Electrical load when everything switched off

[62_Kiwi]

A little while back I had one of those bad "learning experiences" at a busy boat ramp, with a boat full of excited kids and what seemed like the whole world watching... I'd launched the boat, parked the trailer and returned to find that the motor wouldn't turn over - flat battery! I felt very silly in front all the people muttering "didn't he check it beforehand?" and joining the long queue to re-load back onto the trailer, while trying to cheer up a boatload of dissapointed kids, didn't help either.<br /><br />Needless to say, I learnt that lesson and now carry 2 batteries as well as disconnecting them between trips - as well as checking that the motor runs before heading off to the ramp...<br /><br />Here comes the question; When I store the boat, I leave everything electrical switched off (as you do). I've checked very carefully that yes, everything is off. BUT, when I reconnect the battery, I get a very small spark jumping from the lead to the battery as it connects - indicating that there is a current running. Is this normal or do I have an electrical fault ? This might be a silly question - but do boat engines have a capacitor or something similar that draws a current and then stops when you first connect ? <br /><br />The motor is a 1997 Evinrude 115 OceanPro, also on board are a GPS, Fish Finder, VHF, Bilge pump, lights - but all are switched off.<br /><br />The original (4 year old) battery (from story above) was found to be faulty - wouldn't hold a charge after that, so was replaced. I'm not sure whether it was damaged by this possible electrical fault or just died a natural death.<br /><br />Any advice before I get out the multimeter and opening up the wiring ? <br /><br />Thanks in advance.

 

[Mike M2]

Re: Electrical load when everything switched off

You can check your draw at the battery with a meter by disconnecting the positive and running thru the meter on amperage. Not sure what a boat should draw, but your average car draws .03 to.08 with everything off. So, to answer your question, yes there should be a draw. Now whether it's killing your battery depends on the draw.

 

[Trent]

Re: Electrical load when everything switched off

Do as the southern boys do..Put a battery switch and be sure no current is being drawn. <br /><br />Small sparks (as you say) are possible.

 

[62_Kiwi]

Re: Electrical load when everything switched off

Thanks Mike and Trent - I'll try the multimeter current test. The switch sounds like a good idea too.<br /><br />I never realised that cars and boats draw a small current even when switched off.<br /><br />Also, on the subject of batteries. Is it OK to wire 2 identical batteries in parallel on a boat ? So as to get double the capacity ? Or could this cause problems with one drawing off the other ?<br /><br />Thanks again in advance.

 

[ODDD1]

Re: Electrical load when everything switched off

62kiwi, I have found many boat motors that do just this thing [cars too]..the regulators in the charging system need a shot of electricity when first connected...after this initial 'shot' they wont draw more than a milliamp or two unless something is wrong...dont forget, stereo's, radio's witha memory will always draw something...and I have seen newer units that were real power hogs when turned off....

 

[petryshyn]

Re: Electrical load when everything switched off

Hi 62_Kiwi <br />One of my favorite topics....<br /><br />Some draw is normal. As mike m2 says, .05 - .08 of an amp. is common amongst newer computer controlled systems. If your system is not computer controlled, I would consider this amount high. The battery will go dead from this in 1 - 2 months.(pending on battery size) You should check the draw as Mikem2 states, just to see if you have parasitic issues. Even if the draw is within this realm, take Trent's advice and install a disconnect switch. (nothing better for protection)<br /><br />To answer your second question....it is OK to parallel 2 batteries if their open-circuit characteristics are close to identical. Age, group size, brand and state of charge all play a part in this. If you want to know if they are identical in characteristics, put both batteries in parallel and charge them until fully charged. Then separate them by breaking the positive connection and remove charger.(leave the negatives connected) Leave them sit for atleast 24 hours. Then take your ammeter, and bridge the positives together. If there is a current flow more than .050 amp, they are not identical and one will discharge the other in time. There are disconnect switches that will separate the two batteries when not in use. This would address this issue. There is no problem leaving mismatched batteries in parallel if the charging system is working. Its when you leave them sit with no charging occuring, that the imbalance takes place.<br /><br />Good luck!

 

[62_Kiwi]

Re: Electrical load when everything switched off

Thank you Schematic, ODDD1, Trent & Mike - all this information and advice is very helpful to me. I'll check the actual current draw in the morning (finally found the multimeter!) - but I'm pretty certain that it's only a tiny level - within the expected range. The main point is that a tiny current, when everything is switched off, is normal - which I didn't realise before.<br /><br />The switch on the battery is a great idea also and I'll get one.<br /><br />Schematic - thanks also for the info on parallel batteries and how to test whether they'll work together - very valuable info also.<br /><br />I know it's already been said, but this is a fantastic web site, primarily because of the high level of expertise of many of the members and their generous sharing of this information. I've learnt more boating tips here than anywhere else I can think of.<br /><br />Many thanks to all that participate.

 

[Trent]

Re: Electrical load when everything switched off

To answer your next question before you ask it (how to wire)

 

[Neil]

Re: Electrical load when everything switched off

I had a similar problem drawing current.<br /><br />So bad that sometimes I could feel a scock when undoing the terminals to disconnect. I always disconnected to prevent drain.<br /><br />Investigation of the wiring concluded that there were quite a few shorts and bad connections resulting in small circuits, especially when the boat was wet. Major culprit was the automatic bidge level switch.<br /><br />Resolved the issue by replacing the entire wiring from the battery to the switch console, soldering connections, insulating and - a battery switch.<br /><br />I also wired in a cigarette lighter directly to the battery bypassing the switch. This is so I can connect my solar panel which will =ensure I always have a topped up battery. Really cheap, less than 20 pounds. A good boys toy too

 

[62_Kiwi]

Re: Electrical load when everything switched off

I just measured the battery load with everything switched off on my boat, which is 25 mA (0.025 Amps). At 12 volts, I guess that makes it 300mW which is under a third of a watt. Just enough to produce a minute spark as it connects - and just enough to make me think you need to disconnect the battery when parking for long periods...<br /><br />Trent - thanks for the diagram. Yes, a switch that is Off/A/B is the best idea. That way if you forget (these things happen) and leave something switched on and flatten a battery, you can always switch to the other (i.e. not so easy to flatten both).<br /><br />NGriff - wow, sorry that you had the real problem I was worried about (Phew!). Solar panels for the boat is an interesting concept.<br /><br />Thanks again to all contributors to this topic - I hope this has helped others with battery concerns also.

 

[ebbtide176]

Re: Electrical load when everything switched off

I would not take a clocked dev off battery unless i didn't charge the battery regularly. HTH<br />(yes batteries succumb to #charges) this is not meant to offend those who feel differently)

 

[Trent]

Re: Electrical load when everything switched off

Ebbtide..you been drinking? Or did I miss somthing?? Or that just went WAY over this southern boys head!!!!!!!!!

 

[petryshyn]

Re: Electrical load when everything switched off

huhh?

 

[Kiwi]

Re: Electrical load when everything switched off

schematic, your diagrams are AMAZING !<br /><br />