Using copper flat bar to connect the batteries in a battery bank

[svJasmine]

I have used flattened copper pipe for bussing fuse blocks with absolutely no problems. Going strong 20 years later. Cost pennies. Smash it, drill it. Grind off rough edges. Done.

I use cable for battery ties.

[Steven UK]

If your worried about the mechanical stresses setup by the rigid system then bend a 'Z' into the bar so it is now its length is somewhat flexible.

I like the idea of a bussed battery but not the uninsulated part.

[mitiempo]

The problem I see is corrosion. Tinned cable of the correct gauge with closed lugs and heat shrink is a lot better than bare copper bar. I also agree with the need for movement however slight that cable allows but the bar will not allow.

Fuse the main positive of the bank - not need to fuse each battery in a bank.

Never fuse the negative.

[svJasmine]

Cover the copper with large heat shrink for insulation.

Originally Posted by Steven UK

If your worried about the mechanical stresses setup by the rigid system then bend a 'Z' into the bar so it is now its length is somewhat flexible.

I like the idea of a bussed battery but not the uninsulated part.

[mitiempo]

Originally Posted by svJasmine

Cover the copper with large heat shrink for insulation.

The ends will corrode if not tinned.

[senormechanico]

I agree with the need to allow for expansion.
Mechanical stress due to expansion is the primary reason for bad circuit board connections in electronic equipment.
That's why a decently designed board uses U shaped lead wires from components which generate any significant amounts of heat.
My Autohelm 4000 is a perfect example of the designer's failure to do that.
I have to resolder all twelve leads on the four MOSFET transistors every few years.
The leads are very short and direct to the board.
Further, there's not enough room to replace them with new transistors with longer leads shaped into a curve to allow for expansion.

Whenever you read a thread about these autopilots going hard over all of a sudden, that's usually the fix.

[captstu]

I used 1" wide "grounding bar" taken from old phone company installation and bought for the weight of the copper for about $10 for the job. Each piece was 1" wide, 6" long and was, they claimed, 8 gauge copper.

I ran a 16,000 btu/hr air conditioner on the bank of 8 6 volt batteries rated, in total, at 950 Ah for 12 volts.

The replacement of jumper cables with bus bar reduced my voltage drop by 0.08 Amp (measured with a shunt and oscilloscope) during the first few milliseconds of air conditioner start.

I was unable to measure any difference between the shunt wires and the bus bar during any "normal" operation. Each end of the bus bar had a copper washer (on the battery side) and a copper plus stainless washer on the bolt side. The battery posts were, I think, M6 posts that are drilled and taped for allen screws.

The thing looked like a battleship - and since there was very low effective resistance, the bus bars had no measurable heating.

Since I routinely drew well over 100 Amps when running the inverter and air conditioner (or washer/dryer), the lower loss of the bus bar mattered. For other reasons, I don't believe any longer this was a wise idea, but it did for for 5 years with only replacing the alternators (I have 4), the drive belts (I had 6) and the engine (I had two).

If you want this much power on your boat, buy a generator - Tesla was right!

[Zai]

What about using something like these?

Flexible Insulated Busbar – Maxiflex

or these?

http://stormpowercomponents.com/shop-our-stock/braid

[Rigdaddy]

Originally Posted by jeepbluetj

ABYC says to fuse the batteries. I think fusing the batteries is a phenomenally good idea.

As usual, Maine Sail has a good article about it: Battery Bank Fusing Photo Gallery by Compass Marine How To at pbase.com

Thanks for the link to Maine Sail's article.

[mitiempo]

Originally Posted by Zai

What about using something like these?

Flexible Insulated Busbar – Maxiflex

or these?

Braided Connectors | Copper Braid | Shunts

The first still has the problem of corrosion in a marine environment.

The second looks ok but surely more expensive than a proper tinned cable, closed lugs, and heat shrink.

[mickeyelam]

[QUOTE=funjohnson;2298255]? How does voltage not play into the resistance? Isn't that part of Ohm's Law?

Voltage is, indeed, a part of Ohm's Law. However, under discussion here is ampacity not amperes.

A conductor of a known material and size (copper buss bar in this case) can carry a certain current for a given temperature rise (ampacity). The buss bar doesn't care if the current is 100A at 12V or if the current is 100A at 24V; all the buss bar "cares" about is the actual current flowing through it. As mentioned earlier, voltage comes into play for specifying conductors when insulation of the conductor is specified.

[rwidman]

Originally Posted by funjohnson

? How does voltage not play into the resistance? Isn't that part of Ohm's Law?

Matt

Voltage is part of ohm's law but a fixed resistance is the same regardless of voltage.

Imagine a resistor sitting on a bench. Imagine it is color coded (marked) ten ohms. It has ten ohms of resistance regardless. It doesn't have to be connected to a circuit to have ten ohms of resistance.

[rwidman]

Originally Posted by jeepbluetj

ABYC says to fuse the batteries. I think fusing the batteries is a phenomenally good idea.

That is only partially true and misleading. A circuit feeding the starter motor doesn't have to have overcurrent protection.


The house bank should have overcurrent protection as close to the positive battery terminal as possible.

[Cheechako]

If you do I would make them U shaped to avoid stresses...

[pdenton]

holy cow. So many reasons not to use bars. One in particular is that they are not insulated. In building and outfitting a boat real problems show up, difficult decisions need to be made, but how to connect batteries is not one of them. Go with the flow and do what everybody else does.
pdenton