A battery seems like a really simple device. It stores energy and releases it when you ask it to. That is simple. Really simple.
The complicated part is everything else about the battery: physical size, capacity, charging parameters, life cycle, specific gravity, maintenance, etc.
I had to reconfigure the battery stowage compartment to more properly stow the batteries. The batteries sit in a box on the port side, underneath the quarter berth, and conveniently at the seat of the nav desk. Maybe not the best place for the batteries, but that’s where they are. The original batteries were typical big box off-the-shelf “marine deep cycle” batteries. To make a really long story less long, when we bought Emet, we planned on outfitting her with solar panels and new batteries. The original battery charger didn’t work, so we replaced it with an identical unit: Marinco(Guest) 5/5 el cheapo unit. As we don’t plan on docking at marinas in the future, there was no need to spend a pile of money on a really nice AC/DC battery charger. Shortly after the charger install, one of the batteries (the oldest) “outgassed” and was dead. We replaced it with another big box off-the shelf “marine deep cycle” battery. Shortly after that, the other original battery died. At this point, I didn’t want to spend other $100+ dollars on a battery that I didn’t plan on making a part of the new battery bank. I had suspicion that the Marinco charger wasn’t really doing the job I wanted it to and this was confirmed by reading the short manual and taking battery voltage readings on a regular basis on the 2 batteries. I can’t really review the Marinco charger because I am convinced I was using it for a purpose that the manufacturer did not intend it to be used for.
I had to make a decision: buy the batteries I was going to use or buy another less expensive battery for the time being. What follows is my understanding of the situation with batteries and charging systems and what I did. A dissertation could be written on each and every facet of this post and, like most things boat, 4 people will have 5 different opinions.
I did some reading and found that “marine deep cycle” batteries really aren’t. They are basically a start battery to which the manufacturer added a little extra lead. A true deep cycle battery will be heavy (80 pounds versus 60) because of the amount of lead and the manufacturer will have data on the battery data sheet that gives charging voltages, life cycle data, performance data, and temperature/capacity data among other things. An electric vehicle (e.g. fork truck, golf cart, car) battery qualifies as a true deep cycle battery. Discovering this little tidbit explained a lot about the solar charge controller setting instructions that I was reading.
Decision 1: Trojan T-1275 batteries will be used.
Doing more reading and research, I developed a spreadsheet to calculate our projected electrical usage on a daily basis. Our “typical” usage fell somewhere between 100AH and 130AH per day. Giving our battery box size, 2 of the T-1275 would easily fit. Anymore than that and some creative engineering would be required. With 150AH each, that would give us a theoretical 300AH of stored electrical power. At 300AH, the battery bank would be 2 to 3 times our daily electrical power usage. Using 1/3 the bank power is OK. Using 1/2 the bank power is OK on occasion. It would mean that on cloudy days we would really have to “watch” our usage. I would like to have a battery bank of 450AH, but 300AH was easily doable.
Decision 2: 2 batteries would be purchased
We purchased 2 of the T-1275 batteries and I set about “rebuilding” the battery stowage compartment to house the new batteries. It was a very tight fit as there are some physical aspects of the box that must be considered “permanent”. We didn’t plan on completely gutting ANY part of the boat, so structural components had to be worked around. I glassed in some boards to make a level place for the batteries to sit. The previous stowage had some 2×4 chunks that had been cut and stacked to level the battery. Not acceptable. The batteries were installed, wired, and connected to the Marinco charger. Not ideal, but I would purchase the solar system and get it installed ASAP.
I had originally planned on purchasing a complete kit from Renogy Solar. It had 3 x 100W panels, a Tracer MPPT controller, an LCD controller remote display, wires, and connectors; everything that was needed to install a solar system. Go to make the purchase and . . . OUT OF STOCK. WHAT?!? They didn’t have the 40 amp Tracer controller, so that kit was out of stock. What to do. I knew I had to figure something out because I had 2 new batteries that were being charged by a charger that wasn’t designed for our purpose. MPPT or PWM solar charge controller? More reading and research and differing opinions and sales propaganda and confusion. I decided to go with MPPT simply because that is the newer technology and it was part of the controller that I finally settled on. I chose the Midnite Solar The Kid Marine MPPT charge controller. The decision on this was probably the easiest. The controller had the desired form factor, easy setup, integral display, and decent reviews.
Decision 3: 3 of the Renogy 100W panels with a Midnite Solar The Kid MPPT solar charge controller
The controller and panels were ordered. I ordered aluminum plate, tubing, and saddle clamps and fashioned my own mounting system to install the panels on the dinghy davits. We received everything, installed it all and in the end, it looks nice, is functional, and works as expected.
A very short(ish) post can make months of tedious reading and research look like child’s play. Let me just say that in reading forums about all of this stuff it would appear that one wrong decision on ANY of these items and you would create a singularity on your boat that would begin to engulf you, your neighbors, and eventually the universe. Opinions were that vehement.