Correct Battery

[GT Mayhem]

I am in need of replacing 1 of my 2 batteries on my boat. Since there are no stickers om the battery i cant remember what the correct size is. I know that i have always been using deep cycle batteries but on doing some research and speaking to people i have learnt that they are fine for running electronics but not ideal for starting engines. So my question is what type and size battery do i need for my application?
I have 2 x mercury 60hp BF 4 stroke engines.

On my recent trip i found that the 1 battery was running low and not charging by the alternator, on inspection i found that 1 of the fuses in the engines fuse box had melted down and needed to be replaced, once the fuse was replaced the problem was solved...... I think. What could have been the cause of this?

I have all my electronics running off 1 of the batteries, but after the recent addition of a couple more pumps i realise this is too much strain on the 1 battery and decided to run the 2 new pumps off the second battery.

So since my electronics are run off the same batteries i use for starting, what would be the correct battery to use?

[Rory mundy]

you need cranking batteries for your motors, not deep cycles all depends on how much space you have in your battery box and fit the biggest you can
i have 3 deltec 105amp batteries two are connected in series and my one motor and all electronic are on that pair never had a problem

[Rory mundy]

this new range of discover batteries look good, but a good old willards will also be fine

[FishStyx]

If it were my boat, I'd have 2 normal car batteries (45-60Ah), one for each motor, and a smallish deep cycle (45Ah) for electronics only. Deep cycles are not designed for high discharge rates like the current drawn by a starter motor as you have discovered. Not sure what may have blown the fuse.


I have a single motor installation on my little boat and run a small (32Ah) battery for starting the motor. I then have a 100Ah Varta deep cycle for electronics and trolling motor. I also have a circuit (fuse protected) that I can switch on charging when the motor is running so as to charge my deep cycle. I've been running it this way for a few years without issue. If I'm just out for a day, then I charge the deep cycle when I get home. If I'm away for a few days with no means of shore charging, then I switch on the charging circuit while underway to keep the deep cycle topped up.


Keep all batteries topped up when the boat is not in use. Charge to full capacity with a smart charger when you get home and then connect a trickle charger to each while boat is not in use. This way, your batteries will last many years. I have a cheap Midas battery on my generator that has a trickle charger connected and it's now over 10 years old. Starts the genset every time without fail.

[dugong]

If it were my boat, I'd have 2 normal car batteries (45-60Ah), one for each motor, and a smallish deep cycle (45Ah) for electronics only. Deep cycles are not designed for high discharge rates like the current drawn by a starter motor as you have discovered. Not sure what may have blown the fuse.


I have a single motor installation on my little boat and run a small (32Ah) battery for starting the motor. I then have a 100Ah Varta deep cycle for electronics and trolling motor. I also have a circuit (fuse protected) that I can switch on charging when the motor is running so as to charge my deep cycle. I've been running it this way for a few years without issue. If I'm just out for a day, then I charge the deep cycle when I get home. If I'm away for a few days with no means of shore charging, then I switch on the charging circuit while underway to keep the deep cycle topped up.

Keep all batteries topped up when the boat is not in use. Charge to full capacity with a smart charger when you get home and then connect a trickle charger to each while boat is not in use. This way, your batteries will last many years. I have a cheap Midas battery on my generator that has a trickle charger connected and it's now over 10 years old. Starts the genset every time without fail.

40-60ah will be too small for those motors, I have 70ah's Deltecs and they are marginal.....I would go with 90ah minimum.

[dugong]

you need cranking batteries for your motors, not deep cycles all depends on how much space you have in your battery box and fit the biggest you can
i have 3 deltec 105amp batteries two are connected in series and my one motor and all electronic are on that pair never had a problem

I think you mean in parallel

[FishStyx]

40-60ah will be too small for those motors, I have 70ah's Deltecs and they are marginal.....I would go with 90ah minimum.

My 1.4l car uses a 646 battery which is 56Ah... I always feel that boating guys put way too big batteries in... Wasted space and wasted bucks... And heavy. Those mercs are only 1000cc.

[GT Mayhem]

So i just spoke to the technician at Rutherford. He recommended standard 652 or 657 batteries for starting.

So im thinking i should have the standard batteries for starting and use a 105ah deep cycle for electronics. How would i connect these in order to charge my deep cycle from the engines?
Currently i have 1 battery connected per engine and all my electronics connected to 1 battery with an in line cut off switch.

The electronics i have in the boat are as follows...

GPS
SOUNDER
VHF
ANCHOR LIGHTS    NEVER USE THEM
RUNNING LIGHTS.  NEVER USE THEM
2 X 1800GPH BILGE PUMPS FOR HATCH DRAINAGE
2 X 3500 GPH BILGE PUMPS FOR LIVE WELL AND LUNA TUBES

[FishStyx]

My setup is very simple. The motor battery is charged through the main leads that connect to the battery. I then have 2 thin (2.5mm2) wires connected to the + and - of the motor battery going via a switch and a 20A (I think) fuse to the deep cycle battery. I manually switch the charging circuit to the deep cycle as and when needed while the motor is running.

