Electrical question - Do I need a way to cut DC power besides battery switch?

blutow

Member
I'm designing the electrical system for a van that will include ~400 watts solar and a good sized Lifepo battery bank.

I plan to have circuits/switches on a few select DC items (water pump, fridge, battery heaters, etc.), but I don't plan to include a way to cut all DC power except the master battery switch. That master switch will be in the electrical service are of the garage, so not very accessible. All other circuits would just be off the DC fuse block with switches where it makes sense.

I don't anticipate needing to to turn off DC power unless I'm working on the system or putting the van in long term storage (not plannned). I'll have some core stuff running all the time, so it seems like a waste to build in "cutoff" capabilty. The van will be parked outside, so the solar should be more than enough to keep core stuff running and batteries topped off. That said, I see master DC cutoff switches front and center in a lot of Vans/RV's, so maybe it's something I should consider. Another option would be to have a cutoff for "non-core" stuff like lights and plugs to avoid leaving something on, but still leaving core systems connected all the time.

This will be my first RV/Van , so I don't have the experience to know whether this is something that is useful or not. In my boat, I installed a disconnect for everything expect the bilge pump, but it's not really a fair comparison since it doesn't have solar to offset system drains. The boat also has very limited capacity and the van will have a huge reserve.

Any advice is appreciated.
 

RVBarry

Well-known member
Hi, if you have any solar, there should be a cutoff for it as well.
 

blutow

Member
Hi, if you have any solar, there should be a cutoff for it as well.
Yes, I will have a cutoff for solar and dc2dc charger as well. Both will include a mechanical break (via breaker/switch for maintenance) and just disabling them when I don't want charging (via bluetooth).
 

blutow

Member
It's good to have a way to easily cut power in and out of the batteries. I use it to be absolutely sure nothing can shock me while working on my electrical system.

I use inline circuit breakers as my method. You need a fuse anyways, and it lets you easily click off the power.

Something like this: https://www.amazon.com/dp/B0834WH28R/ref=cm_sw_r_cp_apa_i_e6L.FbM10ZTS1?_encoding=UTF8&psc=1
thanks. Yes, I'll have a master battery switch for service (see pic below), but wondering if need something more accessible (to avoid unplanned system drain). The battery switch will be a bit buried in a rear panel in the garage area, so should be fine for when I'm working on electric, but not really convenient if I need to use it on regular basis.

1610506309281.png
 

autostaretx

Erratic Member
The main reason i could see for a quick easily-reachable cut-off would be in case of fire.

If some small fire decided to melt away significant wires' insulation, would they start helping "fan the flames" (as it were).
You speak of it being in the garage ... what's on the other side of the panel it's going to be mounted on?
Perhaps two holes for the wires would let you mount the master switch inside the living area, just a couple of inches away from the original planned location. ("mood lighting" from the bed? Total Darkness?)

Easy-reaching would also mean you might flip it when doing "something simple" instead of skipping the disconnection 'cuz you're only going to be doing "a little thing" (Murphy's Last Words)

--dick
 

Brad75

2013 NCV3
Yes, I will have a cutoff for solar and dc2dc charger as well. Both will include a mechanical break (via breaker/switch for maintenance) and just disabling them when I don't want charging (via bluetooth).
I mounted my dc2dc cutoff switch to the side of the drivers pedestal so it’s right there when I get in an out. They say you shouldn’t float charge lifepo4 so I cut the charger off if I’m not using the house electrical system much.
 
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blutow

Member
The main reason i could see for a quick easily-reachable cut-off would be in case of fire.

If some small fire decided to melt away significant wires' insulation, would they start helping "fan the flames" (as it were).
You speak of it being in the garage ... what's on the other side of the panel it's going to be mounted on?
Perhaps two holes for the wires would let you mount the master switch inside the living area, just a couple of inches away from the original planned location. ("mood lighting" from the bed? Total Darkness?)

