How do I know which battery is correct for my bike
After deciding whether or not you can use a Lithium Ion battery (see above post), the next thing to look at is the different types of batteries available.
Batteries can be found in the following flavors:
- Flooded Cell Lead Acid - This is the style that was generally available when most of our bikes were made and 99% of the time, this is the stock battery type. The only advantage of this type of battery over the other types is that this type is the most resistant to overcharging. Too much voltage and too much current will not damage this battery type except in extreme cases.
- Sealed Lead Acid - This style is not dissimilar to the flooded cell, except that they are sealed to prevent spillage. This makes them "maintenance-free" so that you do not have to top up the electrolytes, but it also leaves them less capable at dealing with excess voltage and current. These can be mounted on their side, but not upside down. Try to mount them vertically if you're able, however. These are generally the cheapest batteries available and can be found in battery backup supplies in alarm systems and computer components. These types of batteries are also known as VRLA, or Valve-Regulated Lead Acid.
- AGM - AGM stands for Absorbed Glass Mat and these types use very little electrolyte. These types of batteries are the most commonly used in automotive applications. They can generally be mounted upright or on their side without any difficulty. They are maintenance free and perform quite well for deep-cycle application (where current is required over long periods). Shallow cycle versions are also available (where a large amount of current is needed, but only for a short period). AGM batteries are the current yardstick and perform adequately for most applications with few negative traits.
- LI-ION - Lithium Ion is the new comer to the automotive battery world. They're expensive and fault intolerant, but they are insanely light and small and can be mounted just about anywhere. LI-ION batteries do not care for a lot of vibrations, they hate overcharging, and they'll probably catch fire if there is any internal electronic failures. Furthermore, any voltage above 14.5V will significantly shorten their lifespan (voltages can exceed 16V on stock charging systems). That said, a lot of folks will use them just because they're cool (yes, I want one, too).
So... maybe you have an idea of what type of battery you want, it's time to investigate the specs for each individual battery. Voltage aside, there will be two numbers which will be of importance.
The primary concern is the battery's Amp Hour rating (usually abbreviated as Ah). This number is an
approximation of how many hours your battery will be capable of discharging it's rated voltage at one amp. So a 9 Ah battery should be able to continuously discharge current at a single amp for nine hours.
Your service manual will specify a minimum number for batteries that go into your bike. You can go smaller, but to do so risks draining the battery even under normal operation of the bike. If your bike has seen some improvements to the alternator, reduction in wattage requirements (LED lights, low-wattage headlights, removal of non-critical electrical systems, etc) you can usually get away with a lower rating.
Your riding habits will also affect your Ah requirements. If you spend a lot of time riding in the city (or otherwise idling the bike) you may not want to drop to anything much smaller. Also, if you spend all your time are redline and haven't upgraded to a modern regulator, you may not want to go with anything smaller (Ah rating is also a battery's resistance to overcharging). If you're cruising on the highway all day every day, you can cut your Ah way down because the battery will be facing very little discharge and won't have to cope with too much overcharge, either.
So, why go smaller on the Ah rating? Well, the Ah rating correlates to the size and weight of the battery. Smaller batteries will generally have lower Ah ratings.
The second rating you will usually find is Cold Cranking Amps (also listed as CCA). This maximum current your battery can provide for a continuous period of 30 seconds at 0°F which maintaining a voltage of at least 7.2V. In reality, this number will indicate how well your battery can turn over your starter motor. This number isn't always listed because it correlates closely to the Ah rating of the battery in most cases. Marine Cranking Amps (MCA) is also sometimes listed and this is the same requirement as CCA, except the battery is measured at 32°F instead of 0°F. Obviously, if your bike doesn't use a starter motor, this rating isn't of much importance to you.