Beneteau relays and fuses, Battery isolator

[mswatsonmd]

I am wondering if anyone has an idea of what the different relays and fuses are in the house battery compartment? (see picture) from left to right 1). 2 inline glass fuses, 2. 20 amp fuse, 40 amp fuse, 12v 50 amp 5 pin rekey, 12v 25 amp 5 pin relay. What I'm really having problem is that my house battery are not charging when engine running, I have tested battery isolator and found that getting good current from alternator, good output to engine battery, but no out put to house battery, green light on on isolator . I am also not sure of the two small wires connected to the isolator. But have found that they are somehow connected to ignition. I also found that when I turn off battery disconnect to engine when running to only charge house batteries , the relay on the right of the photo ( 12v 25 amp) starts to hum. I am thinking that that might be the problem as the relay might be faulty and somehow connected to the isolator and/or ignition!
Any help appreciated?

 

[Davidasailor26]

Looks like a similar setup to our 37. I don't think any of those fuses or relays are really involved in charging from the engine. The glass fuses are for the always-on power to the bilge pump and stereo. One of the other fuses is probably for the line to the battery charger. The other relays I'm not sure about but when I traced them I don't think they were involved in charging.

The two small wires connected to the isolator are just a ground and a battery voltage output for the alternator's ignition sense.

Have you put a multimeter directly on the output posts of the isolator when it should he charging? You should have the same voltage on the output posts and input post at that point. If you don't the problem is probably with the isolator itself. If you do I would trace the output wire that goes to the house bank and see if there is anything else in line, but I doubt it.

Attached is the manual for our isolator. It looks like a different model from yours but the design and concepts are probably the same.

 

[mswatsonmd]

Thanks, I did check output with meter, the input form alternator 14.7, output on post to engine battery also 14.7, output on other post to house 8.7 volts which is what voltage of house battery was. What is the wire for the alternator ignition sense suppose to do? if there is a problem with that would that disconnect current to the house battery post. , or " isolate it"??

 

[Davidasailor26]

output on other post to house 8.7 volts which is what voltage of house battery was.

I know some battery chargers will only give output if they sense a battery there, and sub-9V is sometimes not enough for that. I wonder if the isolator has a similar cutoff. 8.7V is really dead. Are you sure the battery is just run down, and not failed?

What is the wire for the alternator ignition sense suppose to do? if there is a problem with that would that disconnect current to the house battery post. , or " isolate it"??

I don't think that wire would affect the function of the isolator. I think it's just an output to let the alternator know the battery voltage, not an input affecting the behavior of the isolator.

The next thing I would try to troubleshoot is to disconnect the house battery from the isolator, start the engine, and check the voltage on what was the house output post. If it is 14V then the house bank was defective and couldn't be charged. If it does not match the engine battery voltage I would shut down the engine, move the engine output wire to what was the house output post, then start again and see if the engine battery gets the full alternator voltage. If it doesn't then there is something wrong inside the isolator that is not combining that post. If the engine battery does see the full voltage I would then connect the house bank to what had been the post for the engine battery. If the house bank still doesn't take a charge I would assume it's because its voltage is too low. At that point I would look for another battery to use to test the combiner. For example you could grab your car battery, hook it up to your common ground and the isolator, and see if it gets charged. If yes then you know the problem was with your old house bank.

 

[mswatsonmd]

Good advise, will give that a shot!
Thanks