battery management switch

[SkyeToo]

1989 Carver 3607
in aft cabin closet is the 1,2,ALL battery management switch.
tested engine start in all 3 positions and yup, engine started - this is wrong!
gennie works fine, all power, lights, etc. 12v and 120 work fine
all batteries charge perfectly underway
battery charger is relatively new and works great, all LED's show correct voltage levels

BUT house batteries (brand new) drain much too quickly (4-5 hours)
woken up at 3am to the warning screech too many times.

my guess is that the battery switch is either bad or incorrectly wired for some odd reason
the starter and house batteries should be isolated by that switch, right?
engines should NOT start in the "2" (house) position, right?

spring plan is to replace the switch and trace the connections to the battery group and charger

BUT I don't have the electrical schematics for that model. Could someone send me link to the PDF's or some such?

Bruce
PS - love this boat- 7th season coming up. handles nasty weather on Georgian Bay no problem.

[Midnightsun]

Your setup is fine. The battery switch allocates which battery will be used by the house loads and also which will start the engine/s. A standard setup will require you to switch to house bank when at anchor and starting battery to start and run. This avoids draining the start battery when t anchor and makes sure you do not have no start situation. You need to tell us what you have for batteries. Sounds like you only have a single house bank which is not much.

[bud37]

I agree with Hans.....some more info...engines will start in any position ( normal).....its on you to keep what you decide as a house bank, a house bank......so, what batteries do you have on #1, what on #2 and which one is the house bank. That info would help to diagnose, as there are loads hard wired from the factory to position #1 and others to #2. For example a simple stereo with memory function that is on but not playing can draw a fair bit of power etc.

[Viper]

The guys are correct; the switch simply directs which source (battery banks) you want a load (engines, house loads, etc) to draw from. As Bud mentioned, we need to know the specifics of your current setup; what each bank consists of in terms of number of batteries each, their specs, and the brand. Also need to know what loads are running when you say you only get 4-5 hours capacity. Typically a fridge is the highest draw as it'll run often at anchor if you open it a lot, especially if it's an older fridge. If it's the original fridge, it draws much more than the newer designs. For what it's worth, stereo memory alone doesn't have that much of an impact. While it's a part of the overall usage calculation, the draw to maintain stereo memory is minimal and isn't something I'd worry about in this particular case.

When you say the bank only lasts 4-5 hours and you get woken up at 3am, are you saying that you get to your anchorage at 10-11pm and that's when you start tracking how long the bank lasts or are you getting to the anchorage in the morning and running the genny periodically throughout the day to charge the batteries?

Have you checked to ensure all battery connections are in good shape, clean and tight, and that all the wiring is hooked up as it should be? Have you taken proper readings at the batteries to ensure they are fully charging? What brand and model charger do you have? What voltage do you get at each bank while underway?

It would be helpful to know about any additional hardware hooked up to the batteries that was not factory. For example; where is the "screech" coming from? Is there a low voltage warning device of some sort or perhaps an inverter?

[g36]

In addition to above a easy way to determine your loads and what amps are coming from which battery is to use a dc clamp on amp meter, or a amp clamp for your multimeter. These are pretty cheap now days and can be useful for many things beside the boat.

[km1125]

As others have said, your switch is probably correct. I have the same boat (although older - '83) and have the 1-2-all switch too. It just designates which battery you are primarily using. There is no "house" and "engine" unless YOU designate them as such. When the engine(s) are running, they are charging whichever battery you are switched to, either 1, 2 or "both".

What kind of batteries do you have? How old are they? What do you typically leave running on battery when you're on the hook?

With a weaker battery (not bad, just older), some heavier loads (like the fridge and a few non-LED lights and some other stuff), and some resistance in the line caused by a corroded connection or two, your voltage to the device alarming may drop below the threshold. What is causing the "warning screech"?

[SkyeToo]

Thank you all so much for these helpful posts.

First, all the batteries are brand new last July. 2 deep cycle house, 1 ignition, 1 genie.

The marina tech's told me a couple years ago that the switch was mis-wired - 2 being engine start, 1 being house. (backwards)
But that seems very difficult to confirm. I have tried all configurations. Yes, switch is in the "All" underway to ensure full charging (works fine).

Fridge only from say 9-3/4 am should not deplete the 2 deep cycle batteries which made me wonder if the switch was even working. Engine start battery also low overnight (can always start the boat with the genie charge if needed)

The screech comes from the upgraded charger unit - a low-battery warning signal in the unit. Not a bad think to have.

So all this makes me think there may be old corroded wiring that is at least part of the problem as I don't leave lights on overnight. (anchor light is an LED - draws nearly nothing). Ice maker off. Stereo off. In fact, I have even shut off many of the services (other than fridge) from the breaker panel to be sure no current is being drawn.

I still don't see why all 3 positions (1,2,all) permit engine start unless the engines draw from the starter battery regardless of the switch position.

Just can't see why with new charger, batteries etc I should have a low-voltage warnings after 6 or so hours.

Again, many thanks.
Bruce (Midland Ontario)

[tomschauer]

As others have tried to explain, you don't really have a house and start bank. The battery selector switch powers both house and start loads with whatever bank is selected. Soooo, when switch is at 1, all 12 volt loads are powered by whatever batteries are connected to that side, including the engines. Same with the other positions.

[bud37]

Bruce, if you had to guess, how long does your fridge run in say 1 hour.....it cycles so a total would be good so we can calculate what your usage approximates. You really should know which switch position is connected to your 2 deep cycles.

[Midnightsun]

He did say 1 is house so I would think the dual house bank is on 1. Something is not right if you are draining those 2 new batteries in 4-5 hours. In fact that should easily last you all night and well into the morning unless you keep stocking the fridge all night long with warm beer. Maybe a short in one of them? Happens once in a while although rather rare.