Solaris Sunrise Catamaran 36

Solar Panels and Charging

The first thing we did on getting the boat was to ditch the Rutland wind generator - the bearings had gone and it wasn't cost effective to replace them. Solar is so much more efficient that we opted for that. The stainless pole was put to good use though - we sited our 4G antenna on it - see Internet below.

We decided to fit monocrystalline solar panels on the coachroof - paired with an Epever MPPT solar controller. One of the joys of a huge coachroof is the space for panels. Since the boat only came with 200Ah of house batteries and we had a further 200Ah which had been bought the for the last boat, we fitted these at the same time. Not perhaps our best idea since one pair were new and the others were of unknown date/status. As you'll see later in the page under Batteries we subsequently made a major change and replaced all 4 with lead carbon AGM batteries.

The solar panels provided loads of electricity but the house bank didn't manage to hold it - hence the change of batteries. But the solar has been a huge success. So much so that we're thinking we may add more panels if we fit a cockpit cover - the panels, with lead carbon AGM batteries, are fine for everything but late autumn to early spring but we'd like to be self-sufficient all year if we can.

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Batteries 2025

In 2024 our requirements for electricity changed. The skipper now needed long term oxygen ! Well, we could have given up boating but neither of us wanted to do that so we came back to the long discussions - see Battery Choices 2023 below - but now with different parameters.

Through the winter and spring we learned more about what was required and what was feasible. Long term oxygen (about 15 hours a day) needs an oxygen contentrator - most of these run on 240V mains power ; s>me are portable and can run on either mains or 12V (from a cigarette lighter socket). We conducted tests with a 240V household concentrator and were horrified at the drain on the Lead Carbon AGM batteries. The constant drain of of XX amps took the battery SOC (state of charge) down to 70% within about 15 minutes. This was plainly NOT going to work !

Then we tried the portable concentrator, which runs on an "on demand" mechanism rather than a constant supply and the results were better, but still unsustainable from the current batteries. We are perhaps overly sensitive about our batteries but we normally begin to consider running the generator or the engines when the SOC gets below 80% and we were getting there far too fast. It was only March when we conducted the tests so our solar panels weren't providing as much power as they would do later in the year. Nonetheless we decided that we needed to look at batteries which would not be damaged by a constant heavy drain. Thank goodness for YouTube !

We looked at dozens of YouTube videos, gradually picking up lots of knowledge and distinguishing the nonsense from the people who really knew what they were talking about. Our go-to video provider became Will Prowse, the guru.

What Choice Did We Make ? Firstly, LiFePO4 batteries are the obvious solution - very safe and ideal for our needs. But the choice of which LiFePO4 batteries and from which vendor was in itself an entire new project. Purchasers in the UK are in a particularly difficult place since Brexit. Many vendors refuse to sell to the UK, probably because the size of the market doesn't justify the work-load of a separate raft of regulations and paperwork from the rest of Europe or the USA.

We mentioned, in our 2023 investigations, that our insurers were not keen on the idea of lithium or LiFePO4 batteries and required them to be installed by a professional. Which was a pity because we had watched several videos on building and installing your own batteries and it really didn't look like rocket-science. But that was the edict. So then we had to agree not only to a professional installer but also to vendors who were acceptable to the insurers.

To cut a long story, or a zillion in-household conversations, short, we agreed on pre-built batteries from the well-known UK supplier Fogstar - they have a good reputation and conduct lots of tests before marketing batteries. Space was an issue - the only sensible place to put the new battery/batteries was on the bridge deck of the cat, where we currently had four 100Ah AGM batteries. We would have liked a bank with 2 batteries for redundancy but sadly this would have meant extending the space and getting in a carpenter so we opted for one battery, as large as would fit the space available. So a 628Ah Fogstar Drift battery was ordered, along with a raft of other bits - one B2B charger per engine/engine start battery.

Batteries 2023

Were you aware that this is a subject upon which boat owners can wax lyrical, lie awake at night thinking about or, as was the case with us, will discuss the subject to the nth degree of detail ?

How much capacity ? How many ? And, most importantly, what type ? Which then brings you round to the question of how you charge them. Should it be lithium ? If not, then what ? Even at this distance in time (we changed and upgraded the batteries winter 2022-2023) I can still recall almost every discussion we have and I have a plethora of spreadsheets on the subject.

Our position was affected by several factors - weight (it's a cat), space, the fact that we've got 2 engines and 2 alternators and, most importantly, the boat came fitted with Smart charging.

The last issue was an important factor. Although we were keen on changing our lead-acid batteries to lithium the smart charging system would mean that there would be added complexity requiring battery-to-battery chargers on both engines. In addition, we also have one house bank and 2 engine-starting batteries and the whole caboodle is linked. Then there was the attitude of the insurers - they were prepared to accept LiPo batteries but were insistent that they be fitted by an expert outfit. Not many of those around. We also preferred LiPo with independent battery management systems (BMS) since apparently these are the most likely cause of failure. If you have built-in BMS then a fault means replacing the whole expensive item, rather than just the BMS. The issue became even more complicated.

Eventually the research led us to LiPo4 or one of the Absorbed Glass Matt (AGM) variants. Despite the extra weight (by comparison with LiPo4) we opted for lead carbon AGM. These offer a higher number of recharge cycles than straight lead acid or other types of AGM and can support a greater depth-of-discharge (DOD). Not as good in either department as LiPo4 but without the extra costs, complexity and loss of our smart charging. That is a very quick summary of months of research and discussion. The boat now has 4 lead carbon AGM giving a total of just under 400Ah (amp hours). Fortunately our solar MPPT controller and the mains battery charger both offered settings to suit the new batteries.