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Inverter Installation Question- Direct to Battery or Bus Bar?

11K views 37 replies 12 participants last post by  njvagabond 
#1 ·
Installing a 1000W inverter which came with 4 AWG wiring for a direct battery connection (which seems like the easiest option). Is there an advantage/disadvantage to connecting the inverter directly to the battery or should we go to the bus bars we have in place? There's plenty of room on the battery terminals for another connection and it would be easy enough to ground the inverter using a separate wire to the already grounded bus bar.

I guess I'd like to keep the inverter separated as much as possible from my already in place (and working great) system if that makes any sense. Also doesn't help that things are kind of tucked away and not super easy to access.

Thanks for the input.
 
#2 ·
If there's a choice between battery terminals, and already existing (appropriately located) main bus bars, I'd always choose the bus bars. The bus bars will be downstream of your main battery fuse, and downstream of your main battery switch (which, if that wouldn't shut off your inverter also would seem weird to me - it's typically supposed to cut off all loads).

Not that you wouldn't have OCP and a switch for your inverter, but just I pretty much want everything downstream of my main OCP and main battery switch (unless it's a specific item that needs to be "hot" such as a bilge pump on a boat).
 
#4 ·
Use the bus bar, that's what it's there for. This is of course assuming it's rated to handle the combined current draw of your existing system and the inverter. A 1000W load on the inverter will require roughly 85A (not counting loses) from your battery bank.
 
#6 · (Edited)
Installing a 1000W inverter which came with 4 AWG wiring for a direct battery connection (which seems like the easiest option). Is there an advantage/disadvantage to connecting the inverter directly to the battery or should we go to the bus bars we have in place? There's plenty of room on the battery terminals for another connection and it would be easy enough to ground the inverter using a separate wire to the already grounded bus bar.

I guess I'd like to keep the inverter separated as much as possible from my already in place (and working great) system if that makes any sense. Also doesn't help that things are kind of tucked away and not super easy to access.

Thanks for the input.
Typically you'd have a shunt on the battery negative and a main safety fuse or breaker on the battery positive terminal. Those then feed the busbars. Circumventing those by going straight to the house battery means you can't monitor the inverter's power consumption or the battery's state of charge (what the shunt does), and you don't have the two layer protection of 1) inverter fuse/breaker and 2) the main safety fuse/breaker.

You don't need to worry so much about your inverter's DC input and your other DC house power being "separate," but you do need to make sure your cabling to/from your battery and your busbar can handle all of the current it currently handles, plus the current from the inverter, ideally with some overhead. If you don't know, or if you suspect it's not designed for that additional current, seek expert advise, or if you feel DIY proficient and it's someone else's install, consult them if possible, or go check the wire gauge, round-trip length, and ampacity charts, then add up your total existing DC loads (max values) plus the inverter's max draw, and see how the two compare.

Hopefully your busbar is wired with thick enough and short enough cable to handle the added load. If not, upgrade the wiring, or absolute worst case go straight to battery, but expect problems monitoring state of charge.

Cheers.
 
#7 ·
ypically you'd have a shunt on the battery negative and a main safety fuse or breaker on the battery positive terminal. Those then feed the busbars. Circumventing those by going straight to the house battery means you can't monitor the inverter's power consumption or the battery's state of charge (what the shunt does), and you don't have the two layer protection of 1) inverter fuse/breaker and 2) the main safety fuse/breaker.

You don't need to worry so much about your inverter's DC input and your other DC house power being "separate," but you do need to make sure your cabling to/from your battery and your busbar can handle all of the current it currently handles, plus the current from the inverter, ideally with some overhead. If you don't know, or if you suspect it's not designed for that additional current, seek expert advise, or if you feel DIY proficient and it's someone else's install, consult them if possible, or go check the wire gauge, round-trip length, and ampacity charts, then add up your total existing DC loads (max values) plus the inverter's max draw, and see how the two compare.

Hopefully your busbar is wired with thick enough and short enough cable to handle the added load. If not, upgrade the wiring, or absolute worst case go straight to battery, but expect problems monitoring state of charge.

Cheers.
Yeahh the biggest thing I was trying to avoid was having to change my wiring. The biggest wire I have in my system in 6AWG which works fine now, but is going to be too small for the inverter. I figured if I went straight to the battery I might be able to keep it more isolated and avoid having to upgrade my wires.
 
#11 ·
If it's accessible, you can just run a second length of wire from your batteries to your busbar. That's the same as increasing the wire size. Two 6AWG runs = one 3AWG. Just try to keep the lengths the same.

Hopefully that's not too much work versus running new wires for the inverter all the way to the battery. Just be sure to run the second negative length through the shunt (two wires going into shunt and two going out) and ideally run the second positive length through the main fuse, assuming it's a terminal fuse that can handle the amperage or be upgraded. That's what I use. Blue Sea MBRF terminal fuse.

Otherwise you need to add another fuse/breaker of the same exact size to the second positive length, and make sure both fuses and both wires add up to your maximum total amperage, with 1.25 or 1.5 overhead on the fuse (for inductive/capacitive startup loads, and to prevent false trips if you're running near the max acceptable amps for the wiring).

