How many batteries do we REALLY need?

[jennis9]

Got a 22' Starcraft SuperSport, merc 140, merc 9.9 kicker, freshwater/Lake Erie boat.

We are going to add a bow mount to use as our 'auto pilot' - we got the motor, elongated the shaft, got the copilot and quick release mount and are ready to go with installation. In case you want to ask, we cannot use the bow mount as a thruster/trolling motor since Erie can kick up quite a bit. So... in use, the kicker will get us to our target trolling speed and the bow mount will keep us on a straight path and allow both of us to fish. Navigating the boat when netting is quite a juggling act.

The question: do we need to have four batteries on board. The bow mount requires two -- we already have two on the boat. We wired the entire boat to a panel -- and separated the components to go to

battery #1: all main navigational systems, motor, lights, bilge, trim
battery #2: all non-essentials such as radio and gps.
Both are set up on a ProSport II battery charger.

I hate to add the weight of two more batteries and lose the space on board.

How would you set this up?

 

[smokeonthewater]

Re: How many batteries do we REALLY need?

on any boat that the main engine can't be pull started I suggest:
batt 1, engine start ONLY
batt 2, everything else including navigation lights radio bilge live well ... all of it ....this means that no matter what you run for however long you always have a fully charged battery to start the engine

in your case you need 2 batts for a 24 volt trolling motor

you have a couple choices..... you can use the 4th battery to run your accs
or you can split up the accs between the two trolling batts but it's a crap shoot as to how to drain them evenly. it also requires some creative wiring to charge them from the engine

there really isn't a perfect answer to your question but hopefully this will help choosing your tradeoff

many boats are set up with the twin batts for the trolling motor and all accs on the start batt.... that generally works but you lose your safety net. I refuse to give up a dedicated start batt. You do have a kicker to get you in with a dead batt but if a storm kicks up you could be in trouble FAST on erie

 

[zip34788]

Re: How many batteries do we REALLY need?

Two batteries should suffice without any issues, if you have a dual battery switch. When I used to fish Lake Erie in a 24' Sea Ray I felt more safe with 3 batteries. I think it is a mater of your level of comfort.

Personally I would be more concerned with the alternator's amperage and its ability to keep the batteries fully charged.

 

[Silvertip]

Re: How many batteries do we REALLY need?

You need a minimum of three. Two deep cycles in series for the troller. You don't need a switch unless you don't know how to use jumper cables or a jump start unit. That's the simple way and most trouble-free. Adding a switch serves no usefull purpose since you cannot charge the 24 volt system from the engine. What you run from the start battery depends on the current draw of the items. Nav lites, locators, and such draw very little power so if you have a good size marine starting/deep cycle (also called a dual purpose) that would serve well for starting. Downriggers and such do draw a fair amount of current and can be run off ONE of the troller batteries. They could also be run off the starting battery although it would be a good idea to fire the main engine and run it a fast idle for 15 - 30 minues every couple hours to keep that battery up. You definitely don't need four batteries but if space, money, weight, inconvenience and charging are not issues for you - then go for it. I would definitely invest in a bigger three output on-board charger so you could plug in to AC power at home or at the dock to ensure all three batteries are always topped off when you leave.

 

[izoomie]

Re: How many batteries do we REALLY need?

I've heard guys talk about have total redundancy, so that means lots of batteries. I like to run everything but the trolling motors on one battery and keep it maintained and replace it often. That's how you keep the weight down.

 

[jennis9]

Re: How many batteries do we REALLY need?

Thanks everyone - that's exactly what I needed.

Good point on wiring #1 only to engine start - we considered that when doing the wiring, but knew we'd always have the kicker as our backup and as Silvertip suggested - we set up the panel so we could always switch the main over to the aux battery of needed for a startup. I'm relieved that the switch is not necessary for the setup.

We're having the engine rebuilt this winter -- so any electrical will be easy to update since the transom is wide open -- I like the idea of having three batteries and a three bank charger. I am hoping I had the foresight to get a three bank, but am almost positive mine is a double.

The engine gets dropped in the last week of March - and we'll have access to a warehouse for two weeks.

Thanks again for the suggestions -- this makes it easier to prepare for the install.

 

[smokeonthewater]

Re: How many batteries do we REALLY need?

Actually you can charge the 24v pair from the engine..... I saw this today at bass pro to prove it .... prolly get it on iboats too. It is pricey tho at nearly $500.