Electrical Leakage ?

[nial]

I recently installed a new battery and when I leave the boat for a few days with the Perko 4 way switch in the off position it seems to drain the battery. Leave with a reading of 12.5 Volts, two days later its down to 11.5 Volts. I opened the electrical panel and can measure 4 to 6 Volts from the positive lead when the Perko switch is off. Shouldn't it be zero? Also, any idea where I should look for where the battery drain is happening? Thanks.
nial

[btrayfors]

nial,

It's just simple detective work. Could be the Perko switch itself...I've seen 'em go bad.

Ideally, you could use a sensitive clamp-on DC ammeter to see how much current is being drawn from, e.g., the positive lead on the battery. If it's under about 10A, you could use a multimeter with a 10 amp reading capability. Many of them have this ability; just be sure you have the leads plugged into the right holes (read the instructions).

Once you verify that there is indeed some draw from the battery, you can start working your way toward the loads and find out which one or ones is causing the "leak". Some things draw a bit of current even when "OFF", like appliances with "soft switches", including radios, electronic bilge pump switches, TVs, and the like. With a sensitive ammeter at the battery, you can turn all the breakers off, unplug things with "soft switches", and begin turning breakers on one-by-one and plugging things in to see what's drawing current.

Good luck. Let us know what you find.

Bill

[perchance]

Is your bilge pump or any other device wired directly to the battery?

[Ike]

Perchance got it right. On almost all boats there are parasitic loads that are "on" all the time. One is usually the bilge pump which is usually wired direct to the battery. There are others such as alarms and fire fighting systems. You need to check out the systems and find out what is on even when the battery switch is off.

[Capt. lulz]

Originally Posted by Ike

Perchance got it right. On almost all boats there are parasitic loads that are "on" all the time. One is usually the bilge pump which is usually wired direct to the battery. There are others such as alarms and fire fighting systems. You need to check out the systems and find out what is on even when the battery switch is off.

His problem seems to be that his battery isn't just being drained, it's being drained quickly.
Lets assume that the pumps were the culprit. Why would they drain so much power?

[Ike]

They are pumping water. If the pumps are the culprit then that means he has a leak somewhere and the pumps are working a lot.

[osirissail]

Of course, the direct (hot) wired items would be the first to check out. But if nothing is found then an item by item check out as btraysfor outlines would be next.
- - But also there are things like leaking diodes in the alternator or in a charging diode isolator/splitter to check. Current can leak backwards across a diode if it is failing or failed.
- - Then there is the most obvious of them all - the batteries themselves. Are they old and have large internal leakage? Worn out batteries will self discharge rapidly.
- - You can bring in an auto battery and hook it up to the "hot/direct" items and then totally disconnect the ship's batteries and see how fast they self-discharge.

[HopCar]

Do I understand correctly that when the battery switch is in the off position, you can still measure voltage on the output (Common) terminal of the battery switch?
Sounds like a bad switch. OFF should be OFF. Disconect the cables from batteries 1 and 2, then use a multi-meter to see if there is continuity between the output (COM) terminal and either of the input (1 and 2) terminals while the switch is in the OFF position. If there is any continuity, the switch is bad.
Here is a link to the Perko wiring diagram for their battery selector switches: http://www.perko.com/images/catalog/...(8500INS1).pdf

[nial]

Let me be clearer. The battery is brand new. I don't have a sump pump. I can measure voltage at the common when the Perko switch is off. Even so, that shouldn't drain the battery when everything else is off. So, am I correct in assuming that because the switch is never really off it is feeding current to some device or connection that is "leaking" power across it? I don't have a clamp on ammeter but I do have a Fluke multimeter that will serve that purpose when spliced between a lead and it's terminal. Can I not also splice the multimeter between the battery + post and it's disconnected lead to get a read on how much power is still being drained when everything is off?
nial

[HopCar]

Your are correct. You can measure between the positive battery terminal and the wire, with the switch in the off position, to see how much power is leaking. It sounds like you have a bad switch and something drawing power through the bad switch. Once you establish that the switch is bad, with your meter still connected, turn off the breakers one at a time until the current drops to nothing. When that happens you have found the circuit drawing the power.
When you say you don't have a "sump pump", do you mean you don't have an automatic bilge pump? That's a must have for any boat that lives in the water. I'd bet you have at least one somewhere and it's connected directly to the battery without going through the battery selector switch.

[nial]

No, I don't have an electric bilge pump, just a manual one. However what I do have is the engine instrument panel, starter motor and wire to the alternator fed from the common lug on the Perko. None of those are connected thru a circuit breaker. Cabin lights, nav lights, radio, etc. are fed thru the electrical panel in the cabin and that, of course, does have switches. I have a sneaking suspicion the alternator/voltage regulator diodes may not be perfect even though it puts out 14.4 volts. I seem to remember starting the engine with jumper cables from my truck (no battery in the boat) last year and perhaps one of the cables got disconnected while the engine was running. Unfortunately I can't remember exactly if that happened. What the hell, I'm 70 years old.
nial

[goboatingnow]

The other reason is you have a feed around the switch. Ie a positive wire powered up a the time is leaking through some resistance to the positive system elsewhere.

It's a process of elimination.

Dave

[nial]

Originally Posted by goboatingnow

The other reason is you have a feed around the switch. Ie a positive wire powered up a the time is leaking through some resistance to the positive system elsewhere.

It's a process of elimination.

Dave

I have no idea what you mean???????

nial

[goboatingnow]

Originally Posted by nial

I have no idea what you mean???????

nial

For example if there is a leakage path ( damp , bad connections , failed insulation. There could be a circuit " around the switch " from a battery lead thru to the general positive circuit. That would give some voltage on the common side of the switch. ( ie it's probably not a very low resistance )

Disconnect all the wires to the common point of the Perko. Measure. The common stud on the perko , measure the voltages on the other leads that were connected to the common see if the leakage voltage is on these. That will eliminate the Perko, alternator and the general DC circuit. I wonder have you a leakage feed through the alternator. The field supply ? Via the ignition) is definitely getting switched off is it ?

Dave

[osirissail]

Okay, everybody has told you one way or the other how to find your problem. Simply put do the following:
1. With the Battery switch in the off position take any and all wires off the battery switch common terminal.
2. Measure with a voltmeter from the battery common terminal to the ship's battery negative/ground buss.
- - If you are reading any voltage the Battery switch is leaking.
3. Install a new battery switch.
4. Repeat #1 & 2 with the new battery switch.
- - If you are reading "0" volts with the voltmeter in the 0-12VDC or 0-20VDC (depends upon the voltmeter scales) - fine. Reconnect all the wires to the common terminal.
** Part 2 - Assuming your boat has a DC ammeter on the panel . . .
5. Turn on the new battery switch which will connect a battery to the common terminal.
6. Turn off all the circuit breakers and disconnect any wires that are "hot wired" to the battery by opening its/their fuse(s). Leave all the wires that are connected to the common terminal of the battery switch alone.
- - Check each "load side" of each circuit breaker with the voltmeter measuring from the load side of the circuit breaker to the ship's DC ground buss. With the circuit breaker in the "off" position there should be no voltage showing on the meter. If a voltage is present you have a bad circuit breaker. Replace any bad circuit breakers.
7. With all c/b's off and fuses removed, you should see zero draw indicated on the power panel ammeter. If not, there is a stray wire or something touching a feed wire in your circuit panel or your alternator diodes or battery splitter diode (if you have one) is leaking.
8. Find the stray wire and reposition it or replace it. If there are none then take your alternator into the shop and have it checked.