new battery keeps decharging

[grab a fish]

Hi need some help as to what is causing brand new batteries to go flat after only a few days of not being used. Boat is a 1973 Caribbean Invader with an Evinrude 85hp engine. I'm thinking that it must be a wiring problem in the boat itself but am unsure of where to start searching. Or is this usual? A newbie here too. Would appreciate any advice at all please. Very frustrated with not being able to just jump in boat whenever i get the urge and head off without a hassle.

 

[Chris1956]

Re: new battery keeps decharging

If the battery is good, you likely have a current drain in the wiring somewhere. You will need an ammeter+voltmeter to find the issue. Does that motor have a rectifier? If so, that is a good place to check, as they sometimes short to ground.

With engine ign off, and all accessories off, connect the ammeter, set at 10Amps, in series between the positive battery cable and the battery. Just touch it, at first to see if there is a spark signaling a short. If so adjust ammeter to determine the current value of the drain. Now start tracing the power wire and look for bare spots on the wire touching ground, melted wires etc.

Normally, accessory power to the boat is a separate wire on the battery, and will be easy to find and disconnect.

 

[roscoe]

Re: new battery keeps decharging

Hello and welcome to iboats.

THe power drain could be from anything on the boat.
Electronics, stereo, bilge pump, or an old unused wire that is shorting somewhere.

You should install a main power disconnect on the positive battery cable.
All power should then be distributed from the disconnect switch.
This way, you can turn off the switch and cut all power, eliminating any power drain when the boat sits.

Blue Sea 6006200 Battery Switch Mini ON/OFF - Black - Blue Sea Systems - iboats















THe only thing you should have connected directly to the battery is the bilge pump, and it should have an inline fuse on the supply side.

 

[greenbush future]

Re: new battery keeps decharging

The battery switch above is mandatory on all my boats. It is the first thing I install if it doesn't already have one. There are so many wires and places in these wires where a short can occur that this seems to be the quickest way to solve the problem. Of course you need to verify that your new battery is actually a good one, it's entirely possible that you may have some dead cells in your new one. I would check that first, then install the switch.

 

[bruceb58]

Re: new battery keeps decharging

If you do find a drain with you multi meter, you can start pulling fuses to find the offending circuit. A stereo is usually the culprit. Even when off, they can draw down your battery.

 

[alldodge]

Re: new battery keeps decharging

:welcome: to iboats

If the drain is more then 10 it will blow the fuse in the meter. With it killing a new battery in a few days there will probably be a spark every time a wire connection is made or broke.

 

[bruceb58]

Re: new battery keeps decharging

Fortunately, it will be way less than 10A if its taking more than a day to discharge the battery so it will be safe to use a meter in the 10A range.

 

[Redfred1]

Re: new battery keeps decharging

My bet is on the radio; (if it is wired direct). Even when turned off; there is still a drain for the clock and station memory. RF

 

[Silvertip]

Re: new battery keeps decharging

The battery switch above is mandatory on all my boats. It is the first thing I install if it doesn't already have one. There are so many wires and places in these wires where a short can occur that this seems to be the quickest way to solve the problem. Of course you need to verify that your new battery is actually a good one, it's entirely possible that you may have some dead cells in your new one. I would check that first, then install the switch.

Explain how a battery switch "solves" the problem of a "short". Fact is -- it doesn't and it can't. While everyone seems hell bent on finding a short, wouldn't it be apparent that a fuse or fuses would be blown? Just because there is a current draw does not mean there is a short somewhere. What there is is a current draw because something is staying on, or in the case of the engine, something in the charging system has gone bad. Yes -- there may be bad diode in the charging system or a fault in the regulator that can cause a current draw. Doesn't mean there is a short. Short circuits cause smoke, melted plastic and possibly a fire if there is no fuse in the affected circuits. It would be prudent to first identify the circuit causing the current draw. Start with the obvious: Disconnect the
Boat Circuit from the battery. That would be the red, #8 or 10 wire feeding the helm. If the current draw stops, you proved the engine is NOT the problem. If the current draw is still there, you proved the problem IS with the engine. Now you can look at the charging system, stuck, tilt and trip relays, etc., but those circuits are also protected by a 20 amp fuse under the engine cover. If the relays are stuck on, the trim motor would typically run but if the secondary contacts are bad, that may not be the case. Since most bilge pumps are wired directly to the battery, make sure it is operational and not stalled. A stuck float switch can cause that.

If the problem was in the "Boat Circuit" pull fuses at the helm to isolate the circuit then determine why it is energized.