Easy-reaching would also mean you might flip it when doing "something simple" instead of skipping the disconnection 'cuz you're only going to be doing "a little thing" (Murphy's Last Words)

--dick
Thanks, you are hitting on a bunch of items I've definitely debated. The electrical area will be under the bed and would be a bit of a hassel to get to the main disconnect (possibly pulling out bikes, etc.). I tried to figure out a way to locate the switch in a more accessible location, but it would require a decent wire run. Since this is the main battery connect, I'd need to double up 4/0 cables to make the run and it adds complexity and more wire = more opportunity for a wire to be compromised and cause a short.

The current design has very short cable runs battery to switch and then solid bar from switch to distribution block with fuses there. I'm also doing terminal fuses at each of the 4 positive battery terminals, so I'm going max safety, especially on the big amp wires. I don't love the location of the master disconnect, but I've tried to compensate a bit with the extra fuse points. If I do a more accessible disconnect, it would need to be limited to the lower amp DC leg (not the inverter runs) or I'd be running crazy cables or doing something with a relay.
 

blutow

Member
I mounted my dc2dc cutoff switch to the side of drivers pedestal so it’s right when I get in an out. They say you should float charge lifepo4 so I cut the charger off if I’m not using the house electrical system much.
That makes sense. I'll need to look at location options. That's a high amp run, so I'll try to put the breaker/switch as close to the connection point as possible to minimize the length of unprotected wire. For normal operation, I'll be able to turn the charger off via bluetooth, but it's always nice to have the mechanical disconnect available easily for maintenance or in emergency.
 

blutow

Member
As a reference point, I'm basically copying the battery/distribution/inverter section of the setup shown below, but adding termninal fuses on each battery. The smart battery protect device (just to the right of the distribution block) is feeding straight into the DC fuse block. My batteries will also have internal BMS's, so I won't have the external BMS shown.

1610508283542.png
 

kcshoots

VanTripping.com
Glad that you're thinking and asking about a disconnect. It is most certainly prudent for all of the reasons outlined by others. Here are some photos of where I located my house battery disconnect and connection to it from the alternator which may give you ideas for your system. Fuses and inverter are located directly above, batteries directly below, and solar connection directly from above along C pillar. You can also see my AC circuit breaker panel next it, both quickly accessible if needed yet out of the way from the interior space by being in the slider door step. I also have a volt meter directly next to the disconnect showing battery voltage so I can confirm both batteries are disconnected since this is a four-way switch (Battery A, Battery B, Combined or Off). The gray/black panels they are mounted to are perforated so that they receive air flow from below these main electrical components. Incidentally, I have another battery disconnect/interconnect on driver seat base with connections for Starter Battery, Aux Battery, Combined and Off which allows for another disconnect at alternator input as well as to interconnect any combination of Starter, Aux and House batteries for emergency starting or power use. This switch is also visible in the background. I also have a Halon-type fire extinguisher mounted to the B pillar so reachable from electrical cabinet and on the way out the slider door, as well as another mounted to D pillar so accessible from the rear exit if needed. I believe this type of fire extinguisher is prudent in a vehicle as can extinguish electrical fires and do so cleanly in the enclosed space of the van.
 

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blutow

Member
Glad that you're thinking and asking about a disconnect. It is most certainly prudent for all of the reasons outlined by others. Here are some photos of where I located my house battery disconnect and connection to it from the alternator which may give you ideas for your system. Fuses and inverter are located directly above, batteries directly below, and solar connection directly from above along C pillar. You can also see my AC circuit breaker panel next it, both quickly accessible if needed yet out of the way from the interior space by being in the slider door step. I also have a volt meter directly next to the disconnect showing battery voltage so I can confirm both batteries are disconnected since this is a four-way switch (Battery A, Battery B, Combined or Off). The gray/black panels they are mounted to are perforated so that they receive air flow from below these main electrical components. Incidentally, I have another battery disconnect/interconnect on driver seat base with connections for Starter Battery, Aux Battery, Combined and Off which allows for another disconnect at alternator input as well as to interconnect any combination of Starter, Aux and House batteries for emergency starting or power use. This switch is also visible in the background. I also have a Halon-type fire extinguisher mounted to the B pillar so reachable from electrical cabinet and on the way out the slider door, as well as another mounted to D pillar so accessible from the rear exit if needed. I believe this type of fire extinguisher is prudent in a vehicle as can extinguish electrical fires and do so cleanly in the enclosed space of the van.
I'll need to think more on the master switch location. I'm really trying to minimize cable runs and my batteries and distribution is not accessible. Blue sea has a remote disconnect switch I could use (basically a fail safe high amp relay), but it's $200+.

