If you are kind enough to respond to this question please note that when it comes to understanding the electrical systems on our boat my knowledge is VERY basic.

Whenever I leave the boat I always disconnect the batteries (remove the 2 battery "keys"). On a recent visit however I forgot and when I was next on the boat the batteries were dead having drained of all charge. All switches etc were turned off. I don't have a solar panel to charge the batteries when I am not on board and the motor isn't running.

This suggests to me that there must be something that is drawing power even though everything is turned off at the switches. So my first question is this an accurate assumption or do batteries when left connected just drain power even if there is nothing drawing that power?

I have seen / read on here from time to time talk of people checking different systems or electrical components to pinpoint what / where current is being used. Firstly, how do you do this, what are the steps? Secondly, is it likely that this process would identify where the power from the batteries is being lost?

Thanks in advance for your help and assistance.

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MattM14 said..
This suggests to me that there must be something that is drawing power even though everything is turned off at the switches. So my first question is this an accurate assumption or do batteries when left connected just drain power even if there is nothing drawing that power?

I have seen / read on here from time to time talk of people checking different systems or electrical components to pinpoint what / where current is being used. Firstly, how do you do this, what are the steps? Secondly, is it likely that this process would identify where the power from the batteries is being lost?

Thanks in advance for your help and assistance.

Yes, something is draining your batteries if they didn't go flat any other times you left the boat.

Get yourself a multimeter - very handy to have on a boat anyway.

Rather than trying to explain here google "checking battery drain" & you will find plenty of "how to's"

This one is detailed: www.wikihow.com/Find-a-Parasitic-Battery-Drain

Like lazzz said, Get yourself a multimeter,,, Get one with ac/dc clamp meter for measuring current and learn how to use it. You will be able to check for current flow in individual wires without being too intrusive to the electrical system.

Most likely there are loads that are connected ""upstream" of the battery switches. Identify the main (thick) wires going from battery positive poles to the switches. Then look to see if there are any other wires attached either to the battery positives, or to the terminals where these main wires are attached to the switches. Those other (probaly thinner) wires will be the culprits. With a bit of luck you can solve your problem by reconnecting these wires to the load (ie downstream) terminal of the switch.

But even better, find an electrical-savvy mate, and start teaching yourself about sparky stuff.

Oh, and sorry to say, but your batteries will have taken a severe hit to their capacity and lliespan.

Good luck, Graeme

This one is detailed: www.wikihow.com/Find-a-Parasitic-Battery-Drain
Good starter Lazz

I have made up two 20cm cables with a small crocodile clip on one end and a larger one on the other.
One for positive and one for negative.
This allows me to connect to what I want to test hands-free.






Gary

Thanks for the input guys. I'll give the suggested process a try and see how I go at locating the problem.

Matt

Probably worth spending some time while you're at it with a pen and paper to draw how it's all laid out.

In theory, you should have nothing connected directly to the battery, with the exception of an auto bilge. I suspect though you may have something else connected directly that should be on your switch instead.

An awesome resource is some of the boat show talks from Pacific Yacht Systems: Goes through from a very basic level how to setup your system, talks about switched vs unswitched circuits etc.

Hi , first...can you clarify your batteries are disconnected from each other. Or ones all is switched off , 2 batteries connected together will discharging each other.

If you have a car radio type of radio onboard there will be a connection to at least one battery to maintain the presets.
My money is on dirty battery tops!

I'm not quite clear on your battery set up but if one battery has died it'll draw down the others pretty quick.
I'd be charging, separating each battery and testing each one individually to see which is not holding charge.

I've heard of batteries discharging back through an engine alternator,
but i think you would have to leave the ignition on as well for that to happen.

Stray, you correct, some boats have alternator, starter motor, bilge pumps & other accessories bypassing bat. switches .
Internal corrosion / faults they can discharge batteries.
Troubleshooting in any case is very simple, Bat. Fully charged, disconnect plus on bat. measure current between.
Finding the problem can be more challenging.