Dual Battery Help

[Rodb73]

Hi Raiders,

I'm hoping there might be few suggestions here for my new Dual Battery setup.

I am basically after suggestions on which batteries to use.

I have recently purchased 2 (100amp Circiit Breakers), a 120amp Voltage Sensitve Dual Battery Relay and am wanting to run the following;

70hp Mercury

Nav Lights/Anchor Light LED's

Marine Radio

Fish Finder

Phone Charger

LED Strip Lighting

Front/Rear Spots

Underwater LED's

A couple of Courtesy Lights here and there.

Having only 1 motor on the boat, I don't want to get stuck with a flat battery.

Any help would be greatly appreciated.

Thanks.

Rod.

Edited November 21, 2013 by Rodb

[Testlab]

Easy.. you have all the right gear.

Connect the engine to battery A and all the house loads to battery B. Use the VSR to parallel the batteries. this way you start off battery A and the VSR will automatically parallel the battery banks when the charging voltage exceeds the threshold voltage. Thus battery B can go flat and battery A will be protected from discharge.

[Rodb73]

Thanks a lot for the prompt reply.

Do you have any suggestions on battery types/size please?

[Testlab]

This is where it gets a bit tricky. Choosing the right size battery is a balance between capacity of the battery, the capacity of engine alternator, sustained load and the size of your wallet.

For a boat around 5m and average use I would fit something like an Exide ED4 deep cycle as the house battery (batt B in my example). A good quality marine battery rated for your engine size will do as as battery A but make sure it is of similar reserve capacity as batt A.

If you expect to be running a high house load all night then a bigger reserve capacity is needed in both battery and wallet. The bigger the batteries the longer the recharge time so running huge batteries off a small engine means it will take a long running time to get a decent charge back into them. To keep them in good condition you should top off the charging after each deep discharge with a good quality charger matched to the battery size. The VSR will simply parallel the batteries which is not the ideal way to charge them, especially if the batteries are not identical and at different states of charge (as they will be).

Put your circuit breakers as close to the positive poles of the batteries as possible. Depending on the size of our engine you should not put a breaker between the battery and engine. However always locate a breaker close to the battery for any wiring going off to house loads. Size this breaker one third larger than the maximum possible load.

[boattart]

For anyone fishing particularly offshore I don't think you can go past having a jumpstarter onboard. These days they are fairly cheap and compact and if night fishing with lights on you can even plug into the 12v plug to preserve your batteries. I have 2 motors and twin batteries and always carry one. Just remember to keep it charged.

[Scratchie]

For anyone fishing particularly offshore I don't think you can go past having a jumpstarter onboard. These days they are fairly cheap and compact and if night fishing with lights on you can even plug into the 12v plug to preserve your batteries. I have 2 motors and twin batteries and always carry one. Just remember to keep it charged.

I agree boattart.... I always carry one on board whenever I take the boat out. Great peace of mind for very little cost!

Cheers scratchie!!!

[Blairy]

I just bought 2 x Century Yuasa marine batteries - bit early to tell but they certainly look well put together.

And they always seem to get a good rap?

Thanks

[Rodb73]

Thanks to all for your responses. I have certainly got some home work to do on the right battery selections.

Thanks again.

[Testlab]

I just reread what I wrote this morning. When I said 'Size this breaker one third larger than the maximum possible load' I mean one-third larger than the sum of everything added together.

[Flickn Mad]

Should the B battery be a deep cycle battery for this purpose.

One for testlab, are breakers not usually sized to suet cable size.

And do you think these newer chargers with a maintenance mode are worth while.

Re jumpstarters, I have never needed to use mine yet. I have however saved three different fishos from a crappy morning at the boat ramp over the last few years. one with a flat car battery after a night on the water the other two had just cranked there batterys flat after not using there boats for some time. It pays to kick your motor over the arvo before a planned trip just to make sure.

My jump starter cost me 60 bucks and goes with me every time.

[Testlab]

Battery B is the deep cycle.

It is true that breakers are rated for cable size but if you are running a maximum 10A load why fit a 25A breaker. Sometimes it is better to limit the fault current to minimize consequential damage.

If you had a couple of general outlets to plug in a 100W spotlight (8.5A) but you also want to plug in a 240V inverter (high load) then you would be sizing the breaker to the cable to prevent dangerous and potentially fire causing overloading.

[Testlab]

Oh, yeah... A good maintenance mode charger is a good investment. You can buy them for a reasonable price and they will last for a long time if not abused or exposed to the weather.

[Flickn Mad]

Thanks mate. As usual everything you say makes perfect sense.

I just worry when I see guys running 1.5 mm from the battery to the console/dash and then parallel stereo lights circulation pumps and hope for the best.

I ran a 6mm positive and negative to my console to supply a buss bar then distribute power through switch panel from there.

When I got my boat it had a bundle of 1, 1.5 and 2.5 cables running back and forth through the hull all terminated in a corroded mess at the battery terminals, just waiting for a hot joint or short to ruin my day.