Reddit mentions: The best boat battery switches

Thank you all for the constructive comments! I apologize for having confusing information. It even took me a minute to compile it with what I thought to be an understandable manner because it even confuses me if I don't go through it in one breath. I'm going to do my best to clear things up.

u/velaazul , Here is a schematic I drew. - http://imgur.com/a/Zldos
Not the best drawing but I did it as I pieced it together, I could try to do another to clean it up a bit.

HouseBatt is the car battery. Batt1/Batt2 are deep cycle batteries. Currently this draft is a two 12v deep cycle battery operation. I still need to spend some time calculating (and understanding) what my daily/weekly power consumption would look like to see if two batteries will be sufficient for my lifestyle. I'm also trying to figure out how long I will have to run my car to charge these.

I don't necessarily plan on doing this under my current build for more than a year so there is room for improvement beyond this. With that said I know it may not be the most efficient setup possible, but I need to get my feet moving forward and make this happen.

Fuses are something I am conflicted about. I've seen instructionals that incorporate fuses, and I've seen builds that don't. I've heard people say you need them and heard people tell me I don't. If I do indeed need fuses put in place I would put a fuse between the Small Solenoid terminal to the alternator. and the 2nd fuse would be from the House Battery positive wire to the Deep Cycle Battery 2.

u/Y_BOT , am I misunderstanding the function of the solenoid? From what I understood it would function independently and control the flow of electricity from the alternator to the car battery and then to the deep cycle. When I turn the key in the car that should activate the solenoid switch to charge my car battery and deep cycle. When I draw power from the deep cycle the solenoid should act as the barrier between the deep cycle and the car battery so I never drain my cars battery when using the deep cycles. In the schematic I drew I have included the solenoid and an alternative- an isolator switch. If possible I'd prefer to wire the solenoid so I don't have to manually disconnect batteries.

u/MythicalMover , I plan on purchasing 8 guage wire, however I have not purchased any of the materials yet. I have written out a list of necessary equipment for this project with rough cost estimates. I'm trying to square away my setup before I move forward with buying what I need. I plan on going to auto parts stores and Lowe's to browse wires, lugs, batteries, ect. Also you've hit on another point that I need to flesh out. That being the load capacity for the solenoid connected to my alternator and then potentially the fuses and their load capacities.

Every time I come back to work on all this power planning it alternates between seeming simpler than I previously thought to more complicated and back and forth between the two.


Again, thank you all for the direction and the help! I will also attach links to a few products I am looking at buying for this project. I use most of these as visual representations though. I want to go to a store to actually see and hold a tool before I buy it to ensure I feel right about what I need.

Might need these: https://www.amazon.com/Plated-Battery-Terminal-Positive-Nagative/dp/B00ORH1W2W/ref=sr_1_3?s=hi&ie=UTF8&qid=1486148779&sr=1-3&keywords=car+battery+terminal

This is the solenoid that I have in mind. https://www.amazon.com/gp/product/B0064MX7US/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0064MX7US&linkCode=as2&tag=rvlifenetwork-20&linkId=TL56E2B62BVKAEKJ

2nd considered solenoid: https://www.amazon.com/Intellitec-Battery-Disconnect-Relay-Prevents-Batteries/dp/B00KPR8QAO/ref=pd_bxgy_263_img_2?_encoding=UTF8&psc=1&refRID=4S939F2G73BZBDQ6JZA9

Inverter (though I might up it if I need more watt handling if need be): https://www.amazon.com/Cobra-400-Watt-12-Volt-120-Volt-Inverter/dp/B001RNOHBC/ref=sr_1_7?m=A2VVWG2KXGK6N2&s=merchant-items&ie=UTF8&qid=1485455953&sr=1-7

Deep cycle battery consideration: https://www.batteriesplus.com/battery/marine-and-boat/deep-cycle/bci-group-27m/sli27mdc

8 guage wire: https://www.amazon.com/Ancor-Marine-Grade-Duplex-Cables/dp/B000NV0BNM/ref=sr_1_1?s=sporting-goods&ie=UTF8&qid=1486225382&sr=1-1&keywords=8+gauge+wire

(optional) Isolator switch: https://www.amazon.com/Marine-Battery-Disconnect-Switch-Isolator/dp/B00EBQOKEQ/ref=sr_1_2?s=sporting-goods&ie=UTF8&qid=1486225429&sr=1-2&keywords=isolator+switch

I also intend to protect my wires with conduits. If necessary I will need to buy lugs and shrink insulation to "make" my own wires for this project. Crimping is something I would imagine I could find a friend to help with or get done at a store.

