Battery switch

So I've got a new question about the boat ive purchased. It has Two batteries, I'm assuming that the 8D battery is meant only for the engine and the smaller "marine" sized battery is meant for electronics operated in the house. My question is, the battery selector switch has three options 1,2, or all. When I run the boat, and i have been twice a week for the last three weeks or so, I switch the battery selector to "all" everytime thinking that I need to use the electronics and the engine so i need both. I havent tried using one or the other yet So i was just curious what is the correct thing to do? This is a 1963 Royal Craft Commercial Crab Boat that was rewired by the previous owner. Ive got another question but its a different topic.

Start the engine with the switch set to the 8D starting battery. Then switch to all while the engine is running to charge both batteries. Then while on the hook, mooring or away from shore power, switch to the house battery. This keeps the 8D starting battery from running down while you are using the house loads- refrigerator, stereo, lights, etc.

The above assumes that all loads go to the common terminal on the switch and the 8D is connected to the 1 or 2 terminal and the house battery is connected to the other terminal. This is the most common wiring for production boats, but yours may not be wired this way.

David

ok thanks.

djmarchand said:

Start the engine with the switch set to the 8D starting battery. Then switch to all while the engine is running to charge both batteries.

David

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I have always been told not to change battery switch positions while the engine in running. Something to do with possibly causing damage to diodes in the alternator. Have always adhered to this practice but don't know if its valid or not.

Check and see if the 8D is wired to the starter.
Easy to trace the wire to the starter.

The 8D could be the house bank.

Not a lot of cranking amps on an 8D. your start bat may be the other.

If you leave the switch on all after stopping the engine you will run down the start battery. It needs to be isolated so you always have a charged start battery.

SD

I guess i didnt say that I completely shut off the battery switch when the engine is off. I dont have any major electronics being operated inside the boat besides the VHF and GPS/Sounder.

The 8D is in fact the starting battery. It has 1400 cca's

Ive never thought of leaving the house battery on when not in use but a fridge is coming soon so i guess i could leave the house battery on for that??

I personally hate those 1,2,all switches.

something else to remember.

I have 3 switches one for the house bank it is just On. Off.

One for the start battery again an on off.

The third is set to combine the two banks. Just in case I need a little extra umph to start her up

I don't have to remember anything. I won't be running my start bank down listening to tunes at anchor because I forgot to turn the switch to house.

Sd

Without eyeballing the wiring it's tough to give advice...especially a boat with those 2 size batteries..I couldn't even tell you which could/should be wired to what...probably no one else can either.

For your boat...I would want at least an appropriate sized starting battey an a deep cycle 4/8 D for the house...preferably each or have 4-6volts in the house.

If what you have is a small diesel and the smaller batt is starting the engine...then start and run your diesel on the small batt...you can switch to both after an hour or so of charging the start battery as long as it was a normal fast start.

Switching the batt selector switch normally isn't a problem anymore because they are make or break to keep from blowing the alt's diodes...but it should say that right on it or you can buy a Zap Stop protector if it's an old style switch or you don't trust it to corrosion or "bad juju"..

skipperdude said:

I have 3 switches one for the house bank it is just On. Off.

One for the start battery again an on off.

The third is set to combine the two banks. Just in case I need a little extra umph to start her up

I don't have to remember anything. I won't be running my start bank down listening to tunes at anchor because I forgot to turn the switch to house.

Click to expand...

Something like this?:

markpierce said:

Something like this?:

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the most often recommended system...

Here are some previous discussions of electrical systems that might shed some light on your issue.

http://www.trawlerforum.com/forums/s4/house-battery-bank-switch-4202.html

http://www.trawlerforum.com/forums/s4/what-happened-house-batts-went-dead-3845.html

Here's a schematic of how I have connected my battery banks for charging and load. I hope it helps.

My 8 D is wired to my starter and my thruster directly. My panel also has the 3 settings. I always have it on the house bank. If for some reason you needed to use your starter battery to run the house, I can do it by making the switch. Not sure why I would since the 8D isn't a deep cycle. I do not (as others say they do) need to set them to 'all' in order to charge both. My fathers trawler is set up the same way as mine.

dwhatty said:

I have always been told not to change battery switch positions while the engine in running. Something to do with possibly causing damage to diodes in the alternator. Have always adhered to this practice but don't know if its valid or not.

Click to expand...

Those switches are supposed to connect the battery you are connecting before disconnecting the other one, so you don`t fry the diodes in the alternator. Whether they do or not.....best play safe. Actually you may be safe anyway, the way my IG is set up, provided the main battery isolator switches are on it(they always are) I don`t think it matters what happens at the panel switches.BruceK

The usual battery switch is constructed as a "make before brake" so as you switch the next position is made , before the last one is disconnected.

The danger is going to OFF with a cheap rotary switch.

That may cost the diodes in your alternator.

A better rotary will have field disconnect terminals , and if these are properly hooked up , OFF , with engine operating is no danger.

8D is a size , like 9W in shoes , has zero to do with the service the battn is designed to do.

Start batts for start , deep cycle for house loads , in whatever size.

Of course with lead , as the power the more the merrier , heavy is good.

CaptSoterio said:

So I've got a new question about the boat ive purchased. It has Two batteries, I'm assuming that the 8D battery is meant only for the engine and the smaller "marine" sized battery is meant for electronics operated in the house. ......................

Click to expand...

Do not assume anything. My "guess" is, it's the other way around, but if you can't figure this out on your own, get someone who knows about boat electrical wiring to check it and tell you which battery does what.

Battery combining switches are a royal PITA. Consider spending $100 or so (plus installation if you can't do it yourself) for one of several brands of battery combiners or automatic charging relays (two names for the same thing).

With one of these installed, you just start the engine(s) and go. It will take care of the switching automatically.

Battery combining switches are a royal PITA. Consider spending $100 or so (plus installation if you can't do it yourself) for one of several brands of battery combiners or automatic charging relays (two names for the same thing).

Or $18 for the improved RV solenoid style operation.