Yes, you can still have voltage drop in any circuit whether internal to the battery, or external. - there is an inherent voltage drop in any conductor - it is the same basic principle by which resistors work. - If you have a short run of copper cable, you can run a smaller cable, but the more distance the cable has to stretch, the larger wire size (smaller gauge) you will require to carry the same amp load. - It applies in anything electrical including home wiring, computers (network cabling does have limits on how much distance there can be between any two powered connection points), automotive, OPE, etc.
- any resistance in a circuit whether intentional (Resistors, wire size and length, etc.) or not (corrosion, loose connections, broken wire strands,etc.) results in voltage drop across that part of the circuit.
Voltage drop can be *in* the battery, or outside of the battery - that is the basis by which those fancy new battery testers work by - they measure internal resistance of the battery.
Battery can measure 12.8 (full charge) voltage with a multi-meter, but when applying a load (requiring more than the milli-amps drawn by the meter) the resistance in , say, a battery terminal that has separated from the plates internally, will be too great for higher amp loads, and thus deliver less voltage, which is what you would be measuring doing the voltage drop test. - which is how the Carbon Pile testers work - they apply a load and measure battery voltage drop - but they cannot detect internal resistances of the battery... So, voltage dropping a circuit under load is basically the same as using a carbon pile battery tester, but voltage drops can test more than just the battery.
Ive had a battery that passed the test with the fancy internal resistance tester, and yet failed under carbon pile load testing. - Ive also seen it work the other way. (passes load test, fails internal resistance check)
Installing a brand new battery *may* overcome or mask a voltage drop across a circuit (such as a failing solenoid or sticking/worn starter brushes) simply because it delivers more amps flow through the resistance.. but all things being equal, battery life will be shorter in an application where there is a voltage drop enough to stress the battery on a regular basis.... Thus, if you install a new battery and solve the problem, but there is a heavy resistance or voltage drop in your system, your battery will not last as long as it would otherwise.
As to batteries - as far as I know there are NONE that give a warranty greater than 6 months for O.P.E. applications. If you have room to fit one, you may opt to get an automotive battery of a size that will fit that might have a 2 year warranty (but you'll pay LOTS more!) - it will likely have more CCA than a typical OPE battery.
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