Battery banks isolated - not

[cutterorient]

I have House (4 golf cart batteries) and a starter (4D) . I thought they were isolated - thats the theory here right - so if the house are depleted I can still fire up the iron genny (Westerbeke 55B Four). I left for a few days and left the water pressure swith on which keeps a UV bateria killer on. Well it drained the capacity on both batteries.

Needless to say I am unsettled by this and need some help. I do not really know where to start the troubleshooting.

Both charge off a single alternator.

Thanks in advance.

[SEMIJim]

We're going to need a bit more info. How are the "separate" banks wired to the "house" and starter, how are they isolated from one another, and how are they both charged?

Jim

[cutterorient]

Like I said I need help. I am inviting deserved punishment by answering I don't know how they are wired. I took it on faith to this point as there was never a problem and there are plenty - and I stress plenty - of other things to do on the boat.

The starter appears to be wired directly to the battery.

I guess maybe a better question is how should they be wired?

[k1vsk]

From the way in which you described what happened, it's prettty clear that in fact the house and start battery are either not isolated or the isolator/combiner malfunctioned (which isn't likely).

In answer to your q regarding how it should be wired, presuming you don't have a battery switch to cross-connect each bank, the wiring should be completely separate. all you need do is trace it to find out.

[delan]

I use a Blue Sea Isolator to do this.
Start with your starting battery hooked to the starter and the alternator, nothing else, with the negative to the engine block.
connect a second hot from the starting batt to the A side of the isolator.
The house bank should have a pos to the accessory panel, a neg to the engine block, and then add a pos to the B side of the isolator.

Start the motor, the starting battery comes up to 13.5, when the starting battery is charged, the isolator senses this and couples the house bank automatically, and it charges,

When you turn the motor (or shore power charger for that matter) off, the isolator senses this, and uncouples the house bank.

The test to see if it's working is very simple.
Invite a bunch of friends aboard, drink a ton of tequila, fall asleep with all of the lights etc, on.

Wake up to a weird buzzing sound, made by the inverter that's attached to the house bank, with all the lights really dim and the stereo off.

Hit the key, and your motor will spring into life, take a minute to top off your starting bank, then automatically couple your house bank, and start charging it. You're back in business.

[sailingdog]

There are several ways you could wire them.

If you want to isolate the house electronics from the starting loads, I would recommend using a Blue Sea Dual Circuit Plus battery switch and connected the starting bank to one side, and have that feed the starter motor, and connecting the house bank to the other side and have that feed the main DC panel. Then you would want to have the alternator and other charging devices all connected to the house bank and use either an Echo Charger, Duo Charge or battery combiner to charge the starting bank when the house bank is being charged.

The other way to set them up is to connect the house and start banks to a 1/2/Both switch and connect all the charging sources to the house bank and use an Echo Charger, Duo Charge or battery combiner to charge the starting bank when the house bank is being charged. In this case, the house bank is not isolated when the engine is started and the "starting bank" is really an emergency starting bank, and the engine is normally started using the house bank.

Either will work fairly well. The one complaint of the Dual Circuit Plus switch is that in the case of a dead start bank, you risk killing the house bank if you put the switch in the combine position... Generally, the risk of killing the house bank when putting the switch in to the combine position is fairly low due to the size difference between the two banks, but if you're really worried about it, you can always wire a on-off switch into one or the other systems and use it to allow you to start off the house bank without combining batteries.

BTW, you really need to learn how your boat is wired. If you don't know this stuff, in an emergency, you could get royally screwed.

Originally Posted by cutterorient

Like I said I need help. I am inviting deserved punishment by answering I don't know how they are wired. I took it on faith to this point as there was never a problem and there are plenty - and I stress plenty - of other things to do on the boat.

The starter appears to be wired directly to the battery.

I guess maybe a better question is how should they be wired?

[timebandit]

Did you just have the battery selector switch in the all or both position??

[nickmerc]

You may want to consider rewiring the boat if it is older. This way you will know the wiring intimatly, you are sure everything is done to your liking, and if you are already doing a major rennovation you won't mind ripping all of the old wiring out.
________
accommodation in Pattaya