Hopefully I covered everything, let me know if I am still missing any information and again sorry this was all not included in my original post!

1. Wire wise - Amazon - look up Anchor Tinned Wire and get a 25' section of 8ga 2 wire red/black at biggest (radio, plus lights, plus accessories ) but 12ga with 2 wires should be fine for small electronics.
   
   
   Example:
   
   https://www.amazon.com/Ancor-121510-Marine-Duplex-Cables/dp/B000NUYBW0/
   
   
2. Lack of a Switch or Disconnect - don't do this. A) Danger Will Robinson ! B) is not approved by coasties/inspection most places. Get a proper battery switch. Put this switch between the battery Positive and the motor positive and your accessories positive. The ground/black from the motor, from the accessories etc can all go right to the negative terminal on the battery. We're only switching the 12+ Positive side.
   
   
   Example:
   
   
   https://www.amazon.com/Perko-8501DP-Marine-Battery-Selector/dp/B00144B6AE
   
   
   
   
   I say these things for the following reasons:
   
   
3. you'll eventually wanna sell the boat and upgrade to something bigger. When I as a buyer see things like accessory wiring going right to the battery instead of a battery switch - I use items like that to lowball the fuck out of the seller. It also says "if they did this janky to save $20, what else did they do janky" ?
   
   
   
4. Safety - you always need a way to 100% disconnect electronics. This can be because of a fire, a mystery battery drain, long term storage etc. We want a disconnect from the battery. Now that said - plugging and unplugging a quick connect/ disconnect versus a proper battery switch is a GREAT way to blow yourself up depending where the gas fumes are, where your gas tank is, etc. It's one more possible thing to corrode as well as ignite. Make sure when you do your charging etc you are careful (connect the tender first THEN plug it into the wall outlet)
   
   
   
5. Long term usage - the more correct you do it now, the more money you save in the long run making small repairs later.
   
   
   
   Wiring Example:
   
   
   https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRrykWkGL7Y6N6zwAiDNcYPNvgQglOC4aJx0ntB9qn2Iv_INk1TUQ

I like Blue Sea switches. Used them on boats for years. Whatever you get, make sure it's rated for the amps you pass through it.

The fuse/CB size should be the lowest for whatever the max the circuit will draw and the wire will support. Say a fridge draws 4a at normal running but 12a starting, then the fuse should be 15a and the wire sized to the 15a.

I fused my 2 series panels at 15a since 10a would not be enough, so I have 2 fuses because of series 2 in parallel, both on positive side of the panels. You don't need to fuse both sides.

I fuse and switch positive.

Battery cutoff should be before the first load off the batteries and completely isolate them.

The victron BMV will work by itself, all it needs is the shunt and a positive lead.

I disagree that is the "best" MPPT, but use what you want. That one is cheap, but their support is direct from china and they have more than a few reviews of people having hard times with warranty and support, that plus it is very large.

I like Will's videos, but my experience with the victron is not anywhere like what he complained about. The connections are solid and it doesn't get hot at all. Initially I was concerned, so I put a temp monitor inside the compartment and a 12v computer fan on the vent, but even without the fan the compartment that is about 2' x 1' x 1' and under a couch is only about 2 degrees F warmer than the rest of the van when in direct sunlight pulling in nearly all of the 400W.

Fusing the 200a draw is not about the amp-hours of the battery. amp-hours are how long it can discharge, not how fast. you need to find out what the max discharge rate for the batteries are, and the max amp rating of the inverter and size your wires and fuse according to that (along with the length of the run)

"going up one size" on the wire is a general term. Use this instead https://www.wirebarn.com/Wire-Calculator-_ep_41.html

Nice, glad to hear she is back up and running! I've had a slow battery drain in my tow vehicle for years. It will kill a battery while sitting over the course of about 3 weeks. After days of fruitless searches trying to find the drain, I eventually just broke down and left it hooked up to a battery tender so that it was always at full charge when I needed it. For my case, a Battery Tender jr. with a cigarette lighter adapter has worked great for me for over 10 years now. If your boat is not protected from the elements, you could also consider the water proof version of the battery tender.

One last thought that has saved me from worrying about any of this on my boat is to install a battery switch, so that you can simply turn off all connections to the battery when you are not using the boat. I currently use this one with two group 27 batteries. You could do something similar if you suspect you have a power drain. You do not need to add the second battery if you don't want, instead you can just get a simple on off switch like this. Though it is nice peace of mind when you are offshore to know you have a backup. Happy boating! Let me know if you have any more questions.

