Originally Posted by fordem
Just so that you are aware of it, and especially because I didn't see it mentioned before - battery construction is different based on the intended use.
A battery designed for engine starting will have a reduced service life if subjected to repeated deep discharges such as those that occur when used to power a fridge and a battery designed for deep cycle service will have a reduced service lift when subjected to the high amperage current draw required to crank an engine.
Either way, you can expect reduced battery life if you opt for a single battery.
Thanks for the reply. I agree that a battery is usually designed for one or the other, however this battery claims (and has had some good reviews on it) that it is capable of achieving both within reason. Based on the documentation they have given and my small understanding of batteries it seems as though it may just be what im after (a compromise to keep only 1 battery but still use it for what i want).
Having a read of the following document (http://www.centurybatteries.com.au/i...arine-category
) is the following paragraphs:
Car batteries vs Marine batteries
To understand why you should use a marine battery for boating
applications, we can compare a marine battery with a standard
Cars require batteries that provide a high burst of power
for a short time, just long enough to start the car’s engine. Only a
small portion of the battery’s power is used, and this
is restored over time by the car’s alternator.
Standard car batteries have thinner lead plates and porous
active material (lead oxide based paste coated onto the battery
grids) to maximise the surface area of the plate exposed to the
Maximizing the surface area provides higher current delivery
and as a result, greater starting power. However, because car
batteries have thinner plates they are not reliable in providing
longer periods of power while the engine is turned off and the
alternator is not charging.
The main requirement of a marine battery on a boat is
to start the boat’s engine. However, unlike car batteries, marine
batteries are also commonly required to deliver constant power
draw when the engine is switched off.
Generally when a car engine is turned off, the vehicle’s electrical
accessories are no longer in use, or are used
for a very short time only. On a boat, when the engine is turned
off there is usually a number of on-board accessories operating
at once, for extended periods of time.
Standard car batteries have as many thin and porous plates as
possible to maximise surface area and provide a high cranking
current. A deep cycle battery is built with thick plates and a
denser active material designed to withstand deep discharges
but at a lower current flow rate. Standard car batteries with thin
plates will be damaged by deep cycle use and are not reliable
in applications requiring sustained discharge, such as on-board
Also looking at their brochure here (http://www.centurybatteries.com.au/i...arine-brochure
) I see that the Marine Pro 720 is recommended for deep cycle applications as well as starting.
Looking at this page here (Battery Charging
), it appears that their batteries are 100% discharged at 11.9v, which would be their safe rating and what my isolator kicks out at. I have had my isolator kick in about 10 times now and the battery has started the car without hesitation.
I suspect the battery will give me the best possible outcome when running a single battery system as designed in the diagram in first post, with understanding that it is a compromise compared to a dedicated deep cycle battery for auxiliary systems.
Happy to hear of any alternative batteries that i may be able to use.