A couple questions on the pics - how do you like those bluesea 360 panels? I was thinking about using one for AC and another for a few select DC items (fridge, water pump, battery heaters). They look nice and not too crazy expensive and I haven't found anything else I like yet.

Also, did you run a 120v breaker/disconnect between your inverter/shore power and you 120v 360 switch panels? If so, what did you use? I'm struggling to find anything that isn't in a huge box.

Are those cabinets made out of HDPE or something else? How do they hold up to scratches, etc.?
 

kcshoots

VanTripping.com
I installed a Blue Sea ACR with the remote switch in my last van and it worked well, but certainly more expensive than a simple battery disconnect switch. You could install a relay with a control switch for probably much less than $200. I installed a 200 amp capacity one with a timer delay that starts upon the starter motor being energized, so that my house battery charging from alternator is delayed for a preset time after engine starts to allow house and aux batteries, and other electronics to all get voltages up before adding the house battery charging load. You could use a charging relay like this with a remote switch to manually disconnect. The remote switch only needs <1amp of power so very safe and easy to run a smaller gauge wire to a standard rocker switch.

I very much like the 360 panels, albeit expensive but easy to wire, look great, and have been flawless. I will certainly use the same or similar in my next build currently in planning, as well as for most all DC loads, as the circuit breakers are so much easier to use and quickly and visually see status and disconnect. My 30amp shore power connection comes into a BlueSea 30amp ELCI breaker, added photo of it with USB rechargeable flashlight just below. Output goes to the inverter input so that shore power input is further protected. That smaller panel is only about 4" square and tucked into a remote corner as hardly needed but can be reached within seconds.

The inverter's shore power only output supplies the electric water heating element while on shower power which provides domestic hot water & space heating as well as more rapid engine heat up.

And yes, my cabinets are framed in 1" aluminum profile (aka 8020) with 1/4" HDPE panels. Rock solid and indestructible as well as never a worry about water absorption or deterioration. I can yank with all of my strength on the handle attached to that slider panel and only move the entire van but not the cabinet, not even a ting. I literally do pull ups from my lifting bed platform. I've tested with a knife blade pressed against the HDPE and difficult to cause damage to them, which reduces any worries about dog's claws, belt buckles, shoes, skis, bikes, whatever scratching them, plus never a worry about overspray from showering, etc. They will likely outlast the van and absolutely show less wear than wood paneling with time & use. My van is now four years in use and the cabinet panels only need an occasionally wipe down. I have to give @hein and @GeorgeRa the credit for my inspiration to use these panels.
 

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blutow

Member
Thanks, great info. I'm using HDPE with steel frames to build my battery boxes and it's really a great matrial to work with. I'm got the smooth/shiney stuff and it scratches really easy, but the batteries won't be in a visible space. The textured HDPE looks really good and it sounds like it holds up well, I might look at that for cabinets as well. I'd like to use it for a bathroom/shower enclosure, but I think it's too "non-stick" and hard to seal or fasten down unless you're using mechanical fasteners. Even VHB tape struggles to get a good bond on this stuff. I'm gonna go with those 360 panels, I found some good pricing on them.
 

kcshoots

VanTripping.com
Yes, HDPE is very slick and difficult to adhere to something, especially the textured surface as I'm using, but takes fasteners really well. I'd only recommend fastening it. You can even tap it for a lighter connection point or screw into it from one side for a hidden connection.
 

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