Adding a house battery

eeshaw

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I've been kicking around the idea of adding a house battery to my boat to handle the electonic fish finder, a couple LED lights, radio, nav lights, bilge pump and a couple of outlets for USB support (like charging phones, etc.). Currently these items are running off the cranking battery, not ideal. I don't care for this setup and want to put these items on a seperate battery so as not to run down the cranking battery, thus avoid a self induced headache. I can transfer the leads to the new battery and leave the cranking battery as a stand alone battery. When the boat is in storage for winter I can charge these two batteries with a two bank charger. I'm thinking that there should be a simple way to charge both batteries when the motor is running. My question is what is the simplest way to accomplish this?
 

LDUBS

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I asked a similar question a couple years ago when I was adding my trolling motor battery. Initially I was thinking about charging both batteries off the motor using an "automatic charging relay" to manage things. I was made to realize this probably wasn't my best approach. I ultimately ended up keeping my TM battery isolated and depend solely on a smart digital battery charger to keep it juiced up.

Here is a link to that old thread:

https://forum.tinboats.net/viewtopic.php?t=47311
 

GTS225

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A big stumbling block might be the type of battery you choose as a "house" battery. The charging system in your motor is probably not the type you want for a NiCad or Lithium-based battery, so that's out. If you choose an AGM battery, you're still good. (I wouldn't choose another flooded lead-acid.)
If you do go that route, a simple disconnect switch would work quite nicely between the positives of the starting and house batteries. Turn that switch on while running for charging, and turn it off when the motor's off. It would also give you some extra power if you happen to have a starting battery fail two miles out on the lake.

Roger
 

DaleH

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Here's an alternative approach - don't over-think it ... as I don't see you needing one, and here's why, by 'amp draw':

3 amps - Electonic fish finder
1 amp - LED lights
2 amps - AM/FM radio, 1 amp more if a powered antenna and then more if higher powered speakers and amp, where the wattage divided by 12.6 would be the amp draw
1-2 amps receiving/7amps transmitting - VHF radio
3 amps max - Nav lights, if not LED
3-5 amps - Bilge pump, exact model will tell you
1 amp - USB outlet

So that's only ~16-amps total 'worst case' assuming you had ALL of them 'on' at once. With your motor running ...no problemo. Engine off? How many of those are you likely to use? Anything listed in italics is intermittant (non constant) use anyway.

The only items I see being 'on' most of the time would be the fish finder and radio. And if you only use the Nav lights while running, that lowers your draw with the engine off too. Clearly YOUR use is the biggest factor here ... but I don't see the need for a 2nd one IMHO.
 

eeshaw

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Thanks for the replies. I don't use any of the stuff I have connected when the boat is at rest because I don't want to run down the cranking battery. I'd like to be able to listen to the radio while fishing is why I asked. I figured I'd ask, better to be safe than sorry. It also just occurred to me that my kicker motor is pull start capable if the electric start is compromised, duh! Thanks guys!
 

DaleH

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eeshaw said:
I don't use any of the stuff I have connected when the boat is at rest because I don't want to run down the cranking battery. I'd like to be able to listen to the radio while fishing is why I asked.
FWIW I keep my fishfinder/depth finder 'on' all the time, even with my OB off. I've never been concerned with such a small battery drain on a cranking battery. A simple am/fm receiver is ~1 amp while playing.
 

MrGiggles

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Lithiums have come down in price quite a bit. Lightweight, last forever. But you can't charge them with the outboard or most onboard chargers. Noco has an onboard charger that will, otherwise you have to add a separate one.

Minnkota makes a product that can funnel current to up to 3 additional batteries once the starting battery is topped up. I think it's mainly geared for more modern outboards that have good sized charging systems.
 

airshot

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I have run a house battery for many years, never had one run out of charge while on the water !! A good group 27 will run my fishfinder, radio, aerator for the minnow bucket, S to S radio, lights and gps all day long (8hrs) and still have plenty of power. I run a smaller start only battery ( 40hp OB ) and a group 27 deep cycle for house battery, never an issue until the battery gets about 4-5 years old. I use battery tender battety maintainers on each one. When I get home the get plugged in, already for next trip out !!
 

FuzzyGrub

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Having grew up with only manual start outboards and then transitioning to man/elec start, I always fret with elec start only. On my I/O, ended up just going to a larger capacity starter battery. That was more than sufficient to handle DF and radio for hours of motor off periods. It was kept on a small lake though. If I boated over the horizon or out of site of land, I probably would have added a house battery.

