Battery buss - does anyone use them? (1 Viewer)

[Em and Tim]

Right, I am finally getting on top of various wiring/electrical issues, but on most of the online wiring diagrams that I seem to be coming across, the wires run from the batteries to a battery buss, which, for all intensive purposes, acts as a negative or positive post for both batteries, and keeps everything fairly neat, and allows for a battery monitor to be fitted etc.

With the electrical set up we inherited, we have a spaghetti junction of various wires attached to each post of either battery, that i am only now (9 months living in the van around europe) getting my head around, and a shunt that gives a permanent reading of -84.0amps.

Would installing busses be worth the effort? Does anyone in a MH use them? Are they just a neat aesthetic or should we be using them as they are safer? If so, I assume the amp rating should equal the combined amperage of the batteries (260a in this case)? What size cable should be used to connect the batteries and the batteries to the buss bar? (at the moment, I think the cables between batteries are smaller than they should be).

Thanks in advance for you advice, I'm trying to get the electrics in order at the same time as installing new solar.

 

[funflair]

What size cable ultimately depends on what power draw, if an inverter is involved big cables for sure and even if you don’t have an inverter at the moment why not go big and future proof your work.

Martin

 

[Mikeco]

I use a 12v fuse box which has 10 fused connections, this means that there is a single cable to the battery from this box. The only other cable attached to the battery is solar controller one.

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[Two on Tour]

I fitted both a positive and negative bus bar for my 12 volt circuits on our van which are housed individually in a plastic junction box.
Other than neatness, I needed to have just the one cable to the battery negative via a shunt to correctly operate my Victron battery monitor.

 

[Em and Tim]

I use a 12v fuse box which has 10 fused connections, this means that there is a single cable to the battery from this box. The only other cable attached to the battery is solar controller one.

I had in mind that the solar regulator cables (along with mains and alternator charging cables) would go to the buss bar as well, so that the battery monitor would know the inputs along with the outputs.

 

[ctc]

With 12v good connections are vital, if you can find some real copper slip (banned years ago) and smear the connections. If you use flex its well worth investing in ferrules. Corrosion is the enemy and stopping it will improve the life of the system.

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[Em and Tim]

So, I will install buss bars on both + & -, just to check, what size wires/rating of buss bar should I get?

The system is 12v, 2x 110 or 130 ah AGM batteries (depending on which temperature they were measured at), a 250w victron pure sine inverter (max draw 400w). A total of 500w of solar etc.

My reckoning is that the maximum draw will be when the inverter is flat out, (the blender) so that will be putting 33.33 amps across the cables at 12v along with anything else that is happening at the time.

So a 100 amp buss bar should be fine (despite having 220 (or 260) amp hours of batteries), unless there is a short or something. Similarly, what type and size of dables should I run, and how should this be configured?

It is currently just a mess of cables to each of the four terminals, with what look like far too thin cables between them!

 

[Two on Tour]

I used these earth blocks to bring the in battery positive and the negative via the battery meter shunt, and then distribute to the various 12v circuits from the blocks.

https://www.toolstation.com/search?q=earth block

Housed in these junction boxes.

IP20 Junction Box Q12

85 x 85 x 37mm - 15 entries (cable tie facility for strain relief).

www.toolstation.com

 

[Em and Tim]

I had this kind if thing I mind

Amazon product ASIN B07DN8KMTC
Or

Amazon product ASIN B07K2R3CMF
But am keen to get the right wires/cables.

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[Two on Tour]

I have a lot of circuits that I added for various accessories and such to our van so needed bus bars with multiple outlets.
Be careful not to restrict yourself for possible future addon circuits by going to small plus the Amazon one are hellish expensive compared to the ones I used from Toolstation.

 

[peterc10]

So, I will install buss bars on both + & -, just to check, what size wires/rating of buss bar should I get?

If you ever want to get a reasonably accurate reading of the current you are using in real time or have used in the past you will need a shunt connected to the negative on your leisure battery. In that case that should be the only connection on the negative side. I am not sure why you have so many cables on the negative side, given that, like the engine battery, it works on a negative earth system. But if you do have them you should install the bus bar on the shunt.

If you have or are thinking of having a reasonable sized inverter now or in the future you need to think in terms of starter battery or welding sized cable between the two batteries and the wiring to the shunt and to the inverter.

 

[Em and Tim]

If you ever want to get a reasonably accurate reading of the current you are using in real time or have used in the past you will need a shunt connected to the negative on your leisure battery. In that case that should be the only connection on the negative side. I am not sure why you have so many cables on the negative side, given that, like the engine battery, it works on a negative earth system. But if you do have them you should install the bus bar on the shunt.

If you have or are thinking of having a reasonable sized inverter now or in the future you need to think in terms of starter battery or welding sized cable between the two batteries and the wiring to the shunt and to the inverter.

Cheers Peter, we actually took out a big inverter for this one (it was not pure sine and was killing chargers), I'm not sure why you would need a bigger inverter though, this one is great for our needs.

Below is a picture I took last time I was in there to try and work out why the alternator had stopped charging (it was a break at the engine battery end, anyway, i had taken the inverter off the 'wall' above so you get a much better view of it all).

So, in the negative side of the batteries, we have the inverter and to an old shunt (both big black cables), a blue cable between the two batteries, a cable from the current 100w solar, and a cable that runs into the tv cabinet which has a retrofitted circuit in it. After lots of problems, I now know what most things in there do.

