Dual Battery Setup

[Auger01]

This is a schematic of the electrical system that is going into my 78 Glastron. The restoration is amlost to the point where I can get to the wiring.

The main goal of this design was to allow for a day at anchor on the lake listening to the stereo and yet not have to worry about having enough juice to start the motor. I also designed a bit of redundnacy for safety. The system is flexibile, you can start on either battery and keep the batteries seperate or parallel them together. It is also made easy enough to use to that my wife can easily operate it. Two switches control the batteries and the tie switch is usually left in auto. Another feature I like is that the battey disconnect swithes are on the panel. There is no fumbling about openeing hatches getting to the batteries pre or post launch to turn a manual switch. There are widgets you can buy that do almost what I wanted, but none did exacty what I wanted, so I designed my own.

Photos of the rebuild here.

 

[pdgs]

Re: Dual Battery Setup

Auger01, I admire your ingenuity but I have to tell you, you could do everything you want to do with a single Blue Sea Add a Battery system with the Automatic Charging Relay.

One thing we all would like to do is design our boats electrical systems as state of the art. However, we don't, because we know to keep it as simple and stupid as possible. If we do and something fails out on the water, we want to be able to use bubble gum and bailing wire to get back to shore and safety. Admittedly that sounds a little ridiculous but I can guarantee you'll recite it word for word if you ever get stuck out on the lake and can't come up with a simple fix.

That's just advice, you don't have to feel obligated to follow it.

 

[UncleWillie]

Re: Dual Battery Setup

I would have to agree with pdgs, your starter circuit has small 150 amp fuses in series with a set of Contactor Relays.
That is a problematic arrangement.
Be sure to always care spare fuses and Contactors, or at least a jumper cable to bypass the whole system.

Keep it simple. If it doesn't exist, it can't break!

 

[bruceb58]

Re: Dual Battery Setup

Definitely skip the way you are doing things with the relays. Get the BlueSea combiner. Its all solid state and will combine automatically. There is also an input to it to disable it if you don't want it to combine.

What is the full bridge rectifier for? Doesn't really look like its hooked up correctly.

 

[bongodog]

Re: Dual Battery Setup

A voltage dependent relay will join the batteries. and then a starter size cable from one battery +ve to the other with a battery isolator switch in it will do the job ..just throw the switch if you need to parallel the batteries for emergency starting...Keep it simple .....very simple ...

Always charge the batteries at home before a trip.

 

[Don S]

Re: Dual Battery Setup

All the info you could want on the Add-A-Battery - PN 7650 - Blue Sea Systems

You can get one here.
Blue Sea Systems Add A Battery - iboats

 

[Auger01]

Re: Dual Battery Setup

Thanks for all the input guys. Compared the aircraft I normally work on, this IS a simple setup. When stuff breaks at altitude, you can't just pull over and fix it. Redundancy and quality equipment are the keys to success there. It shouldn't be any different on the water.

I would have to agree with pdgs, your starter circuit has small 150 amp fuses in series with a set of Contactor Relays.
That is a problematic arrangement.
Be sure to always care spare fuses and Contactors, or at least a jumper cable to bypass the whole system.

Keep it simple. If it doesn't exist, it can't break!

I might agree that the 150 amp circuit breakers may be too small. Once I get the engine (a Yamaha F90) installed, I will have a better idea of the starting current and will size the breakers accordingly. I figure no more than 250 amps for the starting current and those 150amp circuit brakers will do 200% for 10 seconds. More infomation on the breaker trip curve here.

I am not sure by what you mean by "problematic arrangement." Could you elaborate?

 

[bruceb58]

Re: Dual Battery Setup

There is a simpler solution to what you are proposing and its going to be less expensive and more reliable in the long run. You don't need(and are not required to have) a breaker between your battery and your starter, especially if you get rid of the relays.

You are reinventing the wheel. There are 1000s of boats that are wired differently than what you are proposing and there would have been a trend to what you are proposing if it was actually a better idea.

 

[Grandad]

Re: Dual Battery Setup

Hi Auger, I don't want to pile on, but I do agree with what others have said above. I can't quite read details of the schematic on my screen, but have you considered the parasitic drain on the batteries using those relays/solenoids? If you leave the boat in the water while unattended, you may want to have the bilge pump operable without constantly losing charge to hold a relay contact closed. You've designed a sophisticated system that you feel comfortable with and you feel your wife can operate, but could your wife or someone else get the system operable when offshore if a relay fails? K.I.S.S. A battery selector switch that never fails doesn't necessarily have to be located in a difficult place to access, and really, how often do you need to access it? (see the selector location in my rebuild thread link below) - Grandad

 

[UncleWillie]

Re: Dual Battery Setup

...I am not sure by what you mean by "problematic arrangement." Could you elaborate?

What I was thinking is a Fuse in the starter circuit is a deal killer if it blows.
The picture is fuzzy; I now see you spec a Circuit breaker; Better!

The Relays/Contactors can be an issue in low voltage, high current situations.
There is just not the extra head room to be able to give up as little as a few tenth of a volt when you have less than 12 volt available from the system.

