and help it last longer during those times we get many days off rain. It's also small enough to hide in many places. If you have enough room, a 2 bank 20 amp (10 amp per bank) charger would be nice. At 10 amps per bank, the charger alone would run the pump.

 

[kshelly]

Re: How long before bilge pump kills battery?

Four days after installing my second float switch the boat sank in heavy rains <br />All my efforts were for naught! Anyway, today I received word that the engine is up & running, boat is ready to go. <br />I was told it sank because the bilge pump fell over in the well, basically knocking out my first float switch. The second float switch was hung-up in a rag! Go figure! When the boat was finally lifted out of the water after sinking, the bilge pump came on...a day late and a dollar short! <br />I was told I'm too stern heavy. Time to relocate the batteries, remove the trolling motor I had on the back, and store my gas tanks in the bow when I leave the boat. Hope someone can use some of this info to help them out. When I saw my boat under water, I didn't know whether to cry or throw-up. I hope nobody else goes through the same experience!!!! <br />Happy boating

 

[briannh1234]

Re: How long before bilge pump kills battery?

erau85 -<br /><br />Sorry to hear about the sinking. That's never good news. Usually some stuff floats away never to be seen again. Then there water in the gas tanks, dead batteries etc...<br /><br />I like to keep my boat it's trailer for exactly this reason. It does not sink.<br /><br />I like the two float switch idea. The only down side to the way you have it wired is that when the first and second switch are both closed, the batteries will be connected together through your bilge pump circuit. You need two dioed's rated for the bilge pump amps connected in series with the switches to prevent that.

 

[bruoff]

Re: How long before bilge pump kills battery?

Hey Briannh, I had a neighbor back in the eighties, who sunk his boat on the trailer.<br /><br />In the fall he covered the boat and installed the drain plug, fearing mice would come aboard and make a mess. "Long Story-Short", the cover developed a low spot and served as a very nice funnel filling the boat, to the gunnels, completely covering the little Mercruiser inboard. We promptly openned the drain.(I figured the water had been in there all winter) An hour later the bilge was dry. After changing the oil, removing the plugs and spinning the motor over, it actually started. <br /><br />I don't know what he told the guy who bought it a short time later, but there was "No mouse Damage"

 

[kshelly]

Re: How long before bilge pump kills battery?

Briannh....<br />You're right about the two batteries being connected thru the bilge pump wiring, but they would only be connected if the first switch fails or if a huge amount of water enters the bilge well at once. The batteries will only be connected together when the second switch is "on". The second switch is installed about 2" above the main switch. I was hoping to get away from a diode setup this way

 

[mellowyellow]

Re: How long before bilge pump kills battery?

as someone suggested, look into gettting a good<br />cover and you won't have to worry when it rains.<br />good luck!

 

[briannh1234]

Re: How long before bilge pump kills battery?

tarpon -<br /><br />I am not sure if you should call that a "sinking" or "conversion to a pool". Something like that happened to my Dad's boat once. It sat all winter with the plug out but the bow of the boat lower than the stern. The cover had not done it job too well. We went to attach the boat to the back of his car and could not lift the tonge of the trailer. Pumped out the water and all was well again.<br /><br />erau85 -<br /><br />I was thinking that the second switch was there in case the first battery had died. If the second switch is there in case the first switch fails, then you are probably fine. <br /><br />Just remember that when both switches close, the batteies will be connected. If the Deep Cycle battery is 9 volts and the starting battery is 12 volts, then you will be running the bilge pump and charging the deep cycle battery. This situation may pull enough amp's pop a fuze somewhere, and then the pumping may stop.