[Rory mundy]

you need cranking batteries for your motors, not deep cycles all depends on how much space you have in your battery box and fit the biggest you can
i have 3 deltec 105amp batteries two are connected in series and my one motor and all electronic are on that pair never had a problem

I think you mean in parallel

the one that keeps it 12 volt

[GT Mayhem]

My setup is very simple. The motor battery is charged through the main leads that connect to the battery. I then have 2 thin (2.5mm2) wires connected to the + and - of the motor battery going via a switch and a 20A (I think) fuse to the deep cycle battery. I manually switch the charging circuit to the deep cycle as and when needed while the motor is running.

Cant i keep it connected permanently so that it charges whenever the engines are running?
It charges the battery via 2.5mm wires? Isnt that too thin? Doesnt require normal battery cables?

Please excuse my ignorance, im a lemon when it comes to circuits and electric.

[FishStyx]

Cant i keep it connected permanently so that it charges whenever the engines are running?
It charges the battery via 2.5mm wires? Isnt that too thin? Doesnt require normal battery cables?

Please excuse my ignorance, im a lemon when it comes to circuits and electric.

That's why we have forums  ... We're all here to help. The starter motor draws a huge current (in excess of 100A) whereas charging with that motor will be less than 15A. I prefer having all batteries isolated. I've had issues in the past with one battery draining another because of sulphating. It's also essential that batteries that are interconnected be the same type and same size. A further point is that if you start your engine, you will once again be drawing power off your deep cycle. I'll take some pics of my setup and post them.

[Half-Pint]

If you need an introduction to 12v electrics I suggest you check out this thread from 4x4community

https://www.4x4community.co.za/forum/showthread.php/187502-Electrickery-for-camping

Although from an automotive perspective it explains the concepts of deep cycles vs high cycles and charging rates very well

[GT Mayhem]

Thanks guys.

Anyone else running 2 batteries with a 3rd aux battery? How are your setup?

[L Hooker]

This is how i setup my wiring on my Tomcat..The switch at the motors is a combine switch (Blue Seas Pn011), so if one battery dies i can then start either motor with the battery that is still fine. The front switch is a basic blue seas on off switch to cut power to any electronics. The charging relays are the Blue Seas M-ACR 7601 automatic charging relays, i could have perhaps used 1 charging relay? however i opted for two so when power drifting or when im only using 1 motor either motor still charges the house battery. I purchased all the goodies from Steve at Seaport Durbs. All wiring was Tin Silicone wire, and i made sure to upsize the wiring running from the start batteries to combine switch (12 0r 14mm ?) and 10mm to front panel. My wiring might have been a bit overkill however ive never had any issues what so ever since doing this!

[CRANKMAN]

Nicely done Sheldon.

What about using an intelligent solenoid like we use on dual battery off road vehicles? They manage the standard / deep cycle combination nicely.
If it were wired between your start and deep cycles, then only after 5 minutes of good charge to your start batteries would the solenoid activate allowing charge to flow to the deep cycles. Some models have a bridging mod so that in emergencies the deep cycle can assist with starting.
There would be no risk of forgetting to isolate them when the motors are off (this happens automatically), also charge would only be shared once the cranking batteries are holding a good charge.
These solenoids are quite cheap at Outdoor Warehouse, but I don't know if the are marine grade.
http://www.outdoorwarehouse.co.za/product/national-luna-intelligent-solinoid

[CRANKMAN]

This seems a better option solenoid for marine use

http://4x4direct.co.za/battery-accessories/9193-solid-state-switch-for-double-battery-system.html

[L Hooker]

This seems a better option solenoid for marine use

http://4x4direct.co.za/battery-accessories/9193-solid-state-switch-for-double-battery-system.html

Hi Sean , i suppose it would work ive never used those components before bud? I opted for marine grade components so went with the Blue Seas stuff, salt has a way of stuffing up electronics super fast  . No matter how ive tried sealing joints/connectors etc corrosion always seems to find its way in when using standard copper wiring, non marine grade stainless etc etc, since i ripped that all out and went the tin wire route/marine grade components i have not had a single issue in 4 yrs now i believe?

[CRANKMAN]

This seems a better option solenoid for marine use

http://4x4direct.co.za/battery-accessories/9193-solid-state-switch-for-double-battery-system.html

Hi Sean , i suppose it would work ive never used those components before bud? I opted for marine grade components so went with the Blue Seas stuff, salt has a way of stuffing up electronics super fast  . No matter how ive tried sealing joints/connectors etc corrosion always seems to find its way in when using standard copper wiring, non marine grade stainless etc etc, since i ripped that all out and went the tin wire route/marine grade components i have not had a single issue in 4 yrs now i believe?

I think your relays between your cranking batteries and your house (deep cycle) battery are automatic anyway, only closing when there is charge coming from your motors - or do you switch them manually?
You offshore guys are and need to be a bit sharper than us inlanders, I would forget to switch over if all manual. 

[FishStyx]

I would forget to switch over if all manual. 

I don't... But then again, I drink only a fraction of what you do mate.