Dual battery setup.

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Fanatic1074 · #1 Post by **Fanatic1074** » Fri Oct 21, 2011 6:54 pm

Hello all!

I got a few projects that i am going to work on over the winter months and i need your input!

One of them is i want to setup a dual battery setup in my boat. Currently i just have one battery and no box or anything. I want to get two batteries put them in a dual battery box is possible and put a marine battery isolator on it.

What i am trying to accomplish is to be able to take my boat out on the water or on a shore and play music and charge stuff off my boat without having to worry about the battery charge level. Im under the impression that a battery isolator will do just that. It will drain only one battery while leaving the other for boat stuff and then work out the charging based on battery level. Is this correct?

Or does anyone have any better ideas?

Thanks all!

WoodenPontoon · #2 Post by **WoodenPontoon** » Fri Oct 21, 2011 7:58 pm

Yes you can add a second battery and install a selector switch between them. Blue Seas Systems has a product called "Add-a-Battery" which combines both batteries anytime there is a charge coming into the system and then isolates the batteries when the charge is removed. The charge will be automatically adjusted to match the requirements of each battery. The switch is either "Off-On-Both", with the both position for manually combining the batteries. This is a very reliable and easy to use setup. It allows for a "house" battery and a "starting" battery.

Other Selector switches are likely to be less expensive, but will require more diligence on your part. Typically, they will have "Off-Battery1-Battery 2- Both". You will have to manually make the selection between the batteries.

Good luck!

Fanatic1074 · #3 Post by **Fanatic1074** » Fri Oct 21, 2011 8:54 pm

WoodenPontoon wrote:Yes you can add a second battery and install a selector switch between them. Blue Seas Systems has a product called "Add-a-Battery" which combines both batteries anytime there is a charge coming into the system and then isolates the batteries when the charge is removed. The charge will be automatically adjusted to match the requirements of each battery. The switch is either "Off-On-Both", with the both position for manually combining the batteries. This is a very reliable and easy to use setup. It allows for a "house" battery and a "starting" battery.

Other Selector switches are likely to be less expensive, but will require more diligence on your part. Typically, they will have "Off-Battery1-Battery 2- Both". You will have to manually make the selection between the batteries.

Good luck!

Nice i kinda like that idea. I dont know how much you know about it but do you know if i can simply hook my deep cycle charger to one set of termials and charge both batteries or would i ruin something?

jafo9 · #4 Post by **jafo9** » Sat Oct 22, 2011 6:50 am

i've done the "add a battery" kit and it is great. it took me a while to get my head around the wiring to get it right. i have an entertainment center with fridge i had to add to the mix. i also added a dual bank charger to maintain the batteries independently. i later learned that i needed to add another switch to isolate the batteries when they were on the charger, otherwise, the ACR would combine them and float them as one. pretty simple, i put an inline switch with a waterproof cover next to the charger box that is mounted on an inner fence in the aft/port storage compartment. to put her to bed, i rotate the master switch to off, flip the toggle switch to charge and plug in the dual bank charger.

you could do it with a single bank charger, though, to me it made more sense to float the batteries independently (they are different batteries).

like i said, it was a bit of a hassle getting it all set up, but now i can run the fridge, stereo, lights, etc. and not worry about getting the boat cranked. the only problem (small) is if i forget to turn off the fridge when we go up for the night and it drains the house battery all night to below 10ish volts. the ACR won't let them combine to charge the house battery unless its above something like 10.5volts to protect the start battery. my solution was to force them to combine for a few minutes and then the ACR took over just like normal.

fwiw - i found genuinedealz.com to be far and away the cheapest source for the big battery cables that you will need. they will custom cut them and shrink wrap them for a reasonable price. i think i also bought some of the fuses required through them as well.

dtruly · #5 Post by **dtruly** » Sat Oct 22, 2011 9:05 am

My boat is an older used model which already had a two battery system in it with an isolator switch. I added a Guest intelligent charger which I plug in at the slip. It keeps both batteries fully charged with no need to worry about overcharging as can happen with many trickle chargers. I highly recommend the Guest products.

brianD · #6 Post by **brianD** » Sun Oct 23, 2011 3:01 pm

My new rig (well new to me anyway) has a bit of a silly setup. I have two batteries, and an onboard charger that charges the two independently when on AC, but they're hooked up in parallel, so it's ALWAYS both. I can't separate house from starting without some re-wiring... Looks like I too have a winter project.

