Knowing the difference between a battery that starts an engine, and one that is meant to supply electricity over a long period of time without the benefit of a running engine, can save you a lot of otherwise wasted money.
The basic, and still preferred battery in common use is the very ordinary lead acid type. There are variants of course, such as glass mat and gel types, but standard lead acid batteries are still much loved and the most efficient. Let’s have a look at the jobs these batteries are required to do.
Starter Batteries, as the name suggests, are designed to start an engine. This requires the battery to supply a burst of what is known as ‘cold cranking amps’ or CCA to the engine’s starter motor, for a very short period of time. This burst can run into hundreds of amps if an engine is cold. When the engine starts, it immediately begins to recharge the battery so that the cycle can be repeated as required.
Starter batteries are good at this because of their internal design. The lead pasted plates inside the battery are intentionally made thin as this enables the super fast discharge required in engine starting. However, if you’ve accidentally left your car’s lights on for any length of time, you may well have come back to the vehicle, only to find that the engine won’t start, or is reluctant to start because the battery has been at least partially flattened. Starter batteries are not good at any kind of repeated extended discharge and can be severely damaged in a very short time if used in this way.
To be fit for purpose, Leisure Batteries, as used as domestic batteries on boats, motor homes and as storage devices for solar panel output etc., must be capable of ‘deep cycle’ use. Batteries used to drive electric golf buggies and electric wheel chairs etc., are a typical example of ‘deep cycle’ batteries. These batteries are charged overnight and gradually discharged when in use. If you attempted this with a standard starter battery it would literally die in a very short time.
Deep Cycle Batteries are manufactured with much thicker plates than starter batteries, but will, in fact, start an engine. However, they are not really made for that purpose.
The American battery company, Trojan, manufacture a variety of deep cycle and semi traction batteries and have done so since about 1925. I only mention this because their batteries were my own choice for our boat. We live aboard full time, and reliable battery power is very important to us. In the event of no mains shore power being available, we can produce our own by using our deep cycle leisure battery bank to power an electrical inverter. We can do this, if we need to, over an extended period by using our engine to recharge the batteries.
If you are going to invest in leisure, deep cycle, traction or semi traction batteries make sure that you use a well respected supplier. If you do not, and simply look at the price tag instead, you will more than likely regret it.