Dual Battery setup for bowmount or not ?

[Lancair]

Hi guys,
Basically my question is, which is better, to have a totally independent battery that is charged at home for my bowmount, or have my main boat battery and the bowmount battery linked via either a switch or a set and forget dual battery setup like in a 4x4. My Hilux dual battery system charges the start battery until its charged then swaps to charging the 2nd battery. The drain from accessories on the 2nd battery can NEVER be transferred to the main so I always have a good battery to start with. I guess with having them linked Im still going to have to top up the bowmount battery at home, even though the Etec puts out a heap of charge current. BUT if I spend two or three days out camping and fishing, the bowmount is going to last longer with a top up from the Etec.

Im leaning towards having a manual dual battery switch setup for selecting either battery or off, not a both option. Actually that kind complicates things as I now have all the extras (lights, rado, sounder etc) wired after my battery isolator.

HELP ! Suggestions and or wiring diagrams please.

Cheers

Andrew

[Coontakinta]

Lancair, I'm no gunn in this type of thing, but when i was looking at batteries for this type of application, I was told that a deep cycle was the only way to go, and it may still well be. I have just mounted a standard car battery for now. I can use it for a round 3hrs trolling and it does not drain noticably. Then when I get home I just hook up to battery charger and its rady for the next trip.

If, like I'm told by the breambo pros, that charging a deep cycle from you motor is detrimemtal to the life span of that battery, then I'd suggest u dont do it. If on the other hand you are running a standard car battery like me, then go for a dual set up for sure.

I guess u just have to way up how much of a charge u are going to be able to put into that battery when underway.

[Lancair]

After talking with a battery guy today, I think Ill get a calcium deep cycle battery and keep it seperate from the boat battery and engine.

The advantages of an AGM battery dont really add up to the extra cost, (almost double). I was worried about leaking acid or battery plates cracking with the bowmount battery being in the bow and coping more vibration and pounding. Im told plates are highly unlikely to crack or break unlessI drop it from a great height, in which case the battery case will also be FUBAR'd. Leaking could be an issue, if I tipped the calcium battery upside down, in which case the battery leaking is the least of my troubles if the boat is upside down too. Charging either battery with the motors output isnt really going to do a lot unless Im driving for a long time so just leave em seperate and make things less complicated and less expensive. (no extra switches or cabling)

Does anyone disagree strongly with any of the advice Ive been given ? Please speak up now, not after I have problems I couldve been forewarned about.

Cheers

Andrew

[Tangles]

Deep cycle battery kept seperate is the way they are normally setup

Mike

[Black Pig]

I have just been though this exercise in planning for my new boat. From what I understand, you cannot connect a deep cycle to your main battery for charging for fear of damaging the engine. I was told that you must keep the battery seperate.

I have gone with dual deep cycle batteries at the bow to power a 24 volt Minn Kota. Also went with the on board charger which remains connected to the batteries and simply plugs into mains power fro charging.

[MeePee_99]

I got a hornet and i have a deep cycle separate for a bowmount and cant be happier with it.

[NAGG]

After talking with a battery guy today, I think Ill get a calcium deep cycle battery and keep it seperate from the boat battery and engine.

The advantages of an AGM battery dont really add up to the extra cost, (almost double). I was worried about leaking acid or battery plates cracking with the bowmount battery being in the bow and coping more vibration and pounding. Im told plates are highly unlikely to crack or break unlessI drop it from a great height, in which case the battery case will also be FUBAR'd. Leaking could be an issue, if I tipped the calcium battery upside down, in which case the battery leaking is the least of my troubles if the boat is upside down too. Charging either battery with the motors output isnt really going to do a lot unless Im driving for a long time so just leave em seperate and make things less complicated and less expensive. (no extra switches or cabling)

Does anyone disagree strongly with any of the advice Ive been given ? Please speak up now, not after I have problems I couldve been forewarned about.

