Fusing and busbars

rmaddy

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However we ass u me the ANL sizing next to the battery matches his inverter draw.
But the battery has to power more than just the inverter in many cases. Worse case the inverter could be at max load while the DC loads are at max load. So I would say the battery fuse and wires might need to be slightly bigger than the inverter fuse and wires.
 

PerryB67

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But the battery has to power more than just the inverter in many cases. Worse case the inverter could be at max load while the DC loads are at max load. So I would say the battery fuse and wires might need to be slightly bigger than the inverter fuse and wires.
That's one reason why I used 2/0 rather than 2 awg. A fuse that's too large does not protect the system. I won't go there, because that's how you melt wires and fry batteries, a major cause of RV fires.

Your largest load should be fused at the battery. Our 1500 watt inverter should only need a 200a fuse, but they know that fuse should be next to the battery (6" by code) and already anticipate the other loads, so their advice is a 250a fuse. When inverters screw up they usually draw more than 250a, but you never know, so keep the fuse as small as possible, but not blowing from standard draws. I looked at many inverters to meet our needs and a few just give fuse advice only for the inverter, whereas a vast majority anticipate that fuse to be where it belongs, 6" from the batteries.

Look on the web how the major RV electrical advisors fuse systems. Since they also make money on their Amazon links we are not to link to those places. Read I am banning forum members for using affiliate links. Read the rules! and Official Forum "Code of Conduct" and "Terms of Service"
 
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Zwy

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Cables and wires have a recommended maximum amperes they can safely carry. It depends on the insulation rating which temperature chart is used. I only use marine grade cable so use 105 degree chart. Such as Blue Sea circuit wizard. Or this; https://marinehowto.com/wp-content/uploads/2018/02/04-Fusing-Voltage-Drop.jpg
https://marinehowto.com/wp-content/uploads/2018/02/04-Fusing-Voltage-Drop.jpg
The ampacity of a cable has nothing to do with voltage drop.
Incorrect as the higher the amperage carried on a wire, the higher the voltage drop. Go run the figures thru any calculator if you don't believe me.

Voltage drop is calculated to find the awg you need for the device.

Voltage drop is calculated to determine if excess VD will be on the circuit. Excessive VD causes heating of wires and loads to run inefficiently.

My 2 awg cable is fused at 200 ampere. My 2/0 awg cable is fused at 300 ampere.
 

Zil

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I'm tired of all this misunderstanding of proper wire awg to lower voltage drop and fusing to protect wire from melting; one last time.
In DC systems; Voltage drop tables are used to insure the device receives enough power to properly function. The table is based on distance from power supply (Battery) to the device and the maximum amperes the device will use at full power. This calculates the awg cable to use. With the awg size in hand we now use the ampacity chart to determine the maximum fuse size to use to protect that cable.
Some reasonable argument can be made as to what percentage of the maximum ampacity to actually fuse the cable. I favor toward the upper end as the fuse itself introduces voltage drop. In my limited solar charging and battery storage capacities, I want as much power available as I can muster from that limited system.
Rule Number One; Fuses Protect Wires. period, full stop.
 

Zil

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Rule Number Two: fuses also protect devices. period, but not full stop
in this context you are wrong. devices may have their own fuses internally or close to the device. that is not the fuse on the battery positive end of a circuit that i am discussing.
 

PerryB67

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in this context you are wrong. devices may have their own fuses internally or close to the device. that is not the fuse on the battery positive end of a circuit that i am discussing.
Be more specific. You made a blanket statement and used "period, full stop". In the context I used (devices) I'm correct and "but not full stop". Grammar. Read your second paragraph where you used the word battery once and device twice. Notice I used device in my Rule Number Two and in those instances where you used device I'm also correct. The battery should be fused to handle the largest device plus other draws, but smaller fuses should be before other devices as can be seen in just about every schematic I've seen.
 

dixonge

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Had a good day of reorganizing, resizing cables. Did eight cable ends' worth of cutting, stripping, crimping and heat-shrinking. Came out nice, if I don't say so myself. Seems like most of my lug rings are slightly too big, but that's what they make washers for, right? :rolleyes:

I really love having all the cables being just the right length. Should have just bought some 2awg and lugs and things from the beginning...

rv-solar-bay-rewire-day-1.jpg
 

PerryB67

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Nice neat install! I wish we had that much room to work with. I have to use three portions of walls in a u-shape dinette plus a vertical board on the battery box for our install. The board will be attached to the battery box with Velcro and anchored to the floor with two shelf brackets. Space is at a premium in a 21' fifth-wheel.

Post a picture of your install when finished.