Cheers.
That is a really interesting idea- you had me thinking on that. Would still have to run the wire the same path up into where my stop/start is, which is really the toughest area to access. Thinking we'll just bite the bullet and replace the existing 6 with 4 AWG... 2AWG to be safe?

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#12 ·
Thinking we'll just bite the bullet and replace the existing 6 with 4 AWG... 2AWG to be safe?
What is the length of the proposed [4AWG] wire run? Not "as the crow flies," but the actual round-trip* wire length with all the twists and turns? With that information, plus we already know the size of your inverter, we can calculate exactly what size would be right.

If you can post that, I'll post back my data (as can anyone else then too of course).

*Round trip meaning both the postive and negative sides of the circle. If you haven't run the wire yet I find that a piece of rope works well as a stand-in (string works too, but some rope is usually closer to the wire size). Otherwise it's so easy to underestimate the length.
 
#8 ·
I have positive and negative bus bars.

The cable from the battery positive post has a fuse and disconnect switch and then to the positive post of the house inverter. From the inverter positive post a cable goes to the positive bus bar. The cable from the battery negative post goes to a shunt and then to the negative bus bar. A cable from the negative bus bar goes to the inverter negative post.

The reason I went to the inverter positive post first instead of the positive bus bar was to keep the wiring simpler.

100_1358.JPG | House 12 V DC (ortontransit.info)
 
#28 ·
Essentially the input to your inverter has been turned into a bus bar. It will now have to carry the current and heat dissipation of both the inverter usage, and anything connected downstream that is connected to. While not particularly an issue in your set up, it would still be considered bad practice.

This and improperly wired bus bars are common, in the van world. Some of the worse practices I have seen were done by RV companies with a RVIA sticker on the side.
 
#30 ·
Inverter is in and working. Swapped some 6AWG for 2AWG per suggestions, thank you. Last question- does anyone see anything wrong with the angle of the positive wire coming off of the connection point in the picture? The covers make it so that they wires can only come straight out like they negative wire and I'm wondering if there is a reason for this.
Thanks again for all the input.
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#31 ·
It's always annoying when a tang goes "the wrong way" for your installation. It's probably fine, but in that type of scenario I would probably try to do something with a cushion clamp to keep there from being constant "pull." Maybe in the area of the curve. (Although it looks like you might have to build it up on a small block or something because the tang looks elevated.)

Looking at it more: would there be any advantage to going "up and over" (just under the bed platform) so your curve would come later in the wire's path instead of right after the lug? Or even turning the inverter around? (Then the negative could come off in "the right direction," then loop back and go over the top.)

You might be able to do the "up and over" without changing any wire lengths though (unless there is some reason against it that I can't see).
 
#33 ·
It's always annoying when a tang goes "the wrong way" for your installation. It's probably fine, but in that type of scenario I would probably try to do something with a cushion clamp to keep there from being constant "pull." Maybe in the area of the curve. (Although it looks like you might have to build it up on a small block or something because the tang looks elevated.)

Looking at it more: would there be any advantage to going "up and over" (just under the bed platform) so your curve would come later in the wire's path instead of right after the lug? Or even turning the inverter around? (Then the negative could come off in "the right direction," then loop back and go over the top.)

You might be able to do the "up and over" without changing any wire lengths though (unless there is some reason against it that I can't see).
Yeah we have the inverter in that orientation so that the fans blow away from the rest of the system, and also to leave as much room for any more attachments on the fuse block. The wire doesn't reach with the up and over, and the wiring that we did for the outlet also doesn't reach, so I think we're stuck with how it is. Will look at a cushion clamp- thanks.
 
#34 ·
I see you mounted it that way for good reason. And yeah, you may want to add circuits to the left side of the fuse block in future.

Cushion clamps will "immobilize" the wire if you use the correct size and hence will provide strain relief. (Whereas if it is too large it will only guide, but not immobilize against "pull.") Possibly on a little stand-off (I can't quite see but it looks like it wants to be an inch or so off the backer board).

Just a note while you are gathering parts: The fastener holes in the cushion clamps tend to be a bit larger than you would expect. So you will probably want a truss head screw, or a larger washer behind a regular pan head.

Like so (Ancor cushion clamp shown):
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#36 ·
I see you mounted it that way for good reason. And yeah, you may want to add circuits to the left side of the fuse block in future.

Cushion clamps will "immobilize" the wire if you use the correct size and hence will provide strain relief. (Whereas if it is too large it will only guide, but not immobilize against "pull.") Possibly on a little stand-off (I can't quite see but it looks like it wants to be an inch or so off the backer board).

Just a note while you are gathering parts: The fastener holes in the cushion clamps tend to be a bit larger than you would expect. So you will probably want a truss head screw, or a larger washer behind a regular pan head.

Like so (Ancor cushion clamp shown):
View attachment 174632
Thanks!
 
#38 ·
Is the CCP (bus bar?) 60amp
It depend on the CCP you have;
2015-2019: single CCP=60A. optional 3CCP=180A in parallel. Fairly simple to upgrader from single to triple.
2020 +: single CCP=60A, optional (but pretty common) 2 CCP setup = 1@60A always hot + 1@170A load shed/vehicle off time out regulated. Output is not additive 170A total for both combined. Not sure about ease of upgrade.
 
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