2nd Battery

[Adam F]

I know this has been covered loads in the past - but I being lazy, and just have 2 quick questions.

 

1.) I have a isolation switch fitted already, so if I fit a 2nd Batt - do I just run the +ve and -ve from the batt to the switch??

 

2.) How do I fit a Volt Meter to my boat, and how easy is to do? - Where do I get one?

 

Thanks

 

Adam

[domino]

Adam,

 

I think you'd be better off with a battery changeover/isolator switch - like this.

 

You can then have either, or both, battery connected to the engine for either starting or charging.

 

The attached doc shows how I've connected mine up.

 

A voltmeter simply connects straight across the battery terminals - again this could be connected via a (much smaller) changover swicth to monitor either battery.

 

As for where to get one from... where else??

 

... or any car accessory shop.

 

Alan

Edited May 12, 2004 by whippet

[Adam F]

I already have the switch fitted to the boat - it just runs the one batt at the moment though.

 

Where do I wire the meter though? If I have 2 batts, I need to monitor both of them?

[domino]

I've edited my original post and attached a drawing of how my switch is wired up.

 

The doc attached to this post shows how to wire up a switch and voltmeter - you would need a 3 position switch (centre OFF) to switch between batteries. Suitable toggle switch and splashproof cover can be found here.

 

Hope this helps.

Alan

[Coddy]

Hi Adam

 

Just a thought that if you try to charge both batteries at the same time you may get electrical interferance which can upset your GPS/plotter.

 

Worth being in mind, I always use a deep cycle battery just for electronics and charge at home.

 

Codfather

[Malroy]

Hi Adam,

I would personally stick to having one battery for the engine with one or maybe two auxillary take of points (fused for accesssories e.g. live bait pump etc) and a seperate deep cycle for the electronics side, the whole kit of items normally has a very low discharge rate.

 

Then think about fitting a solar charger of around 5 watts min (not one of these 1-2 watts versions nocking around) to keep this battery topped up.

 

Since I have fitted mine I have not yet had to re-charge the battery since, as it keeps it topped up really well.

 

You will then need no switching from one battery to the other and there is no risk of damage to the charging circuit.

 

When I fitted the solar panel (make sure if you opt for one, where there is a blocking diode fitted to stop discharge at night) I also fitted a 12 volt meter like what you are looking for, to monitor the batteries condition. You can Pick up new marine ones for around the

[Adam F]

Tis a very good point! and now I'm well confused!

 

Many of you swear that 2 batts are a must, and have very valid arguments

 

Others see no need, and would rather not risk damaging the system.

 

My main reason for wanting to fit the 2nd is as a back-up. The battery that is fitted at present has held its charge very well to date and I have had no problems at all. The previous owner has very neatly fitted a Solar charger into the Tonneau canopy. I plug this in whenever Im not using the boat, so it gets at least a weeks charge each time. 2 Questions:

 

1.) How will I know weather I have a 1/2 watt or a 5 watt unit?

2.) What position should I have the batt isolator on when charging via the solar panel? - I usually have it in 'OFF'

 

I think the approach I will take is to fit a 12v Gauge. I will then monitor the batteries condition and make a decision from there.

[duncan]

Adam you almost certainly have a volt meter on board wired in already - it will be a function of at least one of your electronics. Just go into setup and tell it to add to the display data. pound to a penny the sonar will have it

[Malroy]

Sorry Adam, I am by no means an expert on electrical/electronics so don't really know how to measure the watts. It was actually demo'd to me at the time but I can't remember how he set up the metering.

 

However when you start to look around at the sizes of the commercially available panels you can start to gain an indication of how the power levels are proportional to their sizes.

 

When you buy the commercially available ones the watts are normally given any way.

 

Those that only put out around 1-2 watts of power are usually around 9"-10" x about 3"-4" & sell for between

[Newboy]

I'm a little confused now. I was told present day electronics on board draw very little power from the battery. So if we are only fishing for the day, one battery should have enough juice (before it's recharge when we get home) for the eleronics and the only should cope with starting the ob, or shouldn't it?