Enjoy,

Perry
 

Hedges

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Batteries 2s2p
One 2s has skinnier wire than other 2s.
Fuse and shunt both connect to same 2s; should be connected diagonally to balance resistance so current drawn equally.
Longer cable would allow that, although if you moved switch left and let fuse holder dangle, existing wire would fit.

Good that you have insulating caps on positive terminals, so dropped things less likely to short.
Should cover negative terminal of the two batteries on right as well because those are at 6V.
The ring terminals themselves don't stand out as far as the studs but are still exposed. What I did for my bank is I split pieces of heater hose lengthwise, and cable tied them over the ring terminal and stud.

 

dixonge

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Batteries 2s2p
One 2s has skinnier wire than other 2s.
Looks skinnier, but can only be the insulation. All cables on batteries are 2AWG.
Fuse and shunt both connect to same 2s; should be connected diagonally to balance resistance so current drawn equally.
Longer cable would allow that, although if you moved switch left and let fuse holder dangle, existing wire would fit.
I went with this particular wiring strategy mainly to keep connections short and even.

https://www.batteriesinaflash.com/wiring-your-battery-bank-in-series-parallel (scroll down, top left diagram)

Can you point me to a good resource for this diagonal connection strategy? Specifically, one that details the differences... I'm sure I have a remaining cable section long enough to do it, but might be running a bit short on terminal rings for 2AWG...
Good that you have insulating caps on positive terminals, so dropped things less likely to short.
Should cover negative terminal of the two batteries on right as well because those are at 6V.
Wife took picture while work was still in progress. Everything will be capped, but will need something that sticks better to the threaded posts.
The ring terminals themselves don't stand out as far as the studs but are still exposed. What I did for my bank is I split pieces of heater hose lengthwise, and cable tied them over the ring terminal and stud.

I like it! Not sure if I have anything lying around like that, but worst case I'll just order some terminal boots online.
 

Hedges

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Here is a recommendation of diagonal:


Not sure where performance difference is detailed, but you can add up series resistance of wiring to each 2s string.
If you include estimate of battery internal resistance, that should show current imbalance that would occur.

This picture not the way I recommend:
12v-500ah-batteries-wired-series-parallel.png


This picture does it right, for a larger pack:

36v-500ah-batteries-wired-series-parallel.png
 

Zwy

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Nice neat install! I wish we had that much room to work with. I have to use three portions of walls in a u-shape dinette plus a vertical board on the battery box for our install. The board will be attached to the battery box with Velcro and anchored to the floor with two shelf brackets. Space is at a premium in a 21' fifth-wheel.

Post a picture of your install when finished.

Enjoy,

Perry
I made extra room for my install. On a 5'ver, you could do something similar, all depends on layout.
 

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Zil

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Can you isolate the wet batteries from the electronics? Battery fume can burn if subjected to spark. Electronics can corrode if subject to battery fume. Here is a good explanation of connecting multiple batteries in a bank. http://www.smartgauge.co.uk/batt_con.html
 

dixonge

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Can you isolate the wet batteries from the electronics? Battery fume can burn if subjected to spark.
I have a small exhaust fan to remove any hydrogen aerosol, but will also be inserting a shelf between the batteries and the electronics mounted on the wall.
 

dixonge

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Fuse and shunt both connect to same 2s; should be connected diagonally to balance resistance so current drawn equally.
Longer cable would allow that, although if you moved switch left and let fuse holder dangle, existing wire would fit.
I had an existing cable that allowed me to move the negative cable > shunt connection to 'most negative' - this is how I had everything connected previously. I never thought about letting the ANL fuse dangle though. Will keep that in mind.
 

dixonge

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I have to use three portions of walls in a u-shape dinette plus a vertical board on the battery box for our install. The board will be attached to the battery box with Velcro and anchored to the floor with two shelf brackets. Space is at a premium in a 21' fifth-wheel.
That's a baby fiver! Can't imagine doing this in our dinette area. Could barely get the batteries in there, much less the other devices!
 

dixonge

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ok, 98% complete. Still didn't get the one scc temp sensor taped to a battery, might need a few more cable hold-downs, but at least it's not *quite* a rat's nest, and I did save lots of cable length. Some of the odd angles make it look like some sort of weird electronics art project LOL

Also got the SB50 plugs connected to the portable solar panels and tested that all out. Haven't tested the charger yet in this particular configuration, or the inverter. Also need to add some red tape in a few spots. Ran out of daylight...

battery-bay-post-rewire-reorg.JPG

batteries-2s2p-final.jpg
 

dixonge

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also 3 of the chassis need grounding, when I install the ground bar. Maybe in the morning before we head out...
 
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