The schematic does not indicate specifically the quality of your relays/contactors.
In the boating world, Commercial Aircraft Grade STC'd components are not common. $$$

The main start battery wired directly to the starter, with the ability to parallel the Aux battery, is simple and more than sufficient.

With all that said, as a fellow electrical control freak, I do understand your logic.
The ability to determine where every electron goes is a powerful feeling!
I considered something similar at one time but was able to control myself and kept it simple.

 

[Auger01]

Re: Dual Battery Setup

The picture is a bit small, a bigger picture of the diagram is here.

Hi Auger, I don't want to pile on, but I do agree with what others have said above. I can't quite read details of the schematic on my screen, but have you considered the parasitic drain on the batteries using those relays/solenoids? If you leave the boat in the water while unattended, you may want to have the bilge pump operable without constantly losing charge to hold a relay contact closed. You've designed a sophisticated system that you feel comfortable with and you feel your wife can operate, but could your wife or someone else get the system operable when offshore if a relay fails? K.I.S.S. A battery selector switch that never fails doesn't necessarily have to be located in a difficult place to access, and really, how often do you need to access it? (see the selector location in my rebuild thread link below) - Grandad

I have considered the drain of the solenoids, that is why I used "latching" relays for the batteries. They only require power to go from on to off or vice versa. Once on they draw no power so they will stay latched even under heavy voltaqe sags. Concerning a relay failure, most everything will still work even if any single component fails.

Obviously, this setup isnt for everybody. I just though I might show what I am doing with my boat rebuild. After all, isnt that what these forums are for?

 

[Grandad]

Re: Dual Battery Setup

Hey Auger, the latching relay should cure the power drain issue. Will the solenoids be located in a well ventilated area (no fumes)? If you can find solenoids that are "ignition protected", I don't see a problem with using them. Corrosion resistant would be a bonus. And yes, the forum is for sharing ideas like yours. Keep 'em coming. - Grandad

 

[bruceb58]

Re: Dual Battery Setup

The specs on those relays don't give you a lot of margin for current capacity.

 

[glenn property of pam]

Re: Dual Battery Setup

you are correct in saying that most boats have the perko switch in the rear where you have to open a hatch to get to it. the only reason its there is to keep the cost of the wire low. a couple of 500 amp breakers and some heavy gauge wire to off set the voltage drop and you can mount the perko switch next to the helm. your idea looks intresting but if i have to push a button to select a battery i might as well just turn the knob. add a auto transfer relay to charge the second battery if your outboard has enoght ampage to make it worth while. (my on board battery charger is also a auto transfer but with 6amps from the motor it is kinda worthless)

 

[glenn property of pam]

Re: Dual Battery Setup

looking at the diagram the diode bridge looks confussing and has no real use.
most latched relays or at least the cheaper ones have both a latch and unlatch wire the expensive alternating latch can use one button but ive never seen them in high amp use. you could just add a small relay to work the larger contactor but thats just more things to go wrong.
im not sure you realy need a dual/bypass contactor as you could just close both battery switchs at the same time and that would be a advantage as a perko should not be switched while the motor is running.
i do not like the idea that some things are connected to the batteries all the time even if it is just a button. i use my perko mainly for the battery disconnect once turned to off i know everything is off and no amount of rain water can cause a short and turn it back on

 

[etracer68]

Re: Dual Battery Setup

I'm still waiting for Silvertip's opinon. Hey! wheres the popcorn smiley.

 

[Howard Sterndrive]

Re: Dual Battery Setup

Get all unnecessary wiring off any boat and it will be more reliable.
I connected 1 battery with a remote battery minder / disconnect , and carry a booster pack. (itdisconnects everything except the bilge pump circuit at 11V)
The remote is nice. I can turn on the bilge blower from 200 feet away. By the time I reach the boat the bilge is well ventilated.

 

[bruceb58]

Re: Dual Battery Setup

looking at the diagram the diode bridge looks confussing and has no real use.

Looks like its being used as an isolator.

 

[Auger01]

Re: Dual Battery Setup

I finished installing the electrical systerm in the Glastron today. What I installed is follows very close to the schematic I posted above. I did however use more robust components. The remote battery switches are rated for 2500 amps for 10 sec and 500 amp continous. The also have a manual lever as a backup. The blue sea relay I am using a bus (battery) combiner is rated at 1500 amps for 10 sec and 450 amps continous. Everthing is UL listed and ignition protected.

If you look in the picture above, you can see a 10 gauge wire connecting the fuse blocks. That normally wont be used, but if there is a problem, I can open one of the 50 amp breakers above the fuse blocks and plug in a fuse on the 10 gauge purple wire to combine the fuse blocks.

The stereo will have come out again so that is why its wiring is a bit of a mess.

About the only other thing I changed was that Bilge pump A is connected directly to the battery in the Auto mode. As always, comments are welcome.

 

[Silvertip]

Re: Dual Battery Setup

Only one comment -- "Yikes".