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Old 16-01-2025, 12:45   #1
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connecting 2nd battery as house battery an keeping it charged

connecting 2nd boat battery as house battery for MFD,external GPS antenna, VHF radio cabin, NAV,Anchor,
front,rear small flood LEDs. 2 bilge pumps,livewell pump.overboard light in near future a Clairion
music radio.
Typical marine accessories haven’t added all the amp hours each use.

Single main engine 012 Evinrude ETEC 175hp engine has a 50 amp charging sys. Image.
so I can not use a separate battery smart isolator BC the Evinrude has a builtin isolator.
problem is the required (OME premade)cable
is only 16’ long which will only stretch to less than mid ship. I would prefer to have this house battery in bow
area so cable will need to be another 10’15’ minium depended on which side port would be the 15’.

Helm is on starboard side all rigging is on star, ideally placing the battery on bows port side would be desired.
Before I decide where to mount this house battery I will cruise around a bit elevalueate the lest listing it causes
Then mount inside a battery box.

This bow mounted battery will be inside the cabin, which means if the windows are closed I will be exposed
To toxic an flammable battery fumes.
How long can the battery vent tube be? Will this vent tube require a end piece similar to the fuel tanks vent
Which blocks water from entering tube from above? Or can the vent tube outside hull just be bent or elbowed
Downward?

Options for keeping house battery charged.
The Evinrude cable is 5009076 https://www.greatlakesskipper.com/ev...079-16-foot-g2 this seller doesn’t mention the AWG size of the cable it appears to be 4AWG similar to the engines power
Cable.

1.(extend an enlarge the diameter of cable) for the isolator. I was actuely thinking of making my own isolator
Cable an just splicing it into the ETEC prioritized plug at engine image.

2.100watt marine compact solar panel (flat on roof), charge controller. Haven’t crunched the #s on a smallish
solar sys. Being able to replenish the battery as battery is being used.




https://www.amazon.com/gp/product/B0...e_4?smid=&th=1





https://www.amazon.com/gp/product/B0...DKIKX0DER&th=1

Stuff being 12VDC powered
1.RayMarine element 12HV 2 amps per hour image
2.Garmin 24XD GPS antenna receiver/ w/ heading sensor, Input current: 150 mA at 12 Vdc
3.rule 1500GPH bilge pump, just a guess 12.0 amps max current draw
4.Seaflo 800GPH live well pump 3.5 amps max current draw
5.Seaflo 750GPH bilge pump w/ float switch, 2.5 amps max current draw
6. anchor light 3 watts
7.NMEA 2K network
8.NAV lights
9. Standard Horizon GX1600 VHF radio, Current Drain
Standby .................................................. ......................................... 0.45 A
Receiver (at Maximum AF Output) .................................................. ... 0.8 A
Transmit .................................................. ................... 5.0 A (Hi), 1.0 A (Lo
10.cabin lights
Undecided on replenhishing Tablet, Lat top batteries an blue tooth speaker.
thanks for advising about adding house battery
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1977 StarCraft 22' Chieftain pocket cruiser, express conv. enclosed Pilot house/ inboard engine conv to OB 2012 Evinrude ETEC 175HP prop.14.25X21 top speed 54Knt.
https://www.youtube.com/watch?v=nAG42c8x5GY
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Old 16-01-2025, 18:00   #2
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Re: connecting 2nd battery as house battery an keeping it charged

It is a little hard to parse out your questions, but if I understand you have a single battery that acts as start and also runs all your other 12V needs. You want to add a second battery to act as your house bank. I assume your current start battery is some form of lead-acid. You are asking about how best to charge it and what to do about any fumes.

I think your easiest solution is to follow the solution suggested here and skip the Evinrude adapter.
https://marinehowto.com/easy-lifepo4-conversion/

You don't have to use LiFePo4 but it is probably the cleanest solution for you as they are lighter weight, no need to worry about fumes, will be much more tolerant of charging than a AGM deep cycle. You could substitute any battery in place of the LFP as shown.

You do want to keep Flooded Lead Acid batteries in a ventilated area, but a battery box with some sort of vent to an outside is adequate. You do want the air to be able to circulate so a single tube won't give you that. You would want two tubes, one entering from each side and ideally directed to opposite sides of your enclosure.

100w solar probably isn't going to get you very but seems unnecessary on a power boat. However your usage is not clear. Do you go out overnight with refrigeration?
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Old 16-01-2025, 20:09   #3
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Re: connecting 2nd battery as house battery an keeping it charged

Quote:
Originally Posted by hlev00 View Post
It is a little hard to parse out your questions, but if I understand you have a single battery that acts as start and also runs all your other 12V needs.yes You want to add a second battery to act as your house bank.yes I assume your current start battery is some form of lead-acid.yes You are asking about how best to charge it and what to do about any fumes.yes

I think your easiest solution is to follow the solution suggested here and skip the Evinrude adapter.
https://marinehowto.com/easy-lifepo4-conversion/

You don't have to use LiFePo4 but it is probably the cleanest solution for you as they are lighter weight, no need to worry about fumes, will be much more tolerant of charging than a AGM deep cycle. You could substitute any battery in place of the LFP as shown.