There’s cheaper ones and more expensive ones but if you type “RV battery cutoff switch” into google a bunch come up. Mine is mounted outside, on the outside of my battery boxes so I got the slightly more expensive “blue sea” switch, but they all are pretty good and should last for years exposed to the elements.

https://www.amazon.ca/Blue-Sea-Systems-6007-Switch-Red/dp/B000MMFJH0/ref=asc_df_B000MMFJH0/?tag=googlemobshop-20&linkCode=df0&hvadid=292944043432&hvpos=1o3&hvnetw=g&hvrand=10732330413086149174&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=&hvtargid=pla-434093571586&psc=1

(I’m Canadian hence the Amazon.ca link, if your American you’ll get MUCH better pricing!)

First, my needs:

1. Power 1/2 LED monitors at ~30W each
   
2. Occasionally charge laptop
   
3. LED lighting
   
4. 2 Maxxair fans
   
   
   Second, the components:
   
   Panels/controller https://www.amazon.com/gp/product/B00B8L6EFA
   
   Battery https://www.amazon.com/gp/product/B01ACKDGPS
   
   Y connectors https://www.amazon.com/gp/product/B01N4ELRSH
   
   Cable entry https://www.amazon.com/gp/product/B01CSEXW2S
   
   2 Gauge wire https://www.amazon.com/gp/product/B00KD2756W
   
   Terminal rings https://www.amazon.com/gp/product/B005V9UWB2
   
   Crimp tool https://www.amazon.com/gp/product/B003X51S00
   
   Terminal block https://www.amazon.com/gp/product/B000S5Q2VS
   
   Busbars https://www.amazon.com/gp/product/B0091VHLW4
   
   Inverter https://www.amazon.com/gp/product/B004MDXS0U
   
   Vent vans https://www.amazon.com/gp/product/B002OW5JIU
   
   Monitors https://www.asus.com/us/Monitors/PB278Q/
   
   Puck lights https://www.amazon.com/gp/product/B00ODSAR12
   
   Strip lights https://www.amazon.com/gp/product/B01IQOV13G
   
   Fuse box https://www.amazon.com/gp/product/B001P6FTHC
   
   Killswitch https://www.amazon.com/gp/product/B005DUUL9W
   
   Switches https://www.amazon.com/gp/product/B06XFJW1SB
   
   Dimmer https://www.amazon.com/gp/product/B00L8KP16E
   
   
   I know my needs are fairly minimal. I see opportunity to grow with this system if I ever need to. I’m excited to lay it out with the actual parts soon and begin thinking about it in the real world.
   
   Any suggestions, info or questions are completely welcome. I know little about electrical, only what I’ve learned from reddit and youtube. Thanks pals and again /u/StolidSentinel for the help and replies to all my messages and questions!

>I'm fairly ignorant of electric systems on boats.


I hope you're comfortable with how basic 12VDC electrics work and are asking about how to wire them in a marine environment.


Preface, I'm not a certified marine electrician but I've done a ton of work re-wiring, custom work on all kinds of sail and power boats.


Tools:
>I do have a cheap harbor freight multi-meter

good, now you're going to need a way to crimp those shitty connectors and some dielectric grease.


Unless of course you want to solder all your connections (this is my preference as it doesn't vibrate loose or corrode as quickly), then follow NASA's soldering method s and yuu'll need some rosin cored solder and and a soldering iron, you'll also need to use a crimp connector without the pre-molded shrink wrap and some heat shrink tubing


Ok... got your tools? great, now for supplies.


You'll need a buss bar on your ground


Measure how much wire you need, (are you re-wiring the mast?) and use 14/2 AWG marine grade wire.


If you're only using 1 battery you can get away with a simple switch like this. From the devices & lights you listed It sounds like you can use 10AWG to connect your battery to your switch then to the 14 gang panel.


You'll need a way to label your wires, I use one of these but if you're doing one job you might want to use something cheaper.

Ok... now on the to the fun part


Plan where you're going to mount your panel and pull a single RED 10AWG from there to your battery shut off switch and another strand from you battery to the switch.


Pull 10 AWG from the battery to the buss bar.


pull all the 14awg from the lights to the panel labeling each 14/2 wire as you go


red goes to the fuse block, black goes to the buss bar then to the negative on the gang block, label everything at the connection points, big red wire goes from battery switch to the bolt on the 14 gang, big black wire goes to the buss bar.


install new things, as each device is hooked up test the fuse and switch, then install the new thing.