Rhinohio · #7 Post by **Rhinohio** » Mon Oct 24, 2011 1:57 am

I just installed a Blue Seas Add A Battery and a Minn Kota dual bank on-board charger. This is a great setup. I was confused about the two bank charger and the ACR (Automatic Charging Relay) but finally the light come on. I simply hooked the ACR to the load side of the battery switch and the MK210 to the house and start batteries. When the switch is set to off, the ACR is isolated from the two charging sources and doesn't try to combine the batteries as it would if it was connected to the batteries as shown in the diagram.

http://bluesea.com/viewresource/505

This is the charger I bought

http://www.amazon.com/Johnson-Outdoors- ... d_sim_sg_2

I also added a ac outlet which makes it really convenient to maintain the batteries.

http://www.amazon.com/MinnKota-MKR-23-P ... d_sim_sg_1

It all got a little spendy after buying the cables, fuses, miscellaneous hardware and components, but I think it's worth it. When Iâ€™m ready to take the boat out, I turn the switch to on and the ACR tends to the charging of the house and start batteries. When It goes back on the trailer, I switch to off and itâ€™s ready to plug the extension cord in and top the batteries off for the next day of boating. It couldnâ€™t be easier. I'll take some pictures the next time I'm at the boat.

Fanatic1074 · #8 Post by **Fanatic1074** » Mon Feb 27, 2012 5:38 pm

Ok i like the ideas i think im going to go with an auto battery switch and another battery. Here is what another member recomended. Anyone know any cheaper alternatives?

http://www.ezacdc.com/boat-wiring-produ ... h-systems/

Now the other question i have is about the second battery. Currently i have a Deka Marine Master DP24, witch is a Dual Purpose marine battery. 550 CCA. mCCA at 0Â°F: 550amps MCA at 32Â°F: 685amp Reserve Minutes at 25 Amps: 120min.

Im wondering if i should just buy another one of these or get a full deep cycle.

Im going to go ahead and restate what i am trying to accomplish. I want to have plenty of battery power to be able to dock my boat on one of the sandy beaches at the lake and setup shop for the weekend. I will use the power on the boat for the following. Music (Alpine head unit powering 4 infinity 6x9's and a Marine bass tube.) Assume that its running near full power the entire time

. blow up air matresses/floats ect. with a small pump, charge cell phones. I would take the boat out occasionally for a stroll around the lake and i also have a 5amp solar charger that i would prolly hook up while the boat is sitting to help with keeping the juice.

Maybe i am asking too much but i dont think i am. I am very new to this stuff and if im doing something wrong or over expecting then please set me straight

.

Thanks Guys!

slingshot · #9 Post by **slingshot** » Mon Feb 27, 2012 5:51 pm

It's very simple:

Geneva2702 · #10 Post by **Geneva2702** » Mon Feb 27, 2012 5:55 pm

You want deep cycle for your house battery. Cranking for your motor.

JonCBrand · #11 Post by **JonCBrand** » Mon Feb 27, 2012 5:56 pm

I have my boat setup with two batteries. The first is only connected to the motor and gauges. The second runs all lights, stereo and such on the boat. Both batts share a common ground. I have a 100% duty solenoid installed between both positives. The solenoid is powered off the ignition switch. When the ignition is on the solenoid is energized and both batteries are linked and charging assuming the motor is running. When the key is off I can still have the radio on and even if I drain the second battery the first one is un touched allowing me to start the boat. I picked up a solenoid from napa for about 30.

The only down side is if I forget to turn off lights or the radio the 2nd batt will be dead but I still have a full #1 batt.

I can try to get a schematic drawn up for you if this sounds like the setup for you.

Best part no switches, and all was done for under 50 including cables.

RonKMiller · #12 Post by **RonKMiller** » Wed Feb 29, 2012 6:27 pm

Here's my home brewed electrical set up. It includes two IDENTICAL output and age (VERY, VERY important) deep cell batteries, 180 watts of solar panels/regulator, 1000 watt high quality inverter and shore ac connections when available. My engine starting battery is not connected here and is totally independent.

I can power up a 32" HDTV, blue ray disc player, 140 watt stereo - and most importantly - a coffee grinder for some fresh brewed joe. Just not all at the same time.

I've got enough solar to re-charge the batteries the next day if we party late into the night.

What ever you end up doing, make SURE you use oversize multiple stranded cable to connect it all together. Generally speaking the more "strands" the better. The heavy duty end lugs should be crimped/crushed by swaging mechanically and soldered. High quality switch gear won't fail or melt like cheap solenoids.

Notice how all the cable has extra length for vibration attenuation and is secured to the walls/floor. The cabinet has additional ventilation added to promote cooling. This is close to aviation specification design which you SHOULD employ in any marine setup to avoid not only failure but fire danger. If you are anywhere near a fuel tank you MUST have your wiring expertly installed or you could have an explosion risk. Don't take any shortcuts here.

Marine heat shrink tubing (the kind with glue on the inside) is your friend to finish it all off. Details count - even if you are "ONLY" messing around with 12 volt.

It's all a "pipeline"...

The extra time you take to do it right pays off in years of enjoyment without any failures and vastly extended battery life.