electrical challenge Hunter p-42

[Frederick]

Electrical challenge hunter P-42 On my 1991 P-42 I thought I have two “isolated” battery-banks. One house-bank and one engine/generator- starter-bank. I had up to now the impression that both banks are isolated and that I was not able to empty the engine-starter-bank. Trying to understand the P-42 electric system is difficult enough. But last weekend I noticed that I did not understand the electrical system at all. After using and emptying my house-bank, also my starter-bank was under 10.5 volt and unable to start the engine. (I had to maneuver to my berth on sail and with the help of my 5 HP dingy.) Apparently the two banks are not totally separated and the engine-starter-bank is also feeding systems.The engine battery switch was on for the whole weekendCan anybody tell me how the two banks are connected so I can stop the possibility of transferring from the engine-bank to the house-bank.Does somebody have a full electrical system layout to help me out with another couple of electrical questions. Frederick.

 

[Mike]

To start or not to start....

I have a battery switch at the starter battery and another at my house gel bank, all monitored by an ample power 2.I suggest some form of isolation at the starter batery or a battery monitoring system ie. low volt alarm etc.Moving your 42 with a dingy is NOT FUN!!!

 

[SID JARVIS]

H 42 starting battery

I had a similar problem with my 42 nowI make sure that the starter batteryswith is off when using the house batteries for an extented period of time.I aslo carry a set of jumper cables soin an emergency you could probably getenough juice from the three batteriesto start the engine or the genset.

 

[Ed Schenck]

Can you sketch...

a wiring diagram? The problem is that so often the original wiring has been changed, by a previous owner or a yard installing some new gear. Can you trace the wiring?On my boat the only 12V wire to the AC/DC panel is from a post on the starter. That post is "fed" from the alternator and from a red cable that comes from the battery switch. My battery switch connects #1 to the starter battery and #2 is connected to the house batteries. This is the part you need to understand. When I turn off the motor I switch to #2 and there is NO way that anything will use the starter battery(assuming no unnatural conditions). Is it possible to have a bad battery switch where it acts like it is on "ALL" when it is not? Never heard of that but all things are possible with Murphy. I posted a Yanmar diagram of a simple wiring diagram on "Photo Forum" a few weeks back that may be a starting point.Good luck,Ed(schencked@bfusa.com)

 

[Ed Schenck]

An additional thought...

I hate the way an old mind works, ideas come at strange times. But do you have a bilge pump cycle counter Frederick? It is possible that the float switch, which should always be wired to a constant 12V source, goes to the starter battery. If it does and you have bilge water from some source then this could drain your starter battery. Can't think of anything else that might be wired directly but other owners will know.