Battery not holding power

[mcdermaid 0]

I just purchased a used 2000 Monterey 240 EX deck boat and a week after i have it , it does not have enough power in the batteries to start it, previous owners say batteries are good , not that old and say that must be auto bidge pump killing it , boat is on trailer in driveway with no rain and no water on driveway so dont believe the pump comes on , also i had switched the battery switch to off . Any other ideas as to what may draw power with switch off. I plan on pulling batteries to load test them to be sure and will have dealer check charging system but any suggestions what could be draining power with switch off would help

[Ian 0]

Hi

The bilge pump/s remain connected to the battery/s even if the battery switch is off. This is for the obvious reason you don't want your bilge full of water when un-attended

 

Other typical items that remain 'on' even after battery switch is off are radio / stereo memories, clock memories (if fitted), corrosion control systems (if fitted), etc. These are relatively minor but do add up over time. The only true way to disconnect the battery is to lift the cables at the terminals.

 

Even a battery that is disconnected will self discharge over time due to its "internal resistance". This is why they should be maintenance charged if they are not used for long periods of time

 

A bilge pump doesn't have to have water in the bilge to operate. If the float switch that controls the pump is faulty it could permanently turn the pump on. It is a good practice to periodically check the operation of float switches and the pumps. You don't need to fill your bilge with water, just 'lift' the float switch.

 

Batteries can be fickle things and truly react to how well or badly they are treated so the age of a battery in itself, is not always a good indicator of it's condition. Depending on the type of battery, they can be permantly damaged if discharged below a certain point. Generally you will shorten the "life-cycle" of a battery if you discharge it below 10.5 volts. (If you are interested you will find LOTS of information on individual battery manufacturers websites).

 

Your battery is actually made up of 6 individual "cells" connected together inside a box with 2 terminals in what is known as a "series" configuration, giving a total of 12volts (nominal). Depending on the type of battery you have (lead acid, AGM, GEL etc.), it's cell chemistry and the state of charge / discharge , the actual voltage will vary slightly.

 

The problem lies in the "series" connection. If one of the cells is damaged or faulty, it can affect the whole battery performance. A damaged cell is quite often indicated by appearing to be fully charged after being on a charger but then very quickly going 'flat'

 

As you suggest, have them load tested and check out the charging system of the engine/s. Better to have problems on your driveway than on the water. Depending on your actual usage patterns, it might be a good idea to invest in a battery charger incorporating a 'trickle' or 'maintenance' charge once the batteries are at their fully recharged state. Talk to your marine / auto electrician

 

Regards

[pepmyster 0]

Wow,So many things can drain power on a battery. Badly installed stereos....lights etc.... You said you put the battery switch on off and still the batterys are weak? Okay, have a load test done on them. They might have to be fulley charged before a proper test is done. Also... If you start the boat... take a multimeter and see if you have at least 13.5 volts coming to the battery terminals. If not, your alt in not charging..You have to see if you have 12 volts going into the field coil to activate the alt. Start with the load test on the batteries. You can also do a draw test on the system to see if you have any major draws on it. To bad I'm not there to help.

[Wabum71 0]

I know this is going to sound crazy, but prior to load testing and removal, be certain that the cables are not sitting directly on the battery itself. Be sure to install stainless washers over all of your posts and then reconnect the leads. It worked for me

[mcdermaid 0]

Thanks guys .

I will be taking it in this week to winterize and get load test and alt checked . I did a few checks with battery switch on and off to check if any other items such as lights, accesories work with power to batteries cut off and nothing , so either bad batteries , bad alt or bildge float. Float is enclosed so not able to check , water was in bilge and when I turned switch on it pumped out so thinking that is not my drain .