Parallel Batteries

[alaska_av8r]

I am trying to get a handle on this spark chasing stuff so correct me if I am wrong but when I hook two batteries in parallel, haven't I in essence just made that one battery still 12 V but combined amperage?

So when I use up the power from the batteries they essentially go down together, and the alternator charges them together?

 

[JB]

Re: Parallel Batteries

Yup. You got it, av8r.

 

[tashasdaddy]

Re: Parallel Batteries

but if one battery is weaker than the other, it will sap the energy away from the strong battery. in other word, when you connect a strong battery to a weak one, you will get a spark, as the weak one is drawing power from the strong one. same as jump starting a car.

 

[alaska_av8r]

Re: Parallel Batteries

Thanks for the responses guys. I have taken a few days and read as many posts as I can to try and get up to speed.

I just purchased two brand new batteries for my boat, same brand, amp etc.
These I intend to wire in parallel to take care of house items. Now for all my thinking logic I can now consider them one battery and refer to this as my starboard bank.

Now on Port I have a dedicated cranking battery.

My battery charger is a step down charger with 3 separate outputs.

From what I have learned I can wire one charger lead to my port battery and one charger lead to my starboard bank and the third just close it off.

I don't see a need for an ACR or an Isolator in this case, correct me if I am wrong!

Also since my starboard batteries are in parallel, I only need and should run one charger lead to them and not run both leads to those batteries??????

Bare with my naivety but this spark chasing is insane.....

 

[Silvertip]

Re: Parallel Batteries

You have three outputs on the charger -- so use them. No sense leaving one sitting idle. Parallel it with the other output -- double the amperage to the house batteries. Charger outputs can be paralleled just like the batteries. In fact, chargers with isolated outputs can be wired in series as well to provide 24 or 36V operation.

 

[alaska_av8r]

Re: Parallel Batteries

Thanks I didn't realize that but now it seems obvious to me. Another question along those lines of paralleling.....I will be rewiring and adding battery selector switches. I will most likely end up with two battery selectors so I can move sources around.

I was a bit concerned with the both alternators feeding the same battery...i.e. start port engine off battery 1 (port battery) then start starboard engine off battery 1 (port battery). Until I move the selector of the starboard engine back to battery 2 (starboard battery) I would have two alternators feeding the same battery. Would this cause problems or still same rule...paralleling DC is okay???

 

[Silvertip]

Re: Parallel Batteries

I wasn't aware you have a twin engine setup and at this point we also don't know if these are I/Os or outboards. Regardless, I would study your switch plans and switching procedure veeeerrrrry carefully. It appears you have a situation where you could inadvertently leave an engine disconnected from a battery. That will kill an alternator. My suggestion is to have a starting battery for each motor. The house battery (or batteries) can be charged from either engine but not both as the regulators may not figure out how is in charge (so to speak).

 

[alaska_av8r]

Re: Parallel Batteries

Sorry Silver, I have twin Crusader 270's with V-drives.

I found a drawing on boatfix that may help with setting up my wiring. I think I may actually need an "isolator" to do the setup that I want, my boat just has the wrong isolator on it.

I am going to draw up a diagram and when I am done I will post it on here so you guys can look at it. That way I can work out all the kinks before I blow something up....haha