Cranking Battery -Which one is it?

[Dualie]

Hi there,<br />I just bought a boat and I am new to the boating world.. So here goes. <br />My boat has two batteries and a 1,2,All off switch. <br />1) How can I determine which battery is hooked to where 1 0r 2?<br />2) Also, both my batteries are cranking batteries. Is this a problem? One is new this year (880 cca, 1000 mca) and one came with the boat ( 645 cca )<br />3) How do I know which battery is the primary and which is the house?<br /><br />4) When I start the boat should it be set to ALL? And should I keep it there when it is running? <br /><br />Thanks D

 

[amirm]

Re: Cranking Battery -Which one is it?

The way I would answer #1 is to actually trace the wires from the battery. Alternatively, you can disconnect one of the battery cables, set the switch to 1 or 2 and see which one no longer has power.<br /><br />As to both being starting batteries, that is OK if you are not going to pull high currents from one and drain it too low. As to which one should be the house, I would pick the higher capacity one assuming the other was sized properly to start your engine.<br /><br />On #4, there are different schools of thought. Me, I would keep the switch on both when starting and running normally so that less stress is put on the battery when starting, and both get charged. Of course, you then have the risk of being stranded if you let both drain so need to remember to switch one off if this is a possibility. This is why people recommend a combiner rather than 1/2 switch that is so common.<br /><br />Amir

 

[jlinder]

Re: Cranking Battery -Which one is it?

I would add that if you use one for house and drain it down don't set to both to start.<br /><br />You could end up with the fully charged battery supplying current to the house battery at the same time you were trying to start the engine.<br /><br />Set it to both after you start the engine to charge up both batteries.

 

[zlrh11]

Re: Cranking Battery -Which one is it?

There are a couple of very important things you should know about using dual batteries and a switch. Knowing this will help prevent problems with your system. These apply to outboards for sure, and likely to stern drives as well. <br /><br />1) DO NOT operate the motor with the switch in the "OFF" position, as this will likley destroy your alternator and charging circuit($$$).<br /><br />2) Know your equipment. (a) Find the motor cranking amp requirement, as well as the battery spec's and make sure they are compatible. (b) Find the motor's alternator maximum output (amps). (c) Does the switch have "make or break" design? Most modern switches do, but check with the manufacture or a local marine dealer to be sure. This allows the switch, for example, to momentarily make contact to battery 2 before breaking the contact to battery 1, and vice versa. This design prevents two things. (a) The alternator output from having "nowhere to go", and destroying the alternator, and (b) Power is not lost to your users such as electronics, radios, switch circuits, lights, etc. Depending on the manufacture, these warnings may be on the face of the switch.<br /><br />3) Outboard alternators, especially smaller HP engines, typically have a much smaller capacity than their automobile counterparts, which can be up to 100 amps or more. This is because boats generally do not have all the demands (computers, power windows, locks, wipers, headlights, tailights, A/C & heater fans, etc) that an automobile has. As such, don't expect low batteries to be fully charged in few short minutes at idle speed. It may take 30 minutes or even hours at higher speeds to fully recharge the batteries.<br /><br />Think of connecting a typical home charger to a auto battery and seeing it draw a 8-10 amps max charge rate, even overnight to 24 hours for a highly drained battery. If your boat has an amp meter, this will indicate the charging rate of the battery connected to the circuit with the switch (1, 2, all). Having a volt meter will not tell the whole story.<br /><br />Hope this helps!

 

[Dualie]

Re: Cranking Battery -Which one is it?

Ah HA!Thanks everyone for your insight!<br />IT all makes perfect sense and I will get started on your recommendations.<br /><br />The Merc dealer said that I must have a 1000 MCA starting battery for my 200 Merc OB. However, I failed to notice what type of battery it was before I swapped out with the new 1000 MCA batt.<br />This resulted in two craking batts??<br /><br />Currently, I am only running a fixed VHF, nav lights and a bilge pump. I am planning on getting a fishfinder soon. My GPS is a handheld and will not need a 12v source of power.<br />So is this satifactory?<br /><br />One other question for all- Let say my starting battery is 1, can I start the engine on 1, let it warm up and while it's running switch to ALL. Will this destory anything?<br /><br />Thanks Dulie<br />Question- If the switch is set to all

 

[amirm]

Re: Cranking Battery -Which one is it?

Your radio hardly uses any power in receive mode. The bilge pump will also be usually off. The only thing that would use decent amount of power would be your nav lights and I assume during the day you don't them. Summary, you are not going to tax your batteries at all unless you anchor someplace, run the lights with the engine. Otherwise, you should really think of your boat as having a main battery and a back up one.<br /><br />As mentioned before, if you have a newer "make before break switch", you can go from 1 to All without problems.<br /><br />Amir

 

[Dualie]

Re: Cranking Battery -Which one is it?

Thanks Amir!<br />I will find out which Switch I have. I bet it's the older kind since it's an older boat etc.<br /><br />Everyone's info is very helpful and very much needed!<br /><br />Thanks again!<br />D

 

[Richard Petersen]

Re: Cranking Battery -Which one is it?

Check out the switch with the manufacturer or marina. Put in the make before break type.

 

[Dualie]

Re: Cranking Battery -Which one is it?

Check out the switch with the manufacturer or marina. Put in the make before break type.

 

[Dualie]

Re: Cranking Battery -Which one is it?

i do have the older style isolator swtich. i ended up removing all the battery wiring and ended up sanding all the contacts to a shiny silver or bronze vs. the slime that was on it. then threw some dialetric on for a final touch.
AND labeled the batteries and the wires to and fro.

so far so good.

thanks Dualie

 

[Reel Poor]

Re: Cranking Battery -Which one is it?

If your not running a battery isolator, you should. An isolator will help your alternator live longer, will charge the battery with the lowest state of charge first, keeps the alternator from overcharging a fully charged battery, and also keeps the alternator from under charging your batteries.

Here is a couple of typical two battery setup diagrams.