Hello, I am wondering how to size my system amps wise, so I know how big to make my negative and positive bus bars? I know on https://www.mobile-solarpower.com/simplified-400-watt-fewer-wires-and-alternator-charging.html he uses a 250 amp bus bar, but that doesn't seem like enough is I am using a 3000-watt inverter and 300 amps of battery. Granted I don't think it will ever actually run at 3000 watts fully. More like 2500 watts max. Thanks!
How to size a system for Bus Bars!
- Thread starter Eileen
- Start date
The generalized answer is you size busbars in roughly the same way you size wire, figure out the maximum current (amps) that will be flowing through that circuit, select a fuse that is larger than that number (1.25x or greater is the rule of thumb) than size your wire and busbars larger than the fuse.
As an aside, your battery does not have amps, amps are not something that can be stored or had. It is a unit of flow. Batteries are measured in amp-hours, which are a different type of unit, in the context of a battery it measures capacity or stored energy. Separating these two terms and concepts in your head, will help clarify a lot when it comes to properly sizing components.
As it relates to busbars and wire and most other components of your system, how much energy is stored by your batteries (amp-hours) is irrelevant, what matters is how much current will flow through each component of the circuit.
If you have a simple system, where all loads are AC (inverter) loads you can get a rough estimate of max current by calculating:
[Inverter Watts] / [Inverter Efficiency] / [Inverter Low Voltage Disconnect]
For example:
3000W / 0.85 inverter efficiency / 12v = 294A
294A x 1.25 = 367A or larger fuse
You can tailor those numbers to your situation, but that will give you a rough ballpark of maximum continuous current.
If you also have DC loads, they should be accounted for as well.
This observation you made is EXACTLY on point and pushed me into buying one of two options. One, was to buy the 600 amp versions from Blue Seas Systems, or two, buy the Victron Lynx Distributer with 1000 amp rating. The price was about $200 vs $150 and I decided to go the Victron system instead. I think all the sum of the parts add incremental additions to the efficiency of a system that is NOT cheap to begin with. I see a ton of people use undersized EVERYTHING. Crap, you only want to do it ONCE...so do it right.
How do you feel about the lynx distributor? do you like it? was it easy to use? I know you need to use mega fuses with it, and I've already bought a bunch of anl fuses for my system, do you think at that point I should just go with the blue sea bus bar since it's rated at 600-1000 amps?
I had a damn limited amount of room to deal with! I liked the Victron Distributer because you could stack the in and output cables to one side. Or in my case, in on the left (if facing) and down for the outs. But don't forget, the best part was the ground bar (also 1000a) was the only input to the smart shunt. Here is a pic. (Don't forget hard to see, but there are two levels, the hot side is actually inches above the ground terminals...I used 4/0 and it fits just fine.
Now, you'll need to get some additional screws and bolts, but the entire system is very well made and I would use it again.
positive from batteries, 400 amp fuse, to bar to shutoff ALL POWER
after shutoff/on, after bar on, cable travels under to shutoff/on for inverter only
after shutoff/on, all power to Victron busbar
ground from main battery post to smart shunt, bar to GROUND shutoff that feeds busbar
Attachments
I'm not sure, since I'm not sure exactly what you have purchased / are using.
It seems like from your original post you were worried about the busbar being undersized, if this is the case, using fuses sized appropriately for your loads would not remedy the situation as the busbar would still be undersized.
The basic order of things
Determine the max current of your circuits >> Size fuses for each circuit larger than the max current on that circuit >> Size the conductors (this includes wire, busbars, and any other current carrying component) larger than the fuses.
It sounds like (i've no way of knowing for sure) you have selected appropriately sized fuses, but are worried about the busbar being insufficient. If I were in your shoes I would just go a size or two up for peace of mind. Here is a semi-reasonably priced 600A busbar for $75
What size wire are you using with your inverter?
Buss bars are sized the same way we size cables. Know what the highest continuous current expected. I disagree with some thing. (1)Know the amperes. (2)size the cable to the amperes for voltage drop and ampacity. (3)size the fuse to the ampacity of the required cable.
Wits' End
Old guy, wanting to learn new tricks.
Wits' End
Old guy, wanting to learn new tricks.
Victron Smart Shunt
Linx Power In.
Any thoughts on how to best connect these?
For some reason I'm thinking I'll have a ¾" height difference. I'm pretty sure it won't fit 'modularly'. So a short conductor; braided copper? Bus bar? Short cable? jumper cable?
I posted video above, separately. (Fat Fingers) it was supposed to be part of this for images.
Linx Power In.
Any thoughts on how to best connect these?
For some reason I'm thinking I'll have a ¾" height difference. I'm pretty sure it won't fit 'modularly'. So a short conductor; braided copper? Bus bar? Short cable? jumper cable?
I posted video above, separately. (Fat Fingers) it was supposed to be part of this for images.
Wits' End
Old guy, wanting to learn new tricks.
Anyone on how best to connect these two Victron products?
Wits' End
Old guy, wanting to learn new tricks.
I'm just about to start assembly. Anyone have suggestions?
I would mount one of them on a small piece of 3/4" plywood (or similar) to raise the height so they line up so you can use a bus bar. Wire is fine, too ...
Is it too late to use https://www.victronenergy.com/battery-monitors/lynx-shunt-ve-can ?
Is it too late to use https://www.victronenergy.com/battery-monitors/lynx-shunt-ve-can ?
Wits' End
Old guy, wanting to learn new tricks.
Thanks Cinergi! I'm going to play with "height balancing". I think I have 3 different negative posts, I can connect to the "Lynx Power In".
The Lynx Shunt requires a GX device to view the info. The Smart Shunt, is Bluetooth. Will did a VIDEO on it, a few months back.
Sik-wit-it
New Member
I'm using the same that will work just fine
Similar threads