Edit: I forgot to mention, use dielectric grease on all metal fittings to reduce corrosion.


edit 1: put a fuse between your battery and shut off ont the red wire

If you don't have a ton of confidence in wiring, well amigo, you're gonna learn.
https://www.amazon.com/dp/B000RZNP5K/ref=cm_sw_r_cp_apa_i_NNiWCbCM6CCHR

This right here is an AWESOME piece of hardware.

With appropriately placed fuses, you wire your van battery to the relay. The relay connects to the house battery. When the engine is running, it charges the house battery. When you're not running, it disconnects the van battery. So you'll never run your starting battery dry and be stranded.

But, say your van battery starts to take a shit, and you can't crank. You can flick the switch into bypass, and can start using house batteries. Jump yourself. It's awesome.

The 4-way rotary selector is more suited for boats than vans and really, a VSR (Voltage Sensitive Relay) is better for a van as it requires less wiring. An example of the 4-Way isolator my boat uses can be found here: https://www.amazon.com/Battery-Selector-Switch-Distribution-Marine/dp/B00DPX6RR4/ref=sr_1_2?ie=UTF8&qid=1466597409&sr=8-2&keywords=battery+selector

They have 3 studs on the back. The primary stud is the input and is wired directly to the alternators positive output.

All negatives are bonded to a common earth stud welded to the hull (chassis).

The other two studs can be individually linked or both connected to the alternator stud and then either feed through to the starter or leisure batteries or divide the alternators output between both.

I connect my 12V loads and inverter to the alternator input stud so power is taken mainly from the alternator when the engine is running but it also allows them to be isolated from all the batteries when the engine is off powering everything off.

These switches are usually wires with “1” being the engine battery and “2” being your domestic. When the switch is “Off” and you try to start the engine, nothing will happen.

You need the switch to be selected at “1” to crank the engine and leave it on setting “1” for the battery to be topped-up before either selecting “2” or “Both”.

When the engine is off and I am aboard, I have it set to “2” as it links the input stud along with the 12V loads to the domestic battery.

The MPPT solar charger and mains charger are connected to the leisure battery “2” stud so that even when everything is isolated “off”, the leisure batteries are still being charged.

An in-line VSR directly from the engine battery through to the domestics with maybe an additional manual on/off switch is your best solution unless you want to split the starter battery source to two separate leisure banks?

I bought a deep cycle battery and connected it to the car starting battery with a switch http://www.amazon.com/gp/product/B00445KFZ2/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1.

You turn the switch on when driving, which allows your deep cycle to charge, and turn it off when parked so it doesn't draw from your starter.

I then wired up a cigarette lighter to my deep cycle and use it for a 12 v fan, phone charger, and 12 v laptop charger.
http://www.amazon.com/gp/product/B001JT7B3A/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

You drill a hole in the floor of your van and run at least 4 gauge wire from the positive pole of your car starting batter, to the positive pole of your deep cycle with the switch in line. Then you ground your negative pole on your deep cycle to the frame.

After that you can add on whatever components to the deep cycle to draw charge with ring connectors.

The draw back of this set up is that you MUST turn your switch to off when parked otherwise you can draw power of your car battery and be unable to start your car.

Oooh, that sounds interesting.

Previously I stumbled upon a Battery Selector Switch which would allow the operator to select battery 1, battery 2, or both for the starter. But you're talking about something a little different, yes?

Try and find if there is a parasitic draw:

http://www.popularmechanics.com/cars/how-to/a5859/how-to-stop-car-battery-drains/

If you don't want to find the cause of the drain just put in a battery disconnect switch. You could run it all the way to the cabin of the car so you don't need to open/close the hood every time you start the car and turn it off.

For under the hood: http://www.harborfreight.com/battery-disconnect-switch-97853.html

For mounting in car (you'll need to run two wires from battery to this switch): http://www.amazon.com/Marinco-701-Battery-Disconnect-Switch/dp/B005DUUL9W/ref=sr_1_8?s=automotive&ie=UTF8&qid=1452027739&sr=1-8&keywords=remote+battery+disconnect


Super fancy remote controlled one; http://www.amazon.com/Battery-Prog-Brain-T3-Protector/dp/B000P4H9W8/ref=sr_1_1?s=automotive&ie=UTF8&qid=1452027739&sr=1-1&keywords=remote+battery+disconnect

OK, we are going to try to get one of these. How to I know which one is the correct one?

https://www.amazon.com/Perko-8501DP-Marine-Battery-Selector/dp/B00144B6AE/ref=lp_2598388011_1_1?srs=2598388011&ie=UTF8&qid=1554134911&sr=8-1

I suppose the cables go on the same way?

​

Sure, it's exactly what I'm doing with mine. You want a battery selector switch.

