Quote:
Originally Posted by kiettyyyy
Absolutely. I had helped a team in San Diego that had about a 6 FT run of 6 AWG going from their main breaker to the PDP. Shortening the run solved their issue.
Battery voltage can be affected by three factors, temperature, state of charge and current. The one we're really talking about here is current. A lead acid battery has internal resistance. As you move current through the battery, the voltage changes due to its internal resistance.
Lets simplify it a little bit.
When you're charging a battery with some low current, you'll see the battery voltage increase. Charging it with a larger current, you'll really see it increase.
Same thing applies to the discharge. Discharge it with a small current, you'll see it decrease; discharge it with a large current, you'll see the battery voltage really decrease.
Now apply this same theory to having long interconnects with your battery. Say you're drawing current at some C rating that's near the limits of the battery, your voltage will likely be pretty low. Combine that with the voltage drop due to large current draw over a long run of cable.
This situation is extremely prone to causing brownout conditions.
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I suspect the problem with the robot you helped fix was really some bad crimp or the nut on the breaker not being tight, leading to a high resistance connection (this is assuming that the battery did not get changed in the process). The drop caused by the wire resistance, even at 240 A through 6 feet of 6 AWG would be 0.72 V if we use the maximum rated wire resistance. A bad connection can easily give you more voltage drop, up to 12 V.
I am not advocating that we should have excessively long power wiring but we should solve the real problems.