One of the more common problems faced by the average recreational boatie, is having a flat battery. The boat will not start once at the ramp, or even worse, you're left stranded at sea in need of a tow. The main reason for this is the fact that people leave their boats sitting in the driveway for weeks or even months on end after a trip out fishing and then just jump straight back in and head out on the water without even giving the battery system a thought.
The running time (travelling to and from your fishing spot) is normally minimal, so there is minimal charge going into the batteries and at the same time the chartplotter, sounder, VHF, FM radio, pumps and an array of other power-sucking techo toys are in full use.
Each time you head out on the water, you are putting less charge back in the battery compared to what is being sucked out. At the end of the day a battery is no different to a bucket of water. If every time you took 5 liters of water out you put 3 liters back in, sooner or later you will have an empty bucket. But, its actually worse than that. Flat batteries sulphate (a chemical process), the longer it is left to occur the more damage is done to the batteries and also degrades their performance and recovery. This chemical process is easily rectified or reversed with a proper recharging. Batteries should be left fully charged when not in use.
Once you have drained a deep cycle battery past 60% of its Ampere hour capacity (you have used 60% of the total ampere hour rating) then you are also damaging the battery! Its life, in cycles, decreases! Again a bucket of water best describes this. If you have a ten litre bucket of water and you take MORE than 6 liters of that water out, which is more than 60% of what the bucket can hold. Then you are damaging it!
It could be compared to drilling a hole in the bucket 10ml from the top. Now you can’t fill the bucket back up to the top and it can only hold 9.6 liters of water. So you can see that over the course of 6 months or a year of doing this there's been lots of holes drilled further and further down the side of the bucket and its capacity keeps decreasing, 9.2 liters, 8.8, 8.0, 7.5 etc...
It’s not hard to understand how you can kill perfectly good/brand new batteries by either over-cycling or a lack of charging. Putting your batteries on charge after each trip on the water and again before each trip out, is a habit worth developing! It can be made easy with charger connectors and will save you both time and money!
When building the Techno Viking, a lot of thought has gone into batteries!
I have had a couple of long conversations with the boys at Battery Town about their Hella Endurant batteries, and OzCharge battery chargers to find out which ones would suit us best, but more importantly to work out how much power is required each time we head out on the water. I wrote down every little techo toy on the boat that requires power, then what its ampere hour draw was and then how many hours it would be used for on an average trip. Also taking into account that for every hour traveling in the boat, our outboard was putting 52 amps back into the system, (only at peak RPM). We built the Techno Viking so we can stay on the water for a few days at a time and to be able to fish those magic twilight hours, dawn and dusk. There was a lot to consider!
Once we had the number of total amps required for each day of a trip, we needed a battery bank that with those amps sucked out it would not drain the Techno Vikings deep cycle battery bank below 60% of its total capacity so that our batteries will last the distance. It sounds like a lot of work and to be honest it was! But, its gonna save us both time and money in the long run! AND...Even after all of this, before and after each trip the batteries will still get plugged into the charger at home!
The Techno Viking is also in full survey under Maritime New Zealand's new MOSS system. Under survey you must have a battery dedicated for starting only! and you must also have a backup power source that can start the motor in case of emergency (a switch linking your house bank to the start battery is the norm). It worked out cheaper and less time consuming with the way Techno Viking is laid out to have 2 start batteries down the back close to the Suzuki (one battery is put there only as a back up start battery). The house bank and start batteries are wired as 2 completely different systems each with their own switches. We will always be able to start the engine and get ourselves back to port no matter what might go wrong with the house bank system or anything that is wired to it. Which is great piece of mind.