The down side is you need to manually switch your power source.

Doesn't seem to take long to top them off either.. maybe 1 or 2 hours driving?
This is what I use:
battery switch I run off the main battery: https://www.amazon.com/dp/B000K2NYEC

and I've got a bunch of these on every battery connection and on the inverter connection: https://www.amazon.com/YOUNG-MARINE-Circuit-Trolling-Mount-60A/dp/B076P8PS3Y/

and heavy gauge wire all around: https://www.amazon.com/InstallGear-Gauge-Power-Ground-Touch/dp/B01LWV0IYJ/

bigger alternator isn't necessary unless you're looking for fast charging or if the batteries arent enough

for the anything else stuff:

I usually do a 200 amp breaker near the battery, with a home build beaker panel using these things as needed Most applications wont need a bunch of different circuits. And i hate not having fuses around when you need one... so breakers are great imo.

Will do. https://www.amazon.com/BEP-701-Battery-Switches-On-Off/dp/B005DUUL9W/ref=sr_1_7?ie=UTF8&qid=1521649402&sr=8-7&keywords=battery+cutoff

And yeah, the idea is to not kill myself. This is my first large project, although I have messed with low voltage stuff in the form of robotics for years.

This sub has been very helpful. I mean except for the shitter who keeps on hoping I die, thats not very helpful.

30% over rated continuous draw for switches/breakers/fuses/wires, etc.

https://www.amazon.com/BEP-720-Heavy-Switch-Continuous/dp/B000Y85RHE

http://www.amazon.com/Heater-Craft-Position-Rotary-Switch/dp/B00CH3FT6I/

Don't do that just replace it

Blue Sea Systems Push Button Reset Only Quick Connect 15A Circuit Breaker https://www.amazon.ca/dp/B000K2MAPG/ref=cm_sw_r_cp_apa_i_2BrNDbQTNXGTF

I don't think the 4th one would work, but any of the others should, if you can get the wiring figured out. As for a disconnect, try:

http://www.amazon.com/Blue-Sea-Systems-Voltage-Disconnect/dp/B00GZOP53M/ref=sr_1_5?ie=UTF8&qid=1458696594&sr=8-5&keywords=low+voltage+disconnect

https://www.amazon.com/Blue-Sea-Systems-Contura-Control/dp/B005CSVQ44/ref=sr_1_2?s=sporting-goods&ie=UTF8&qid=1502480286&sr=1-2&keywords=boat+dimmer this is the dimmer I got. I'm just not sure which wires to hook up where

Use deep cycle batteries, not car batteries.

Many charge controllers have a low voltage shutdown. Or build your own using an arduino and a beefy relay. Use a voltage ladder to knock down your voltage to under 5v so the arduino can read it.

Or buy this:
https://www.amazon.com/gp/aw/d/B00GZOP53M/ref=pd_aw_sim_sbs_86_1?ie=UTF8&psc=1&refRID=74SR3BAA4M7772YPQ3CK

I'm going to be disabling all the power buttons on all my everythings as soon as he can crawl.

Actually, I'm replacing the computer's with a lock switch

As u/edman007 stated, a relay that's wired to the vehicle's keyswitch will prevent the trailer from being powered, except when the vehicle is on.

You don't want to cause an electrical fire if there's a short circuit in the trailer's wiring (or possibly if the trailer battery is completely dead,) so you'll want this wire protected from high currents with either a fuse or a circuit breaker. I'd suggest a circuit breaker, since self-resetting is nice.

https://www.amazon.com/attwood-7623-7-50-Amp-Circuit-Breaker/dp/B00BV89QXW

I wouldn't be too worried about killing a vehicle's electrical system - the alternator on any modern vehicle can put out enough excess power to trip your breaker.

You likely have a battery selector switch. You only need 1 battery. The other is a backup. If you run your trolling motor, livewell, stereo, etc you might kill the battery. In that case you would just switch to the other battery.

Any competent electrician will warn you against repeatedly using a breaker as a switch (but yes, I have). They DO have a limited lifespan. It's big, but so are the consequences of you being unlucky and it failing. I'd use a dedicated switch (I use this: https://www.amazon.com/gp/product/B00445KFZ2/) and a fuse rated to 150% of the max expected current. Keep in mind, your inverter is designed to handle a surge, and most electrical things draw a huge surge when they start for a brief moment. You have to consider that current in your fuse selection as well. I always kill the inverter when not in use. It arguably increases its lifespan as well. It's one less thing to fail while I sleep, while I am away from the van, or while I am driving down a mountain in snow!!!