Any advantage to common Bus for all I / O

[Blackcherry04]

Is there any Advantage / Disadvantage to having a common Bus connection for all In / Out connections to a battery bank. If a Inverter is pulling from the Bus will the Input go to it first ??, then any excess to the batteries ??

[westbranch]

Not being facetious, but in my mind electrons follow the path of least resistance and do not differentiate what they are flowing to. ie if more than the pv output is needed by an inverter, the flow to it comes from all sources to satisfy the demand.

I don't think there is any question as to effectiveness of buss bars, just imagine the battery post with all the different connections made to a single point and think about my previous statement.

HTH

[BB.]

In general, following the recommendations for connecting the batteries (balanced wiring) and creating a single "ideal" bus connection that has very low resistance to the battery bank--Then connecting all the loads and all the charging sources to the common bus is the best way to do it.

Note, there are some wiring diagrams that create two "ideal" connection points. You could place chargers on one and loads on another--But I am not sure there is any advantage to that (with an otherwise properly designed battery/bus bar system).

If your charge controller has remote voltage sense leads (MorningStar TS family, new version Rogue), then connecting those directly to the battery connection point (instead of the bus bar) could save a bit of voltage drop (my personal recommendation, try to not have more than 0.05 to 0.10 volt "rise" between charger and battery bank--Higher voltage "rises" will tend to slow down battery bank charging--reduce charge rate faster than "ideal").

-Bill

[Cariboocoot]

A bus bar is just a different common connection point from the battery post. Usually they are only used when you have a lot of wires that have to go to the same place (parallel battery strings). Otherwise it's another connection point (possible something to go wrong) and expense. No real advantage in current flow otherwise. The batteries will not be deprived of charge by the current from the controller going to the inverter "first".

[Blackcherry04]

I was asked the question because a ME type posed it to me because he planed to use two charging sources and wondered if one had a advantage over the other. I usually do a diagonal battery bank connection or a paralleled bank and really didn't have a answer about one over the other. I'v used the Scan Gauge information on cabling.

[SolaRevolution]

Busbars are great!
Just remember that busbars are conductors. They have ampacity and tempurature ratings.

The panel-mounted busbars like the ones in Midnite E-panels and Outback power panels are typically rated at 180 amps (AC or DC). I have found overheated neutral wires in a common busbar. There were 4, 60 amp charge controllers all fed to one end of a 180 amp busbar of a grid-tied battery-bassed system. The insulation had been melting back and the copper #6 wires were discolored and very brittle.

Also, the "factory" built power panels are often pre assembled with a #2 wire feeding the positive busbar. This would limit the current to 130 amps.

-Alex Aragon

[Blackcherry04]

I asked this question because of something I noticed when charging with a Honda EU 2000. This morning I was able to do a little test. I took 2 chargers one Iota 55 amp and a old 25 amp. The Iota 55 is wired to my battery bank. I hooked the 25 amp directly to the inverter input lugs. If being on a common bus makes no difference then I shouldn't notice any difference on the inverter draw or a change in the charger output or the Honda's ECO throttle. The bank is 10 GC-2, @ 12v.

I fired up the Honda and both chargers on ECO throttle. The Iota 55 was putting out a steady 55.8 amps and the 25 amp about 15 amps. Both being 3 stage, I thought they must be fighting each other and the 25 amp had cut back some. I kicked on the refrigerator as a Inverter load and the Honda started to increase the throttle in response to the load. The Battery / Buss voltage remained at a steady 13.3 volts and the Iota 55.8. The 25 Amp hooked to the Inverter was now putting out 25 amps.

So in essence the Inverter is taking a extra 10 amps from the charger and not pulling it from the buss or batteries because it's being fed off the 25 amp charger.

To test it farther I removed the Iota's 55.8 amps from the buss and left the 25 amp hooked to the inverter inputs. Every time the refrigerator would kick in the incoming amps would drop on the buss but the charger was still putting out 25 amps and the inverter was taking it and the voltage was steady.

My conclusion is it does make a difference and the inverter will take the power either from the buss or the charger. How much difference does it make ?? Is it more efficient the current is not being converted to battery storage and then to the inverter power ?? The Honda reacts to the draw thats for sure. In essence you have one inverter feeding another anyway. My only thoughts is can you cut conversion loss any ??

Any thoughts.

[Cariboocoot]

This would be a difference in the wiring resistance between the connection points where the two chargers were attached. This is particularly noticeable on 12 Volt systems where even a small amount of resistance makes a significant change in performance. And of course the higher the current involved the greater the effect.

[Blackcherry04]

This would be a difference in the wiring resistance between the connection points where the two chargers were attached. This is particularly noticeable on 12 Volt systems where even a small amount of resistance makes a significant change in performance. And of course the higher the current involved the greater the effect.

Thats my thoughts also. I can kind of tell more over a period of time on fuel consumption and recharge times. I'll run a couple A/C's tonight and the mix the generator in. I usually charge at bed time and run them at night. If true, it would save me big time, anytime I can keep from running the 20 KW generator is $10.00 a hour saved, not to mention the batteries.

[topper]

The biggest advantage to using a common buss is everything comes to and from a common piont of reference. Everything can be calculated from that point. Master battery cables to buss have a voltage drop of 'X". Volt drop from buss to inverter is "X".
Normally most power panels have the buss mounted almost directly to the inverter, That should put all charge controllers and inverters on the same voltage plane. But there are line losses from the controllers to that buss as well to take into account.