House system help

[sailingdoc]

I bought a 1983 Ericson 30 a few months ago. One of the POs had rewired to build a 4-battery house bank with a charge sharing device that is fed off of the alternator. Also has an AC charger charging both house and start batteries.

Things worked fine for first month. Was out on water this weekend and the house system went out. When I went below, I found that I could turn back on certain devices but if I turned on others, everything went dead.

Spent this AM with a voltmeter and ohm meter trying to sort it out. What I find is that with AC charger and engine off, house bank reads about 12.5 V. When I turn on some of the lights (e.g. bow, steaming) or some devices (e.g. fresh water pump), voltage goes to zero and everything shuts off. The depth sounder was one of those devices that turned everything off but I found that if I switched the DS to "day" mode so that the internal light wasn't on, then I could turn that on without it shutting everything else off.

With an ohm-meter, I find that those devices that lead to voltage zeroing out all have a very low resistance between the lead at the breaker and the ground bus on the panel.

The panel is a Blue Sea system. Fairly straightforward.

I've checked to see if bilge water might be shorting things out but that doesn't seem to be the case.

All I can think of as causes are:
1. very debilitated batteries that just don't have the juice to power some of the higher current circuits
2. some massive short but this doesnt make sense given devices both at the bow and stern affected with wires going through different parts of the boat.

Would be interested to know if anyone has ever encountered this kind of problem or has any other ideas.

Thanks,

[hellosailor]

Find the date code on the batteries. It is often stamped or embossed on one side, within an inch of the top, and covered by the battery label in order to obscure it. Although sometimes stamped or punched in a label right on top. If they are 6+ years old, throw them out and replace them. If they are less than four years old, load test them. (Look that up if you need to, or take at least two into a battery distributor and they can do that for you, usually free since they plan to sell you new ones.) FWIW, Walmarts can test them, free, and sell new ones very competitively. If they are simply old and sulphated the load test will show they are worthless and no further troubleshooting is needed. But on a used boat, it often pays to literally trace every wire and make a schematic of the whole electrical system, especially when someone has put "splitters" and other pieces into it. Load test first.

[Wolfy]

Sounds as if you have a short in one or more ccts, I would recommend isolating all ccts and checking every single cct for a low resistance (<50ohms) reading or even a possible dead short.
Please make sure that your ohm meter setting is set at the minimal range setting i.e. 1k full scale or lower, the reason for doing this is to prevent false readings that will make you think that every cct has a short
i.e. try setting the ohm meter on the Mega Ohms setting and hold one test lead in each hand......the result is....what appears to be a short, actually you'll be reading around half a Meg Ohm, but, to the untrained eye you have a reading, any reading may indicate a short to anyone who's not familiar with electrical test equipment.
So, make sure you totally isolate each circuit at both ends and test between the +ve and the -ve of each circuit, there should be zero ohms being shown on a circuit that is good, if you have ANY reading what so ever then that circuit is drawing excess current from your battery bank and therefore the wiring itself requires replacing or corrective action.
Hope this snip tip helps you....it can be a little frustrating, but you'll find the problem.
The Batteries may be on their last legs too, but, from how your describing the problem you're having I seem to want to bet on the Short cct somewhere.
Best of luck.

[a64pilot]

I think your going to find a loose, or dirty connection to the batteries or the batteries themselves, one loos or high resistance connection is all it takes.
Take them all loose, clean and re-install

It's not a short, but causes an open under load

[DeepFrz]

I second a64pilot's diagnosis and recommendations.

[pesarsten]

Had a very similar problem on my boat, try opening the dc breaker panel and clipping a jumper across the main dc breaker ( !!! Only for testing don't leave it !!! ). Then power up your loads. I presume that you have multiple devices on multiple breakers that all shut down.

[pesarsten]

If you have a meter check the voltage drop across the main dc breAker when some devices are powered up. A breaker gets corroded up over time and will have a high resistance. This causes the voltage supplied to the devices to get lowere and lower as the load increases.

[CharlieJ]

Problem is not a "short" unless heat, sparks, flame a tripped circuit breaker or a blown fuse occurred. Probably a very poor connection; either loose or corroded.

[sailingdoc]

Thank you all. Problem seemed to be 2 of the 4 batteries in the bank that were no good on testing.

I simplified and am just using one of the 2 good ones. The system is up and running now. Less amp-hours but at least things are working.




Sent from my iPhone using Cruisers Sailing Forum

[hellosailor]

We had pretty much done a gut rewire on a boat, leaving very few pieces of the old wiring, including the battery-to-engine-bed ground cable. And some weeks later, looking aft in the dark spaces to see why something wasn't quite right, happened to see the blue flashes from that ground cable--which was shifting around on the engine bed bolt it was all tied together on. Way back out of sight.

Boat ran just fine that way, nothing seemed to mind the sparking. Still...it needed fixing.
Lesson learned: Assume nothing, there are plenty of unlikely failure modes.

Doc-
You might want to consider why just those two were dead. Either they were much older than the two good ones, or there's something that was set up (or used) incorrectly in the system. A pencil and big paper, and a hand-drawn rough schematic of the entire system, can be priceless to have as a reference.

[deblen]

Originally Posted by CharlieJ

Problem is not a "short" unless heat, sparks, flame a tripped circuit breaker or a blown fuse occurred. Probably a very poor connection; either loose or corroded.

When I see a poster write "you have or may have a short" in power wiring,I'm fairly sure they have no electrical knowledge.

If you have a short you will know it by the "spizensparken" & other things mentioned by CharlieJ.

Actual shorts are rare.

Much more common are corroded/loose connections in pos. & neg. & batteries with bad cells or down on "water".

Testing for voltage when there is nothing turned on (no loads) doesn't tell you much. You must have current flowing to find voltage drops.

Hope this helps.

/ Len

[Stu Jackson]

And, if you haven't already, draw a wiring diagram.

Good luck.