Electrical System Puzzle

[Gary Wyngarden]

I've been trying to get a more in-depth understanding of my electrical system and have been tracing circuits, sticking my head into hard to reach places, etc. I'm confused on one point. I have two batteries with the usual four position switch. From the battery charger, two hot lines run back to the batteries, one connecting to the positive terminal on each battery. However the hot line from the alternator only goes to the positive terminal of the house battery. I know the alternator will charge both batteries if the switch is in the "all" position. So why are there two hot lines from the battery charger? Thanks for your help.Gary WyngardenS/V/ Shibumi H335

 

[Michael McCann]

Puzzle

Gary;What is the model of the battery charger? Most units will charge multiple banks, and do not need the switch in the all position to do so. The unit I have will charge 3 banks, and has a 'hot' lead to each battery (bank). I usually will charge the batteries when I am away from the boat so the 4 position switch is in the off position.Mike

 

[Bob Fuller]

Electrical redo

I am just finishing up with a fairly extensive upgrade of the primary side of the 12 volt system in my 33.5. If you would like to know about some of the changes I made, contact me through the owners links.

 

[Jim Sullivan]

battery isolation

Gary: What Michael said is correct. This is to charge both, without physically making a parallel connection.

 

[Garry @ S/V TASHTEGO]

Charging

When your battery switch is in the "ALL" (BOTH on my switch) the current from the alternator goes to house battery then through the wire to the switch then on to the starting battery. The two leads allow the charger to charge each battery independently. If your staring battery is full but the house battery is doen the charger will just charge the house battery and vice versa. If you put your switch on either one or two the alternator won't charge the starting battery. This isn't a great idea since you will probably set the switch to the starting battery when starting up or atleast you should. If the house battery is a deep discharge battery and the starting battery is a high amperage battery you shouldn't have the switch on both when starting; its bad for the house battery. Once the engine is running you will have to pop down below and switch back to both in order to charge both batteries - something that you will probably forget in the hustle and bustle of getting underway. The better approach is to install a battery combiner which will electronically put the current from the alternator to the discharged battery until its voltage rises and the alternator can charge bot batteries. Connect the hot lead from the starting battery direct to the starter and you're done although you may want a switch to allow starting off the house battery if the starting battery fails. Have a look at the West Advisor at the link below for some more guidance.

 

[Tom Ehmke]

WM dual bank starting system

Gary,Follow Garry's advice. I did the WM recommended upgrade before the start of the season after having battery problems for 3-4 yrs. This season was without problems, even though I discovered half-way through the season that my house battery wasn't holding a charge properly. With the 3-switch arrangement, I was never without power to operate the house system or start the engine. I have had the WM battery combiner for several seasons, but never got optimal use from it until I changed over to the combiner/3-switch system. I didn't change alternators. I still use the 35amp Mitsubishi, OEM on my 272.Next season I will replace the house battery and will be very selective about what I install this time. No more bargain batteries.Tom