Originally Posted By: neilwestlawn
He says he wants the biggest battery with the most amps.
Is his method sound? Does anyone know of any alternatives to the 121R group size?
This is not unsound. A bigger battery will have more capacity, and in a slow drain present on all modern vehicles, 3+ weeks with no driving, it will stand a battery chance of having enough juice left to start the vehicle.
If one is simply impressed with high CCA numbers, Look to Odyssey AGM batteries. I have a group 27 Northstar AGM and its ability to crank my engine quickly is just scary impressive. It can also handle being deep cycled as long as it receives high initial amperage on recharge and is charged until amps taper to 0.5% of the 20 hour AH capacity at 14.46volts at 77F.
Starting batteries can fudge for super high CCA numbers with thinner more numerous more porous plates. But these thinner plates are more fragile and will be damaged more when discharged below 80%.
My personal preference, since I do intentionally deep cycle my battery then require it to start my vehicle, is to get a battery which can handle deep cycles. The AGM can be a much better' marine/ dual purposes battery, compared to flooded batteries sold as marine batteries. If I were to choose between two batteries of the same dimensions and price tag, I would get the one with lesser CCA's as it is likely more resistant in deep cycle usage.
Consider that when a modern car sits undriven for 3 weeks or so without a maintainer attached, the battery is essentially being deeply cycled.
A prompt recharge to a true 100% is best. It will take at least 7 hours of driving, for a healthy battery to return to 100% charged when it is drawn to the point it needs to be jumpstarted.
Most people assume the alternator is a magical instant battery recharger, but Lead acid batteries can reach 80% charged quickly, but that last 20% takes hours, no matter What.
There is no way to force a battery to 100% charged any faster. Voltages should not exceed 15 on a 12v battery.
People like to talk about this battery or that battery being well made and lasting X amount of time, as if the battery itself is responsible for its longevity, or lack there of.
90% of a Lead acid battery's lifespan is directly proportional to how much of its lifespan it remains as close to fully charged as possible. So brag about battery life if you must, but instead of praising any brand of battery for long life, praise instead the vehicle's voltage regulator, and one's driving habits that allow the battery to stay up near 100% charged for its whole existence.
The hotter the battery the faster its acid eats its plates too, but a hot environment is not the death knell of batteries. Hot weather increases the self discharge too, Self discharge can be 15% a month at 77F, and significantly higher than this when the battery is aged, and higher in higher temperatures.
So again the thin plate starting battery might be being deeply cycled through sitting undriven, and increased self discharge higher temps and the fact that it takes a long time to fully charge a battery, all collude to send a battery to the recyclers.
Good luck on finding a suitable battery. If you want it to last as long as possible, get a charger which can fully 100% charge it overnight, and use it monthly, even if it is a daily driver.