I am about to install 400w of solar and a battery monitor, so need to beaten it all up, my hang ups are about cable sizing, and then the buss/block being able to accommodate the required cables. I also want to get it all neater, and not in the open locker which generally gets stuff put on top of it.

So I guess the cable sizes between batteries and onto the shunt and onto the buss block things is the key question, along with the size that the cables should be to our wee inverter?

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[two]

This is what I did. Note how the batteries were connected. You don't have to use thick (single) wires, it can be difficult (or costly) to do, you could just add extra ones (double-up).

 

[peterc10]

We have a 2000W modified sine wave inverter. It is only used for my wife's hairdryer, so for about 5 or 10 minutes every few days. The hairdryer uses 1200watts so that means about 100 amps being taken out of the battery. For this type of use a modified sine wave inverter is good enough. But it does mean we used starter battery type cables between the two batteries and to and from the inverter and shunt. I work on the principal that the larger the better and the less voltage drop.

I would question why you want a small inverter. In my experience just about everything with a small to medium electrical draw such as phones, tablets, laptops, TVs, shavers, toothbrushes etc can be run off 12v with the correct adaptors, and that will be much more efficient, given that all of those things run on low voltage DC internally. But, if you want it, a 250w inverter will draw about 20amps on full power. The size of the cables needed will depend upon how long they are going to have to be. The shorter the better. I will leave it to the electrical engineers to tell you what size for your particular set up.

 

[Em and Tim]

I would question why you want a small inverter. In my experience just about everything with a small to medium electrical draw such as phones, tablets, laptops, TVs, shavers, toothbrushes etc can be run off 12v with the correct adaptors, and that will be much more efficient, given that all of those things run on low voltage DC internally. But, if you want it, a 250w inverter will draw about 20amps on full power. The size of the cables needed will depend upon how long they are going to have to be. The shorter the better. I will leave it to the electrical engineers to tell you what size for your particular set up.

It is for laptops we both work & study remotely, living in the MH, the blender, toothbrush chargers and not much else. To be honest, I know that you can get 12v charger versions for most of these, but I have never found them even close to reliable. I don't think a small inverter is less inefficient than the unreliability & hassle of trying to find decent/reliable 12v chargers, but then that why we went that way, it works well for our needs.

The max draw will be the blender which only ever runs briefly pulling 33amps (despite it being a 250w inverter, it gives a max of 400w), but I suspect we should allow for that wattage for a wee big longer in our specs. The cable length to the inverter is about 45cm negative and 2 x 30cm positive (it goes to an isolator switch which is in a stupid place and I may move it in this overhaul).

This is what I did. Note how the batteries were connected. You don't have to use thick (single) wires, it can be difficult (or costly) to do, you could just add extra ones (double-up).

View attachment 350097

That's really useful, what size is your inverter? I am thinking that I will re-deploy the big inverter cables as battery link cables if I can (the old inverter was a 2500w non pure sine beast that killed chargers for fun).

Edit:
I'm an idiot, the information I need re cable size for the inverter is in the manual which is about 4 feet away from me in a folder.

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[peterc10]

It is for laptops we both work & study remotely, living in the MH, the blender, toothbrush chargers and not much else. To be honest, I know that you can get 12v charger versions for most of these, but I have never found them even close to reliable. I don't think a small inverter is less inefficient than the unreliability & hassle of trying to find decent/reliable 12v chargers, but then that why we went that way, it works well for our needs.

The max draw will be the blender which only ever runs briefly pulling 33amps (despite it being a 250w inverter, it gives a max of 400w), but I suspect we should allow for that wattage for a wee big longer in our specs. The cable length to the inverter is about 45cm negative and 2 x 30cm positive (it goes to an isolator switch which is in a stupid place and I may move it in this overhaul).

That's really useful, what size is your inverter? I am thinking that I will re-deploy the big inverter cables as battery link cables if I can (the old inverter was a 2500w non pure sine beast that killed chargers for fun).

Edit:
I'm an idiot, the information I need re cable size for the inverter is in the manual which is about 4 feet away from me in a folder.
View attachment 350122

I work occasionally while we are away so always have my laptop with me. I have had no problem in finding and using decent and reliable 12V adaptors for my last two HP business laptops or my present Microsoft Surface Pro. If your system is critical for your work you probably need to build in redundancy anyway with duplicate components, whether they are 12V adaptors or 240V inverters and chargers.

Your laptops will have external bricks (some may be internal) that convert high voltage AC to the low voltage DC needed for the laptop. It is very inefficient from a power point of view to convert low voltage DC from your batteries into high voltage AC and then use the laptop brick to convert that back down to low voltage DC again. I assume here that you will not be on EHU and you will be relying only on your solar power to cover the power you use, but even then you will have to be much more careful with the power you use especially in the winter months.

By the way the maximum power quoted for the inverter is for instantaneous peaks. Run it at that for more than a few seconds and it will stop. And I assume that when you do use the blender you will unplug the laptops.

 

[Happy1]

This keeps things neat, neg bars at top, wired direct to battery with inline fuse, the loop at the bottom connects left and right positive feeds to fuses
Ebay purchase

 

[autorouter]

This keeps things neat, neg bars at top, wired direct to battery with inline fuse, the loop at the bottom connects left and right positive feeds to fuses
Ebay purchase

Standard Blade Fuse Box With LEDs - 10 Way

10-way standard blade fuse box with individual LEDs that light to indicate that a fuse has blown. 6.3mm blade terminals, clear cover and mounting holes.

www.12voltplanet.co.uk

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