[Malroy]

One decent power battery should always be able to deal with ALL the boats electrics plus have plenty in reserve.

 

The BIG however though, has a lot to do with the safety aspect. There is an ever increasing move towards having a second back up everything, hence the move over to adopting the practise of two batteries.

 

Batteries need plenty of TLC, and there is nothing worse than having a back up that isn't in use & you never know its state.

 

Car type batteries are designed to be used in conditions where there is no deep cycle i.e. the battery is constantly being charged from the engine alternator/generator and never normally goes down to a low state of charge.

 

Where a battery is constantly subject to being charged then discharged, the cycle becomes much deeper hence the need for a different type of battery, i.e. the deep cycle leisure type batteries like used on caravans.

Hence the ideal tends to be car type battery supporting the engine, with everything else from the leisure battery.

 

You may reduce the life expectency of a car type battery if using a lot in deep cycle conditions on the boat, this being more likely if you do a lot of night fishing using powerful spots etc.

[Newboy]

The prices on leisure batteries have came down so much over the last few years. I remember a few year ago, a leisure battery for caravan will cost in the region of

[Paul D]

Regarding charging two batteries at the same time having an affect on the electronics. There will be no difference in charging one battery to two batteries.

 

Never had any problem with interference and since fitting my second battery I always go out charging two batteries - when I remeber to put switch in BOTH postition ( 2 batteries in parallel is exactly the same as having a battery of twoce the capacity ).

 

One thing worth bearing in mind is that when switching from battery 1 to BOTH to battery 2, if this is done whilst the engine is running then you should NEVER switch from 1 to OFF to 2, which could/will damage the alternator/rectified.

 

The Garmin GPS you have Adam will give a battery alarm if the voltage falls below a value set in the setup screen. ( You will know this works as the voltage will momentarily drop and trigger the alarm when starting the engine - at least it does on my boat ! ).

[Adam F]

Right - Decided to go for the 2nd battery.

 

But where to go? I dont want quite as big a unit as the 1st batt, and I am weight concious.

 

Anyone have any suggestions for a bargin battery? Also - Battery cable, what size and where from?

[Newboy]

I got my 85 ah from Towsure in Soton for

[Afishionado]

I got my 85 ah from Towsure in Soton for

[Adam F]

Sounds good to me - Ill call in 2morro and treat myself. I also need a box and a length of cable.

 

Will 85 AmpHR be Ok for my 2nd batt??

[Maverick Martin]

Adam

 

I have two 85 AH bats on my boat and never had a problem except when I left my electrics switched on for 3 weeks

 

Martin

[Paul D]

Adam,

 

85 AH will be ample ( excuse the pun )

 

RE: Cable to join the negatives of teh two batteries together, I used a starter motor lead from Halford (

[Coddy]

Adam

 

DO NOT FOGET TO FIT A FUSE

 

I use a 15amp fuse in the main feed (Red wire) which comes off the 2nd battery terminal and goes to the main +ve bus bar where all other take off points are made for other functions, plotter, gps, lights, bilge pump etc.

 

Bought my fuse set up from Halford's in the radio spares section.

 

In my case I do not charge the second battery from the engine but use it just to supply everything else EXCEPT to start the engine.

 

You should of course have a seperate fuse to every function, normally about 3 amps.

 

If you are going to use your switcher for charging from the engine, you will have an additional supply feed (connection) to run all the equipment. Put a fuse in this line to make sure that if you get a short circuit it does not start a fire

 

Regarding size of wire, suggest you use same size cable as car starter cable because if you use the second battery to start the engine the current draw (amps) can be very high (60+amps in cold weather on a cold engine)

 

I hope I have not confused you too much.

 

I have seen some bad electrics in boats and I shudder to think what would happen if some water got mixed around with the wiring. Better to fit lots of fuses or trip switches than have a wiring harness fire when out at sea!

 

You then have to think about what sort of fire exstinguisher you have on board to cover electrical fires!

 

Sorry to be a bit of a downer but safety is paramount

 

Codfather