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Originally Posted by Jaxonalden
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"Still have not found the strong electrical drain on my battery. I have to disconnect battery if I let car sit longer than 3 hours! Alternator works great! New 850ca Bosche battery."
It's a new battery (old probably drained also), and the guy lives in Southern Cali. I know all too well about old battery’s and cold weather, they lose their capacity, I grew up in northern Wisconsin. This guy’s situation is different; he has a major short plain and simple. If it's the battery the chances of it affecting both are too great. You said you isolated the problem circuit(s) with a repair or pulled the fuse. What was the problem with the circuit? A short? What was the amp rating on the fuses? A short that didn't blow a fuse yet drained a battery in a couple of hours?
I'm still with Paul on this one.
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OK, let’s look at your questions in the order you stated:
1. “New battery” is a relative term. Assuming the battery has a design capacity, say 800 amps; that level of output only exists when the unit is first put into service (read that as the first time it sees any level of discharge). The reason is that batteries live (and die) by what the battery industry calls “cycles”, which is defined as any level of discharge followed by any level of recharge equaling one “cycle”. All lead-acid batteries have a defined number of cycles in their life expectancy; it has been that way since Gaston Plante invented batteries as we know them in 1859. Simply put, the battery will live through so many cycles, and that is it (more on this in a bit). The lead-acid “SLI” (starting, lighting, & ignition) batteries used in cars (regardless of design) use metallic lead frames that are filled with lead oxide paste. The lead metal frames are only there to conduct electricity and take no part in generating current, which is done by a chemical process between the lead oxide paste and the sulfuric acid solution surrounding it. The lead oxide reacts with the acid to form lead sulfate, releasing electrical current, which provides the juice to run the cars systems. When recharged, either by an external charger or the car’s alternator, the lead sulfate is converted back into lead oxide. The problem is that the chemistry is not perfect, and some of the lead sulfate is not converted back to the oxide form and over time the level of unconverted sulfate continues to grow, which does three bad things: The output capacity of the battery is reduced by some level, the batteries life is reduced, and the internal resistance inside the battery rises (which is why really weak batteries take a long time to charge, get very warm, and still do not put out much power). A couple of more points about the oxide/sulfate conversion problem is that the deeper the level of discharge from total remaining capacity per cycle, the worse the sulfating per cycle becomes, and the harder the battery is to recharge. Add in the environment and the problems are compounded further: In the cold, the electrochemical process that generates the power is reduced, regardless of the batteries state of condition (this is why otherwise fine batteries suddenly die on the first cold morning). Batteries exposed to higher temperatures do just the opposite, they tend to generate more power faster, but in the process sulfate more, which is not converted back to the oxide form, and their lives are shortened accordingly. This is one of the reasons many cars locate the battery close to the front grill to get it away from as much engine heat as possible, and batteries used in very hot climates die sooner. So, it is entirely possible to have a relatively “new” battery that demonstrates reduced current output levels, often 25% or more below the “design” level when subjected to load testing. This is also why using a proper load testing procedure is the only true method of determining a battery’s operating condition.
2. In the cases we have seen, the source of the problems varied. All cars have constant low level current draws caused by everything from the ECU memory to the radio station pre-sets, navigation systems, alarms, immobilizers, remote entry systems, and keeping the clock accurate. This is why a brand new Porsche, depending upon how it is equipped from the factory, can kill an otherwise good battery when parked for a relatively short time frame, and why Porsche (and others) offer battery maintainers. These draw sources are on multiple circuits; but the important point is that their impact on the battery is cumulative. Even a cell phone charger left plugged in to the cig lighter causes some level of discharge, even when the phone isn’t attached. In our experience, we have found excessive current draws caused by everything from a faulty CD changer (ever wonder how a CD change can eject the disc cartridge with out the key in the ignition? Simple, there is power to the unit when the car is off, and if the unit goes bad, the draw rises, adding to the load on the battery), to seat heater relays, and quite often aftermarket add-ons. One of our favorites was a couple of year old, but immaculate second owner turbo with a new replacement battery that went dead after only a couple of days in relatively mild weather. We traced the problem to three aftermarket electronics power supplies that were installed (and very well hidden) that were tapped into multiple “always hot’ circuits like the cig lighter and relay panel circuits. Each charger demonstrated a low individual draw, but whey combined with all the other “native” or active aftermarket draws and the battery had a problem. We also load tested the battery and found it to be well below what you would expect for its age (probably due to the constant multiple low current draws), so we got it replaced under warranty for the client. We also moved some of his after market power taps to “switched” circuits as they really didn’t need to always be hot. The customer’s problem has not returned, even in very cold weather.
I hope this addresses your questions…………………