Three battery on a two way switch

[grizzreaper]

Tried searching but I didn't see anything. I want to put three batteries in the boat. Two cranking and one deep cycle. On the switch it will be one for the cranks and two for the deep (house). Is it better to hook the cranking in series or parallel. The motor is a 1985 3.0 mercrusier. The Alternator I'm not sure if it will be big enough to charge both batteries. I also will have a three bank onboard charger that will plug in when not fishing. Thanks in advance.

 

[alldodge]

Don't connect series, that makes the output 24V and things will burn up

The house would be parallel (treated as one bat) and the start would be by its self. Suggest using an ACR to charge all bats once motor is running. It will do it automatically but still may need a onboard bat charger for the house, if your motor does not run long enough.

 

[dingbat]

Why the third battery? Running a trolling motor?

 

[The Force power]

Let me explain the terminology series & parallel;

hook up in series - the cables would go from first battery's neg.post to the pos. post of the 2nd. then the remaining posts from both batteries are hooked to the pos. & neg. hook up to the boat. this will double the voltage 12 V. + 12 V. = 24 volt

hook up parallel - all pos. joint & all neg. joint together, the voltage stays 12 volt. just your "storage" increased.

Hook up your starting batteries parallel on one side of switch the deep-cycle "can" go on the other side of switch.
a thou it's not recommended to charge a deep-cycle battery & starting batteries at the same time through the charging-system.( specially if you already have an on board charging charger, I would let the deep-cycle get charged by the charger)

 

[grizzreaper]

Ok that makes more sense .thank you all for replying. To answer the three battery ? I don't want to get stranded out on the lake with a dead battery. But hooking up the starting batteries and leaving the deep cycle alone makes sense. Thanks again

 

[The Force power]

In addition.....run your trolling-motor /stereo / entertainment equipment of the Deep-cycle battery, they are designed for deep discharges meaning long continuous draw. Starting batteries are NOT by any means. a few deep discharge & they're done!

No draw on your starting batteries = no dead batteries on the lake

 

[Fed]

It all depends on your usage but I've gone back to basics.
One good deep cycle / hybrid and a jump starter.
Less equipment to fail.

 

[Scott Danforth]

why would anyone need two cranking batteries for a 3.0?

I can see one cranking battery and two house batteries

 

[The Force power]

Agree, I'd rather have two deep-cycle batteries as well & only one good starting battery (31D size) but my advise was based on what what he's got.

 

[grizzreaper]

Ok so let's be clear. I have one marine starting battery, one deep cycle / starting battery and 1 deep cycle. Some of you prefer a two battery system. I have seen and read of four battery system that some have preferred. My preference is 3 battery. Not to sound rude or distasteful to all answers but I wanted to know how to wire it.i understand starting batteries don't like to be discharged and deep cycles like to be drained, then slowly recharged. But I should of stated the other starting battery was a deep cycle/ starting. I assumed it was both deep and start. Again my fault for not putting that out there. Again thanks for everyone's input and knowledge

 

[The Force power]

You can make any set-up you want & now you know how
SO...no harm done

 

[dingbat]

.i understand starting batteries don't like to be discharged and deep cycles like to be drained, then slowly recharged.

Starting batteries don’t like to be discharged, but deep cycle batteries don’t need to be recharged slowly.

I have two. They’ve lived a very long live charged solely off the boats charging system via a ACR

The secret to long live is sizing the battery(s) to limit depth of discharge and to immediately replace the charge when used.

 

[cptbill]

I ran a 3 batt. set up but it was 1 starting and 2 house run in parallel, had a 3 batt charger on the shore power side and one 2 batt switch. switched to that set up because I got tired of the head mot working correctly at 4am while at anchor so there's no reason you couldn't do it with 2 starting and 1 house

 

[The Force power]

As I said earlier; you can make the set-up that you want (nothing wrong with it) and just to Clarify;
Deep-cycle batteries do not require a "slow/trickle" charge, they accept a full amp-out charge from being drained.
Starting Batteries when drained will not except a full amp-out charge, they start with accepting a low charge & will increase slowly as the battery is being charged
It's not recommended to have a drained starting-battery manual (switch/selector) set to high output, start of low 2 amps for a couple of hours & increase as needed.

 

[TBarCYa]

To accomplish what you want, I would suggest using two ACRs, an on/off switch and a dual circuit on/off switch. Blue Sea sells a package with the ACR and the dual circuit switch.

Connect the start battery and engine to one circuit of the dual circuit switch and the deep cycle and house loads to the other circuit with the ACR in parallel, just like the instructions for the ACR specify. This is a pretty normal setup.

Connect the start/deep battery to one post of the on/off switch and the start battery to the other post. The second ACR would go in parallel with the on/off switch.

With the dual circuit turned on and the other turned off, you would have power to the engine and house loads and when the alternator is charging the two ACRs would close so that all 3 batteries get charged. In the event that your starting battery is drained and you need to use the start/deep battery, turn the on/off switch on to connect it to the start battery.

 

[sam am I]

TBarCYa's post got me thinking and his method for 3 batts using 2 ACR's, a off/on/both switch(dual circuit switch) and a on/off switch is one way, not sure i'd use his way as I'm not sure his way can switch the 3'rd batt in for the house loads however,

If I was to want to use ACR's (not a fan) with my 3 batts and guy was to split the house loads up and use two off/on/both switches (dual circuit switches), here is another way it can be done.



Switches "SW-2b" and "SW-1a" circuits contacts are redundant in that they're in parallel and feed the start batt when SW1 and SW2 are "on" position but, when either/both switch/s is in their emergency "both'ing" position (SW-1c and SW-2c contacts), this paralleling junction provides the required crossover of either (or both) house batts into the start batts side depending on which switch gets set into "both"....

Of course when SW1 ans SW2 are in their respective normal (99.99% of time) "on" positions and the engine is off, all batts go into their safely isolated mode automatically.

With engine running and switches still in their "on" (99.99% of time) position, both house batts charge as needed and independently when the ACR's parallels the two together with the start batt as expected.

 

[TBarCYa]

I was only considering the 3rd battery as a backup to start the engine, not for house loads. Replacing the on/off with a 1/2/all/off with the start/deep battery on the common post, start battery on 1 and house battery on 2 would allow it to be used for either.

 

[grizzreaper]

So a long story short. Transom rotted. Pulled n a new one epoxies n ready to go back in. I have three bank battery charger in boat. I have one Perko battery selector hooked up to two starting batteries. Now I have a deep cycle battery in the cuddy I want to run my lights and Garmin when I am running my 15 HP kicker. I want to put another battery selector in the cuddy. Leave it on 1 to run the big inboard and then put it on 2 to run my electronics when using the kicker . Didn't want to start a new post so I high jacked my old one. What wire would be the common then one with 2 running the deep cell. Thanks for all responses and help. Sorry for the book

 

[alldodge]

two starting batteries. ...... have a deep cycle battery in the cuddy
What wire would be the common then one with 2 running the deep cell.

I think your saying, have 2 start and one deep cycle bats. What size wire would be used between deep and electronics when running on kicker

Is this correct?

 

[grizzreaper]

No the two starting batteries are hooked up at the back to the motor . My kicker is old Johnson 15 with no starting wire she is a good ole pull start. What I want is the deep cell hooked up to a seperate selector in the cuddy but still be able to run my electronics so my starting batteries are off .hope that helps