Cheers

Andrew

Andrew ..... Stick with a separate bow mount battery & if $ allow include the onboard charger ..... then its just a case of plug it in & charge
AGM deep cycles are exceptional .... but they are expensive! However they will outlast a wet cell / calcium battery ! , can be discharged to a lower state of charge continuously without damaging the battery ..... They charge faster.
i'm guessing you are just getting a 12 volt system ......... so if you want a long run period .... you need to buy the biggest possible 150-200amp ( 120amp is a minimum IMO)

Cheers

Nagg

[shandos]

Andrew
I have two deep cycle batteries in the bow of my 4.2 polycraft not connected to the motor charging circuit. I am running a 55 lb thrust 12 v Minn Kota. I have placed a heavy duty battery switch in the circuit that allows me to quickly shift from one battery to the other (or isolate both batteries). I find this an excellent option as I never need to run a battery right down and when traveling the power is isolated completely from the electric motor.

Shandos

[Lancair]

Thanks Nagg and others.
I wont be trying to link the batteries.
Maybe I should go looking at other battery resellers because the local guy I went to doesnt have anything over 90AH in Calcium deep cycle. Ideally, I want the biggest capacity battery I can fit in the 330mmx190mm battery tray I have. He has another 120ah battery but its a wet cell not calcium. Id prefer not to have any leakage, I imagine battery acid and aluminium doesnt go too well.

Andrew

[shandos]

Hi again

As i suggested in the previous post -- maybe 2 smaller batteries would be better than one large capacity one.

Shandos

[NAGG]

Thanks Nagg and others.
I wont be trying to link the batteries.
Maybe I should go looking at other battery resellers because the local guy I went to doesnt have anything over 90AH in Calcium deep cycle. Ideally, I want the biggest capacity battery I can fit in the 330mmx190mm battery tray I have. He has another 120ah battery but its a wet cell not calcium. Id prefer not to have any leakage, I imagine battery acid and aluminium doesnt go too well.

Andrew

Andrew

Do a google search for Deep cycle batteries ....... you'll find a heap of places that carry a great range ( & not the rip of places like battery world etc) ...... There are a few good ones in Brissy & Sunshine coast areas ..... places that are involved in solar power etc
Check it out

By the way ..... Even though they are a wet cell ( Trojans) they are the pick of the crop & were designed for submarines!
Best of luck with it

Nagg

[Lancair]

Shandos, thanks for the suggestion, I like it and it has merit for sure. I already have a battery tray built under the front hatch but maybe your suggestion might work, if I can find two that will fit. Id rather not have to spend more on modifying what I have already had made.

Nagg, last time I did a google search, it didn't turn up a lot of info that was helpfull. Like price and more to the point, the physical sizes of batteries. Ill give it another more thorough search tonight. Sure the wet cells Trojans are the pick of the crop for deep cycling etc, however mounted in the bow of a 4.2m tinny thats driven in all sorts of water conditions at all speeds, is probably not where the designers had in mind for testing the durability of their batteries.

Cheers

Andrew

[the gecko]

I have my deep cycle (sealed unit) connected to the main battery, and I am happy. Been running that way for 12 mths with no probs.

Once the main is fully charged, the relay allows the alternator to charge the deep cycle while under way. All accessories are running off the deep cycle. It gives me about an extra hour of leccy use per session.

Ive never heard people saying its a potential problem, thats rubbish. Its only an issue if your main is faulty and wont fully charge. Apart from that, there is no wear and tear, and perhaps regular upcharging is even beneficial.

Theres been a few threads on this before, do a search.

Im no expert, so take your time and talk to some marine electricians. I found some at coomera marine centre who were very helpful.

cheers
Andrew

[NAGG]

Shandos, thanks for the suggestion, I like it and it has merit for sure. I already have a battery tray built under the front hatch but maybe your suggestion might work, if I can find two that will fit. Id rather not have to spend more on modifying what I have already had made.

Nagg, last time I did a google search, it didn't turn up a lot of info that was helpfull. Like price and more to the point, the physical sizes of batteries. Ill give it another more thorough search tonight. Sure the wet cells Trojans are the pick of the crop for deep cycling etc, however mounted in the bow of a 4.2m tinny thats driven in all sorts of water conditions at all speeds, is probably not where the designers had in mind for testing the durability of their batteries.

Cheers

Andrew

Hi Andrew

My reference to Trojans are for a quality wet cell ....... Many people use them for their bow mount leccy @ $250-$300 for a 120amp
I use Absorbed power AGMs for my 24 volt system ( just about the best available ...... but $350+ for a 100amp)
Check out

www.renewablestore.com.au (http://www.renewablestore.com.au)
&
www.solaronline.com.au (http://www.solaronline.com.au)

From memory they were pretty good

Nagg