I recently did a lot of research on batteries and thought I would share what I found. The original thread is
>here< but I'll summarize everything in this thread. Thanks to all the board members and their quick replies to help teach me about batteries.
First off is a post from Speedzilla that got me started.
The stock battery specification considers how much current is needed for a start, the range of operating temperatures, the reserve needed for repeated starts, and the charging system capacity. A larger capacity battery will be a lot kinder to your charging system.
The principal advantage of using a larger capacity battery is to be able to restart repeatedly. When you don't ride long enough to recharge fully between restarts, a larger capacity battery is an advantage. A lower capacity battery will need to be trickle-charged more often and the chance of a deep discharge (that reduces battery life) is greater with small capacity ones. Further, a battery's capacity drops when it gets cold so when you ride in cool weather, a smaller capacity battery will have an even smaller reserve for starting at low temperatures.
Consider also, that the early pre-1998 bikes have an alternator with a lower charging current output, so they'll take longer to fully recharge the battery. A prolonged 30 amp charging current is one contributing factor to why Ducati voltage regulator/rectifiers and stator wires fail prematurely.
In 2001, the bikes were fited with a revised starter motor gear ratio that drew less current and made it possible to start the bike using a smaller battery. The starter gearing on the early bikes are not well suited to the smaller batteries.
Standard battery 1994 - 2001 model years:
Yuasa YB16AL-A2 (16 AH, 200 CCA, 11.5 lbs.) 8" x 2.625" x 6.5"
Standard battery 2001 - model years:
Yuasa YT12B-BS (10 AH, 125 CCA, 7.6 lbs.) 6" x 2 3/4" x 5 1/8"
Commonly used alternate batteries
For the track, light weight is really important:
Yuasa YTZ7S (6 AH, 130 CCA, 4.6 lbs.)
On the street, reliable operation is of a higher concern to most of us, so consider the following maintenance-free batteries:
Fiamm-GS F19-12B (19 AH, 200 CCA)
GS Battery GT12B-4 (12 AH, 200 CCA, 10 lbs.)
Yuasa YTZ12S (11 AH, 210 CCA, 10 lbs.)
Power Source WP22-12B-4 (10 AH, 220 CCA, 15.5 lbs.)
Odyssey PC680MJ (19 AH, 280 CCA, 14.7 lbs.) (dry cell technology, my personal choice)
I installed a Odyssey PC680MJ in my 916 in May 2001. Stlll going strong.
Note that the old Yuasa YB16AL-A2 is the type of battery that you need to fill with water and check on once in a while. I believe this type is called flooded cell since you have fill it with distilled water and then charge it before you use it. The newer bikes has nice little sealed batteries so you don't have to deal with maintenance.
But you want replace your OEM battery otherwise you wouldn't be interested in this thread. So you can either blindly use batteries that others have found to work or you can read on and learn why those alternate batteries work.
So, first let's look at the AH rating. AH stands for Amp Hours and is essentially how long the battery will last. Here's a longer explanation that was given to me.
Sitting batteries drain over time, dropping the voltage available for starting. This capacity is defined by the amount of amperage a battery can dole out over time-its amp/hour (Ah) rating. For example, a 50Ah battery can power a 1-amp device for 50 hours, continuously, without being disconnected or recharged. So, the time it takes for a battery to drain depends on whether or not there's an excessive parasitic draw.
For reference, a '92 Civic's expected parasitic draw is roughly 10 mA, or .01 amps. A stock Civic battery is rated at about 40 Ah. This resting Civic would run completely dry in 4,000 hours, or about five and a half months. Compare that with an Odyssey PC545 that is rated at 13 Ah and will die in about 1,300 hours, or almost two months. Keep in mind though that you can forget about starting that Civic once below 10 volts and 12-14 days is just about the maximum any lightweight race battery should remain connected to a non-operating vehicle.
Next we look at the CCA which stands for cold cranking amps. The higher the number, easier it will be to start your bike. Again, another longer winded explanation:
Look no further than the definition of CCAs to make sense of this. The rating was developed for colder climates. Like we said, batteries and cold weather don't get along so the rating represents the extreme. A battery's capacity is reduced roughly 35 percent when subjected to a temperature of 32 degrees F, for example. At 0 degrees F, capacity drops another 60 percent. It's for this reason the CCA rating was developed-to define a battery's ability to start an engine during cold temperatures.
The CCA rating is the amount of amperage a brand-new, fully charged battery can output at 0 degrees F for a full 30 seconds while maintaining at least 7.2 volts. It goes without saying that the strain a battery undergoes during this test is much worse than what it would otherwise normally be subjected to. In other words, a car may need a certain number of cranking amps to start at 0 degrees F, yet this number is only 60 percent of what the battery's actual rating is at normal temps. As such, when choosing a car battery, consider not just the CCA rating but also the intended climate. Even those living in cold climates tend to store their vehicles during the winter. A lightweight, low CCA battery can be used the rest of the year in cases like these and hooked up to a battery-conditioning device the remainder of the time, but don't always take the CCA rating at face value. Swapping a battery is just as reasonable a winterizing effort as changing to snow tires.
So, now that you know what it means to have a battery with 16AH and 200CCA, how far can you vary from those values without hurting anything? Well, you can go as high as you want because the bike won't draw any more than it needs. How about lower? On the older monsters, people have used the smaller new batteries and gotten by. It really depends on how cold it gets where you are. A lower AH value will mean that you might have to charge your bike more often but the bigger concern would be a lower CCA value in cold climates. AH and CCA are related proportionately as well. If the bike has been sitting a while and you no longer have your full 16AH then your CCA won't be as high as it could be either.
Let's say you go out to a friend's house and stay until 1 in the morning and it's winter. How cold is it? Will your bike start? Maybe you should've gotten something closer to the stock rating or maybe even larger.
Ah, a couple notes about the batteries listed in the Speedzilla post:
1. I couldn't find anything about the Fiamm GS.
2. Looking at the Odyssey site, I found that there is a normal PC680 which is slightly smaller and only slightly weaker than the PC680MJ but is still "better" than the stocker.
That's the one I'm gonna go for.3. Another battery that some recommend is a DEKA ETX14.
edit 3.10.11 : After calling the shop that I was going to order from, I found out what the MJ stands for in PC680MJ. MJ means metal jacket which helps it handle the heat and vibrations better. Since the battery is practically sitting on top of the engine, they recommended that I go with the MJ. I brought this up with other members and
nobody really thought that it was worth it and a few members piped up saying that they're running the regular PC680 for 6yrs+ just fine. I thought it over and since it was someone else getting it for me for my birthday I went with the PC680MJ. It is slightly larger than the PC680 and is a
VERY tight fit on my '95m900 and requires a little tweaking. On my battery box, the side closest to the rider bends in a bit and I had to push this out to let the battery slide in. I also had to cut the rubber padding on the bottom of the box to allow for the extra thickness of the Odyssey. Without cutting the rubber padding, the battery could not sit flat on the bottom of the box and because the battery is already ever so slightly taller than the stocker, it hits the bottom of the tank. I guess vertical clearance is kinda close. I had to adjust the ends of my cables too because the terminals are farther in on the Odyssey and stock angle of the cable ends doesn't reach. But, after that little bit of tweaking, it fits and works fine.