Most recently, on my son's new boat, added LiPO4 battery to run the DF. We can go hours before we refire the outboard. Again, a larger capacity starter battery would probably suffice, but couldn't bring myself to discarding a "new" LA battery. Considered SLA at first but ended up with the Li 20AH. It can't be charged from motor, and requires special charger, but it can go more than two complete days of fishing without needing a recharge. Partially to get experience with these batteries. When our flooded trolling motor batteries need replacing, wanted to be sure expensive Li would be the right direction.

As the starter battery ages, I'll probably add a set of jumper cables, just for added insurance. ;) Again, I always fret that the motor won't start at the most inconvienent time.
 

cyclops2

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Why I keep my electric start 30 hp motor in perfect run & start condition with a hand starting rope.
 

airshot

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Having grew up with only manual start outboards and then transitioning to man/elec start, I always fret with elec start only. On my I/O, ended up just going to a larger capacity starter battery. That was more than sufficient to handle DF and radio for hours of motor off periods. It was kept on a small lake though. If I boated over the horizon or out of site of land, I probably would have added a house battery.

Most recently, on my son's new boat, added LiPO4 battery to run the DF. We can go hours before we refire the outboard. Again, a larger capacity starter battery would probably suffice, but couldn't bring myself to discarding a "new" LA battery. Considered SLA at first but ended up with the Li 20AH. It can't be charged from motor, and requires special charger, but it can go more than two complete days of fishing without needing a recharge. Partially to get experience with these batteries. When our flooded trolling motor batteries need replacing, wanted to be sure expensive Li would be the right direction.

As the starter battery ages, I'll probably add a set of jumper cables, just for added insurance. ;) Again, I always fret that the motor won't start at the most inconvienent time.
Not sure I would jump a std battery and a lipo battery together, that woukd be like using the wrong charger...boom!!
 

thill

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As stated earlier, if you use a group 27 deep cycle battery, you won't have any problems, unless you have a very powerful stereo system and are playing it loudly for a long period of time with the engine off.

For what it's worth, I use a 9AH AGM battery as a backup on the little boat, and that thing is excellent. Will run everything on my boat (LED nav lights, BT stereo, fishfinder/GPS and courtesy light) for a number of hours and will even start my 50 HP engine a few times. And it's cheap, like $23

Here is the exact one I have:
https://www.amazon.com/dp/B00K8V2Y8W

It is virtually identical to my ATV battery, but with different terminals. I used to use it as a primary, but then moved to a regular group 24 battery. Now the little one is backup. I made a harness for it, in case of emergencies. It's a great little battery!
 

LDUBS

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As stated earlier, if you use a group 27 deep cycle battery, you won't have any problems, unless you have a very powerful stereo system and are playing it loudly for a long period of time with the engine off.

For what it's worth, I use a 9AH AGM battery as a backup on the little boat, and that thing is excellent. Will run everything on my boat (LED nav lights, BT stereo, fishfinder/GPS and courtesy light) for a number of hours and will even start my 50 HP engine a few times. And it's cheap, like $23

Here is the exact one I have:
https://www.amazon.com/dp/B00K8V2Y8W

It is virtually identical to my ATV battery, but with different terminals. I used to use it as a primary, but then moved to a regular group 24 battery. Now the little one is backup. I made a harness for it, in case of emergencies. It's a great little battery!

Great idea. Saves a lot of space and weight.
 

airshot

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As stated earlier, if you use a group 27 deep cycle battery, you won't have any problems, unless you have a very powerful stereo system and are playing it loudly for a long period of time with the engine off.

For what it's worth, I use a 9AH AGM battery as a backup on the little boat, and that thing is excellent. Will run everything on my boat (LED nav lights, BT stereo, fishfinder/GPS and courtesy light) for a number of hours and will even start my 50 HP engine a few times. And it's cheap, like $23

Here is the exact one I have:
https://www.amazon.com/dp/B00K8V2Y8W

It is virtually identical to my ATV battery, but with different terminals. I used to use it as a primary, but then moved to a regular group 24 battery. Now the little one is backup. I made a harness for it, in case of emergencies. It's a great little battery!
I have a similiar battery that I have had for over 5 years with no issues. Mine is 12v but a 12 amh rating. It has powered my 30 lb trolling motor for my pond jon boat and use it to power my boom sprayer to spray my 5 acer yard. Never has it run out of power yet....38 bucks shipped to my front door, and it is sealed. Used it as a replacement battery in my grandaughters battery powered Dora atv. Added double the run time and twice as fast as the original battery that came with it. The power wheels replacement battery was 75 bucks.....twice the run time and twice the power for half the cost. Mine is a true deep cycle, designed to run a power wheel chair....
 

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