You do want to keep Flooded Lead Acid batteries in a ventilated area, but a battery box with some sort of vent to an outside is adequate. You do want the air to be able to circulate so a single tube won't give you that. You would want two tubes, one entering from each side and ideally directed to opposite sides of your enclosure.

100w solar probably isn't going to get you very but seems unnecessary on a power boat. However your usage is not clear. Do you go out overnight with refrigeration?
yes I overnight sometimes 2 nights on a 3 day cruise. no frige, still using coolers. the basic stuff to power MFD pumps/lights ect.
to bad the engines isolator cable is only 16'. of course I could make this cable.
here's an exploded veiw of current plan.


yes I'd like to use the current lead acid deep cycle battery which was my previous engines start battery which also powered all the house stuff to.
w/ new engine it requires 1000MCA so I'll be getting a new start battery used only for engine.
thanks
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1977 StarCraft 22' Chieftain pocket cruiser, express conv. enclosed Pilot house/ inboard engine conv to OB 2012 Evinrude ETEC 175HP prop.14.25X21 top speed 54Knt.
https://www.youtube.com/watch?v=nAG42c8x5GY
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Old 16-01-2025, 20:53   #4
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Re: connecting 2nd battery as house battery an keeping it charged

Quote:
Originally Posted by Capt. Steve1 View Post
yes I overnight sometimes 2 nights on a 3 day cruise. no frige, still using coolers. the basic stuff to power MFD pumps/lights ect.
to bad the engines isolator cable is only 16'. of course I could make this cable.
here's an exploded veiw of current plan.


yes I'd like to use the current lead acid deep cycle battery which was my previous engines start battery which also powered all the house stuff to.
w/ new engine it requires 1000MCA so I'll be getting a new start battery used only for engine.
thanks
It would be unusual for a start battery to be deep cycle. Sometimes they were referred to as dual purpose but really they are only thin plate starting batteries. What is the make and model?

You can try it out but likely you are going to need to buy a new house battery at some point. So if you go with the configuration similar in the video link, it will give you flexibility to change out the lead acid when it poops out and the option to replace it with a lithium. The downside of using the OEM dual battery charger is that you will always be forced to use lead acid, or rewire something like the video anyway. A lithium battery will give more power in the same space with half the weight.

Putting the battery up in the bow isn't terrible but you will have to think about cable size to support the expected charge rate, especially if lithium.

Be sure to change out any lights to LED if you use them without the engine on for extended periods - inside cabin, anchor, etc. Nav lights don't matter as you have the motor on when you are running.

Remember to plan fusing as needed.

Lithium is easy but it is true that some insurance companies have specific clauses about it. So worth checking if you go that way. However almost every insurance company does say that all work must be to professional standards, so whatever you do, it would be a good idea to first pay a pro to give your plan a once over, with the understanding you would pay to have them come in and review the work and sign-off on it when you are done. Not all that different from having a building inspector approve wiring you do at home. Many of us don't do that at home but we (I) should.
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Old 17-01-2025, 20:22   #5
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Re: connecting 2nd battery as house battery an keeping it charged

Quote:
Originally Posted by hlev00 View Post
It would be unusual for a start battery to be deep cycle. Sometimes they were referred to as dual purpose but really they are only thin plate starting batteries. What is the make and model?
https://www.costco.com/interstate-27...100476408.html


You can try it out but likely you are going to need to buy a new house battery at some point. So if you go with the configuration similar in the video link, it will give you flexibility to change out the lead acid when it poops out and the option to replace it with a lithium. The downside of using the OEM dual battery charger is that you will always be forced to use lead acid,

yes I think your correct if the engine builtin isolator was used bot batterys would have to be lead acid

not a big deal bc the next start battery will be a lead acid

or rewire something like the video anyway. A lithium battery will give more power in the same space with half the weight.also I concerned the lithium batteryis a potentioale explosion


Putting the battery up in the bow isn't terrible but you will have to think about cable size to support the expected charge rate, especially if lithium.

Be sure to change out any lights to LED if you use them without the engine on for extended periods - inside cabin, anchor, etc. Nav lights don't matter as you have the motor on when you are running.

Remember to plan fusing as needed.

Lithium is easy but it is true that some insurance companies have specific clauses about it. So worth checking if you go that way. However almost every insurance company does say that all work must be to professional standards, so whatever you do, it would be a good idea to first pay a pro to give your plan a once over, with the understanding you would pay to have them come in and review the work and sign-off on it when you are done. Not all that different from having a building inspector approve wiring you do at home. Many of us don't do that at home but we (I) should.
I'm not powering much w/ the house battery. do you think a 100watt solar panel flat on roof will keep the battery replenhished as I'm using it. like bilge pumps are hardly on, live well isn't on all the time same w/ lights. an yes I do have LEDs even though they expell radiation.
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1977 StarCraft 22' Chieftain pocket cruiser, express conv. enclosed Pilot house/ inboard engine conv to OB 2012 Evinrude ETEC 175HP prop.14.25X21 top speed 54Knt.
https://www.youtube.com/watch?v=nAG42c8x5GY
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